Neuro Flashcards
Central Sulcus
This anatomic landmark separates the frontal lobe from the parietal lobe,
and is useful to find if you haven’t learned the lazy Neuroradiolgisf s go to descriptor “fronto-parietal region.”
Practically speaking, this is the strategy I use for finding the central sulcus:
Pretty high up on the brain, maybe the 3rd or 4th cut, I find the pars marginalis. This is called the “pars bracket sign” - because the bi-hemispheric symmetric pars marginalis form an anteriorly open bracket. The bracket is immediately behind the central sulcus. This is
present about 95% o f the time - it’s actually pretty reliable.
Central Sulcus Trivia - Here are the other less practical ways to do it.
Superior frontal sulcus / Pre-central sulcus sign: The posterior end o f the superior frontal sulcus joins the pre-central sulcus
Inverted omega (sigmoid hook) corresponds to the motor hand
Bifid posterior central sulcus: Posterior CS has a bifid appearance about 85%
Thin post-central gyrus sign - The precentral gyrus is thicker than the post-central gyrus (ratio 1.5 : 1).
Intersection - The intraparietal sulcus intersects the post-central sulcus (works almost always)
Midline sulcus sign - The most prominent sulcus that reaches the midline is the central sulcus (works about 70%).
Superior frontal sulcus
often intersects the pre CS
inverted omega
On the central sulcus
represents the motor hand
intraparietal sulcus
intersects the post CS
precentral is
thick
postcentral is
thin
the post cs is bifid
about 85% of the time
Homunculous Trivia
The inverted omega (posteriorly directed knob) on the central sulcus /
gyrus designates the motor cortex controlling hand function.
ACA territory gets legs,
MCA territory hits the rest.
Normal Cerebral Cortex
As a point of trivia, the cortex is normally 6 layers thick, and the hippocampus is normally 3 layers thick. I only mention this because the hippocampus can look slightly brighter on FLAIR compared to other cortical areas, and this is the reason why (supposedly).
Dilated Perivascular Spaces (Virchow-Robins):
These are fluid filled spaces that accompany perforating vessels. They are a normal variant and very common. They can be enlarged and associated with multiple pathologies; mucopolysaccharidoses (Hurlers and Hunters) / ‘gelatinous pseudocysts” in
cryptococcal meningitis, and atrophy with advancing age. They don’t contain CSF, but instead have interstitial fluid. The common locations for these are: around the lenticulostriate arteries in the lower
third of the basal ganglia, in the centrum semiovale, and in the midbrain.
Cavum septum pellucidum
-100% of preterm infants,
- 15% of adults.
- Rarely, can cause hydrocephalus
- Anterior to the foramen of Monroe
- Between frontal horns
Cavum Vergae
- Posterior continuation of the cavum septum pellucidum (never exists without a cavum septum pellucidum)
- Posterior to the foramen of Monroe
- Between bodies of lateral ventricles
Ventricular Anatomy
You have two lateral ventricles that communicate with the third ventricle via the interventricular foramen (of Monro), which in turn communicates with the fourth ventricle via the cerebral aqueduct.
The fluid in the fourth ventricle escapes via the median aperture (foramen of Magendie), and the lateral apertures (foramen of Luschka). A small amount of fluid will pass downward into the spinal subarachnoid spaces, but most will rise through the tentorial notch and over the surface of the brain where it is reabsorbed by the arachnoid villi and granulations into the venous sinus system.
Blockage at any site will cause a noncommunicating hydrocephalus. Blockage of reabsorption at the villi / granulation will also cause a noncommunicating hydrocephalus.
Arachnoid Granulations
These are regions where the arachnoid projects into the venous system
allowing for CSF to be reabsorbed. They are hypodense on CT (similar to CSF), and usually round or oval. This round shape helps distinguish them from clot in a venous sinus (which is going to be linear). On MR they are typically T2 bright (iso to CSF), but can be bright on FLAIR (although this varies a lot and therefore probably won’t be tested). These things can scallop the inner table (probably from CSF pulsation).
Basal Cisterns overview
People say the suprasellar cisterns look like a star, with the five corners lending themselves nicely to multiple choice questions. So let us do a quick review; the top of the star is the interhemispheric
fissure, the anterior points are the sylvian cisterns, and the posterior points are the ambient cisterns.
The quadrigeminal plate looks like a smile, o r … I guess it looks like a sideways moon, if you
don’t like smiles.
The Ambient Cistern is
a bridge between the
Interpeduncular C. ► Quadrigeminal C.
suprasellar cistern star
Anterior interheispheric cistern
sylvian cistern sylvian cistern
ambient cistern ambient cistern
quadrigeminal plate citern (sideways moon)
Midbrain tectum vs tegmentum
Cerebral peduncle Cerebral peduncle
(usbstantia nigra) (substantia nigra)
tegmentum tegmentum
(red nucleus) (red nucleus)
tectum (aqueduct) tectum
Foramen rotundum
showing Foramen Rotundum (FR) in the coronal and sagittal planes is a very common sneaky trick.
On the coronal view, FR looks like you are staring into a gun barrel.
On the sagittal view, think about FR as being totally level or horizontal.
Foramen spinosum and ovale
With regard to the relationship between Spinosum and Ovale, I like to think of this as the footprint a
woman’s high heeled shoe might make in the snow, with the oval part being Ovale, and the pointy
heel as Spinosum.
Hypoglosal canal
The Hypoglossal Canal is very posterior
and inferior.
This makes it unique as a skull base foramen.
Jugular foramen overview
The jugular foramen has two parts which are
separated by a bony “jugular spine.”
Pars Nervosa
The nervous guy in the front. This contains the Glossopharyngeal nerve (CN 9), along with it’s tympanic branch - the “Jacobson’s Nerve
Pars Vascularis
This is the “vascular part” which actually contains the jugular bulb, along with the Vagus nerve (CN 10), Auricular branch “Arnold’s Nerve,” and the Spinal Accessory Nerve (CN 11)
Bony Anatomy: Orbital Fissures and the PPF
overview
The relationship between the Superior Orbital Fissure (SOF), the Inferior Orbital Fissure (IOF), Foramen
Rotundum (FR), and the Pterygopalatine Fossa (PPF) is an important one, that can really lead to some
sneaky multiple choice questions (mainly what goes through what - see chart
page 17 volume 2
sagittal top to bottom sof iof fr ppf
coronal sof iof fr ppf
Anatomy: Cavernous Sinus
whts in it
CN 3, CN 4, CN VI, CN V2, CN 6, and the carotid - run through it.
Anatomy: Cavernous Sinus
whats not in it
CN 2 and CN V3 - do NOT run through it.
Anatomy: Cavernous Sinus
anatomy trivia
The only other anatomy trivia I can think of is that CN6 runs next to the carotid, the rest of the nerves are
along the wall. This is why you can get lateral rectus palsy earlier with cavernous sinus pathologies.
Anatomy: Internal Auditory Canal - “IAC’
overview
The thing to remember is “7UP, and COKE Down”
- with the 7th cranial nerve superior to the 8th
cranial nerve (the cochlear nerve component).
As you might guess, the superior vestibular branch
is superior to the inferior one.
Anatomy: Internal Auditory Canal - “IAC’
ideal sequence
The ideal sequence to find it is a
heavily T2 weighted sequence with
super thin cuts through the IAC.
Anatomy: Internal Auditory Canal - “IAC’
sagittal
ante/superior post/superior
CN7 Superior vestibular
CN8 inferior vestibular
Contents
Foramen Ovale
CN V3, and Accessory Meningeal Artery
Contents
Foramen Rotundum
CN V2 (“R2V2”),
Contents```
Superior Orbital Fissure
C N 3 , CN 4, CN V I, CN6
Contents
Inferior Orbital Fissure
CN V2
Contents
Foramen Spinosum
Middle Meningeal Artery
Contents
Jugular Foramen
Pars Nervosa: CN 9,
Pars Vascularis: CN 10, CN 11
Contents
Hypoglossal Canal
CN 12
Contents
Optic Canal
CN 2 , and Opthalmic Artery
Contents
Cavernous Sinus
CN 3, CN 4, CN VI, CN V2, CN 6, and the carotid
Contents
Internal Auditory Canal
CN 7, CN 8 (Cochlear, Inferior Vestibular and Superior
Vestibular components). “7 Up - Coke Down”
Contents
Meckel Cave
Trigeminal Ganglion
Contents
Dorello’s Canal
Abducens Nerve (CN 6), Inferior petrosal sinus
Vascular Anatomy
overview
Arterial vascular anatomy can be thought o f in four sections. (1) The branches o f the external
carotid (commonly tested as the order in which they arise from the common carotid).
(2) Segments o f the internal carotid, with pathology at each level and variants. (3) Posterior
circulation, (4) Venous anatomy
(11 Branches of the External Carotid
Some Administrators Love Fucking Over Poor Medical Students
from first off to last branch Superior Thyroid 9anterior) Ascending Pharyngeal (superior Lingual (anterior) Facial (Anterio thens uperior) Occipital (posterior superior) Posterior Auricular (posterior superior) Maxillary (anterior) Superficial Temporal (supeior)
THIS VS THAT: External vs Internal Carotid via Ultrasound
internal
no branches
posterior
low resistance (continous diastolic)
no change in waveform with temporal tap
THIS VS THAT: External vs Internal Carotid via Ultrasound
external
branches
anterior
high resistance
waverform areacts to temporal tap
Segments of the Internal Carotid
Internal Carotid
• The bifurcation of the IAC and ECA usually occurs at C3-C4
• Cervical ICA has no branches in the neck - if you see branches either
(a) they are anomalous or more likely
(b) you are a dumb ass and actually looking at the external carotid.
*Remcmber finding branches is a way you can tell ICA from ECA on
ultrasound.
• Low resistance waveform with continuous forward flow during diastole
• Flow reversal in the carotid bulb is common
Segments of the Internal Carotid
Cl (Cervical)
Atherosclerosis: The origin is a very common location
Dissection: Can be spontaneous (women), and in Marfans or Ehlers-
Danlos, and result in a partial Homer’s (ptosis and miosis), followed by
MCA territory stroke.
Can have a retropharyngeal course and get “drained” by ENT accidentally.
Pharyngeal infection may cause pseudoaneurysm at this level.
to the level of the carotid canal
The internal carotid artery (C1 segment) enters the skull base through the carotid canal, where it begins a series of 90° turns which lead it to eventually terminate as the middle and anterior cerebral arteries.
Segments of the Internal Carotid
C2 (Petrous)
Not much goes on at this level.
Aneurysms here can be surprisingly big (thats what she said).
in the carotid canal
It first turns 90° anteromedially within the carotid canal as the C2 segment to run through the petrous temporal bone.
Segments of the Internal Carotid
C3 (Lacerum)
Not much here as far as vascular pathology. The anatomic location is
important to neurosurgeons for exposing Meckel’s cave via a transfacial
approach
from the carotid canal to the level of the petrolingual ligament
As it exits the carotid canal it lies superior to the foramen lacerum (C3 segment) and then turns 90° superiorly and then immediately another 90o turn anteriorly to groove the body of the sphenoid
Segments of the Internal Carotid
C4 (Cavernous)
This segment is affected by
multiple pathologies including
the development of cavernous -
carotid fistula.
Aneurysms here are strongly
associated with hypertension,
from the petrolingual liament to the dural ring
enter the medial aspect of the cavernous sinus (C4 segment). Within the cavernous sinus the abducens nerve is intimately related to the artery on its lateral side.
Segments of the Internal Carotid
C5 (Clinoid)
Aneurysm here could compress the
optic nerve and cause blindness.
in the dural ring
At the anterior end of the cavernous sinus, the ICA makes another 90° turn superiorly (C5 segment) and a final 90° turn posteriorly
Segments of the Internal Carotid
C6 (Ophthalmic
- Supraclinoid):
Origin at the “dural ring” is a
buzzword for this artery.
Common site for aneurysm formation.
to pass medial to the anterior clinoid process (C6 segment)
Segments of the Internal Carotid
C7
Communicating
Aneurysm here may compress CN
III and present with a palsy.
The terminal ICA (C7 segment) abruptly divides into the middle and anterior cerebral branches and gives off two smaller posterior branches, the anterior choroidal artery and the posterior communicating artery.
Internal carotid anatomy total
Course
The cervical segment of the ICA courses posterior to the ECA after its origin and ascends in the neck within the carotid sheath. As it ascends on the pharyngeal wall and the buccopharyngeal fascia, it is consecutively crossed laterally by the pharyngeal branch of the vagus nerve (CN X), glossopharyngeal nerve (CN IX), and the stylopharyngeus and styloglossus muscles.
The internal carotid artery (C1 segment) enters the skull base through the carotid canal, where it begins a series of 90° turns which lead it to eventually terminate as the middle and anterior cerebral arteries.
It first turns 90° anteromedially within the carotid canal as the C2 segment to run through the petrous temporal bone. As it exits the carotid canal it lies superior to the foramen lacerum (C3 segment) and then turns 90° superiorly and then immediately another 90o turn anteriorly to groove the body of the sphenoid and enter the medial aspect of the cavernous sinus (C4 segment). Within the cavernous sinus the abducens nerve is intimately related to the artery on its lateral side. At the anterior end of the cavernous sinus, the ICA makes another 90° turn superiorly (C5 segment) and a final 90° turn posteriorly to pass medial to the anterior clinoid process (C6 segment). The terminal ICA (C7 segment) abruptly divides into the middle and anterior cerebral branches and gives off two smaller posterior branches, the anterior choroidal artery and the posterior communicating artery.
Branches
Except for the terminal segment (C7), the odd-numbered segments usually have no branches. The even-numbered segments (C2, C4, C6) often have branches, although they are inconstant and usually small, therefore often not visualized even on high-resolution digital subtraction angiography. The exception is the ophthalmic artery, which is seen in nearly all cases
what branche first posterior communicating or anterior choroidal
p comm
ICA lateral vs anterior
ACA is antioer
MCA is lateral
Acute CN3 Palsy (unilateral
pupil dilation)
classic neurology boards question -
grab a relax hammer STAT!
The answer is PCOM aneurysm until proven otherwise (although it can also be caused by an aneurysm at the apex of the basilar artery or its junction with the superior cerebellar / posterior cerebral arteries).
The reason is the relationship
between the CN3 and vessels
(arrows).
Circle willis anatomy
23
Vascular Variants
Fetal Origin o f the PCA
Most common vascular variant (probably) - seen in up to 30% of general population.
Definitions vary on what a fetal PCA is. Just think of this as a situation where the PCA is feed primarily as an anterior circulation artery (occipital lobe is feed by the ICA).
Therefore, the PCOM is large (some people define this vessel as PCOM larger than P 1).
Another piece of trivia is that anatomy with a fetal PCA has the PCOM superior / lateral to CN3 (instead o f superior / medial - in normal anatomy).
Vascular Variants
Persistent Trigeminal Artery
Persistent fetal connection between the cavernous ICA to the basilar.
A characteristic “tau sign” on Sagittal MRI has been described.
It increases the risk of aneurysm (anytime you have branch points).
Sag - C o n n e c ted B a s ila r an d ICA
L o o k s like a “T ” au
Anastomotic Vein of Trolard
Connects the Superficial Middle Cerebral Vein and the Superior Sagittal Sinus
Anastomotic Vein of Labbe
Connects the Superficial Middle Cerebral Vein and the Transverse Sinus
Trolard =
top
labbe =
lower
Superficial cerebral veins
Superior Cerebral Veins
Superior Anastomotic Vein of Trolard
Inferior Anastomotic Vein of Labbe
Superficial Middle Cerebral Veins
Deep cerebral veins
Basal Vein of Rosenthal
Vein of Galen
Inferior Petrosal Sinus
cerebral veins collateral pathways
The dural sinuses have accessory drainage pathways (other than the jugular
veins) that allow for connection to extracranial veins. These are good because they can help
regulate temperature, and equalize pressure. These are bad because they allow for passage o f
sinus infection / inflammation, which can result in venous sinus thrombosis.
cerebral veins inverse relationship
There is a relationship between the Vein o f Labbe, and the Anastomotic
Vein o f Trolard. Since these dudes share drainage o f the same territory, as one gets large the
other get small.
Vein o f Labbe
Large draining vein, connecting the superficial middle vein and the
transverse sinus
Vein o f Trolard
Smaller (usually) vein, connecting the superficial middle vein and
sagittal sinus
Basal veins o f Rosenthal
Deep veins that passes lateral to the midbrain through the
ambient cistern and drains into the vein o f Galen. Their course is similar to the PCA.
Vein o f Galen
Big vein (“great”) formed by the union o f the two internal cerebral veins.
Venous Gamesmanship
overview
An embolus o f venous gas is common and often not even noticed. The classic location is the cavernous sinus (which is venous), but if the volume is large enough, air can also be seen in the orbital veins, superficial temporal veins, frontal venous sinus, and petrosal sinus.
Venous Gamesmanship
why does this happen
Peripheral (or central IV) had some air in the tubing. Thats right, you can blame it on the nurse (which is always satisfying). “Nurse Induced Retrograde Venous Air Embolus ”
Venous Gamesmanship
significance
Don’t mean shit. It pretty much always goes away in 48 hours with no issues.
Venous Gamesmanship
most common spot
and the other sights
cavernous sinus
orbital veins and superficial temporal
The Concha Bullosa
This is a common variant where the middle concha is pneumatized. It’s pretty much o f no consequence clinically unless it’s fucking huge - then (rarely) it can cause obstructive symptoms.
CN 3 Palsy
Think Posterior Communicating Artery Aneurysm
CN 6 Palsy
Think increased ICP
Increased ICP >
Brain Stem Herniates Interiorly —► CN 6 Gets Stretched
Brain Myelination
overview
The baby brain has essentially the opposite signal characteristics as the adult brain. The T1 pattern
of a baby is similar to the T2 pattern of an adult. The T2 pattern o f a baby is similar to the T1
pattern of an adult. This appearance is the result o f myelination changes.
The process o f myelination occurs in a predetermined order, and
therefore lends itself easily to multiple choice testing. The basic
concept to understand first is that immature myelin has a higher
water content relative to mature myelin and therefore is brighter
on T2 and darker on T1. During the maturation process, water
will decrease and fat (brain cholesterol and glycolipids) will
increase. Therefore mature white matter will be brighter on T1
and darker on T2.
Brain Myelination
testable trivia
the T1 changes precede the T2 changes (adult T1 pattern seen around age 1, adult T2 pattern seen around age 2). Should be easy to remember (1 fo r Tl, 2 for T2).
Brain Myelination
take home point
Tl is most useful for assessing myelination in the first year (especially 0-6 months), T2 is most useful for assessing myelination in the second year (especially 6 months to 18 months).
Brain Myelination
order of progression
Just remember, inferior to superior, posterior to anterior, central to peripheral, and sensory fibers prior to motor fibers. The testable trivia is that the subcortical white matter is the last part of the brain to myelinate, with the occipital white matter around 12 months, and the frontal regions
finishing around 18 months. The “terminal zones” o f myelination occur in the subcortical frontotceporoparietal regions - finishing around 40 months.
Brain Myelination
another form of testable trivia
the brainstem, and posterior limb of the internal capsule are normally myelinated at birth.
Brain Myelination Pattern
Inferior to Superior, Posterior to Anterior
Immature
Myelin
High water
low fat
t1 dark
t2 bright
mature myelin
low water
high fat
t1 bright
t2 dark
Pituitary development overview
Both the Anterior and Posterior Pituitary are T1 Bright at Birth (anterior only T1 bright until 2 months).
Pituitary birth
Ant T1 Hyper
Posterior T1 Hyper
pituitary adult
ant t1 iso, t2 iso
posterior t1 hyper, t2 hypo
Brain Iron
Brain Iron increases with age (globus pallidus darkens up).
skull bone marrow signal
Calvarial Bone Marrow will be active (T1 hypointense) in young kids and fatty (T1 hyperintense) in older kids
Sinus Development
overview
Sinus Development:
The sinuses form in the
following order:
1- Maxillary,
2- Ethmoid,
3- Sphenoid,
4- Frontal
Most are finished
forming by around 15
years.
Sinus Development
detailed
Order Visible on CT
Maxi.l..l ary 1. Present at _5 month
Ethmoid 2 Present at birth 1. year
Frontal 4 Not Present at Birth 6 years
Sphenoid 3 not present at birth 4 years
Congenital Malformations overview
This is a very confusing and complicated topic, full o f lots o f long Latin and French sounding
words. If we want to keep it simple and somewhat high yield you can look at it in 5 basic
categories: (1) Failure to Form, (2) Failure to Cleave, (3) Failure to Migrate,
(4) Development Failure Mimics, and (5) Herniation Syndromes.
Failure to Form • Dysgenesis / Agenesis of the Corpus Callosum
overview
A classic point o f trivia is that the corpus callosum forms front to back (then rostrum lastl. Therefore hypoplasia o f the corpus callosum is usually absence o f the splenium (with the genu intact).
Failure to Form • Dysgenesis / Agenesis of the Corpus Callosum
front to back
rostrum genu body isthmus splenium
Failure to Form • Dysgenesis / Agenesis of the Corpus Callosum
gamesmanship
With agenesis of the corpus callosum, a common
trick is to show colpocephaly (asymmetric dilation
o f the occipital homs).
When you see this picture you should think:
(1) Corpus Callosum Agenesis
(2) Pericallosal Lipoma
Colpocephaly
(asymmetric dilation of the occipital homs).
Failure to Form - Dysgenesis / Agenesis of the Corpus Callosum Continued
other common ways to show this
The steer horn appearance on coronal
vertical ventricles - widely spaced (racing car) on axial
Why are the lateral
ventricles widely spaced
when you have no corpus
callosum ?
There are these things called “Probst bundles” which are densely packed WM tracts - destined to cross the CC - but can’t (because it isn’t there). So instead they run parallel to the interhemispheric fissure - making the vents look widely spaced.
Failure to Form - Associations - Intracranial Lipoma
overview
Dysgenesis / Agenesis o f the Corpus Callosum is associated with lots o f other syndromes/
malformations (Lipoma, Heterotopias, Schizencephaly, Lissencephaly, e tc…). Some sources
will even say it is the “most common anomaly seen with other CNS malformations. ” —
whatever the fuck that means.
Failure to Form - Associations - Intracranial Lipoma
trivia
. CNS Lipomas are congenital malformations, not true neoplasms.
• “ Maldifferenitation o f the Meninx Primitiva “ - is a meaningless French
sounding explanation for the frequent pericollasal location.
• Non Fat Sat T1 is probably the most helpful sequence (most non-bleeding
things in the brain are not T1 bright).
• These things d o n ’t cause symptoms (usually) are rarely treated.
Intracranial lipoma
The most classic association with CC Agenesis. 50% are found in the interhemispheric fissure, as shown here. The 2nd most common location is the quadrigeminal cistern (25%).
Anencephaly
overview
Neuro Tube Defect
(Defect at the top o f head)
The Top of the Head is Absent
(Above the Eyes)
Reduced /Absent cerebrum and cerebellum.
The hindbrain will be present.
Mercifully, not compatible with life.
Potential to he awful at Jeopardy
Anencephaly
Classic Image Appearance:
Incredibly creepy “Frog Eye” appearance on
the coronal plane (due to absent cranial bone /
brain with bulging orbits).
Anencephaly
Secondary Signs / Gamesmanship:
• Antenatal Ultrasound With Polyhydramnios
(hard to swallow without a brain)
• AFP will be elevated
(true with all open neural tube defects)
Iniencephaly
overview
Neural Tube Defect
(Defect at the level o f the cervical spine)
Deficient Occipital Bone with Defect in the Cervical Region. Inion = Back of Head / Neck
Extreme Retroflexion of the Head.
Enlarged foramen magnum.
Jacked up spines.
Often visceral problems.
Usually, not compatible with life.
When they do survive, they tend to have a
natural talent for amateur astronomy
Iniencephaly
classic imaging appearance
“Star Gazing Fetus” - contorted in a way that
makes their face turn upward (hyper-extended
cervical spine, short neck, and upturned face).
It’s every bit as horrible as the Frog Eye thing
(both would make incredible Halloween costumes.)
Iniencephaly
secondary sigs/gamesmanship
AFP will be elevated
true with all open neural tube defects
Failure to Form - Open Neural Tube Defects - Encephalocele ( meningoencephalocele)
Neural tube defect where brain + meninges herniate through a defect
in the cranium. There are lots o f different types and locations — but
most are midline in the occipital region.
There are numerous associations: - most classic = Chiari III
Rhombencephalosynapsis
vermis is absent
note the vertical lines across the cerebellum
Rhombencephalosynapsis
classic imaging appearance
Transversely oriented single lobed cerebellum as shown above (this is an Aunt Minnie).
Absence of the vermis results in an abnormal fusion of the cerebellum.
Small 4th Ventricle
Rounded Fastigial Point, Absent Primary Fissure
Rhombencephalosynapsis
associations
Holoprosencephaly Spectrum
Joubert Syndrome
Vermis is Absent (or Small)
Joubert Syndrome
classic imaging appearance
“Molar Tooth” appearance of the superior cerebellar peduncles (elongated like the roots of a tooth).
Small Cerebellum
Absence of pyramidal decussation (whatever the fuck the means)
Large 4th Ventricle “Batwing Shaped”
Absent Fastigial Point, Absent Primary Fissure
Joubert Syndrome
associations
Retinal dysplasia (50%), Multicystic dysplastic kidneys (30%). Liver Fibrosis (“COACH” Syndrome)
Failure to Form - Cerebellar Vermis
Gamesmanship:
If you are faced with this level of trivia (on an intermediate level exam), first start by looking for
the two markers of normal vermian development: (1) the primary fissure and (2) fastigial point -
both of which arc best seen mid sagittal. The ‘fastigial po in t” is normal angular contour (not
round) along the ventral surface of the cerebellum. The primary cerebellar fissure is a deep
trapezoid shaped cleft along the posterior cerebellum. Absence or abnormal morphology of these
landmarks should trigger a multiple choice brain reflex indicating the vermis is not normal.
Classic Dandy Walker
3 key findings
1 Hypoplasia of the Vermis (usually the inferior part) 2 Hypoplastic Vermis is Elevated and Rotated 3 Dilated Cystic 4th Ventricle
Classic Dandy Walker
axial
On axial, there is the nonspecific appearance o f an
enlarged posterior fossa CSF space. It can look like a
retrocerebellar cyst on axial only (although it’s not a cyst
- it’s the expanded 4th ventricle).
The cerebellar hemispheres will be displaced forward
and laterally but their overall volume and morphologic
characteristics should be preserved.
“TORCULAR-LAMBDOID INVERSION”
overview
This classic buzzword(s) describes the torcula
(confluence o f venous sinuses) above the level of the
lambdoid suture, secondary to elevation of the tentorium.
It’s worth mentioning that this inversion is often NOT
seen in the “variant” version of Dandy Walker.
“TORCULAR-LAMBDOID INVERSION”
quick
- Normal -
Lambdoid
Above Torcula - Dandy Walker -
Torcula Above Lambdoid
‘ High-Inserting
Venous Confluence “
“C la s s ic ” Dandy W a lk e r
trivia
Often identified on OB screening US.
Otherwise, presents with symptoms of increased intracranial pressure (prior to month 1)
Most Common Manifestation = Macrocephaly (nearly all cases with the first month)
Associations: Hydrocephalus (90%), Additional CNS malformations (~ 40%) (agenesis of the corpus callosum, encephaloceles, heterotopia, polymicrogyria, etc…).
Failure to Form - Dandy walker and Friends
from least to most severe
Mega Cisterna Magna
Blake Pouch
“Variant” DWM
“Classic” DWM
Variant DWM name
hypoplastic rotated vermis
Mega Cisterna Magna
Overview: normal variant. focal enlargement of the retrocerebellar CSF space
Vermis: normal
4th Ventricle: normal
Cerebellar Hemispheres: normal
Posterior Fossa: normal
Torcula: normal
Hydrocephalus: no
Trivia: no supratentorial abnormalities
Blake Pouch
Overview: sac like cystic protrusion through the foramen of magendie into the infra/retro cerebellar region
Vermis: normally formed but upwardly displaced
4th Ventricle: dilated
Cerebellar Hemispheres: normal
Posterior Fossa: normal
Torcula: normal
Hydrocephalus: yes
Trivia: choroid from the 4th ventricle swinging into the pouch is classic (but not always present)
the pouch only communicates with the 4th ventricle not the internal CSF
“Variant” DWM
Overview: hypoplastic vermis with dilation of the 4th ventricle
Vermis: hypoplastic (less severe)
4th Ventricle: dilated
Cerebellar Hemispheres: hypoplastic
Posterior Fossa: normal
Torcula: normal
Hydrocephalus: 25% of cases
Trivia: Diagnosis on antenatal ultrasound must be done after 18 weeks (prior to 18 weeks the vermis hasnt finished forming).
“Classic” DWM
Overview: hypoplastic, elevated, rotated vermis with cystic dilation of the 4th ventricle
Vermis: hypoplastic and rotated
4th Ventricle: markedly dilated
Cerebellar Hemispheres: normal in size but diplaced anteriolaterally
Posterior Fossa: expanded
Torcula: high insertion
Hydrocephalus: 90% of cases
Trivia: Diagnosis on antenatal ultrasound must be done after 18 weeks (prior to 18 weeks the vermis hasnt finished forming).
Failure to Cleave - Holoprosencephaly ( HPE)
This entity also occurs along a spectrum with the common theme being some element of abnormal
central fusion. Although, it isn’t actually a fusion problem. Instead, it is a failure to perform the
normal midline cleaving. In the normal embryology, the fancy latin word ‘“P-lon ” starts out like a
peanut butter sandwich, then mom cuts the bread into two perfect halves (separate lateral
hemispheres). The sandwich cutting (cleavage) always occurs back to front (opposite of the
formation of the corpus callosum), so in milder forms the posterior cortex is normal and the anterior
cortex is fused.
Holoprosencephaly
least to most severe
lobar
seim-lobar
alobar
lobar holoprosencephaly
Overview: Focal areas of incomplete fusion anteriorly (usually the fomix)
Ventricles: Variable mild fusion of the frontal horns of the lateral ventricles.
Thalamus: normal
Absent structures: septum pellucidum, corpus callosum (partial vs normal)
Horrible things: …..
Outcome: survive into adulthood
semi-lobar holoprosencephaly
Overview: The back is cleaved (not the front), >50% fusion of the frontal lobes.
Ventricles: the body of the lateral ventricles are 1 chamber. occipital and temporal horns are partially developed.
Thalamus: fused (partial or complete)
Absent structures: Septum Pellucidum, Corpus Callosum (partial), Anterior Interhemispheric Fissure, Anterior Falx Cerebri
Horrible things: cleft lip/palate, borat brother bilo (hes the retard)
Outcome: surbibe into adulhood but terrible at jeopardy.
alobar holoprosencephaly
Overview: Zero midline cleavage. Cerebral hemispheres are fused and there is a single midline ventricle
Ventricles: Single Ventricle (distinct lateral and third ventricles are absent)
Thalamus: Fused
Absent structures: Septum Pellucidum, Corpus Callosum, Interhemispheric Fissure, Falx Cerebri
Horrible things: Cyclops Monster Face (one eye, one nose hole, etc)
Outcome: Mercifully Bad (stillborn / dead < 1 year)
Face predicts Brain, BUT Brain doesn’t predict Face Possible BUZZWORDS for HPE spectrum.
Monster Cyclops Eyes
Cleft lips / Palates
Pyriform Aperture Stenosis (from nasal process overgrowth)
Solitary Median Maxillary Incisor (MEGA-Incisor)
Arhinencephaly
“Minor” HPE expression.
Midlinc olfactory bulbs / tracts are absent.
“Can’t Smell” - is the clinical buzzword.
Could be tested as Kallmann Syndrome
(which also has hypogonadism, & mental
retardation).
Meckel-Gruber Syndrome
Classic triad:
- Occipital Encephalocoele
- Multiple Renal Cysts
- Polydactyly
Also strongly associated with
Holoprosencephaly
Septo Optic Dysplasia
overview
This “Minor” HPE expression could be referred to by its French sounding name, for the sole purpose of fucking with you — ”de Morsier Syndrome ”
The classic findings are inferred by the name.
Absent Septum Pellucidum “Septo ” and
Hypoplastic “Optic ” structures such as the Optic Chiasma (circle) and Optic Nerves
Septo Optic Dysplasia
trivia
Associated with Schizenccphaly
Septo Optic Dysplasia
gamesmanship
The other thing they can show is
an azygos anterior cerebral artery - which is basically
a common trunk of the AC As. This is rare , but
associated with SOD and lobar HPE.
Cortical Formation
prologue
The brain is said to form “inside-out, ” as neurons that will eventually make up the cortex are originally birthed from a thick slurry surrounding the fetal ventricles. Sleep inducing texts will
refer to this as the “proliferative neuroepithelium.” I prefer the term “Lazarus Pit,” or just the “Pit.”
It is from this Periventricular Pit, where cells will make “the climb” to the cortex.
Cortical Formation
Act 1 - Proliferation
Before making “the climb” to the cortex the neuronal-glial stem cells are
bom into (and molded by) the darkness of the periventricular Lazarus Pit. It is there that they learn
the truth about despair, first by dividing into additional stem cells in a symmetric fashion (1 stem cell
splits into 2 stem cells). Later this process will change to asymmetric proliferation (1 stem cell splits
into 1 stem cell and 1 differentiated cell - glial cell or neuron). This process continues for several
cycles until the stem cells receive the signal to undergo apoptosis - they expect one o f us in the wreckage brother.
The number of neurons in the cortex is determined by the frequency and
number of symmetric / asymmetric divisions by these stem cells.
Disturbance in this process will therefore result in either too many, too
few, or improperly differentiated neurons.
Cortical Formation
Act 2 - Migration (RISE)
From the periventricular proliferative pit of despair, cells will make the
climb. As they climb to freedom, they are guided by structural cells, chemical signals, and the chant
“Deshi, Deshi, Basara, Basara.” They make the climb in 6 waves, with the first generation forming
the “pre-plate” and the second generation forming the more permanent “cortical plate.”
In other words, the younger cells always moving past the older ones
becoming more superficial in their final position, (hence the idea -
“inside out” or “outside last”). Disturbance in this mechanism
(guidance, timing of detachment e tc…) will result in undermigration,
over-migration, or ectopic neurons.
Cortical Formation
Act 3 - Organization
At this point you may think the cells have given
everything to the cortex, and they don’t owe them anymore. But, they haven’t
given everything… not yet. There is still the process of cortical folding
(gyrification).
The process actually occurs simultaneously with and depends heavily on the first two steps. The
differential speed of cortex expansion (relative to the deeper white matter) is probably the key
mechanism for brain folding. For this expansion to occur properly there needs to be the right
number of cells (act 1) migrated in the right order (act 2). There is the additional mechanism of
continued differentiation into structural cell types which organize into horizontal / vertical columns
creating an underlying cytoarchitecture need for structure and function. Disturbance in these
mechanisms will result in an absence of or excessive number of folds.
Failure to Proliferate: Hemimegalencephaly
Rare, but unique (Aunt Minnie), malformation characterized by enlargement (from hamartomatous
overgrowth) of all or part/s of one cerebral hemisphere. The presumed cause is a failure in the
nonnal neuronal differentiation in the involved hemisphere - resulting in an “abnormal mixture of
normal tissues” - which defines a hamartoma. This process is often mixed with other errors in
migration resulting in associated polymicrogyria, pachygyria, and heterotopia.
Hemimegalencephaly
big side with big ventricle = hemimegalencephaly
hamartomatous overgrowth of all or part of a cerebral hemisphere, seocndary to differentiation/migration failure.
Rasmussen’s Encephalitis
small side with big ventricle = atrophy
the shrunken half is atrophic resultingin ex acuo dilation ofthe ventricle
zebra viral (or maybe autoimmune disease that annihilates half the brain
just like an old grandpa brain (only thing is this is just half the braina nd the kid is usually less than 10)
Dyke-Davidoff-Masson (Cerebral Hemi-Atrophy):
This is another zebra that can look a lot like Rasmussen encephalitis - but also has weird unilateral skull thickening and expanded sinuses. The superior sagittal sinus and fissure are moved across the midline. It is supposedly caused by an in utcro or childhood stroke (supposedly).
Since literally anything is fair game on this exam. I’m including it for completeness (it’s probably low yield).
Lissencephaly
“Classic” Type 1
Smooth Surface Thick Cortex Colpocephaly Figure 8 Shape Undermigration Failure to migrate both in amount an in order - with a reverse outside-in pattern. Large numbers of neurons do not even reaching the cortical plate, depositing diffusely between the ventricular and pial surfaces. The distribution is fucked with 4 thick layers formed instead of 6
As a result of this disorganized / inadequate migration the process of cortical folding does not take place. Smooth Surface, Thick Cortex Colpocephaly is Common. “Figure 8” shaped brain on axial -due to shallow, vertical Sylvan fissures Autosomal Inheritance (M=F) Associated with CMV (maybe)
Double Cortex
Band Heterotopia
Undermigration Considered the mildest form of Classic Lissencephaly Disorganized migration results in a second layer of cortical neurons deep to the more superficial cortex. This creates the classic “double cortex” appearance.
Associated with seizure disorders. Gyral pattern is normal (or mildly simplified). Subcortical band of heterotopic gray matter X-Linked Inheritance (F>M)
Lissencephaly “cobblestone” Type 2
Overmigration Instead of failing to migrate an adequate number of neurons to the cortical surface (as is the case in the classic type of lissencephaly), this pathology is the result o f an over migration. This over migration results in an additional layer o f cortex composed on gray matter nodules. These nodules come in a variety o f shapes and sizes (unilateral, bilateral, small, large, symmetric or asymmetric). Most commonly It is commonly located adjacent to the Sylvian fissures
Cobblestoned Cortex (variable in size / location) Associated with congenital muscular dystrophy, and retinal detachment - "muscle- eye-brain disease
Periventricular nodular heterotopia
Failed Migration Neurons in the periventricular (subependymal) region were too lazy to migrate to the cortex. The result is nodular grey matter deposition along the ventricle borders. Most common location for grey matter heterotopia. Associated with seizure disorders.
THIS VS THAT:
heterotopia vs supendymal tubers of TS
THIS VS THAT: Heterotopias follow grey matter on all sequences and NOT enhance. Subependymal tubers o f TS are usually brighter on T2 relative to grey matter and may also be calcified.
Failure to Organize: Polymicrogyria “PIKIG”
I’ve heard people blame this on TORCH infections, toxic exposure, chromosomal issues, God’s wrath
for “stuff the Democrats do.” There are likely many causes. I wouldn’t expect someone to ask for
“the cause,” other than perhaps the broad category of failed organization.
Having said that. I’ve read some PhD papers saying that layer 5
gets obliterated (by infection, toxins, wrath, etc..) after
completion of normal migration. With layer 5 gone the other
more superficial layers overfold and fuse resulting in an excessive
number of small folds - the hallmark finding.
Failure to Organize: Polymicrogyria “PIKIG”
classic look
Fine undulating / bumpy cortex.
This anomaly come in a variety of shapes and sizes
(unilateral, bilateral, small, large, symmetric or asymmetric).
Most common location is adjacent to the Sylvian fissure Fine Undulations / Bumps
bilaterally.
Failure to Organize: Polymicrogyria “PIKIG”
trivia
Zika Virus is the most common cause of PMG in Brazil and South America
Failure to Organize: Schizencephaly— “Split Brain”
Just like polymicrogyria there are likely many causes and I wouldn’t expect someone to ask for “the
cause,” other than perhaps the broad category of failed organization.
Having said that, one popular theory is the idea of a vascular insult. What is this vascular insult ?
Well, you could say it’s the cortex’s reckoning (it damages the radial glial fibers). These radial glial
fibers are in charge (or at least they “feel in charge”) of the ropes used by neurons to “make the
climb.” Although, I’ve head it’s best to make the climb as the child did - without the rope. I mention
this because about 30% of patient’s with schizencephaly also have non-CNS vascular stigmata
(example = gastroschisis - which supposedly occurs from a vascular insult to the abdominal wall).
Failure to Organize: Schizencephaly— “Split Brain”
classic look
Schizencephaly literally means “split brain” with the defining feature being a cleft
(lined with grey matter) connecting the CSF spaces with the ventricular system. How wide this cleft is
depends on the flavor; Closed Lip (20%) or (2) Open Lip (80%), although in both cases the cleft
should span the full thickness of the involved hemisphere. The clefts can be unilateral or bilateral.
Failure to Organize: Schizencephaly— “Split Brain”
closed lip
Closed Lip (20%) - Less Common, Less Seve
i In this fonn, the “Lip” will
;appear closed without a
I CSF filled cleft. To make
! the call you want to look
I for is the grey matter
i running across the normally
j uniform corona radiata.
j Sometimes you can see a “nipple” o f grey mater
j pouching at the ependymal (ventricular) surface
Failure to Organize: Schizencephaly— “Split Brain”
open lip
Open Lip (80 %) - More Common, More Severe This one is more obvious. To make the call you want to see a CSF-filled cleft (lined with grey matter) extending from the ventricle to the pial surface. IThe gray matter lining is often weird looking j(kinda nodular like a heterotopia).
Failure to Organize: Schizencephaly— “Split Brain”
associations
Absent Septum Pellucidum (70%), Focally Thinned Corpus Callosum,
Optic Nerve Hypoplasia (30%), Epilepsy (demonic possession)
Porencephalic Cyst
Least Severe
brain cleft/hole from a prior ischmic event resulting in ecneaphalomalacia.
cyst/cleft can communcate with the subarachnoid space (external) micmiching an open lip schizencephaly or communicated only with the ventricular system (internal)
Hydranencephaly
bilateral ICA occlusion causes massive destruction of both cerebral hemispheres. only the cerebellum, midbrain, andthe falx (usually) remain
hepres is the most classic, but in utero infection with toxo or CMV are also described causes
Developmental Failure Mimics— Hydranencephaly and the Porencephalic Cyst
These can be thought of along a
spectrum of severity
These things may look like a severe developmental anomaly but the underlying mechanism is different. They are “acquired.” Classically by a vascular insult - but really from anything that can cause encephalomalacia (focal necrosis of both the gray matter and white matter with eventual cystic degeneration). This would include a trauma after birth (this doesn’t have to happen in utero). Understanding that the brain develops normally first - then gets crushed, helps to remember the key findings. In particular, the absence of a gray matter lining along the defect. It’s almost like someone took an icecream scoop to the brain. In the case of Porenchephaly, they just took one scoop. In the case of Hydranencephaly, the glutinous pig took pretty much the entire brain - leaving only the cerebellum, midbrain, and the falx.
THIS v s THAT
open lip schizencephaly
Brain cleft / hole from a prior event (maybe ischemic) resulting in damage to the structural cells needed to properly organize the cortex. Not Normally Formed
CSF-filled cleft extending from the ventricle to the pial surface.
Cleft is
Lined with
Gray
Matter
THIS v s THAT
porencephalic cyst
Brain cleft / hole from a prior ischemic / traumatic event resulting in encephalomalacia. Normally formed - but massive insult make it look developmental.
CSF-filled cleft extending from the ventricle and/or the pial surface.
Cleft is
NOT Lined
with Gray
Matter
The brain appears screwed with corticle mantle
falx present - sever hydrocephalus
falx gone - Holoprosencephaly - Alobar
—Anterior falx usually missing in the semi-lobar form
—lobar (mild 1 subtype should still have the nax
the brain appears to be screwed without cortical mantle
hydranencephaly
“Cephalocele”
is an umbrella term for a herniation of the cranial contents through a defect in the
skull. While retaining the suffix “cele” they are then sub-classified based on (1) location, and (2)
what is in the herniation sac
cephalocele locations
nasal frontoethmoid transsphenoid parietal occipital
HERNIATION SAC CONTENTS
Meningocele
-CSF &
Meninges
-NO BRAIN
HERNIATION SAC CONTENTS
Meningo-
Encephalocele
Meningo-
Encephalocele
-CSF, Meninges,
and BRAIN
*For the purpose of fucking with you,
Meningoencephaloceles are sometimes
called Encephaloceles
Cystocele
CSF, Meninges,
Brain, and Ventricle
Myelocele
Spinal Cord
Chiari Malformations quick
type 1
Herniation of cerebellar
tonsils (more than 5
mm)
Classic Association
(not always present):
• Syrinx (cervical cord)
Chiari Malformations quick
type 2
Relatively less tonsillar herniation. Relatively more cerebellar vermian displacement
Classic Features
- Low lying torcula
- Tectal beaking
- Hydrocephalus
- Clival hypoplasia
Chiari Malformations quick
type 3
Features o f Chiari 2
AND
Occipital Encephalocele
Chiari Malformations quick
type 4
Historically used to describe severe cerebellar hypoplasia without herniation. The term has fallen out of favor with the powerful men and women who control the Chiari nomenclature. We shall not speak of it again
Chiari Malformations quick
type 1.5
Hybrid term used to describe conditions that have features of
both type 1 and type 2.
Not associated with neural tube defects, despite the significant
downward movement of the tonsils and brain stem.
Chiari Type I classicly
Classically defined as i or
both tonsils > 5mm below
the level of the
Basion Opisthion.
Chiari Type I classic mechanism
Congenital underdevelopment
of the posterior fossa, leading
to overcrowding, and
downward displacement.
Chiari Type I non-classic mechanism
Post traumatic
defonnity - acquired later in
life.
Chiari Type I clinical symptoms
1) Occipital headache from pressure of the cerebellar tonsils - worse with sneezing (2) Weakness, spasticity, and loss of proprioception from pressure on the cord
Chiari Type I classic association
(not always present):
• Syrinx o f the cervical cord
Chiari Type I less-classic association
(but still highly testable) association: -Klippel-Feil Syndrome (congenital C-spine fusion). NOT associated with a neural tube defect
Chiari Type II
findings
Thinned Corpus Callosum Tectal Beak
clival hypoplasia
*Also note (^3 the long skinny 4th ventricle, and the “towering cerebellum.”
Interdigitated Cerebral Gvri (most classically demonstrated on axial CT)
Low Lying
Torcula
Opposite o f
Dandy Walker
Chiari Type II
classic mechanism
Neural Tube Defect
“sucks” the cerebellum downward prior to full
development o f the cerebellar tonsils.
Chiari Type II
classic assocation
-Lumbar myelomeningocele / Spina Bifida
only seen in pts with neural tube defect
Chiari Type III
Occipital Encephalocele, (meningoencephalocele) containing cerebellum and/ or the brainstem, occipital lobe, and sometimes even the fourth ventricle. PLUS features of o f Chiari 2
Chiari Type III
Classic Associations
• Syrinx (cervical) • Tethered cord • Hydrocephalus • Agenesis of the corpus callosum Only seen in patients with a neural tube defect (NTD). Encephalocele = NTD
Special Topic - Mesial Temporal Sclerosis
This is a pattern of findings (hippocampal volume loss + gliosis / scar), which classically result in
intractable seizures. The etiology is not certain, but it is most likely developmental (hence the
inclusion in this section).
Special Topic - Mesial Temporal Sclerosis
clinical trivia
This is the most common cause of partial complex epilepsy.
Special Topic - Mesial Temporal Sclerosis
clinical trivia 2
Surgical removal can “cure” the seizures / demon. Alternatively, perfect
W / i intracranial positioning of a tooth (from a red haired woman) has been described as
therapeutic in the Kazakhstani literature.
Special Topic - Mesial Temporal Sclerosis
imaging findings
• Reduced Hippocampal Volume (best seen when compared to the opposite site).
*10% o f the time volume loss is bilateral - other findings are necessary to exclude fuckerv
• Increased T2 Signal (from gliosis / scar)
• Loss of Normal Morphology (loss of normal interdigitations)
• Atrophy of the ipsilateral fornix and maxillary body
• Contralateral amygdala enlargement
Special Topic - Mesial Temporal Sclerosis
mri epilepsy protocol trivia
• T1 - Superior for Cortical Thickness, Eval of Grey / White
• FLAIR - Superior for Cortical / Subcortical Hight Signal (Gliosis)
• T2* / SWI - Superior for Blood Breakdown Products (for other things that can cause seizures;
calcifications of tuberous sclerosis, Sturge-Weber, Cavemomas, Gangliogliomas etc..)
Monro-Kellie Hypothesis
The Monro-Kellie Hypothesis is the idea that the head is a closed shell, and that the three
major components: (1) brain, (2) blood - both arterial and venous, and (3) CSF, are in a state
o f dynamic equilibrium. As the volume o f one goes up, the volume o f another must go
down
Intracranial Hypotension
if you are leaking CSF, this will decrease the overall fixed volume,
and the volume o f venous blood will increase to maintain the equilibrium. The result is
meningeal engorgement (enhancement), distention o f the dural venous sinuses, prominence
o f the intracranial vessels, and engorgement o f the pituitary (“pituitary pseudo-mass”). The
development o f subdural hematoma and hygromas is also a classic look (again, compensating
for lost volume).
Idiopathic Intracranial Hypertension (Pseudotumor Cerebril
Classic scenario o f a fat
middle-aged women with a headache. Etiology is not well understood (making too much
CSF, or not absorbing it correctly). It has a lot o f associations (hypothyroid, cushings,
vitamin A toxicity). The findings follow the equilibrium idea. With increased CSF the
ventricles become slit-like, the pituitary shrinks (partially empty sella), and the venous
sinuses appear compressed. You can also have the appearance o f vertical tortuosity o f the
optic nerves and flattening o f the posterior sclera.
Changes in intracranial pressure can create a downward displacement o f the brainstem
stretching the 6th cranial nerve - it is said that 1/3 o f patients with pseudotumor cerebri have
sixth nerve paresis as their only neurologic deficit
Hydrocephalus
communicating
-All Ventricles are Big (25% o f the time the fourth ventricle is normal) -Level o f obstruction between basal cisterns and arachnoid granulations - CSF can exit all the ventricles
Hydrocephalus
communicating true obstruction
Blood, Pus, and Cancer - Anything that
plugs up the villi - the three most common
causes being SAH, Meningitis (TB or
Bacterial), and Carcinomatous Meningitis.
Hydrocephalus
communicating without obstruction
Brain Atrophy (ex-vacuo)
Normal Pressure Hydrocephalus
-see discussion below
Choroid Plexus Papilloma
- Tumor that secretes CSF.
- Discussed more later in the chapter
Hydrocephalus
non-communicating
-Upstream Ventricles are Big -Level o f Obstruction is within the ventricle System - CSF can NOT exit all the ventricles
Hydrocephalus
non-communicating
level of obstruction
Foramen of Monro = • Colloid Cyst Aqueduct = ’ • Aqueduct Stenosis • Tectal Glioma 4th Ventricle = • Posterior Fossa Tumor • Cerebellar Edema / Bleed
Hydrocephalus
non-communicating
level of obstruction
Foramen of Monro = • Colloid Cyst Aqueduct = ’ • Aqueduct Stenosis • Tectal Glioma 4th Ventricle = • Posterior Fossa Tumor • Cerebellar Edema / Bleed
Normal Pressure Hydrocephalus
it s not well
understood - and idiopathic. The step 1 trivia is “wet,
wackv. and wobbly” - describing the clinical triad of
urinary incontinence, confusion, and ataxia. The key
points clinically are the patient is elderly (60s), and
the ataxia comes First and is most pronounced.
Normal Pressure Hydrocephalus
buzz phrase
The buzz-phrase is “ventricular size out of proportion
to atrophy.” The frontal and temporal horns of the
lateral ventricles are the most affected. “Upward
bowing of the corpus callosum” is another catch
phrase. On MR1 you may see transependyma 1 flow
and/or a flow void in the aqueduct and 3rd ventricle.
This is treated with surgical shunting
Syndrome of Hydrocephalus in the Young and Middle-aged Adult (SHYMA
Similar to NPH but in a
middle aged population - and more headaches less peeing of the pants (HA+Wacky+Wobbly).
Communicating Hydrocephalus + Middle Aged + Headache = SHYMA.
Communicating Hydrocephalus +
Elderly + Ataxia -
NPH
Congenital Hydrocephalus
There are several causes of hydrocephalus that can be present at birth or be related to fetal
development. These conditions are typically diagnosed prior to birth via routine ultrasound
Congenital Hydrocephalus
big 4
The big 4 are: (1) Aqueductal stenosis, (2) Neural tube defect - usually Chiari II, (3) Arachnoid cysts,
and (4) Dandy-Walker.
Aqueductal Stenosis
This is the most common cause of congenital obstructive hydrocephalus. Classically from a web or
diaphragm at the aqueduct (hence the name). Because of the location you get a “non-communicating”
pattern with a dilation of the lateral ventricles and 3rd ventricle with a normal sized 4th ventricle. You
can have a big noggin (macrocephaly) with thinning of the cortical mantle.
Aqueductal Stenosis
treatment
Treatment is going to be either shunting or
poking a hole in the 3rd ventricle (third ventriculostomy).
Aqueductal Stenosis
clinical trivia
Question header may describe “sunset eyes” or an upward gaze paralysis
Aqueductal Stenosis
clinical trivia 2
A male with “flexed thumbs ” should make you think about the x-linked variant.
(Bickers Adams Edwards syndrome).
Arachnoid Cysts
As the name implies, these are cysts located in the subarachnoid
space. They are CSF density, without any solid components, or
abnormal restricted diffusion. You wouldn’t even notice them
expect that they can exert mass effect on the adjacent brain, or in
the context of this discussion block a CSF pathway (obstructive
type).
Normal CSf shunt
The most basic shunt consists of a proximal tube (usually placed in
the frontal horn of the lateral ventricle just anterior to the foramen of Monro), a
valve to control flow, and a distal tip (usually dumped in the peritoneum, but
can be placed in the pleural space or right atrium).
Shunt Evaluation Options
Your first line options for shunt evaluation are going to be (a) non-con CT or
(b) rapid single shot T2 sequence - mainly looking at catheter position and ventricle size. *May need to
verify shunt settings with a plain film post magnet. If the ventricles are big (shunt is not working) you
might follow that up with a radiograph series (neck, chest, abd) to make sure the catheter is intact.
Ultrasound or CT can be used to inspect the distal tip for a fluid collection. Alternatively (if you are a
weirdo) you can inject < 0.4ml pertechnetate into the shunt reservoir and take images to look for leakage
or blockage (remember to not aspirate when you inject).
CSF Shunt Malfunction
undershunting
Proximal obstruction:
- Proximal > Distal
- Most common cause = ingrowth of choroid piexus and particulate debris / blood products
- Can also be from catheter migration
Distal Obstruction:
-Pseudocyst (loculated flu id along the distal tip)
-Catheter migration
(more common in children)
CSF Shunt Malfunction
overshunting
-“Slit Like Ventricles” - can be meaningless or
suggest too much shunting.
- The big fear is that not enough CSF will cause subdural hygroma or hematoma formation via Monroe Kelly mechanics (less CSF - more
blood).
CSF Shunt Malfunction
infection
-Usually within 6 months of placement
-Blood cultures are usually negative (fluid from
the shunt should be cultured instead).
-Mild enhancement after catheter placement can
be normal - be on guard for fuckery.
-The best sign is debris within the ventricles,
ideally shown with DWI - this is the weapon of
choice for diagnosis of ventriculitis.
-Late stigmata may include ventricular
loculations - which can cause restricted flow /
obstruction and in some case isolate or “trap” the
4th ventricle — as shown in diagrams.
CSF Shunt Malfunction
hydrothorax
Either deliberately or via migration the catheter can end up in the pleural space. A little
bit of pleural fluid doesn’t mean shit. But, if the volume gets large enough and the
patient becomes symptomatic - then revision might be needed.
CSF Shunt Malfunction
ascites
Usually the ascites from a VP shunt isn’t symptomatic, although there are reports of inguinal hernias and hydroceles forming secondary to the increased abdominal pressure.
Cytotoxic Edema
This type o f edema can be thought about as intracellular swelling secondary to
malfunction o f the Na/K pump. It tends to favor the gray matter, and looks like loss of the
gray-white differentiation. This is classically seen with stroke (or trauma), and is why
EARLY signs o f stroke involve loss o f the GM-WM interface.
Vasogenic Edema
This type o f edema is extracellular, secondary to disruption o f the blood-brain
barrier. It looks like edema tracking through the white matter (which is less tightly
packed than the gray matter). This is classically seen with tumor and infection. You can
also see this type o f edema as a LATE stage o f cerebral ischemia. A response to steroids is
characteristic o f vasogenic edema.
Cytotoxic Edema
quick
Failed Na/K Pump (BBB intact)
Classic = Ischemia (EARLY)
White Matter + Gray Matter - “blurring
Vasogenic Edema
quick
Increased Capillary Permeability (BBB NOT intact) Classic = Tumor, Infection, Ischemia (LATE) White Matter (Spares Gray Matter
Subfalcine (Cingulate) Herniation
This is just a fancy way of saying midline shift (deviation of
ipsilateral ventricle and bowing of the falx). The trivia to know is that the ACA may be compressed,
and can result in infarct.
Descending Transtentorial (Uncal) Herniation
The uncus and hippocampus herniate through the
tentorial incisura. Effacement of the ipsilateral suprasellar cistern occurs first.
Descending Transtentorial (Uncal) Herniation
Things to know
• Perforating basilar artery branches get compressed resulting in “Duret Hemorrhages
classically located in the midline at the pontomesencephalic junction (in reality they can also
affect cerebellar peduncles).
CN 3 gets compressed between the PCA and Superior Cerebellar Artery causing ipsilateral
pupil dilation and ptosis
• “Kemohan’s Notch / Phenomenon” - The midbrain on the tentorium forming an indentation
(notch) and the physical exam finding of ipsilateral hemiparesis - which Neurologists call a
“fa ls e localizing sign. “ Of course, localization on physical exam is stupid in the age of MRI,
but it gives Neurologists a reason to carry a reflex hammer and how can one fault them for
that.
Ascending Transtentorial Herniation
Think about this in the setting of a posterior fossa mass. The
vermis will herniate upward through the tentorial incisura, often resulting in severe obstructive hydrocephalus.
Ascending Transtentorial Herniation
Things to know
The “Smile” of the
quadrigeminal cistern will
be flattened or reversed
“Spinning Top ” is a buzzword, for the appearance of the midbrain from bilateral compression along its posterior aspect
Severe hydrocephalus (at the level of the aqueduct).
Cerebellar Tonsil Herniation
Can be from severe herniation after downward transtentorial herniation. Alternatively, if in isolation you arc thinking more along the lines of Chiari (Chiari I = 1 tonsil - 5 mm).
Osmotic Demyelination or
Central Pontine Myelinolysis
most classic scenario
Asshole drunk Hobo shows
up to the ER with a low Na. Like most asshole
drunks in the ER, he starts out demanding a
cheeseburger and a Sprite (not a fucking Sierra
Mist!), then threatens to leave against medical advice.
.. .after finishing the burger.
Family Medicine Resident begs him to stay
(a decision he will soon regret). The Resident
eventually tires of his bullshit and decides to correct
his hyponatremia as rapidly as possible - with the
goal of expediting discharge.
2 days later the guy is still in house, acting like a
massive prick - acutely encephalopathic with spastic
quadriparesis.
Neurology gets consulted and writes “pseudobulbar
palsy” in the chart. Family Medicine Resident
doesn’t know what the fuck that means, but is humble
enough to ask. A below average 2nd year medical
student explains to him that it is slurred speech,
sensitive gag reflex, and being an even bigger cry
baby than normal- “labile emotional response”.
Coma, the above MRI, death, then a lawsuit follow
(in that order).
Osmotic Demyelination or
Central Pontine Myelinolysis
MRI
T2 bright in the central pons (spares periphery)
Earliest change: restricted diffusion in lower pons
Osmotic Demyelination or
Central Pontine Myelinolysis
trivia
Osmotic Demyelination or
Central Pontine Myelinolysis
Wernicke Encephalopathy
classic scenario
Very friendly Hobo - known
for singing songs from the 70s (mostly Supertramp’s
goodbye stranger) - starts acting squirrelly. “His
tempo seems o ff’ - notes the feminine male nurse.
An above average medical student suggests he is
exhibiting the clinical triad o f ( 1) acute confusion.
(2) ataxia, and (3) ophthalmoplegia, but is dismissed
by the Medicine intern who talks non-stop about
going into Cardiology (“Cards” - he calls it).
Only moments later the same Intern will suggest to
his Attending the same triad of findings before
stating “my medical student” seems disinterested and
may benefit from more call.
Still desperate to honor the clerkship, the student
suggests thiamine (vitamin B it deficiency as the
etiology, and says the symptoms could progress to
chronic memory loss and confabulation (Korsakoff
psychosis) or even death.
The cycle repeats - additional call is assigned, and a
formal letter of reprimand is issued to the student.
Wernicke Encephalopathy
imaging findings
• T2/FLAIR bright classically seen in medial/dorsal
thalamus (around the 3rd ventricle), periaqueductal
gray, mamillary bodies, and the tectal plate.
• Enhancement is classic in the mamillary bodies
Wernicke Encephalopathy
treatment
thiamine replacement
Marchiafava-Bignami
most classic scenario
• Swelling / T2 bright signal at the corpus callosum
(represents an acute demyelination)
• Order is progressive - typically beginning in the
body, then genu, and lastly splenium
• “Sandwich sign” on sagittal imaging - describes
the pattern of preference for central fibers with
relative sparing of the dorsal and ventrals fibers
• Chronic Phase: Thinned corpus callosum + cystic
cavities favoring in the genu and splenium
Marchiafava-Bignami
imaging
• Swelling / T2 bright signal at the corpus callosum
(represents an acute demyelination)
• Order is progressive - typically beginning in the
body, then genu, and lastly splenium
• “Sandwich sign” on sagittal imaging - describes
the pattern of preference for central fibers with
relative sparing of the dorsal and ventrals fibers
• Chronic Phase: Thinned corpus callosum + cystic
cavities favoring in the genu and splenium
Direct Alcoholic Injury:
Most Common / Classic Finding(s):
Brain Atrophy. Particularly the cerebellum
and especially the cerebellar vermis
Copper & Manganese Deposition
Tl Bright Basal Ganglia
-Non-Specific and related To Liver Disease.
-Can be seen without hepatic encephalopathy
-Also seen in TPN, Wilson’s Disease,
-Also seen in Non-Ketotic Hyperglycemia (HNK) in
which it’s often unilateral
Methanol Toxicity:
“Drinking Windshield Wiper Fluid” as an idiotic attempt to get drunk. Can also be seen from consuming “poorly adulterer moonshine” - or “West Virginia Budweiser.” Classic Findings: Optic nerve atrophy, hemorrhagic putaminal and subcortical white matter necrosis
H IS VS THAT: Carbon Monoxide vs Methanol
Carbon
Monoxide:
CT Hypodensity / T2 Bright: Globus Pallidus
(carbon monoxide causes “globus ” warming
Methanol
T2 Bright: Putaminal - which may be
hemorrhagic, and thus CT Hypcrdense.
PRES (Posterior Reversible Encephalopathy Syndrome]:
classic features
• Asymmetric cortical and subcortical white matter edema (usually in parietal and occipital regions *but doesn’t have to be - superior frontal sulcus is
also common).
• Does NOT restrict on diffusion (helps tell you it’s not a stroke).
PRES (Posterior Reversible Encephalopathy Syndrome]:
classic historr
Acute Hypertension or Chemotherapy
PRES (Posterior Reversible Encephalopathy Syndrome]:
etiology
Poorly understood auto regulation fuck up.
Post Chemotherapy
two main looks
(1) PRES - As above, chemo is a classic cause. BUT! It tends to have a “non-classic” look relative
to the hypertension type. It will often spare the occipital lobes, and instead target the basal
ganglia, brainstem, and cerebellum.
(2) Leukoencephalopathy (treatment induced): The classic look would be centered in the
periventricular white matter - bilateral, symmetric, confluent, T2/FLAIR bright changes (history
is obviously key to the diagnosis).
Post Chemotherapy
It is fairly common. There are lots of named offenders. Methotrexate seems to be the one people
write the most papers about (especially in kids with ALL)
Post Chemotherapy
Other Misc trivia
Can progress to brain atrophy.
“Mineralizing Microangiopathy - the vocab word to use if there are calcifications
“Disseminated necrotizing leukoencephalopathy” - severe white matter changes, which
demonstrate ring enhancement, classically seen with leukemia patients undergoing radiation
and chemotherapy. It is bad news and can be fatal (it believes in nothing Lebowski).
Post Radiation
The quick and dirty version is that after radiation therapy to the brain you can see T2 bright areas
and atrophy corresponding to the radiation portal. You can also sec hemosiderin deposition and
mineralizing microangiopathy (calcifications involving the basal ganglia and subcortical white
matter). There is a latent period, so imaging findings don’t typically show up for about two months
post therapy. Now… if you want to get crazy, you can discuss changes at different time periods.
Post Radiation
Acute
(Days-Weeks):
Too rare to give a fuck about (at least for the test)
Post Radiation
Early Delayed
(1-6 months):
The classic look is similar to chcmo - high T2/FLA1R
signal in the periventricular white matter.
This is reversible
change (usually).
Post Radiation
Late Delayed
(6 months):
Described as a “mosaic” pattern with high WM signal
changes again favoring the deep white matter. Can
appear “mass-like” and expansile.
Classically sparing of the U-Fibcrs & Corpus Callosum.
Progressive… but
reversible (mostly)
Post Radiation
Long Term
Sequela
Radiation-Induced Vasculopathy
Strokes and Moya-Moya type of look
Post Radiation
Long Term
Sequela
Mineralizing Microangiopathy
1 mentioned this on the previous page. This is a
delayed finding — like two years following treatment. Think calcifications (basal
ganglia and subcortical white matter) - hence the term “mineralizing.”
Post Radiation
Long Term
Sequela
Radiation-Induced Vascular Malformations
The most classic types are capillary
telangiectasias / cavernous malformations. The most classic scenario is a kid
getting whole brain radiation for ALL. Remember the key finding is blooming on
GRE/SWI sequences.
Post Radiation
Long Term
Sequela
Radiation-induced Brain Cancer
- XRT is the “most important risk factor” for primary CNS neoplasm.
- Most common type is a meningiomas (70%) - usually seen ~ 15 years post XRT
- More aggressive types Gliomas, Sarcomas, etc, have a shorter window < 10 years
Chasing the Dragon” - Heroin Inhalational leukoencephalopathy
Most toxic lcukoencephalopathies (either from chemotherapy, immunosuppressives, antibiotics,
or the aristocratic art of paint thinner huffing) all create a similar non-specific pattern of widespread
high T2/FLAIR signal in the supra and infratentorial white matter. The “Chasing the Dragon”
pattern is also not specific - but it does have a catchy name, so people love collecting cases of it to
show in conference (“catchy name” = high yield for boards).
The most classic look (diagrams are FLAIR sequences):
Chasing the Dragon” - Heroin Inhalational leukoencephalopathy
imaging
Symmetric “Butterfly” in the Centrum Semiovale
High Signal in the Posterior Limb of the Internal Capsule
High Signal in the Deep Cerebellar White Matter
Sparing of the dentate nucleus (arrows)
Multiple Sclerosis
overview
Size can be helpful. A single
lesion > 15 mm in size suggests the underlying etiology is not
vascular.
Certain locations will also make you think “not
vascular.” When you think “not vascular
pattern” you should think dcmyelinating.
When you think dcmyelinating you should think
MS first (it’s by far the most common).
Multiple Sclerosis
vascular
Size can be helpful. A single
lesion > 15 mm in size suggests the underlying etiology is not
vascular.
Certain locations will also make you think “not
vascular.” When you think “not vascular
pattern” you should think dcmyelinating.
When you think dcmyelinating you should think
MS first (it’s by far the most common).
Multiple Sclerosis
mcdonalds criteria
- Usually targets women 20-40 (in children there is no gender difference).
- There are multiple sub-types with the relapsing-remitting form being the most common (85%).
- Clinical history o f “separated by time and space ” is critical.
Multiple Sclerosis
epidemiologial trivia
- Usually targets women 20-40 (in children there is no gender difference).
- There are multiple sub-types with the relapsing-remitting form being the most common (85%).
- Clinical history o f “separated by time and space ” is critical.
MS
Vascular vs perivascular pattern
Vascular Pattern Perivascular Pattern (MS Corpus Callosum RARE COMMON Juxtacortical RARE COMMON Infratentorial RARE COMMON Basal Ganglai COMMON RARE
Additional MS Related Trivia
• Most Classic Finding: T2/FLA1R oval and periventricular perpendicularly oriented lesions.
• Involvement o f the calloso-septal interface is 98% specific for MS (and helps differentiate it
from vascular lesions and ADEM).
• In children the posterior fossa is more commonly involved.
• Brain atrophy is accelerated in MS.
• Solitary spinal cord involvement can occur but it is typically seen in addition to brain lesions.
• The cervical spine is the most common location in the spine (65%).
• Spinal cord lesions tend to be peripherally located.
• FLAIR is more sensitive than T2 in detection o f juxtacortical and periventricular plaques.
• T2 is more sensitive than FLAIR for detecting infratentorial lesions
• MR spectroscopy (discussed later in the chapter) will show reduced N AA peaks within the
plaques.
MS Active vs Not Active
Acute demyelinating plaques should enhance and restrict diffusion (on
multiple choice tests and occasionally in the real world).
Tumor vs MS
You can sometimes get a big MS plaque that looks like a tumor. It will ring
enhance but classically incomplete (like a horseshoe), with a leading demyelinating edge.
Tumor =
Complete Ring
Demyelination =
Incomplete Ring
Multiple Sclerosis Variants
ADEM
Acute Hemorrhagic Leukoencephalitis
Devics
Marburg Variant
ADEM
(Acute Disseminated Encephalomyelitis): Typically presents in childhood or
adolescents, after a viral illness or vaccination. Classically has multiple LARGE T2 bright
lesions, which enhance in a nodular or ring pattern (open ring). Lesions do NOT involve the
calloso-septal interface.
Acute Hemorrhagic Leukoencephalitis
(Hurst Disease): This a fulminant form o f ADEM with
massive brain swelling and death. The hemorrhagic part is only seen on autopsy (not imaging).
Devics
(neuromyelitis optica): Transverse Myelitis + Optic Neuritis.
Lesions in the Cord and the Optic Nerve
Marburg Variant:
Childhood variant that is fulminant and terrible leading to rapid death. It
usually has a febrile prodrome. “MARBURG!!! ” = DEATH
Subcortical Arteriosclerotic Encephalopathy ISAE1
Also referred to as Binswangcr Disease - for the purpose of fucking with you.
It’s best thought of as a multi-infarct dementia that ONLY involves the white matter
Subcortical Arteriosclerotic Encephalopathy ISAE1
trivia
• Strong association with Hypertension.
• It’s seen in older people - 55 and up
• If they show you a case that looks exactly
like SAE but that patient is 40 and has
migraines they are leading you to the
genetically transmitted form of this disease
called CADASIL.
• It favors the white matter of the centrum
semiovale (white matter superior to the
lateral ventricles / corpus callosum).
• Classically spares the subcortical U fibers
WTF are “U Fib e rs” ?
They are the fibers under the cortex, that look like “U”s. They come up a lot, as being spared or not spared.
CADASIL
(Cerebral Autosomal Dominant Arteriopathv with Subcortical Infarcts & Leukoencephalopathy)
Basically it is SAE in a slightly younger person (40), with migraines.
CADASIL
classic scenario
40 year old presenting with migraine headaches, strokes, then eventually
dementia. CADASIL is actually the most common hereditary stroke disorder.
CADASIL
step 1 trivia
NOTCH3 mutations on chromosome 19
CADASIL
classic imaging findings
Severe white matter disease (high T2/FLAIR signal) involving multiple
vascular territories, in the frontal and temporal lobe. The occipital lobes are often spared. Temporal
lobe involvement is classic.
Dementia Disorders
nucs
FDG PET for dementia is a worthless and expensive component o f the workup. Like most
imaging exams it is ordered with no regard to the impending collapse o f the health care
system under crippling rising costs (with inevitable progression into a Mad Max style
dystopian future or even better Mega-City 1). As such, it is standard practice in most
academic centers to obtain the study.
The idea is that “demented brain” will have less perfusion and will have less metabolism
relative to “not demented brain.” PET can assess perfusion ( 15O-H20) but typically it uses
l8FDG to assess metabolism (which is analogous to perfusion). Renal clearance o f 18FDG is
excellent, giving good target to background pictures. Resolution o f PET is superior to
SPECT.
HMPAO, and ECD (tracers that are discussed in more depth in the nukes chapter) can also be
used for dementia imaging and the patterns o f pathology are the same.
It’s important to remember that external factors can affect the results; bright lights
stimulating the occipital lobes, high glucose (>200) causes more competition for the tracer
and therefore less uptake, e tc .. .e tc … so on and so forth.
On FDG PET the motor strip is always preserved
in a
dgsenerative type o f dementia.
Alzheimer Disease
Most common cause Tauopathy, Amyloid Cascade, and Neurofibrillary Tangles are all buzzwords people use when they pretend to understand the pathophysiology.
Alzheimer Disease
Risk Factor(s):
The biggest one is Age. A more obscure one (but certainly testable) is Downs Syndrome. Downs patients nearly always get AD, and they get it earlier than normal - that extra 21st isn’t doing them any favors.
Alzheimer Disease
Most Classic Feature(s):
hippocampal atrophy (which is first and out of proportion to the rest of the brain atrophy). They could ask temporal horn atrophy > 3 mm , which is seen in more than 65% of cases.
Alzheimer Disease
FDG Pattern
Low posterior temporoparietal uptake - "headphones ” or "ear muffs. ” 11C PiB (Pittsburgh compound B) is an even better way to waste money making this diagnosis. It works as an Amyloid Binding Tracer.
Multi-infarct Dementia
2nd most common
Also called “Vascular
Dementia” - for the purpose of
fucking with you.
Multi-infarct Dementia
Risk Factor(s):
• McDonalds, Burger King, Taco Bell, Pizza Hut • Hypertension, • Smoking (tobacco), and • CADAS1L
Multi-infarct Dementia
Most Classic Feature(s):
Cortical infarcts and lacunar
infarcts are seen on MR1. Brain
atrophy (generalized) is usually
advanced for the patients age
Multi-infarct Dementia
FDG Pattern:
Multiple scattered areas of decreased activity. No specific lobar predominance. Unlike the neurodegenerative dementias - this one could knock out the motor strip (if the strokes happen to involve that region). This is different that AD and DLB.
Dementia with LewyDodies
3rd most common Alpha synuclein and synucleinopathy are buzzwords people use when they pretend to understand the pathophysiology
Dementia with LewyDodies
Clinical Scenario
There is a triad of classic features. (1) Visual hallucinations (2) Spontaneous parkinsonism, (3) Fluctuating ability to concentrate / stay alert
Clinical picture can be similar to Parkinson’s dementia - the major difference in DLB, the dementia comes before the Parkinsonism
Dementia with LewyDodies
Most Classic Feature(s):
Mild generalized atrophy without lobar predominance (unlike multi-infarct). Hippocampi will be normal in size (unlike AD)
Dementia with LewyDodies
FDG Pattern
decreased FDG uptake in the lateral occipital cortex, with sparing of the mid posterior cingulate gyrus (Cingulate Island Sign).
Picks
Also be referred to a “frontotemporal dementia ’’ - for the purpose of fucking with you.
Picks
clinical
Onset is earlier than AD (like 40s-50s). Classic presentation is described as “compulsive
or inappropriate behaviors.” In other words, acting like an asshole (fucking prostitutes, and buying
miracle weight loss potions from Dr. Oz - when you aren’t even going to the gym or trying to cat
right). Just being a real Prick.
Picks
classic features
Severe symmetric atrophy of the frontal lobes (milder volume loss in the
temporal lobes).
Picks
FDG Pattern
Low uptake in the frontal and temporal lobes.
FDG PET-Brain quick
Alzheimers
Low posterior temporoparietal cortical activity -Identical to Parkinson Dementia -Posterior Cingulate gyrus is the first area abnormal
FDG PET-Brain quick
Multi Infarct
Scattered areas o f decreased
activity
FDG PET-Brain quick
Dementia with Lewy Bodies
Low in lateral occipital cortex
Preservation o f the mid
posterior cingulate gyrus
(Cingulate Island Sign
FDG PET-Brain quick
Picks / Frontotemporal
Picks / Frontotemporal
The Defias Brotherhood of Neurodegeneration
Fahr Disease
(syndrome)
Hallervorden
Spatz
Amyotrophic
Lateral
Sclerosis
Cortico-basal
Degeneration
Huntington
Disease
Leigh
Disease
Hurler
Syndrome
MELAS
Syndrome
Parkinson
Disease
(PD)
“Parkinson- Plus” Multi- System Atrophy (MSA)
Parkinson- Plus” Progressive Supranuclear Palsy (PSP)
Wilson Disease
Fahr Disease
syndrome
Also called “Bilateral Striatopallidodentate Calcinosis", and sometimes "Primary Familial Brain Calcification ” for the sole purpose of fucking with you on the exam. Many are asymptomatic. Others go insane and start stumbling around
Fahr Disease
(syndrome)
Imaging
Extensive Calcification in the Basal Ganglia and Thaiami. *Globus is typically involved first
Hallervorden Spatz
Also called PKAN (pantothenate kinaseassociated neuropathy) for the sole purpose of fucking with you on the exam. Etiology: Iron in the Globus Pallidus T2 Dark Globus with central bright area of necrosis “Eye o f the Tiger”. No enhancement. No Restricted Diffusion.
Hallervorden Spatz
Imaging
T2: Dark Medial Basal Ganglia (Globus),
with centraI high signal dot (necrosis
Amyotrophic Lateral Sclerosis
Upper motor neuro loss in the brain and
spine. Most people die within 5 years
(unless you are really good at physics).
Amyotrophic Lateral Sclerosis
Imaging
Does NOT show gross volume loss.
T2/FLAIR tends to be Normal (rarely can
be bright in the posterior internal capsule).
Cortico-basal Degeneration
Tauopathy (whatever the F that means).
Awesome clinical manifestations like the
“Alien limb phenomenon ” -50% of cases.
Cortico-basal Degeneration
Imaging
Asymmetric frontoparietal atrophy.
Huntington Disease
One of those AD repeat sequence things. What Sequence ? 38 CAGs Mother Fuckers. Yes, I still remember that worthless factoid from Step 1. Why? It’s a curse. My mind is like a bear trap, you gotta chew your leg off to get out. So, between Step 1 & the CORE exam. I’ve got tons of worthless bullshit up there. Remember these poor guys turn into huge assholes - then start flopping around.
Huntington Disease
Imaging
Caudate Atrophy and reduced FDG uptake.
The frontal horns will become enlarged and
outwardly convex (from the atrophy pattern)
Leigh Disease
Mitochondrial Disorder
Elevated Lactate peak at 1.3 ppm
Leigh Disease
Imaging
T2/FLA1R bright lesions in the Brainstem,
Basal Ganglia , and Cerebral Peduncles.
They can restrict, but do NOT enhance.
MELAS Syndrome
Mitochondrial Disorder
Lactic Acidosis, Seizures, and Strokes
Elevated Lactate “doublet” at 1.3 ppm
MELAS Syndrome
Imaging
with a nonvascular distribution (usually
occipital and parietal).
Underlying WM is normal
Hurler Syndrome
Lysosomal Storage Disease /
Mucopolysaccharidoses
Hurler Syndrome
Imaging
(1) Macrocephaly with Mctopic “beak”
(2) Enlarged Perivascular Spaces
(3) Beaked Inferior L 1 Vertebral Body
Parkinson Disease (PD)
Classic Clinical Hx: Resting tremor, Rigid /
Slow movements (shuffling gate, etc..).
Etiology: Reduced dopaminergic input to
striatum (whatever the fuck that means).
Parkinson Disease (PD)
imaging
DAT Scan - loflupane 123 - This exotic
Nukes study is certainly fair game for an
“intermediate level” exam., commas instead of periods
Impossible to diagnose on CT or MR alone -
but supposedly has mild midbrain volume
loss with a “butterfly” pattern (this would
have to be stated, it is too subtle to show).
Worth noting in the sparing of the midbrain
and superior cerebellar peduncles. This is a fairly high yield piece of trivia as it helps
distinction Parkinsons from multi-system
atrophy.
Wilson Disease
AR copper metabolism malfunction. Once
the liver fills up with copper it starts
spilling over into other organs including the
brain.
Wilson Disease
trivia
Trivia: “Kayser-Fleischer Rings” - seen in
95% of patients. Prepare the Slit Lamp.
Trivia: Cortical Atrophy is the most
common CT finding (although obviously
non-specific).
Trivia: T 1 Bright BG is the most common
initial MR findings (supposedly).
“Parkinson- Plus” Multi- System Atrophy (MSA)
This is a monstrously complex entity, that is actually 3 separate renamed entities (“P”, “ Q " an(j “A”). The highest yield pearl is the appearance of the Cerebellar subtype MSA-CI Trivia: 1-123 M1BG can be used to differentiate PD from MSA, by looking at the cardiac/mediastinal ratio (which is normal in MSA, and abnormal in PD)
“Parkinson- Plus” Multi- System Atrophy (MSA)
imaging
Cerebellar Hemisphere /
Peduncle Atrophy with a
Shrunken Flat Pons &
an enlarged 4th vent.
Hot Cross Bun
Sign (loss of the
transverse fibers)
“Parkinson- Plus” Progressive Supranuclear Palsy (PSP)
• Also called Steele-Richardson-Olszewski for the purpose of fucking with you. • PSP = Most Common Parkinson Plus • Unlike PD & MSA, PSP is a Tauopathy (whatever the fuck that means).
“Parkinson- Plus” Progressive Supranuclear Palsy (PSP)
imaging
Micky Mouse Sign: Tegmentum Atrophy
with Sparing of the Tectum & Peduncles.
*If needed anatomy refresher - page 14
Hummingbird Sign: Midbrain volume loss
with a concave upper surface + relative
sparing of the Pons
Wilson Disease
imaging
Panda Sign: T2 Bright Tegmentum with
normal dark red nuclei & substantial nigra
T1 and T2 Bright Basal Ganglia
T2 Bright Dorsal Medial Thalamus
Deep Brain Stimulators
I want to quickly touch on deep brain stimulators. These things are used in the treatment of Parkinson disease, essential tremor, and chronic pain. It is common to get a CT immediately after DBS placement to evaluate for correct positioning of the electrode or any obvious complications (bleeding, etc...). Knowing the “correct” position is the most useful piece of trivia. For Parkinson Disease, the electrodes are typically positioned in the sub thalamic nucleus with the tips of the electrons located 9 mm from the midline (just inside the upper most margin of the cerebral peduncle).
Introduction to MRI Spectroscopy
overview
The general idea is that the various metabolites which exist on the cellular level (choline,
lactate, N-acetylaspartate “NAA,” etc… etc…, so on and so forth…) occur in different concentrations
depending on the pathology. For example, “NAA” is a neuronal marker. Things that destroy neurons
(like tumors) will decrease NAA. So, in general the lower the NAA the higher the grade tumor.
You will see a graph like this one, with “PPM” on the X-Axis, and “Intensity” on the Y-Axis.
Introduction to MRI Spectroscopy
itnensity
Intensity is going to tell you “how much” of a thing there is. It’s not a raw number, and better thought of as a ratio.
Introduction to MRI Spectroscopy
PPM
PPM stands for parts per million. Better understood as a percent of the Larmor Frequency
(1 ppm = 1 millionth of the Larmor frequency). This is important because each metabolite will
have a unique frequency distribution. For example NAA is at 2.0 ppm.
Introduction to MRI Spectroscopy
why are the numbers backward ont he scall
I’m going to answer this with the same
explanation I received as a small child when I asked why I couldn’t just eat my dessert first, and my
vegetables last — “because I’m your mother that’s why!”
Introduction to MRI Spectroscopy
hunters angle
This is a method to quickly
decide if the MRS is normal or not. Under
normal conditions Choline, Creatine, and NAA
should ascending in that order. Using a line to
connect the tips gives you a 45 degree~ish angle.
If it slopes the other way (as shown) then it is
not normal.
Reversed Hunter’s
Angle in a
High Grade
Glioma (GBM)
MRI Spectroscopy High Yield Pearls
Lipid
0.9-1.4 Product of brain destruction - lipids are present in necrotic brain tissue (necrosis marker). Necrotic Tissue (spilling of membrane lipids). Elevated with high grade tumors, brain infarcts, and brain abscess.
MRI Spectroscopy High Yield Pearls
Lactate
1.3 Product of anaerobic metabolism. Absent under normal conditions. Brain tumor has outgrown its blood supply - is forced into anaerobic pathways for metabolism. Also elevated with cerebral abscess. Classic Trivia: It’s normal to see lactate elevated in the first hours of life Classic Trivia: Lactate and Lipid peaks superimpose - you need to use an intermediate TE (around 140) to causes an “inversion” of the lactate peak (so you can see it)
MRI Spectroscopy High Yield Pearls
Alanine
1.48 Amino Acid Found in Meningiomas
MRI Spectroscopy High Yield Pearls
N-acetvlaspartate
“NAA”
2.0 Neuronal Marker (Neuron Viability). Usually the tallest peak. Glial tumors have NAA. The higher the Glial tumor grade, the lower the NAA Classic Trivia: NAA peak is super high with Canavans
MRI Spectroscopy High Yield Pearls
Glutamine -
“GLX”
2.2-2.4 Neurotransmitter Increased with Hepatic Encephalopathy
MRI Spectroscopy High Yield Pearls
Creatine - “C r”
3.0 Energy
Metabolism Decreased in tumor necrosis.
MRI Spectroscopy High Yield Pearls
Choline - “Co”
3.2 Cell Membrane Turnover More turnover more Choline (thus elevated in high grade tumor, demyelination, inflammation).
MRI Spectroscopy High Yield Pearls
Myoinositol -
“ml”
3.5 Cell Volume Regulator and Byproduct of Glucose Metabolism. - Elevated in low grade gliomas. - Elevated in Alzheimer’s (decreased in other dementias) - Elevated in Progressive multifocal leukoencephalopathy (PML) - Reduced in high grade gliomas - Reduced in Hepatic Encephalopathy
h is vs THAT: Demyelinating vs Dysmyelinating
Demyelinating disease Example = MS Disease that destroys normal myelin
Dysmyelinating disease Example = Mctachromatic leukodystrophy
disease that disruptst he normal formation and turnover of myelin
Leukodystrophy
Fucked White Matter in a Kid
Leukodystrophy
(ALD)
“X-Linked
Metachromatic
Alexander Disease
Canavan Disease
Krabbe
Pelizaeus-
Merzbacher
Leukodystrophies & Friends
On the prior page, I introduced the vocab work “dysmyelinating” disease. Leukodystrophies are the classic
example o f this group o f pathologies. Technically speaking Leukodystrophies can occur from deficiencies
in lysosomal storage, peroxisomal function, or mitochondrial dysfunction. I’m gonna hit on mitochondrial
diseases separately as they tend to be more asymmetric and favor the grey matter. Where as the classic
forms target the white matter in a more symmetric and extensive manner
Leukodystrophy
(ALD)
“X-Linked
Normal Head Size Parieto-occipital Predominance “Extends across the Splenium of the Corpus Callosum” Sex-linked recessive (peroxisomal enzyme deficiency) Male Predominant Can Enhance & Restrict
Metachromatic
Normal Head Size Frontal Predominance Periventricular and Deep White Matter - Tigroid Pattern (stripes of milder disease). Most common Leukodystrophy. U-fibers are relatively spared
Alexander Disease
Weird Bie Head Frontal Predominance Also hits the cerebellum and middle cerebellar peduncles Can Enhance
Canavan Disease
Weird Bin Head Diffuse Bilateral subcortical U fibers. “Subcortical Predominance” Elevated NAA (MRS).
Krabbe
Small Head Centrum semiovale and periventricular white matter with parietooccipital predominance High density foci on CT (in the thalamus, caudate, and deep white matter). Earlv sparine of the subcortical U fibers
Pelizaeus-
Merzbacher
Normal Head Size Typically diffuse “total lack of normal myelination” with extension to the subcortical U fibers. Patchy variant is also described as “tigroid” - although that term is more classic for Metachromatic No enhancement. No restricted diffusion
Leukodystrophies & Friends continued
As discussed on the prior page Leukodystrophies can occur from deficiencies in lysosomal storage,
peroxisomal function, or mitochondrial dysfunction. The classic forms tend to target the white matter in a
more symmetric and extensive manner. This is different than mitochondrial diseases which are more
asymmetric and favor the grey matter. Grey Matter needs more oxygen than White Matter (and White
Matter needs more oxygen than trial lawyers). Inability to process oxygen (mitochondrial dysfunction) -
helps me remember the grey matter > white matter thing.
MELAS
Mitochondrial Enccphalomyopathy, Lactic
Acidosis, and Stroke-like episodes. This is a
mitochondrial disorder with lactic acidosis and stroke
like episodes.
Tends to have a parietooccipital distribution
MELAS BUZZWORD(s
migrating infarcts
typical MRS pattern for MELAS
increased lactate and decreased naa
Leigh Disease
Also called Subacute Necrotizing Encephalo-Myelopathy - for the purpose of fucking
with you.
White Matter Distribution: Focal areas of subcortical white matter.
Gray Matter Distribution: Basal ganglia and Periaquaductal Gray
Leigh Disease trivia
Head size tends to be normal.
Brain tumors approach
The strategy is as
follows; (1) decide if it’s single or multiple, (2) look at the age o f the patient - adults and kids
have different differentials, (3) look at the location - different tumors occur in different spots,
(4) now use the characteristics to separate them. The strategy centers around narrowing the
differential based off age and location till you are only dealing with 3-4 common things, then
using the imaging characteristics to separate them. It’s so much easier to do it that way.
Multiple Masses approach
multifocal primary from seeding
mets (50% at solitary)
syndromes (example nf2)
single mass adult approach
cortical
intraventricular
cp angle
infratentorial
single mass kid approach
supratentorial
skull base/dura
sella/parasella
pineal gland
Before we get rolling, the first thing to do is to ask yourself is this a tumor, or is it a mimic?
Mimics would be abscess, infarct, or a big MS plaque. This can be tricky. If you see an
incomplete ring - you should think giant MS plaque. If they show you diffusion, it is either
lymphoma or a stroke (or an abscess) - you’ll need to use enhancement to straighten that out
(remember lymphoma enhances homogeneously).
Yes… GBM can restrict, but for multiple choice it is way more likely to be lymphoma.
intra-Axial” vs “Extra-Axial”
The Brant and Helms discussion on brain tumors will have you asking “ intra-axial” vs
“extra-axial” first. This is not always that simple, but it does lend itself very well to
multiple choice test questions (therefore it’s high yield).
Basically yo u need to memorize the “signs o f extra-axial location “
• CSF Cleft
Displaced Subarachnoid Vessels
Cortical Gray matter between the mass and white matter
Displaced and expanded Subarachnoid spaces
• Broad Dural Base / Tail
• Bony Reaction
Why Do Things Enhance
Understanding the WHY is very helpful for problem solving. Let me first answer the
question “Why D O N ‘T things enhance?” They DON’T enhance because o f the blood brain
barrier. So, when things DO enhance it’s because either:
(a) They are outside the blood brain barrier (they are extra-axial), or
(b) They have melted the blood brain barrier.
In other words, extra axial things (classic example is meningioma) will enhance. High
grade tumors (and infections) enhance. Low grade tumors ju st aren’t nasty enough to
take the blood brain barrier down
Why Do Things Enhance
exceptions
Gangliogliomas and Pilocytic Astrocytomas are the exceptions - they are low-grade
tumors, but they enhance.
Multiple Masses
In adults or kids, if you see multiple masses you arc dealing with mets (or infection). Differentiating
between mets and infection is gonna be done with diffusion (infection will restrict). If they want you
to decide between those two they must show you the diffusion otherwise only one or the other will be
listed as a choice.
Mets — High Yield Trivia
• Most common CNS met in a kid = neuroblastoma (BONES, DURA, ORBIT - not brain)
• Most common location for mets = Supratentorial at the Grey-White Junction (this area has a lot of
blood flow + an abrupt vessel caliber change… so you also see hematogenous infection / septic
emboli go there first too).
• Most common morphology is “round” or “spherical”
• Remember that mets do NOT have to be multiple. In fact, 50% of mets are solitary. In an adult, a
solitary mass is much more likely to be a met than a primary CNS neoplasm.
• MRCT is the mnemonic for bleeding mets (Melanoma. Renal, Carcinoid / Choriocarcinoma,
Thyroid).
• Usually Mets have more surrounding edema than primary neoplasms of similar size.
Mets
gamesmanship
“Next Step Gamesmanship ” - Because the most common intra-axial mass in an adult is a met, if
they show you a solitary mass (or multiple masses) and want a next step it’s gonna be go hunting
for the primary (think lung, breast, colon… the common stuff).
Tumors that Like to be Multifocal
Mets — you should still think this first when you see multiple tumors
Lymphoma
Multiccntric GBM
Gliomatosis Cerebri
Tumors that are Multifocal from Seeding
Mcdulloblastoma
Ependymoma
GBM
Oligodendroglioma
SYNDROMES - Tumors in Syndromes are more likely to be Multifocal
NF 1 NF 2 “MSME” Tuberous Sclerosis VHL
NF 1
Optic Gliomas
Astrocytomas
NF 2 MSME
Multiple Schwannomas
Meningiomas
Ependymomas
Tuberous Sclerosis
Subependymal Tubers
IV Giant Cell
Astrocytomas
VHL
Hcmangioblastomas
Cortically Based
Most intra-axial tumors arc located in the
white matter. So when a tumor spreads to or
is primarily located in the gray matter, you
get a shorter DDx. High yield piece of trivia
regarding the cortical tumor / cortical met is
that they often have very little edema and so
a small cortical met can be occult without IV
contrast.
Cortically Based
ddx
P-DOG: Pleomorphic Xanthoastrocytoma (PXA) Dysembryoplastic Neuroepithelial Tumor (DNET) Oligodendroglioma, Ganglioglioma
PXA (Pleomorphic Xanthroastrocytoma
Superficial tumor that is ALWAYS supratentorial and
usually involves the temporal lobe. They are often in
the cyst with a nodule category (50%). There is usually
no pcritumeral T2 signal. The tumor frequently invades
the leptomeninges. Looks just like a Desmoplastic
Infantile Ganglioglioma - but is not in an infant
PXA (Pleomorphic Xanthroastrocytoma
quick
PEDS (10-20) Will Enhance Dural Tail*** Cyst with Nodule Temporal Lobe
D N E T (Dysembryoplastic Neuroepithelial Tumor)
Kid with drug resistant seizures. The mass will always be in
the temporal lobe (on the test - real life 60% temporal).
Focal cortical dysplasia is seen in 80% of the cases. It is
hypodense on CT, and on MRI there will
be little if any surrounding edema.
High T2 signal “bubbly lesion.”
Bright Rim Sign -
Bright Rim Sign
Persistent rim of FLAIR signal
* Looks Similar to T2-FLAIR
Mismatch of Astrocytomas
**discussed later
DNET quick
PEDS (< 20) No enhancement High T2 Signal with Bright FLAIR Rim “Bubbly” Temporal Lobe
Oligodendroglioma
Remember this is the guy that calcifies 90% of the time. It’s
most common in the frontal lobe and the buzzword is
“expands the cortex”. This takes after its most specific
feature of cortical infiltration and marked thickening. It’s 0
likely you could get asked about this Ip/I9q deletion which I ^
will discuss later when I go into detail about Gliomas
Oligodendroglioma
quick
ADULT - (40s-50s) Can Enhance Calcification Common “Expands the Cortex” Frontal Lobe 1p /19q
ribbon calcifications
Ganglioglioma
This guy can occur at any age, anywhere (usually temporal
lobe), and look like anything. However, for the purpose of
multiple choice testing the classic scenario would be a 13
year old with seizures, and a temporal lobe mass that is
cystic and solid with focal calcifications. There may be
overlying bony remodeling.
Ganglioglioma
quick
Any Age Can Enhance Can look like Anything Temporal Lobe Not bubly
Mixed Cystic
& Solid
Ventricular wall and septum pellucidum ddx
F.pendvmoma (TEDS) Medulloblastoma (TEDS) SEGA (Subependymal Giant Cell Astrocytoma) = PEDS Subependymoma (ADULT) Central Neurocytoma (YOUNG ADULT)
choroid plexus ddx
Choroid Plexus Papilloma (PEDS in Trigone) (ADULT in 4th Vent) Choroid PlexusCarcinoma (TEDS) Xanthogranuloma t “Found“ in ADULTS)
misc intraventricular ddx
mets
meningioma
colloid cyst
Ependymoma
overview
Bimodal distribution on this one (large peak around 6 years o f age,
tiny peak around 30 years o f age). I would basically think o f this as a PEDS tumor.
They come in two flavors:
Ependymoma
4th ventricle
4th Ventricle - which is about 70% o f the time. There is frequent extension into the
foramen o f Luschka and Magendie. They are the so-called “plastic tumor” or
“toothpaste ” tumor because they squeeze out o f the base o f the 4 th ventricle.
Ependymoma
parenchymal supratentorial
Parenchymal Supratentorial - which is about 30% o f the time.
These are usually big (> 4cm at presentation).
Medulloblastoma
overview
Let us just assume we are talking about the “Classic Medulloblastoma”
which is a type o f PNET. If you want to understand the genetic spectrum o f these things, read
Osborn’s Brain — seriously don’t subject yourself to that.
Medulloblastoma
epidiomology and location
This is a pediatric tumor - with most occurring before age 10 (technically there is a second
peak at 20-40 but for the purpose o f multiple choice tests I’m going to ignore it). These guys
are cerebellar arising from vermis / ROOF o f the 4th ventricle - project into 4th ventricle. They
are much more common than their chief differential consideration the Ependymoma (which
originates from the FLOOR o f the 4th ventricle).
Medulloblastoma
classic look
The classic look is a dense mass on CT, heterogeneous on T1 and T2, and enhances
homogeneously. They are hypercellular and may restrict. They calcify 20% o f the time (less
than Ependymoma).
Medulloblastoma
mets to
This is a tumor that loves to met via CSF pathways — they like to “drop met.” The buzzword is
“zuckerguss” which apparently is German for sugar icing, as seen on post contrast imaging of
the brain and spinal cord (leptomeningeal carcinomatosis). As a point of absolute trivia, they
are associated with Basal Cell Nevus Syndrome and Turcots Syndrome.
Gorlin Syndrome
Gorlin Syndrome - If you see a Medulloblastoma next look for dural calcs.
If you see thick dural calcs you might be dealing with this syndrome.
»’v i ‘\ They get basal cell skin cancer after radiation, and have odontogenic cysts.
Medulloblastoma next step
Preoperative imaging o f the entire spinal axis should be done in
any child with a posterior fossa neoplasm, especially if Medulloblastoma or
Ependymoma is suspected. Evidence o f tumor spread is a statistically significant
predictor o f outcome.
M e d u llo b la s tom a
quick
More common
Originate from Vermis /ROOF o f the 4th Ventricle
Can project into 4th ventricle, do NOT usually
extend into basal cisterns
Enhance Homogeneously
(more so than Ependymoma anyway)
Calcify Less (20%)
Linear “icing-like” enhancement o f the brain
surface is referred to as “Zuckerguss”
Ependymoma
quick
Less Common
Originate from the vermis/ floor of the 4th ventricle
Can extend into basal cisterns like tooth
paste pushing though foramina o f
Luschka and Magendie
Enhance Heterogeneously
Calcify More (50%)
Subependymal Giant Cell Astrocytoma (SEGA):
This is going to be shown
in the setting o f TS. They will more than likely show you renal AMLs or tell you the kid has
seizures / developmental delay.
Because it’s syndromic, you see it in kids (average age 11).
It will arise from the lateral wall o f the ventricle (near the foramen o f Monro), often causing
hydrocephalus. It enhances homogeneously.
THIS vs THAT: SEGA vs Subependymal Nodule (SEN)
The SEN will stay stable in size,
the SEGA will grow. The SEGA is found in the lateral ventricle near the foramen o f
Monroe, the SEN can occur anywhere along the ventricle. SENs are way more common.
Both SEN and SEGA can calcify.
THIS vs THAT: SEGA vs Subependymal Nodule (SEN)
pearl
Enhancing, partially calcified lesion at the foramen o f Monro, bigger than 5 mm is a SEGA not a SEN.
Subependymoma
Found in ADULTS. Well-circumscribed IV mass most commonly
at the foramen of Monro and the 4th ventricle. They can cause hydrocephalus. They
typically don’t enhance. They are T2 bright (like most tumors).
Central Neurocytoma
This is the most common IV mass in an ADULT aged 20-40. The buzzword is “swiss cheese,” because o f the numerous cystic spaces on T2. They calcify a lot (almost like oligodendrogliomas). Swiss Cheese + Calcification in the Ventricle
Choroid Plexus Papilloma / Carcinoma
Can occur in peds (85% under the age o f 5) or
adults. They make up about 15% o f brain tumors in kids under one. Basically you are
dealing with an intraventricular mass, which is often making CSF, so it causes
hydrocephalus.
Choroid Plexus Papilloma / Carcinoma
here is the trick
Brain tumors are usually supratentorial in adults and posterior fossa
▼ in kids. This tumor is an exception. Remember exceptions to rules are testable.
Choroid Plexus Papilloma / Carcinoma
trivia
• In Adults it’s in the 4th Ventricle, in Kids it’s in the lateral ventricle (usually trigone).
• Carcinoma type is ONLY SEEN IN KIDS - and are therefore basically ONLY SEEN IN
LATERAL VENTRICLE / TRIGONE
• Carcinoma association with Li-Fraumeni syndrome (bad p53)
• Angiography may show enlarged choroidal arteries which shunt blood to the tumor,
• Carcinoma type o f this tumor looks very similar (unless it’s invading the parenchyma) and
is almost exclusively seen in kids.
• The tumor is typically solitary but in rare instances you can have CSF dissemination
Xanthogranuloma
This is a benign choroid plexus
mass. You see it all the time (7%)
and don’t even notice it.
Xanthogranuloma
trick
The trick is that they restrict on diffusion, so they are trying to trick you into working them up. They are benign... leave them alone.
Intraventricular mets
The most common location o f intraventricular metastasis is the trigone o f lateral
ventricles (because o f the vascular supply o f the choroid). The most common primary is
controversial - and either lung or renal. I f forced to pick I’d go Lung because it’s more
common overall. I think all things equal renal goes more - but there are less renal cancers.
It all depends on how the question is worded
Colloid C yst
These are found almost
exclusively in the anterior part o f the 3rd
ventricle behind the foramen o f Monro.
They can cause sudden death via acute onset
hydrocephalus.
Colloid C yst
appearance
Their appearance is somewhat variable and
depends on what they are made of. If they have
cholesterol they will be T1 bright, T2 dark. If
they do n ’t, they can be T2 bright. The trick is a
round well circumscribed mass in the anterior
3rd ventricle. If shown on CT, it will be pretty
dense.
Colloid C yst
quick
- Anterior 3rd Ventricle
- Hyperdense on CT
Intraventricular meningioa
Can occur in an intraventricular location, most commonly (80%) at the
trigone of the lateral ventricles (slightly more on the left). Details on meningiomas are
discussed on the following page.
Cerebellar Pontine Angle (CPA)
Age is actually less o f an issue here because the DDx isn’t that big. Most of these are adult
tumors, but in the setting of NF-2 you could have earlier onset.
Cerebellar Pontine Angle (CPA)
Epidemiology
Vestibular Schwannoma is #1 - making up 75% o f the CPA masses, #2 is the
meningioma making up 10%, and the Epidermoid is #3 making up about 5%. The rest are
uncommon.
Cerebellar Pontine Angle (CPA)
Schwannoma (Vestibular)
These guys
account for 75% of CPA masses. When they are bilateral
you should immediately think NF-2 (one fo r each side).
Enhances strongly but more heterogeneous than
meningomas. May widen the porus acousticus resulting
in a “trumpet shaped” IAC. “Ice Cream Cone IAC. ”
Cerebellar Pontine Angle (CPA)
Meningioma
Second more common CPA
mass. One o f the few brain tumors that is more common
in women. They can calcify, and if you are lucky they
will have a dural tail (which is pretty close to
pathognomonic - with a few rare exceptions). Because
they are extradural they will enhance strongly. Radiation
o f the head is known to cause meningiomas
Cerebellar Pontine Angle (CPA)
Meningioma trivia
•Most common location of a meningioma is over the cerebral convexity.
^Meningiomas take up octreotide and Tc-MDP on Nuclear Medicine tests (sneaky).
Cerebellar Pontine Angle (CPA)Epidermoid
Can be congenital or acquired (after trauma - classically after LP
in the spine). Unlike dermoids they are usually off midlinc.
They will follow CSF density and intensity on CT and MR1
(the exception is this zebra called a “white epidermoid” which is
T1 b r ig h t- just forget I ever mentioned it).
(5%)
Cerebellar Pontine Angle (CPA)
Epidermoid key points
(1) Unlike an arachnoid cyst they are bright on FLAIR
(sometimes warm - they don’t completely null), and
(2)They will restrict diffusion.
Epidermoid - Follows CSF
Signal - Restricts Diffusion
Cerebellar Pontine Angle (CPA)
Schwannoma quick
Enhance Less Homogeneously Invade IAC IAC can have “trumpeted” appearance
Cerebellar Pontine Angle (CPA)
Meningioma quick
Enhance Homogeneously Don't Usually Invade IAC Calcify more often
Cerebellar Pontine Angle (CPA)
Dermoid C yst
This is about 4x less common than an epidermoid. It’s more common in kids / young adults. Usually midline, and usually are found in the 3rd decade. They contain lipoid material and are usually hypodense on CT and very bright on T l. They are associated with NF2.
Cerebellar Pontine Angle (CPA)
Dermoid C yst trivia
•These are usually midline
• Most common location for a
A dermoid cyst is the suprasellar
4 9 1 1 cistern (posterior fossa is #2)
Cerebellar Pontine Angle (CPA)
The Ruptured Dermoid
It is possible for a dermoid cyst to explode
-rare in real life, common on multiple choice.
Sometimes this is after a trauma, but usually
it’s spontaneous. The most common clinical
scenario is “headache and seizure” - which is
pretty much every brain tumor, so that is not
helpful.
The Ruptured Dermoid
buzzword
“Chemical Meningitis ”
The Ruptured Dermoid
aunt minnie
Fat droplets
(typically shown as low density on CT, or
High Signal on T i l floating in the ventricles
and/or subarachnoid space.
THIS vs THAT: Dermoid vs Epidermoid
The easy way to think o f this is that the
Epidermoid behaves like CSF, and the Dermoid behaves like fat.
I AC Lipoma
It can occur, and is basically the only reason you get a Tl when you are
working up CPA masses. It will fat sat out - because it’s a lipoma. There is an association
with sensorineural hearing loss, as the vestibulocochlear nerve often courses through it
Arachnoid C yst
Common benign lesion that is
located within the subarachnoid space and contains
CSF. They are increased in frequency in
mucopolysaccharidoses (as are perivascular spaces).
They are dark on FLAIR (like CSF), and will NOT
restrict diffusion.
How can yo u tell an epidermoid
from an arachnoid cyst?
The epidermoid restricts,
the arachnoid cyst does NOT.
Infratentorial
Most are PEDS (Hemangioblastoma is the exception).
Infratentorial
Atypical Teratoma I Rhabdoid Tumor
“AT/RT”
Highly malignant tumors (WHO IV), and
rarely occur in patients older than 6 years. The average
age is actually 2 years, but they certainly occur in the
first year of life.
They can occur in supra and infratentorial locations
(most common in the cerebellum). These are usually
large, pissed off looking tumors with necrosis and
heterogeneous enhancement. They believe in nothing
Lebowski. They fuck you up. They take the money
Infratentorial
THIS vs THAT:
AT/RT v s Medulloblastoma
Both are WHO Grade 4 destroyers (AT/RT is worse) that are often seen in the posterior fossa of a kid. Technically they are both subtypes of Medulloblastoma - but that’s the kind of knowledge that causes you to miss multiple choice questions. For the purpose of multiple choice: • AT/RT is a 2 year old • Medulloblastoma is a 6 year old • AT/RT has calcifications • Medulloblastoma does not
Infratentorial
Medulloblastoma & Ependymoma
discussed with intraventricular
Infratentorial
Juvenile Pilocytic Astrocytoma
(JPA):
Just think cyst with a nodule in a kid.
They are WHO grade 1, but the nodule will still
enhance. This will be located in the posterior
fossa (or optic chiasm).
Infratentorial
Hemangioblastoma:
First things first - immediately think
about this when you see a cyst with a nodule in an ADULT. Then
think Von Hippel Lindau, especially if they are multiple. These
things are slow growing, indolent vascular tumors, that can cause
hydrocephalus from mass effect. 70% of the time you will see flow
voids along the periphery of the cyst. About 90% of the time they
are found in the cerebellum. There is an association with polycythemia
Infratentorial
Ganglioglioma
Occurs at any age, anywhere, can look like anything - see cortical lesions
Infratentorial
Diffuse Pontine Glioma (DPG):
Seen in kids age 3-10. Most common location is the pons,
which is usually a high grade fibrillary glioma. It’s going to be T2 bright with subtle or no
enhancement. 4th ventricle will be flattened. Imaging features arc so classic that no biopsy is needed
Atypical Teratoma I Rhabdoid Tumor
(“AT/RT”)
buzzword
“Increased Head Circum ference ”
Juvenile Pilocytic Astrocytoma
(JPA):
gamesmanship
if they don’t tell you the age, you can look for enhancement of the cystic wall which
JPA can have (-50%) but Hemangioblastomas don’t
Pilocytic Astrocytoma quick
Cyst + Nodule in Kid
I Say Posterior Fossa Cyst
with a Nodule - PEDS,
JPA
I say Posterior Fossa Cyst
with a Nodule - ADULT
Hemangioblastoma
Supratentorial - Adults Tumors
Astrocytomas
Most common primary brain tumor in adults. There is a trend towards “genetically
classifying” tumors - this actually changes the way they arc treated and could be the source of trivia.
I’m going to attempt to simply this - because it can get pretty fucking complicated
The new way to think about these things is a spectrum of severity
based on genetic classification - and the treatment and prognosis
follows that.
Supratentorial - Adults Tumors
Astrocytomas simple terms
In the simplest terms, you have the neurons and you have the glial
cells. The glial cells are the “support staff’ — there are lots of them
and lots of different kinds. Astrocytes and Oligocytes share a
common origin (both are support staff - “glial cells”) and have a lot
of similarities. In other words, they are both “Gliomas” and are
going to get lumped together in this discussion.
Supratentorial - Adults Tumors
Ribbon pattern of
calcification
Classic for
Oligodendroglioma
Supratentorial - Adults Tumors
Astrocytoma
IDH Mutation
(earliest genomic event) yes
Yes (10%)
Astrocytoma Grade 4 - Glioblastoma - Younger Patients -Better prognosis -Probably “Secondary GBM” from progression of a previous lowergrade tumor
1p/19qd deletion positive
Oligodendroglioma Calcification on preoperative CT is associated with codeletion (Ip/I9q)
1p/19qd deletion negative
Astrocytoma
Low Grade
Supratentorial - Adults Tumors
Astrocytoma
IDH Mutation
(earliest genomic event) no
no 990%0
Astrocytoma Grade 4 - Glioblastoma -Older Patients -The Worst Prognosis -Probably “Primary GBM”
Astrocytoma Higher Grade -Grade 2 - Diffuse -Grade 3 - Anaplastic T 2 - FLAIR Mismatch Sign
Supratentorial - Adults Tumors
Astrocytoma prognosis
You probably noticed me using this WHO classification (1-4). All brain tumors are bad, but 4 is the
worst - this is your GBM. On the following page, I’ll get into a few more details on each type but as a
general rule low grade tumors don’t typically enhance (WHO 2) and higher grades do (mild for grade
3, and intense for grade 4 GBM). The exception to this rule is the pilocytic astrocytoma which often
has an enhancing nodule, and the Subependymal Giant Cell Astrocytomas which enhances because of
its location (Intraventricular).
GBM is the beast that cannot be stopped. It believes in nothing Lebowski. It grows rapidly, it can
necrose (creating the ring of enhancement, with a non-enhancing central necrotic co re), it can cross
the midline, and it can restrict diffusion. Remember Turcot Syndrome (that GIpolyp thing), and NF
1 are associated with GBMs.
Astrocytoma
Grade 1
Subependymal Giant
Cell Astrocytomas
Intraventricular mass near the foramen of Monro in a young patient with tuberous sclerosis. -Can cause obstructive hydrocephalus
Astrocytoma
Grade 1
Pilocytic Astrocytoma
- Cyst with nodule in the posterior fossa of a kid Remember these tumors break the rule - and enhance despite being low grade.
Astrocytoma
Grade 2 - Diffuse
White Matter is Preferred NO ENHANCEMENT T2 Bright - FLAIR Iso (mismatch sign)
Astrocytoma
Grade 3 - Anaplastic
White Matter is Preferred Mild ENHANCEMENT T2 Bright-FLAIR Iso (mismatch sign)
Astrocytoma
Grade 4- GBM
White Matter is Preferred - can cross the midline. RING ENHANCEMENT (can also be diffuse heterogenous enhancement) T2 & FLAIR Bright Central locations (like the thalamus) are worse than normal. NF type 1, Turcot syndrome, Li Fraumeni syndrome
T2 / FLAIR Mismatch
Seen with WHO 2
(diffuse) and 3 (anaplastic) astrocytoma, not
with WHO 1. T2 tumor has high signal with
surrounding vasogenic edema. On FLAIR the
tumor signal become isointense
Siupratentorial adults
Gliomatosis Cerebri
A diffuse glioma with extensive infiltration. It involves at least 3 lobes
and is often bilateral. The finding is usually mild blurring of the gray-white differentiation on CT, with
extensive T2 hyperintensity and little mass effect on MR. It’s low grade, so it doesn’t typically
enhance.
Siupratentorial adults
mets
The most common supratentorial mass. Just like mets favor the lower lobes in the lungs, the
cerebrum is favored over the cerebellum (it is a blood flow thing). They arc usually multiple, but can
be solitary — some sources say 50% of the time, so don’t be fooled a solitary lesion can totally be a
met. Some other trivia worth knowing — melanoma can be T1 bright even if it doesn’t bleed.
CT-MR is a good way to remember the ones that like to bleed (Choriocarcinoma / Carcinoid, Thyroid,
Melanoma, Renal).
Siupratentorial mets quick adults
Irregular
Margin
-Multifocal
(25-50% solitary)
-Favors
Grey-White Junction
Siupratentorial GBM quick adults
Spherical
-Solitary
) (25%> multifocal)
-Favors Deep White Matter
Supratentorial - Adults Tumors
Primary CNS Lymphoma:
Seen in end stage AIDS patients, and those post-transplant. EB
virus plays a role. Most common type is Non-Hodgkin B cell.
Supratentorial - Adults Tumors
Primary CNS Lymphoma: classic
Classic picture would be an intensely enhancing homogeneous solid mass in the periventricular
region, with restricted diffusion. However, it can literally look like and do anything.
Classic Multiple choice test question is that it is Thallium Positive on SPECT
(toxo is not).
Supratentorial - Adults Tumors
I say restricting brain tumor, you say
Lymphoma (although GBM can do this also)
THIS vs THAT: P e r iv e n tr icu la r / Ep e n d ym a l E n h a n c em e n t P a tte rn s
thin smooth and linear
Ependymitis - £
(Classic Example
= CMV)
thick and irregular
lymphoma (rim phoma)
Supratentorial - Peds Tumors
DNET & PXA (Pleomorphic Xanthroastrocytoma):
Discussed under the cortical tumors .
Supratentorial - Peds Tumors
D e smo p la s t ic Infantile Ganglioglioma I As tro cy toma “DIG”:
These guys arc large cystic tumors that like to involve the superficial
cerebral cortex and leptomeninges. Unlike the Atypical Teratoma /
Rhabdoid, these have an ok prognosis (WHO 1). They ALWAYS arise in
the supratentorial location, usually involve more than one lobe (frontal
and parietal most commonly), and usually present before the first birthday.
Supratentorial - Peds Tumors
D e smo p la s t ic Infantile Ganglioglioma I As tro cy toma “DIG”: buzzword
“rapidly increasing head circumference.”
Skull Base
Chordoma
This is a locally aggressive tumor that originates from the notochord.
WTF is the “notochord” ? It’s an embryology thing that is related to spine development.
The thing you need to know is that the notochord is a midlinc structure. Therefore all
Chordomas are midline - either in the clivus, vertebral bodies (especially C2), or Sacrum. You
can NOT get them in the hips, ribs, legs, arms, or any other structure that is not totally midline
along the axis o f the axial skeleton.
Skull Base
Chordoma facts
*lt is most common in the sacrum (#2 is the clivus)
*When it involves the spine, it’s most common at C2 - but typically extends across a disc
space to involve the adjacent vertebral body.
.It’S T2 Bright
*Ifs ALWAYS Midline. — it is never in a leg, arm, e tc … ONLY MIDLINE structures.
Ch on d ro sa r coma
skull base
This is the main differential o f the chordoma in the clivus. The thing
to know is that it is nearly always lateral to midline (chordoma is midline). These are also T2
bright, but will have the classic “arcs and rings” matrix o f a chondrosarcoma. Obviously you’ll
need a CT to describe that matrix.
Dura
Meningioma
As described above, it is common and enhances homogeneously. The most
common location is over the cerebral convexity and it has been known to cause hyperostosis.
Dura
H em an g iop e r ic y toma
This is a soft tissue sarcoma that can mimic an aggressive
meningioma because they both enhance homogeneously. They also can mimic a dural tail, with a
narrow base of dural attachment. They won’t calcify or cause hyperostosis , but will invade the
skull.
Dura
metd
The most common met to the dura is from breast cancer. 80% will be at the gray-white
junction. They will have more edema than a primary tumor o f similar size.
Sella I Parasella - Adults
Pituitary Adenoma
The most common tumor o f the sella. They are seen 97% o f the
time in adults. If they are greater than 1 cm they are “macroadenomas.” When functional,
most are prolactin secreting (especially in women). Symptoms are easy to pick up in women
(menstrual irregularity, galactorrhea). Men tend to present later because their symptoms are
more vague (decreased libido). On MR, 80% are T1 dark and T2 bright. They take up contrast
more slowly than normal brain parenchyma. Next step = Dynamic contrast enhanced MR.
Sella I Parasella - Adults
Pituitary Adenoma thingsj to know
• Microadenoma under 10 mm,
• Macroadenoma over 10 mm.
m • Microadenomas typically form in the adenohypophysis (anterior 2/3).
• Prolactinoma is the most common functional type.
• Typically they enhance less than normal pituitary.
Sella I Parasella - Adults
Pituitary Apoplexy
Hemorrhage or Infarction o f the pituitary, usually into an enlarged
gland (either from pregnancy or a macroadenoma). Here are the multiple choice trivia
association: taking bromocriptine (or other prolactin drugs), “Sheehan Syndrome” in
postpartum woman, Cerebral Angiography. They will be T1 bright (remember adenoma is
usually T1 dark). Supposedly this is an emergent finding because the lack o f hormones can
cause hypotension.
Sella I Parasella - Adults
Rathke Cleft Cyst
Usually an incidental finding. Rarely symptomatic. The “cleft” is
between the anterior and posterior pituitary. They are variable on T1 and T2, but are usually
very bright on T2. They do NOT enhance
Sella I Parasella - Adults
Epidermoid
Discussed on page 80. Remember these guys restrict diffusion.
I say “Midline Suprasellar Mass that Restricts Diffusion ”, You say Epidermoid.
Sella I Parasella - Adults
Craniopharyngioma
They come in two flavors: (a) Papillary - 10% and (b)
Adamantinomatous - 90%. The Papillary type is the adult type (Papi for Pappi). They are solid
and do not have calcifications. They recur less frequently than the Adamantinomatous form
(because they are encapsulated). They strongly enhance. The relationship to the optic chiasm is
key for surgery. These things occur along the infundibulum. Pediatric type is discussed below
(under on the next page with the peds tumors).
Sella I Parasella - Peds
Craniopharyngioma
As stated above, they
come in two flavors: (a) Papillary and
(b) Adamantinomatous. The kid type is the
Adamantinomatous form. These guys are calcified
(papillary is not). These guys recur more (Papillary
does less - because it has a capsule).
Sella I Parasella - Peds
Craniopharyngioma buzzword
“machinery oil. “
Sella I Parasella - Peds
Craniopharyngioma imaging
- Tl Bright
- T2 Bright
- CT / GRE = Calcifications
- Enhance Strongly (in the solid parts)
Sella I Parasella - Peds
Hypo tha lamic Hamar toma
A classic Aunt
Minnie. This is a hamartoma o f the tuber cinereum (part
o f the hypothalamus located between the mammillary
bodies and the optic chiasm). The location is the key
Sella I Parasella - Peds
imaging
Tl Iso
T2 Iso
Do NOT enhance.
Sella I Parasella - Peds
Hypo tha lamic Hamar toma classic history
The Classic History is Gelastic Seizures
although precocious puberty’ is actually more common
Pineal Region
There are 3 main characters here, all o f which can present
with “vertical gaze palsy” (dorsal Parinaud syndrome).
Pineal Region
G e rm in om a :
The most common o f the 3, and seen
almost exclusively in boys (Germinomas in the suprasellar
region are usually in girls). Precocious puberty may occur
from secretion o f hCG. Characteristic findings are a mass
containing fat and calcification with variable contrast
enhancement. It is heterogeneous on T1 and T2 (because
o f its mixed components).
Pineal Region
G e rm in om a : quick
“Engulfed” Calcification Pattern
Pineal Region
P in eo b la s tom a
Does occur in childhood. Unlike the
pineocytoma, these guys are highly invasive. Some people
like to think o f these as PNETs in the pineal gland. They
are associated with retinoblastoma (“trilateral” ). They”
are heterogeneous and enhance vividly.
Pineal Region
Pineoblastoma & Pineocytoma quick
“Expanded’’ Calcification Pattern
Pineal Region
P in eo c y tom a
Rare in childhood. Well-circumscribed,
and non-invasive. Tend to be more solid, and the solid
components do typically enhance.
Pineal Region
P in e a l Cys t
An incidental findings that is
meaningless… although frequently obsessed over. They can
have thin enhancement. Calcifications occur in 25%.
Pineal Region
P in e a l Cys t quick
Classically— looks like a cyst
A Few Extra Tips op Characterization
“Restriction”
If they show a supratentorial case with restriction it’s likely to be one o f two things
(1) Abscess or (2) Lymphoma. Technically any hypercellular tumor can restrict
(GBM & Medulloblastoma), but lymphoma is the one they classically show restricting.
If it’s a CP angle case, then it’s an Epidermoid.
Lastly, a dirty move could be to show Herpes encephalitis restricting in the temporal horns.
A Few Extra Tips op Characterization
“Midline Crossing”
If they show it crossing the midline, it’s most likely going to be a GBM or Lymphoma.
Alternative sneaky things they could show doing this would be radiation necrosis, a big
MS plaque in the coipus callosum, or Meningioma o f the falx simulating a midline cross.
A Few Extra Tips op Characterization
“Calcification”
If they show it in the brain it is probably an Oligodendroglioma. The trick is that
Oligodendrogliomas calcify 90% o f the time by CT (and 100% by histopathology),
whereas astrocytomas only calcify 20% o f the time. But astrocytoma is very common and
oligodendroglioma is not. So in other words, in real life it’s probably still an astrocytoma.
A Few Extra Tips op Characterization
“T1 Bright”
Most tumors are T l dark (or intermediate).
Exceptions might include a tumor that has bled
(Pituitary apoplexy or hemorrhagic mets).
Hemorrhagic mets are classically seen on MR and
CT (Melanoma, Renal, Carcinoid /
Choriocarcinoma, Thyroid). Tumors with fat will
also be Tl bright (Lipoma, Dermoid). Melanin is
Tl bright (Melanoma). Lastly think about
cholesterol in a colloid cyst.
A Few Extra Tips op Characterization
“T1 Bright” quick
Fat: Dermoid, Lipoma
Melanin: Melanoma
Blood: Bleeding Met or Tumor
Cholesterol: Colloid Cyst
Special Topics - Syndromes
NF-1
Optic Nerve Gliomas
Special Topics - Syndromes
NF-2
MSME: Multiple Schwannomas, Meningiomas, Ependymomas
Special Topics - Syndromes
VHL
Hemangioblastoma (brain and retina)
Special Topics - Syndromes
TS
Subependymal Giant Cell Astrocytoma, Cortical Tubers
Special Topics - Syndromes
Nevoid Basal Cell
Syndrome (Gorlin)
Medulloblastoma
Special Topics - Syndromes
Turcot
GBM, Medulloblastoma, Intestinal Polyposis
Special Topics - Syndromes
Cowdens- “COLD”
Lhermitte-Duclos (Dysplastic Cerebellar Gangliocytoma)
MSME
If you see tumors EVERYWHERE then you are
dealing with NF-2. Ironically there are no
neurofibromas in neurofibromatosis type 2 (obviously
that would make a great distractor).
Just remember MSME
Multiple Schwannomas,
Meningiomas.
Ependymomas
L h e rm itte -D u c lo s (Dysplastic Cerebellar Gangliocytoma)
This thing is very uncommon, but when you see it you need to have the following thoughts:
- Hey! That is Lhermittc Dulcos….
- I guess she has Cowdcns syndrome….
- I guess she has breast CA
Next Step? - Mammogram
The appearance is classic, with a “tiger stripe” mass, typically
contained in one cerebellar hemisphere (occasionally crosses
the vermis). It’s not a “cancer”, but actually a hamartoma -
which makes sense since Cowdens is a hamartoma syndrome.
Brain Tumors - MRS Pearls
As cell walls get broken down NAA (a maker for neuronal viability) will go down,
Creatine (marker for cellular metabolism) will go down, and Choline (a maker for cell
membrane turnover) will go up. This is why the ratios o f NAA/Cho, Cho/Cr and NAA/Cr
get throw around.
Brain Tumors - MRS Pearls
Other relevant marker changes:
• Lactate may go up. You see this in the scenario o f a high grade tumor outgrowing its
blood supply and changing over to anaerobic pathways.
• Lipids may go up. You see this in the scenario o f a necrotic tumor. Lipids are associated
with necrosis.
• Alanine - is associated with meningiomas.
• NAA - This is a glioma maker. Non gliomas tend to have little or no NAA.
Brain Tumors - MRS Pearls
um o r Grade:
Higher Grade Tumors will have more cellular destruction, inflammation, and more ischemia / necrosis. Higher Grade Will Have: Less NAA Less Creatine More Lactate More Choline More Lipids Relative to a lower grade tumor.
Brain Tumors - MRS Pearls
R e c u rre n t T um o r vs
R ad ia tio n N e c ro s is
Recurrent Tumor: Rising choline infers that cell walls are being turned over (something is growing). Mo Choline, Mo Problems Radiation Necrosis: When you think necrosis you should think elevated lipids (found in necrotic tissue) and elevated lactate. You could also reason that NAA, Creatinine, and Choline (makers o f cell integrity, metabolism, and turnover) would also be low - if the tissue in that region was fried like chicken (or bananas - if you enjoy denying your true nature as the apex predator)
Brain Tumors - MRS Pearls
GBM vs Met:
Both can look gnarly on conventional MR (big enhancing tumor). The GBM is classically underestimated on brain MRI (if you are ju st looking at the solid enhancing tumor). The surround T2 edema often contains infiltrative mircotumor. By using a multiple voxel analysis (looking at the tumor, and also surrounding tissue) MRS supposedly adds value (allegedly). For the puipose o f multiple choice, elevated Choline in the T2 signal surrounding the tumor = infiltrating glioma (rather than a met)
Brain Tumors - MRS Pearls
Voxel Selection
It is important to choose an area o f interest with enhancing tumor (avoid
cystic parts o f the tumor, calcifications, blood, or frank necrosis).
Neonatal Infections
Wc are talking about TORCH infections. The first critical thing is that they only really matter in
the first two trimesters (doesn’t cause as much harm in the third trimester). Calcifications and
microcephaly are basically present in all o f them.
Neonatal Infections
CMV Trivia
Most Common TORCH (3x more common than Toxo - which is the second most common).
Neonatal Infections
CMV Classic Look
It prefers to target the germinal matrix
resulting in periventricular tissue necrosis.
The result is the most likely test question =
Periventricular calcifications.
Of the TORCHs CMV has the highest
association with polymicrogyria.
Neonatal Infections
CMV Highest Yield Trivia
Most Common TORCH Periventricular Calcifications Polymicrogyria
Neonatal Infections
Toxoplasmosis Trivia
This is the
second most
common
TORCH.
Neonatal Infections
Toxoplasmosis Classic Look
The calcification pattern is more random,
and targets the basal ganglia (like most
other TORCH infections).
The frequency is increased in the 3rd
trimester (but only causes a problem in the
first two).
Associated with Hydrocephalus
Neonatal Infections
Toxoplasmosis Highest Yield Trivia
Hydrocephalus,
Basal Ganglia
Calcifications
Neonatal Infections
Rubella Trivia
Less common
because of
vaccines
Neonatal Infections
Rubella Classic Look
Calcifications are less common than in other TORCHs. Focal high T2 signal might be seen in white matter (related to vasculopathy and ischemic injury).
Neonatal Infections
Rubella Highest Yield Trivia
Ischemia.
High T2 signal
Fewer
Calcifications
Neonatal Infections
HSV Trivia
It’s HSV-2 in
90% of cases
Neonatal Infections
HSV Classic Look
Unlike adults, the virus does not primarily
target the limbic system but instead prefers
the endothelial cells resulting in thrombus
and hemorrhagic infarction with
resulting encephalomalacia and atrophy
Neonatal Infections
HSV Highest Yield Trivia
Hemorrhagic Infarct, with resulting Bad Encephalomalacia (Hydranencephaly)
Neonatal Infections
HIV Trivia
Not a TORCH but does occur during pregnancy, at delivery, or via breast feeding.
Neonatal Infections
HIV Classic Look
You may have faint basal ganglia enhancement seen on CT and MRI preceding the appearance of basal ganglia calcification. Brain atrophy pattern favors the Frontal Lobes
Neonatal Infections
HIV Highest Yield Trivia
Brain Atrophy,
predominantly in
the Frontal Lobes
Infections of the Immunosuppressed
The most common opportunistic infection in patients with AIDS is
toxo. The most common fungal infection (in people with AIDS) is .
Cryptococcus. Two other infections worth talking about are JC .
Virus, and CMV.
Infections of the Immunosuppressed
Gamesmanship
nipple rings = aids
from south africa = aids
Infections of the Immunosuppressed
HIV Encephalitis
The encephalitis that people with AIDS get. This is actually pretty common and affects about 50% of AIDS patients.
We are talking about a
situation with a CD4 < 200.
These tend to spare the
subcortical U-Fibers (PML
will involve them).
Infections of the Immunosuppressed
HIV Encephalitis imaging
Symmetric increased T2 / FLAIR signal in the deep white matter. T1 will be normal. The lesions will not enhance. There may be associated brain atrophy.
Infections of the Immunosuppressed
Progressive Multifoca l Leukoencephalopathy (PML):
Caused by the JC virus. We are talking about a
situation with a CD4 < 50
Will involve
subcortical U-fibers
Infections of the Immunosuppressed
Progressive Multifoca l Leukoencephalopathy (PML): imaging
CT will show single or multiple scattered Hypodensitics, with corresponding T1 hypointensity (remember HIV was T1 normal), T2/FLAIR hyperintensities out of proportion to mass effect - buzzword
Infections of the Immunosuppressed
C M V
Think about brain atrophy, periventricular
hypodensities (that are T2/FLAIR bright), and thin
ependymal enhancement
Infections of the Immunosuppressed
C ry p to co c cu s
The most common fungal infection in AIDS. The most common
presentation is meningitis that involves the base o f the brain (leptomeningeal enhancement).
The most likely way this will be shown on a multiple choice exam is dilated perivascular
spaces filled with mucoid gelatinous crap (these will not enhance). The second most likely
way this will be shown is lesions in the basal ganglia “cryptococcomas” - these are T1 dark,
T2 bright, and may ring enhance.
Ependymal cells
Ependymal cells are the cells that line
the ventricles and central portion o f
the spinal cord.
Infections of the Immunosuppressed
toxo
Most common opportunistic infection in AIDS. Classically we are talking about T1
dark, T2 bright, ring enhancing (when larger than 1 cm) lesions. These guys will NOT show
restricted diffusion. Just think “ ring enhancing lesion, with LOTS o f edema
Infections of the Immunosuppressed
toxo high yeild trivia
Toxo is Thallium Cold, and Lymphoma is Thallium hot
Infections of the Immunosuppressed
imaging
Tl+C Ring Enhancing T2 Lots of Edema DWI: NO Restriction
WTF ?!
i thought abscesses
restrict diffusion
Typical they do. However, atypical infections like Toxo or fungal don’t always follow this rule
THIS vs THAT
toxo and lymphoma
toxo: Ring Enhancing Hemorrhage more common after treatment Thallium Cold PET Cold (acts like necrosis) MR Perfusion: Decreased CBV
Lymphoma: Ring Enhancing Hemorrhage less common after treatment Thallium HOT PET Hot (acts like a tumor) MR Perfusion: Increased (or Decreased) CBV
Infections of the Immunosuppressed quick
AIDS
Encephalitis
Symmetric T2
Bright
Spare U Fibers
Infections of the Immunosuppressed quick
PML
Asymmetric T2
Bright
t1 daark
involve u fibers
Infections of the Immunosuppressed quick
CMV
periventricular t2 birght
thin pendymal nhancement
Infections of the Immunosuppressed quick
toxo
ring enhancement plus lots of edema
no restricted diffusion
thallium cold
Infections of the Immunosuppressed quick
cryptoccis
dilated perivascular spaces
basila meningitis
TB M en in g itis
Has a predilection for the basal cisterns
(enhancement o f the basilar meninges
with minimal nodularity).
May have dystrophic calcifications.
Enhancement o f the Basilar Meninges + Hydrocephalus = TB
*Sarcoid can have a nearly identical appearance.
If it looks like TB - but that isn ’t a choice, it’s probably Sarcoid
TB M en in g itis
complications
Complications include vasculitis which may
result in infarct (more common in children).
Obstructive hydrocephalus is common
HSV - “Herpes” or “The Dirty Herp
HSV 1 in adults and HSV 2 in neonates. I mention that because (1) It seems like testable trivia and (2) They actually have different imaging appearances (as previously mentioned, type 1 prefers the limbic system).
HSV - “Herpes” or “The Dirty Herp
imaging
Earliest Sign = Restricted Diffusion - related to vasogenic edema. This could be tested by asking “What sequence is more sensitive? ”, with the answer being that diffusion is more sensitive than T2. Blooming on gradient means it’s bleeding (common in adults, rare in neonate form).
HSV - “Herpes” or “The Dirty Herp
THIS vs THAT:
HSV spares the
basal ganglia
(distinguishes it
from MCA stroke).
HSV - “Herpes” or “The Dirty Herp”
quick
For the purpose of a multiple choice test think swollen T2 bright (unilateral or bilateral) medial temporal lobe.
Lim b ic E n c e p h a litis :
Not an infection, but a commonly tested mimic. It is a paraneoplastic syndrome (usually small cell lung cancer), that looks very similar to HSV. This could be asked by showing a classic HSV image, but then saying the HSV titer is negative. The second order question would be to ask for lung cancer screening.
W e s t Nile
Several viruses characteristically involve the
basal ganglia (Japanese Encephalitis, Murray
Valley Fever, West Nile…), the only one
realistically testable is West Nile
W e s t Nile
classic look
Classic Look: T2 bright basal ganglia and
thalamus, with corresponding restricted
diffusion. Hemorrhage is sometimes seen.
CJD: C re u tz fe ld t-J a k o b D is e a s e
The imaging features arc variable
and can be unilateral, bilateral,
symmetric, or asymmetric
CJD: C re u tz fe ld t-J a k o b D is e a s e
random facts
- Characteristic look on EEG the “periodic sharp wave ” (whatever the fuck that is). - “ 14-3-3” protein assay is a CSF test neurologists order.
CJD: C re u tz fe ld t-J a k o b D is e a s e
3 types
- Sporadic (80-90%),
- Variant “Mad Cow” (rare)
- Familial (10%).
CJD: C re u tz fe ld t-J a k o b D is e a s e
dwi
DWI Cortical Gyriform Restricted Diffusion- Supposedly diffusion is the most sensitive sign. & the cortex is the most common early site of manifestation. Basal Ganglia may also be involved
CJD: C re u tz fe ld t-J a k o b D is e a s e
hockey stick sign
- Bilateral FLAIR bright dorsal
medial thalamus - Described in the variant
subtype.
CJD: C re u tz fe ld t-J a k o b D is e a s e
pulvinar sign
- Bilateral FLAIR bright
pulvinar thalamic nuclei
(posterior thalamus). - Classic in the variant subtype
CJD: C re u tz fe ld t-J a k o b D is e a s e
another way to show
Another way to show this (which would be more work for the test writer - and is therefore less
likely) would be a series of MRs or CTs showing rapidly progressive atrophy.
N e u ro c y s tic e rc o s is
Caused by eating pig shit (or undercooked pork).
The bug is tinea solium (pork tapeworm).
Trivia: Involvement of the basal cisterns carries the
worst outcome.
N e u ro c y s tic e rc o s is
Most common locations (in descending order):
1- Subarachnoid over the cerebral hemispheres,
2- Basal cisterns,
3- Brain parenchyma,
4- Ventricles
N e u ro c y s tic e rc o s is
stage 1
Stage I: Vesicular
Cyst + Scolex
No Enhancement
N e u ro c y s tic e rc o s is
stage 2
Stage 2: Colloidal
CT: Hyperdense Cyst
MR: Edema + Enhancement
N e u ro c y s tic e rc o s is
stage 3
Stage 3: Granular CT: Early Calcification MR: Smaller Cysts, Less Edema, Less Enhancement
N e u ro c y s tic e rc o s is
stage 4
Stage 4: Calcified / Involution CT: Calcification MR: Blooming on SWI (T2* etc..)
M e n in g itis and C e re b ra l A b s c es s
You can think of meningitis in 4 main categories:
bacterial (acute pyogenic), viral (lymphocytic), chronic
(TB or Fungal), and non-infectious (sarcoid).
M e n in g itis and C e re b ra l A b s c es s
vocab
Leptomeningeal: Pial +Arachnoid
Pachymeningcal: Dural
M e n in g itis and C e re b ra l A b s c es s
Complications include
Venous thrombosis, Vasospasm (leading to the stroke), Empyema, Ventriculitis, Hydrocephalus, Abscess
M e n in g itis and C e re b ra l A b s c es s
lumpy and thicker
Fungal and Carcinomatous
meningitis tend to be “more lumpy”
and “thicker”
M e n in g itis and C e re b ra l A b s c es s
essentially
Essentially, we are talking about thick leptomeningeal enhancement, in the appropriate clinical setting
This pattern can be seen with Bacterial Meningitis or Carcinomatous Meningitis
M e n in g itis and C e re b ra l A b s c es s
Leptomeningeal (Pia-Arachnoid)
Enhancement
Fills the subarachnoid
spaces & extends into the sulci & cisterns
M e n in g itis and C e re b ra l A b s c es s
trivia
A very testable piece of trivia is that infants will often get
sterile reactive subdurals (much less common in adults).
Abscess Facts (trivia)
- DW1 - Restricts
- MRS - Lactate High
- FDG PET - Increased Metabolic
a ch ym e n in g e a l (D u ra l) E n h a n c em e n t
Key Feature: Enhancement does NOT extend into the sulci
Seen this with lots of stuff: Intracranial Hypotension, Dural attachment of
a Meningioma , Sarcoid, TB, Wegener’s , Fugal Infections.
Both Breast and Prostate Cancer can deposit a solitary dural met.
Secondary CNS Lymphoma is often extra-axial and can be dural based or
fill the subarachnoid space ( “Rim Phoma ”)
Empyema
Can be subdural or epidural (just like blood).
Follows the same rules as far as crossing dural
attachments (epidurals don’t) and crossing the
falx (subdurals don’t).
Subdurals are more common and have more
complications relative to epidurals.
The vast majority of subdurals are the sequela of
frontal sinusitis. The same is true of epidurals
with some sources claiming 2/3 of epidurals are
secondary to sinusitis.
empyema classic look
T1 bright and restrict diffusion.
Tl+C
Subdural Empyema
Dural Enhancement
Intraaxial Infections
Abscess
A cerebral abscess is a cavity that contains pus, debris, and necrotic tissue. These can
develop secondary to to bacterial, fungal, or parasitic infection - most commonly via
hematogenous spread. For the purpose of multiple choice, remember to think about right-to-left
shunts and pulmonary AVMs. Direct spread (example = sinus) is possible, but just less common
because of the dura.
Intraaxial Infections
Abscess ct
Focal area of low density with surrounding low density vasogenic edema.
Intraaxial Infections
Abscess t1+c
Smooth Ring
Enhancement with
Multiple Lesions -
Suggests Abscesses
Intraaxial Infections
Abscess t2
Multiple Lesions
with Vasogenic Edema
— this is nonspecific
(could be mets)
Intraaxial Infections
Abscess DWI
Typical Abscess (bacteria) will restrict. Remember Atypical (Toxo etc..) doesn’t always restrict
Intraaxial Infections
Cerebritis
is the early form of intra-axial
infection, which can lead to Abscess if not
treated. The typical look is the vasogenic
edema without the well defined central
enhancing lesion. There may be spotty
restricted diffusion.
Intraaxial Infections
Ventriculitis
Usually the result of a shunt
placement or intrathecal chemo - as discussed
on page 51. The ventricle will enhance and you
can sometimes see ventricular fluid-fluid levels
If septa start to develop you can end up with
obstructive patterns of hydrocephalus.
The intraventricular extension of abscess is a
very serious / ominous “pre-terminal event
Intraaxial Infections
Multiple Rings Mets vs Abscess
The smooth margin suggests Abscess, but
doesn’t exclude mets. The difference is that
tumor usually starts out as a solid enhancing
mass then becomes ring enhancing with
necrosis. Also, Abscesses tend to be smaller
(usually less than 10mm).
Intraaxial Infections
Smooth Ring =
Abscess
Abscess Rings tend to be thicker on the “Oxygen Side” or "Grey Matter Side" of the Brain - and thinner towards the ventricle.
Intraaxial Infections
Irregular Ring
tumor
“Bumpy” or “Shaggy”
inner lip of the ring is
supposed to suggest
necrosis
Intraaxial Infections
Both Tumor & Abscess will have
vasogenic edema
MRl Gamesmanship - Enhancement Patterns
In general, to solve MR puzzles you will need to be able to work through some MR sequences.
The trick is to have a list o f things that are T1 bright, T2 bright, Restrict diffusion, and Enhance.
Plus you should know the basic enhancement patterns (homogenous, heterogenous, ring, and
incomplete ring).
STROKE vs TUMOR vs ABSCESS vs MS Plaque
T2
For the most part, T2 is not super helpful for lesion characterization
- as stroke, tumors, abscess, MS, all have edema.
STROKE vs TUMOR vs ABSCESS vs MS Plaque
DWI
This is helpful only if they follow the classic rules. Out o f those 4 (stroke, tumors, abscess,
MS) the classical diffusion restrictors are: Abscess, and Stroke. Certain hypercellular tumors
(classically lymphoma) can restrict, and demyelinating lesions with acute features can restrict
STROKE vs TUMOR vs ABSCESS vs MS Plaque
Enchancement
In this situation this is probably the most helpful.
Out o f those 4 (Tumor, Abscess. MS, and Stroke) each should have a different pattern.
• Tumor usually heterogeneous or homogenous if high
grade (or none if low grade). Technically ring
enhancement can also be seen with Gliomas, and Mets
(though I expect this is less likely to be shown on multiple
choice).
• Abscess will classically have RING pattern.
• MS will classically have an INCOMPLETE RING pattern.
• Stroke will have cortical ribbon (GYRIFORM) type
enhancement in the sub-acute time period (around 1
week).
STROKE vs TUMOR vs ABSCESS vs MS Plaque
Enchancement
how many rings
The number of rings can be a
helpful strategy. A single ring is more likely to be tumor
(around half of mets and 3/4
of gliomas are solitary).
Abscess and MS Lesions are
almost always (like 75-85%)
multiple.
STROKE vs TUMOR vs ABSCESS vs MS Plaque
Enchancement
heterogenous
-Most likely Tumor
higher grade
STROKE vs TUMOR vs ABSCESS vs MS Plaque
Enchancement
ring
-Can be lots of
stuff: Abscess and
Tumor are both
prime suspects
STROKE vs TUMOR vs ABSCESS vs MS Plaque
Enchancement
incomplete ring
-Can be lots of
stuff: Abscess and
Tumor are both
prime suspects
STROKE vs TUMOR vs ABSCESS vs MS Plaque
Enchancement
gyriform
-Classic for subacute stroke (can also be seen with P R E S or encephalopathy / encephalitis)
Parenchymal Contusion
The rough part of the skull base ean scrape the brain as it slides
around in a high speed MVA. Typical locations include the anterior temporal lobes and inferior frontal
lobes. The concept of coup (site of direct injury) and contre-coup (opposite side of brain along vector
of force). Contusion can look like blood with associated edema in the expected regions.
Diffuse Axonal Injury/Shear Injury
There are multiple theories on why this happens
(different density of white and gray matter etc…) they don’t matter for practical purposes or for
multiple choice.
Diffuse Axonal Injury/Shear Injury
Things Worth Knowing
• Initial Head CT is often normal
• Favorite sites of DAI are the posterior corpus callosum, and
GM-WM junction in the frontal and temporal lobes
• Multiple small T2 bright foci on MRI
Diffuse Axonal Injury/Shear Injury
DAI Grading
Grade 1 = Grey-White Interface
Grade 2 = Corpus Callosum
Grade 3 = Brainstem
Subarachnoid Hemorrhage
Trauma is the most common cause. FLAIR is the most
sensitive sequence. This is discussed in more later in the chapter.
THIS vs THAT: Subdural v s Epidural
Epidura l
Classic History:
Trauma Patient - with a
skull fracture
“Bi-convex” or
Lenticular
can cross micline
cannot cross a suture
usually arterial
can rapidly expand kill you
THIS vs THAT: Subdural v s Epidural
Sub dural
Classic History: Elderly alcoholic with a shriveled up atrophic brain spent the evening with a bottle of “Rotgut - Hobo Tranquilizer” brand whiskey, then fell over stretching & tearing his cortical bridging veins. A week later he seems to be acting progressively more confused.
“Bi-concave”
Does not cross the midline, may extend
into interhemispheric fissure
Can cross a suture
Usually venous
More mass effect than expected for size
Subdural quick
- Crescent Shape -No Respect For the Sutures
epidural quick
- Lentiform Shape -Skull Fracture -Respect for the Sutures
How Old is that Blood
CT
This is an extremely high yield topic. Maybe the most high yield topic in all o f neuro,
with regard to multiple choice. The question can be asked with CT or MRI (MRI more
likely). If they do ask the question with CT it’s most likely to be the subacute subdural that is
isointense to brain, with loss o f sulci along the margins. They could also show the “swirl
sign” - see below.
Blood on CT
Flyperacute Acute (< 1 hour)
Hypodense
Blood on CT
Acute (1 hour - 3 days)
Hypodense
Blood on CT
Subacute (4 days - 3 weeks)
Progressively less dense, eventually becoming
isodense to brain. Peripheral rim enhancement
may occur with contrast.
Blood on CT
Chronic (> 3 weeks)
Hypodense
Sw irl Sign
This is an ominous sign o f active
bleeding. The central low attenuation blood
represents hyper-acute non-clotted blood, with
surrounding acute clotted blood.
Blood Age V ia MR
MRI is more difficult to remember. Some people use the mnemonic “IB, ID, BD, BB, DD” or “ It Be Iddy Biddy, BaBy, Doo-Doo” which I find very irritating. I prefer mnemonics that employ known words (just my opinion). Another one with actual words is “George Washington Bridge” For T1 (Gray, White, Black), and Oreo Cookie for T2 (Black, White, Black).
Blood Age V ia MR (c o n tin u e d ):
Another strategy (which is somewhat unconventional) is to actually try and understand the
MRI changes (I strongly discourage this). If you insist on trying to understand this I have a 40
min lecture on TitanRadiology.com explaining it (this lecture is also free on my YouTube
Channel — google “Prometheus Lionhart Blood Age”).
Blood Age V ia MR
Hyperacute
24 hours
Oxyhemoglobin, Intracellular
T l- Iso, T2 Bright
Blood Age V ia MR
acute
1 -3 days
Deoxyhemoglobin, Intracellular
T1 - Iso, T2 Dark
Blood Age V ia MR
Early Subacute
> 3 days
Methemoglobin, Intracellular
Tl Bright, T2 Dark
Blood Age V ia MR
Late Subacute
> 7 days
Methemoglobin, Extracellular
Tl Bright, T2 Bright
Blood Age V ia MR
Chronic
> 14 days
Ferritin and Hemosiderin, Extracellular
T1/T2 Dark Peripherally,
Center may be T2 bright
Atraumatic Subarachnoid Hemorrhage
Yes, the most common cause is trauma. A common point
o f trivia is that the most sensitive sequence on MRI for
acute SAH is FLAIR (because it wo n ’t suppress out -
making it hyperintense). Be aware that supplemental
oxygen (usually 50-100%) can give you a fake out that
looks like SAH on FLAIR.
Sequela of SAH
(1) Hydrocephalus - Early
(2) Vasospasm - 7-10 days
(3) Superficial Siderosis - Late
When the blood is real, in the absence o f trauma, there are a few other things to think about
Aneurysm
Benign Non-Aneurysm Perimesencephalic hemorrhage
Superficial Siderosis
Benign Non-Aneurysm Perimesencephalic hemorrhage
This is a well described entity (although not well
understood). This is NOT associated with aneurysm
(usually - 95%), and may be associated with a venous
bleed. *You have to prove that - you need a negative CTA.
The location o f the blood - around the midbrain and pons
without extension into the lateral Sylvian cisterns or
interhemispheric fissures is classic. Just think anterior to
the brainstem. Re-bleeding and ischemia are rare- and
they do extremely well
Superficial Siderosis
This is a si^e effect o f repeated episodes o f SAH. I like to think about this as “staining the surface o f the brain with hemosiderin. ” The classic look is curvilinear low signal on gradient coating the surface of the brain. The classic history is sensorineural hearing loss and ataxia.
P s eu d o -S u b a ra ch n o id H em o rrh a g e
This is a described mimic of SAH that is seen in
the setting of diffuse cerebral edema (most
commonly anoxic brain injury). Near
drowning, or suicide attempt by hanging would
be classic clinical vignettes
P s eu d o -S u b a ra ch n o id H em o rrh a g e
qwhat youre actually seeing
What you are seeing is actually two things at
once. (1) You are seeing diffuse edema which
lowers the attenuation of the brain (makes it
darker). (2) You are seeing compression and
collapse of the sub arachnoid spaces which
gives them a hyper dense appearance. The
combination of these factors gives the
suggestions of hyper density in the cerebral
sulci, fissures, and cisterns which can mimic
SAH (hence the name).
THIS vs THAT: Pseudo SAH vs Real SAH
If they give you history that should help (anoxic brain
injury vs headache / trauma). The absence of any intraventricular bleeding can suggest pseudo SAH.
Lastly density of the Pseudo SAH will be less than 40. Acute blood tends to be around 60-70 HU.
Intraparenchymal Hemorrhage
Hypertensive Hemorrhage
Amyloid Angiopathy
Septic Emboli
Other Random Causes
Hypertensive Hemorrhage
Common locations arc the basal ganglia, pons, and cerebellum.
For the purpose of multiple choice tests, the basal ganglia is the most common location
(specifically the putamen). You typically have intraventricular extension of blood.
Amyloid Angiopathy
History of an old dialysis patient (or some other history to think
Amyloid). The classic look is multiple lobes at different ages with scattered microbleeds on
gradient.
Septic Emboli
These are seen in certain clinical scenarios (IV drug user, organ transplant,
cyanotic heart disease, AIDS patients, people with lung AVMs). The classic look is
numerous small foci of restricted diffusion. Septic emboli to the brain result in abscess
and mycotic aneurysms (most commonly in the distal MCAs), The location favors the
gray-white interface and the basal ganglia. There will be surrounding edema around the tiny
abscesses. The classic scenario should be parenchymal bleed in a patient with infection.
Other Random Causes of intraparenchymal hemorrhage
These would include AVMs, vasculitis, brain tumors (primary and
mets) - these are discussed in greater detail in various sections of the text
Intraventricular Hemorrhage
Not as exciting. Just think about trauma, tumor, hypertension, AVMs, and aneurysms - all
the usual players.
Epidural I Subdural Hemorrhage
Obviously these are usually post-traumatic.
Dural AVFs and High Flow AVMs can bleed causing subdurals / subarachnoid hemorrhage.
These are discussed further later in the chapter.
Stroke
Stroke is a high yield topic. You can broadly categorize stroke into ischemic (80%) and
hemorrhagic (20%). It’s critical to remember that stroke is a clinical diagnosis and that imaging
findings compliment the diagnosis (and help exclude clinical mimic o f stroke - tumor etc..).
Stroke
Vascular Territories
Below is a diagram showing the various vascular territories. The junction
between these zones is sometimes referred to as a “watershed’. These areas are prone to ischemic
injury, especially in the setting o f hypotension or low oxygen states (near drowning or Roger
Gracie’s mounted cross choke or a Marcello Garcia high elbow guillotine).
aca mca pca lenticulostriate anterior choroidal
Watershed Ischemia
favors the border zones o f different vascular territories (just like the bowel). Border Zone Between AC A and MCA The classic clinical scenario for watershed infarcts would be severe hypotension (shock / CPR / E tc ..), severe carotid stenosis, or a 2009 IBFFJ worlds match up with Roger Gracic.
looks up borders betweent he aca, mca, and pca
Watershed Ischemia
gamesmanship
Watershed Infarcts
in a Kid = Moyamoya (Idiopathic
supraclinoid ICA vasculo-occlusive
disease)
Subacute Infarct
Unique that it Enhances but creates NO Mass Effect
Stroke Imaging S ign s on CT
Dense MCA Sign Insular Ribbon Sign Loss of GM-WM differentiation Mass Effect Enhancement
Stroke Imaging S ign s on CT
Dense MCA SigDn
Intraluminal thrombus is dense, usually in the M1 and/or M2 segments
Stroke Imaging S ign s on CT
Insular Ribbon Sign
Loss of normal high density insular cortex from cytotoxic edema
Stroke Imaging S ign s on CT
Loss of GM-WM
differentiation
Basal Ganglia / Internal Capsular Region and Subcortical regions
Stroke Imaging S ign s on CT
Mass Effect
Peaks at 3-5 days
Stroke Imaging S ign s on CT
Enhancement
Rule of 3s: Starts in 3 days, peaks in 3 weeks, gone by 3 months.
Fogging
This is a phase in the evolution of stroke when the infarcted
brain looks like normal tissue. This is seen around 2-3 weeks
post infarct, as the edema improves.
“Fogging” is classically
described with
non-contrast CT, but T2 MRI sequences have a similar effect (typically occurring around day 10). In the real world, you could give IV contrast to demarcate the area of infarct or just understand that fogging occurs.
Artery of Percheron Stroke
Classic V Shaped bilateral infarct o f the paramedian thalami.
This can only occur in the setting of the Artery o f Percheron
vascular variant. This variant is characterized by a solitary trunk
originating from one of the two PCAs to feed the rostral midbrain
and both thalami (normally there are several bilateral paramedic
arteries originating from the PCAs).
Recurrent Artery of
Heubner Stroke
Classic Caudate Infarct The Artery of H is a deep branch off the proximal AC A This thing can get “bagged” during the clipping of ACOM artery aneurysm.
Cardioembolic Stroke:Cardioembolic Stroke:
This has the classic pattern of multiple foci of restricted diffusion scattered bilaterally along multiple vascular territories. The clinical history is usually A-Fib or endocarditis.
Fetal PCOM Stroke Pattern
This pattern demonstrates infarcts in both the anterior and posterior circulation of the same hemisphere. This pattern is possible as the variant anatomy with the PCA feeds primarily from the ICA.
Not Everything That Restricts
is a Stroke
Bacterial Abscess, CJD (cortical), Herpes,
Epidermoids, Hypercellular Brain Tumors
(Classic is lymphoma), Acute MS lesions,
Oxyhemoglobin, and Post Ictal States. Also
artifacts (susceptibility and T2 shine through).
stroke restricted diffusion
Acute infarcts usually arc bright from about 30
mins after the stroke to about 2 weeks.
Restricted diffusion without bright signal on
FLAIR should make you think
hyperacute (< 6 hours).
Stroke enhancement
The rule of 3’s is still useful. Starts day 3, peaks ~ 3 weeks, gone by 3 months
Stroke enhancement
Diffusion
0-6 hours 6-24 hours 24 hours -1 week
Bright Bright Bright
Stroke enhancement
FLAIR
0-6 hours 6-24 hours 24 hours -1 week
NOT BRIGHT Bright Bright
Stroke enhancement
T1
0-6 hours 6-24 hours 24 hours -1 week
Iso Dark Dark, with Bright Cortical Necrosis
Stroke enhancement
T2
0-6 hours 6-24 hours 24 hours -1 week
Iso Bright Bright
H em o rrh a g ic T ra n s fo rm a tio n :
This occurs in about 50% of infarcts, with the typical time period
between 6 hours and 4 days. If you got TPA it’s usually within 24
hours of treatment.
People break these into (1) tiny specs in the gray matter called
“petechial” which is the majority (90%) and (2) full on hematoma
- about 10%.
H em o rrh a g ic T ra n s fo rm a tio n
Who gets it
People on anticoagulation, people who get TPA,
people with embolic strokes (especially large ones), people with
venous infarcts.
Venous Infarct
Not all infarcts are arterial, you can also stroke secondary to venous occlusion (usually the sequelae
of dural venous sinus thrombosis or deep cerebral vein thrombosis). In general, venous infarcts arc at
higher risk for hemorrhagic transformation. In little babies think dehydration, in older children think
about mastoiditis, in adults think about coagulopathies (protein C & S dcf) and oral contraceptives.
The most common site of thrombosis is the superior sagittal sinus, with associated infarct occurring
75% of the time
Venous thrombosis signs
Venous thrombosis can present as a dense sinus (on non-contrast CT) or “empty delta” (on contrast
enhanced CT). Venous infarcts tend to have heterogeneous restricted diffusion. Venous thrombosis
can result in vasogenic edema that eventually progresses to stroke and cytotoxic edema.
Arterial stroke
Cytotoxic Edema
Venous Stroke
Vasogenic Edema + Cytotoxic Edema
Stigmata of chronic venous thrombosis
the development of a dural AVF, and/or
increased CSF pressure from impaired drainage.
ASPECTS
Alberta Stroke Program Earty CT Score)
ASPECTS
overview
This was developed to give “providers” a more specific guideline for giving TPA - as an
alternative to the previous 1/3 vascular territory rule. The idea being that the greater the vascular
territory involved, the worse the clinical outcome (post TPA bleed etc..).
The way this works is that you start out with 10 points, and lose points based on findings of acute
cytotoxic ischemia to various locations (example: minus 1 for caudate, or lentiform nucleus, or
insular ribbon, etc.. etc.. so on and so forth).
ASPECTS
testable pearls
• This is for MCA ONLY (not other vascular territories)
• This is for ACUTE ischemia (don’t subtract points for chronic lacunar infarcts etc..)
• A score of 8 or greater has a better chance of a good outcome (score of 7 or less may
contraindicate TPA — depending on the institutional policy.
CT Perfusion - Crash Course
After an arterial occlusion perfusion pressure is going to be rapidly reduced. Millions of neurons will
suddenly cry out in terror then suddenly silenced, unless they are lucky to have arteriolar dilation with
capillary recruitment to bring in as much blood to that area of brain as possible. This process is called
physiologic auto-regulation and should result in an increase in capillary blood pool. The key point is
that you need live neurons (penumbra) to cry out for help. If they cry out and are suddenly silenced
(infarct core) you won’t see any auto regulation attempts. This physiology makes up the basis of
perfusion for stroke.
CT Perfusion - Crash Course
parameters
• Cerebral Blood Flow (CBF): Represents instantaneous capillary flow in tissue.
• Cerebral Blood Volume (CBV): Describes the blood volume of the cerebral capillaries and venules
per cerebral tissue volume.
• Mean Transit Time (MIT) = CBV divided by CBF ; it is the average length of time a certain
volume of blood is present in the capillary circulation.
• Time to Peak (TTP): This is the opposite of CBF. Less flow = Longer Time to reach maximum
concentration of contrast.
The primary role of perfusion is to distinguish between
salvagable brain (penumbra), and dead brain. The penumbra may benefit from therapy. The dead brain will not- "He s Dead Jim ’’ - Dr. McCoy
Peniumbra
decreased CBF, increased CBV, increased MTT
Infarct core
Decreased CBF (alot), Decreased CBV
Aneurysm
Who gets them
People who smoke, people with
polycystic kidney disease, connective tissue disorders
(Marfans, Ehlers-Danlos), aortic coarctation, NF, FMD,
and AVMs.
Aneurysm
Where do they occur
They occur at branch points (why
do persistent trigeminals get more aneurysms ? -
because they have more branch points). They favor the
anterior circulation (90%) - with the anterior
communicating artery being the most common site.
As a piece of random trivia, the basilar is the most
common posterior circulation location (PICA origin is
the second most common).
Aneurysm
When do they rupture
Rupture risk is increased with
size, a posterior location, history of prior SAH, smoking
history, and female gender.
Aneurysm
Which one did it
A common dilemma is SAFI in the
setting of multiple aneurysms. The things that can help
you are location of the SAH/Clot, location of the
vasospasm, size, and which one is the most irregular
Focal out-pouching - “Murphy s tit ”)
Dolichoectasia of the
Basilar Artery
This refers to a widened elongated twisty appearance of the basilar artery. This is probably the result of chronic hypertension (abnormal vessel remodeling). The height of the bifurcation and the more lateral the position of the vessel (relative to the clivus) the more severe - so says the Smoker criteria.
Dolichoectasia of the
Basilar Artery
complications
Complications include: nothing
(most have no symptoms),
dissection, compression of cranial
nerves (hcmi-facial spasm), stroke
Aneurysm locations
ACA~ 35%
M1/M2
Junction
~ 30%
ICA / PComm Junction ~ 30%
Basilar Tip ~ 3%
PICA - 2%
Saccular (Berry):
The most common type and the most common cause o f nontraumatic SAH. They are commonly seen at bifurcations. The underlying pathology may be a congenital deficiency o f the internal elastic lamina and tunica media (at branch points). Remember that most are idiopathic (with the associations listed above). They arc multiple 15-20% o f the time.
Fusiform Aneurysm
Associated with PAN,
Connective Tissue Disorders, or Syphilis. These
more commonly affect the posterior circulation.
May mimic a CPA mass
Pseudoaneurysm
Think about this with an
irregular (often saccular) arterial out-pouching
at a strange / atypical location. You may see
focal hematoma next to the vessel on noncontrast.
Pseudoaneurysm
traumatic
Often distal secondary to
penetrating trauma or adjacent fracture.
Pseudoaneurysm
mycotic
Often distal (most commonly in the MCA), with the associated history of endocarditis, meningitis, or thrombophlebitis
Blister Aneurysm
This is a sneaky little dude
(the angio is often negative). It’s broad-based
at a non-branch point (supraclinoid ICA is the
most common site).
Infundibular Widening
Not a true
aneurysm, but instead a funnel-shaped
enlargement at the origin o f the Posterior
Communicating Artery at the junction with the
ICA. Thing to know is “not greater than 3
mm. ”
AVM A s s o c ia te d
P e d ic le A n eu ry sm :
Aneurysm associated with an AVM.
The trivia to know is that it’s found on the
artery feeding the AVM (15% of the time).
These may be higher risk to bleed than the
AVM itself (because they are high flow).
Aneurysm Rupture Trivia:
• Aneurysm > 10mm have a 1% risk of rupture per year. • Although controversial, 7 mm is often thrown around as a treatment threshold for anterior circulation aneurysms • In general, posterior circulation aneurysms have a higher rate of rupture per mm in size.
A neury sm S u b typ es S um m a ry
Saccular Branch Points - in the
(Berry) Anterior Circulation
Fusiform Posterior Circulation
Pedicle
Aneurysm
Artery feeding the AVM
Mycotic Distal MCAs
Blister Broad Based Non-Branch Aneurysm Point (Supraclinoid ICA)
M a x im um B le ed in g
- A n e u ry sm L o c a tio n
ACOM Interhemispheric Fissure
PCOM Ipsilateral Basal Cistern
MCA trifurcation
Sylvian fissure
Basilar tip intrapeduncular cistern or intraventricular
PICA
Posterior Fossa or
Intraventricular
H i g h F l o w
A VM
• Most Common Most Common Type of High Flow
• Congenital malformation
• Supratentorial location (Usually)
• Most common complication = bleeding (3% annual)
• Risk increased with: Smaller AVMs (they are under
higher pressure), Small Draining Veins (can’t reduce
pressure), Perinidal Aneurysm, and Basal Ganglia
location
. Symptoms: Headache (#1), Seizure (#2)
H i g h F l o w
A VM
imaging
Arterial Component
Nidus
Draining veins
Adjacent brain may
be gliotic (T2 bright)
and atrophic.
Dural AVF
• Flow Rate is Variable (can be high or low flow)
• SPINAL AVFs are actually the most common type of
AVFs - a helpful hint is the classic clinical history of
“gradual onset LE weakness”
• Risk of Bleeding - increased with direct cortical venous
drainage.
• These aren’t congenital (like AVMs) but instead are
acquired — classically from dural sinus thrombosis
• Symptoms: Tinnitus — especially if the sigmoid sinus
is involved
Dural AVF
imaging
• No Nidus • Can be occult on MR1/MRA - need catheter angio if suspicion high
DVA
• Variation in normal venous drainage
• Resection is a bad idea = venous infarct
• Associated with cavernous malformations.
• They almost never bleed in isolation. If you see
evidence of prior bleeding (blooming on gradient) there
is probably an associated cavernoma.
DVA
Imaging
• “Caput medusa” or “large tree with multiple small branches” - collection of vessels converging towards an enlarged vein (seen on venous phase only). • Can have a halo of T2 bright gliosis
Cavernous
Malformation
(cavernoma, or
cavernous angioma)
• Low Flow - WITHOUT intervening normal tissue
• Can be induced from radiotherapy
• Can ooze some blood, but typically don’t have full-on
catastrophic bleeds. Presence of a “fluid-fluid” level
suggests recent intralesional hemorrhage
• Single or multiple (more common in Hispanics).
• Classic gamesmanship is to show you a nearby DVA
Cavernous
Malformation
(cavernoma, or
cavernous angioma)
imaging
Popcorn like with “Peripheral Rim of
Hemosiderin.”
Best seen on
gradient
Capillary
Telangiectasia
• Low Flow - WITH intervening normal tissue
• Can also be radiation induced
• Usually don’t bleed (thought of as an incidental
finding)
• Classic Look = Single lesion in the Pons
Capillary
Telangiectasia
imaging
• Brush-like” or “Stippled pattern” of enhancement • Best seen on gradient (slow flow and deoxyhemoglobin)
Mixed vascular malformations
• Wastebasket term, most often used for DVA with AV
shunting or DVAs with telangiectasias
Calcification Rapid Review I Summary
Pineal Gland
- Common in adults, Rare in kids. If you see
calcification in a kid under 7, it could suggest underlying neoplasm.
—Germinoma = “Engulfed” Pattern “ 1”
—Pineoblastoma & Pineocvtoma: “Expanded” Pattern “2”
Calcification Rapid Review I Summary
Habenular
Curvilinear structure (solid white arrow) located a few
millimeters anterior to the pineal body (open arrow). About 1 in 5
normal adults will have calcification here. The trivia is an increased
association with schizophrenia
Calcification Rapid Review I Summary
Choroid plexus
Common in adults. Remember there is no choroid
plexus in the frontal/occipital horn of the lateral ventricles or the
cerebral aqueduct.
Calcification Rapid Review I Summary
Dural Calcifications
Common in adults. If the calcs are bulky and
there are a bunch of tooth cysts (Odontogenic keratocysts) think Gorlin
Syndrome.
Calcification Rapid Review I Summary
Basal Ganglia
Very common with age, favors the globus pallidus. If
extensive & symmetrical think Fahr disease
Calcification Rapid Review I Summary
Tuberous Sclerosis
Calcifications of the subependymal
nodules are pathognomonic typically found at the
caudothalamic groove and atrium. You can see calcified
subcortical tubers - more typical in older patients.
Calcification Rapid Review I Summary
Sturge-Weber
Tram
track / double-lined
gyriform pattern parallel to
the cerebral folds.
Tuberous Sclerosis - Calcifications of the subependymal
nodules are pathognomonic typically found at the
caudothalamic groove and atrium. You can see calcified
subcortical tubers - more typical in older patients.
Etiology = subcortical
ischemia secondary to pial
angiomatosis.
Calcification Rapid Review I Summary
Congenital CMV
Periventricular calcifications.
Can also have brain atrophy
Calcification Rapid Review I Summary
Congenital Toxo
Basal Ganglia Calcifications +
Hydrocephalus,
Calcification Rapid Review I Summary
Neurocysticercos
Etiology: Eating Mexican pork
sandwiches -end-stage will have scattered quiescent
calcified cyst remnants.
Calcification Rapid Review I Summary
Cavernoma
Cavernoma
scattered
dots or stippled
“popcorn” calcification
Calcification Rapid Review I Summary
AVM
calcifications in
the tortuous veins or the
nidus
Calcification Rapid Review I Summary
Brain Tumors can calcify. The ones most people talk about are
Old Elephants Age Gracefully
O: Oligodendroglioma - variable, but “ribbon” pattern is most commoon
E: Ependymoma (Medulloblastomas can also calcify - just less often)
A: Astrocytoma
G: Glioblastoma - mural calcified nodule
Even though more Oligodendrogliomas calcify, Astrocytoma is still the
most common calcified tumor (because there are alot more of them).
Craniopharyngioma, Meningioma, Choroid plexus tumors are all known
to calcify as well. Osteosarcoma mets famously calcify.
Vasospasm
Vessels do not like to be bathed in blood (SAH), it makes them freak out (spasm). The
classic timing for this is 4-14 days after SAH (NOT immediately). It usually looks like
smooth, long segments o f stenosis. It typically involves multiple vascular territories. It can
lead to stroke.
Vasospasm
Who gets it?
It’s usually in patients with SAH and the more volume o f SAH the greater the
risk. In 1980 some neurosurgeon came up with this thing called the Fisher Score, which
grades vasospasm risk. The gist o f it is greater than 1 mm in thickness or intraventricular /
parenchymal extension is at higher risk
Vasospasm
Are there Non-SAH causes o f vasospasm?
Yep. Meningitis, PRES, and Migraine Headache.
Vasospasm
Vasospasm is a delayed side effect o f SAH. It does NOT occur
immediately after a bleed. You see it 4-14 days after SAH.
“Crescent Sign”oi Dissection
- it’s the T1 bright intramural blood.
Vascular Dissection
Vascular dissection can occur from a variety
o f etiologies (usually penetrating trauma, or a
trip to the chiropractor). /
Penetrating trauma tends to favor the
carotids, and blunt trauma tends to favor the * * mm
vertebrals.
This would be way too easy to show on CT
as a flap, so if it’s shown it’s much more •
likely to be the T1 bright “crescent sign”, or
intramural hematoma.
Vasculitis
You can have a variety o f causes o f CNS vasculitis. One way to think about it is by clumping it into (a) Primary CNS vasculitis, (b) Secondary CNS vasculitis from infection, or sarcoid, (c) systemic vasculitis with CNS involvement, and (d) CNS vasculitis from a systemic disease
They all pretty much look the same with multiple segmental areas o f vessel narrowing, with alternating dilation (“beaded appearance"). You can have focal areas o f vascular occlusion
PAN is the Most Common systemic vasculitis to involve
the CNS
SLE is the Most Common
Collagen Vascular Disease
Primary CNS Vasculitis
Primary Angiitis o f the CNS (PACNS)
Secondary CNS vasculitis
from infection, or sarcoid
Meningitis (bacterial, TB, Fungal),
Septic, Embolus, Sarcoid,
Systemic vasculitis with
CNS involvement
CNS vasculitis from
PAN, Temporal Arteritis, Wegeners, Takayasu’s,
CNS vasculitis from a
Systemic Disease
Cocaine Use, RA, SLE, Lyme’s
Moyamoya
This poorly understood entity (originally described in Japan - hence the name),
is characterized by progressive non-atherosclerotic stenosis o f the supraclinoid ICA, eventually
leading to occlusion. The progressive stenosis results in an enlargement o f the basal
perforating arteries.
Moyamoya
trivia
Buzzword = “P u ff o f Smoke ” - for angiographic appearance
Watershed Distribution
In a child think sickle cell
Other notable associations include: NF, prior radiation, Downs syndrome
Bi-Modal Age Distribution (early childhood and middle age)
Children Stroke, Adults Bleed
Crossed C e re b e lla r D ia s ch is is (CCD
Depressed blood flow and metabolism affecting the cerebellar hemisphere after a
contralateral supratentorial insult (infarct, tumor resection, radiation).
Creates an Aunt Minnie Appearance
Crossed C e re b e lla r D ia s ch is is (CCD
mechanism/gamesmanship
When I was a medical student, I
had to memorize a bunch o f tiny little tracks and pathways all over
the brain, cerebellum, and spine. It (like many things in medical
school) made me super angry because it was such a colossal waste
o f time. More PhD bullshit, lumped right in with those step 1
‘‘what chromosome is that on ? ” questions.
Crossed C e re b e lla r D ia s ch is is (CCD
corticopontine-cerebellar pathway
Redemption for the PhDs has arrived. Apparently, one o f these
pathways, the “corticopontine-cerebellar pathway,” is actually
important. S orta….
Allegedly, this pathway connects one cerebral hemisphere to the
opposite cerebellar hemisphere. If the pathway gets disrupted (by
tumor, radiation, e tc …), then metabolism shuts down in the
opposite cerebellum even though there is nothing structurally
wrong with it. That is why you get this criss-crossed hypometabolic
appearance on FDG-PET.
The trick is to show you the FDG-PET picture, and try and get
you to say there is a pathology in the cerebellum. There isn ’t! The
cerebellum is normal - the problem is in the opposite cerebrum
where the pathway starts.
NASCET Criteria
The North American
Symptomatic Carotid Endarterectomy Trial
(NASCET) criteria, are used for carotid
stenosis.
The rule is: measure the degree o f stenosis
using the maximum internal carotid artery
stenosis ( “A ”) compared to a parallel (noncurved)
segment o f the distal cervical
internal carotid artery (“B ”).
You then use the formula:
[1- A/B] X 100% = % stenosis
Carotid endarterectomy (CEA) is often performed
for symptomatic patients with > 50% stenosis.
LeFort Fracture
Buzzwords 1
“The Palate
Separated from the Maxilla”
or “Floating Palate
LeFort Fracture
Buzzwords 2
2:“The Maxilla
Separated from the Face” or
“Pyramidal”
LeFort Fracture
Buzzwords 3
“The Face
Separated from the
Cranium”
LeFort Fracture
E s s en tia l E lem en ts
All three fracture types share the pterygoid process fracture. If the
pterygoid process is not involved, you do n ’t have a LeFort. Each has a unique feature (which
lends itself easily to multiple choice).
LeFort Fracture
E s s en tia l E lem en ts 1
- LeFort 1: Lateral Nasal Aperture
LeFort Fracture
E s s en tia l E lem en ts 2
- LeFort 2: Inferior Orbital Rim and Orbital Floor
LeFort Fracture
E s s en tia l E lem en ts 3
- LeFort 3: Zygomatic Arch and Lateral Orbital Rim/Wall
M u co c e le
If you have a fracture that disrupts the frontal sinus outflow tract (usually
nasal-orbital-ethmoid types) you can develop adhesions, which obstruct the sinus and result
in mucocele development. The buzzword is “airless, expanded sinus.” They are usually Tl
bright, with a thin rim o f enhancement (tumors more often have solid enhancement). The
frontal sinus is the most common location - occurring secondary to trauma (as described
above).
CSF L e ak
Fractures o f the facial bones, sinus walls, and anterior skull base can all lead
to CSF leak. The most common fracture site to result in a CSF leak is the anterior skull base.
“Recurrent bacterial meningitis ” is a known association with CSF leak.
T bone fractures
The traditional way to classify these is longitudinal and transverse, and this is almost
certainly how the questions will be written. In the real world that system is old and
worthless, as most fractures are complex with components o f both. The real predictive
finding o f value is violation o f the otic capsule - as described in more modern papers
T bone fractures
longitudinal
Long Axis of T-Bone More Common More Ossicular Dislocation Less Facial Nerve Damage (around 20%) More Conductive Hearing Loss
T bone fractures
transverse
Short Axis of T-Bone Less Common More Vascular Injury (Carotid / Jugular) More Facial Nerve Damage (>30%) More Sensorineural hearing Loss
Th in g s to K n ow A b o u t F a c ia l F ra c tu re s
• Nasal Bone is the most common fracture
• Zygomaticomaxillary Complex Fracture (Tripod) is the most common fracture
pattern, and involves the zygoma, inferior orbit, and lateral orbit.
• Le-Fort Fractures are both a stupid and a high yield topic in facial trauma - for
multiple choice. Floating Palate = 1, Pyramidal = 2, Separated Face = 3
• Transverse vs Longitudinal Temporal Bone Fractures - this classification system
is stupid and outdated since most are mixed and otic capsule violation is a way
better predictive factor… but this is still extremely high yield
TEMPORAL BONE
It would be very easy to get completely carried away with this anatomy and spend the next
20 pages talking about all the little bumps and variants. I’m gonna resist that urge and instead
try and give you some basic framework. Then as we go through the various pathologies I ’ll
try and give “normal” anatomy comparisons and point out some landmarks that are relevant
for pathology. Additionally, I’m gonna do a full anatomy T-Bone talk for RadiologyRonin
this year - so if your really want to understand this deeper, that might be helpful
TEMPORAL BONE
anatomy
At the most basic level you can think about 3
general locations: External, Middle, and Inner
TEMPORAL BONE
anatomy
The External car
is everything superficial to the ear drum (tympanic membrane).
TEMPORAL BONE
anatomy
The Inner ear is everything
deep to the medial
wall of the tympanic cavity.
TEMPORAL BONE
anatomy
The Middle ear is
is everything in-between
TEMPORAL BONE
anatomy
The Epitympanum
also called “the attic” is
basically everything above the tip of the scutum
TEMPORAL BONE
anatomy
The Hypotympanum
is everything below the
tympanic membrane. This is where the
Eustachian tube arises.
TEMPORAL BONE
anatomy
The Mesotympanum
The Mesotympanum is everything in-between
or everything directly behind the ear drum
The scutum
is a “shield” like osseous spur formed
via the lateral wall of the tympanic cavity. This anatomic
land mark is often brought up with discussion of the
erosion pattern of Cholesteatomas.
Cholesteatoma
The simple way to think about this is “a bunch o f exfoliated skin
debris growing in the wrong place.” It creates a big inflammation ball which wrecks the
temporal bone and the ossicles.
There are two parts to the ear drum, a flimsy whimpy part “Pars
Flaccida” , and a tougher part “Pars Tensa.” The flimsy flaccida
is at the top, and the tensa is at the bottom.
If you “acquire” a hole with some
inflammation / infection involving the Pars
Flaccida you can end up with this ball o f
epithelial crap growing and causing
inflammation in the wrong place.
Cholesteatoma
dwi
restrict
Cholesteatoma
Pars Flaccida Type
Acquired Types are more common - typically involving
the pars flaccida. They grow into Prussak’s Space
The Scutum is eroded early (maybe first)- considered
a very specific sign o f acquired cholesteatoma
The Malleus head is displaced medially
The long process o f the incus is the most common
segment o f the ossicular chain to be eroded.
Fistula to the semi-circular canal most commonly
involves the lateral segment
Cholesteatoma
Pars Tensa Type:
•The inner ear structures are involved earlier and more often •This is less common than the Flaccida Type
P ru s s a k ’s S p a c e and S cu tum Erosion
The membrane is usually too thin to see, but it’s right around
there. Remember the flimsy Flacida is at the top and the
thicker Tensa is at the bottom.
There are two white arrows here.
The top arrow is pointing to a space between an ossicle
(incus) and the lateral temporal bone. This is called
“Prussak’s space” and is the most common location of
a Pars Flacida Cholesteatoma. Remember the incus was
the most common ossicle eroded.
The bottom arrow is pointing to a bony shield shaped
bone - “the scutum” which will be the first bone eroded
by a pars flaccida.
L a b y rin th in e F is tu la (p e rilym p h a tic fis tula
This is a potential complication o f
cholesteatoma (or other things - iatrogenic,
trauma, e tc …). What we are talking about here
is a bony defect creating an abnormal
communication between the normally fluid
filled inner ear and normally air filled tympanic
cavity. In the case o f cholesteatoma, the
lateral semicircular canal (arrows) is most
often involved.
L a b y rin th in e F is tu la (p e rilym p h a tic fis tula
classic history
The classic clinical history is “sudden fluctuating sensorineural hearing loss and vertigo.’
L a b y rin th in e F is tu la (p e rilym p h a tic fis tu
CT
On CT, you want to see the soft tissue density o f the cholesteatoma eating through the otic capsule into the semicircular canal. The presence o f air in the semicircular canal (pneumolabyrinth) is definitive evidence o f a fistula (although it’s not often seen in the real world).
Otitis Media (OM)
This is a common childhood disease with effusion and infection of the
middle ear. It’s more common in children and patients with Down Syndrome because of a more
horizontal configuration of the Eustachian tube. It’s defined as chronic if you have fluid persisting for
more than six weeks.
It can look a lot like a cholesteatoma (soft tissue density in the middle cart
Complications of OM
Coalescent
Mastoiditis
Erosion of the mastoid septae with or
without intramastoid abscess
Complications of OM
Facial Nerve
Palsy
Secondary to inflammation of the tympanic segment (more on this later in the chapter). Adjacent inflammation may cause thrombophlebitis or thrombosis of the sinus. This in itself can lead to complications:
Complications of OM
Dural Sinus
Thrombosis
Venous Infarct: This can occur secondary to dural sinus thrombosis
Otitic Hydrocephal us: Lateral sinus thrombosis can alter resorption of CSF and lead to hydrocephalus
Complications of OM
Meningitis,
and
Labyrinthitis
it can happen
L a b y rin th itis O s s ific a n s
• Gamesmanship - “history o f childhood meningitis. ”
• You see it in kids (ages 2-18 months).
• Classic Appearance on CT - Ossification o f the
membranous labyrinth.
• They present with sensorineural hearing loss.
• Calcification in the cochlea is often considered a
contraindication for cochlear implant.
WTF is a “membranous labyrinth ” ?
The world “Labyrinth” most commonly refers to the timeless 1986 science fiction adventure staring David Bowie as Jareth the Mother Fucking Goblin King. Another less popular use o f the word “Labyrinth” is the anatomical blanket term encompassing the Vestibule, Cochlea, and Semicircular Canals. Under the umbrella o f the “Labyrinth” you can have the bony portion (the series o f canals tunneled out o f the tbone), and the membraneous portion (which is basically the soft tissue lining inside the bony part). You can then further divide the “membranous” portion into the cochlear & vestibular labyrinths.
Chronic Otitis
Media
Mastoids:
Middle Ear Opacification:
For the purpose of multiple choice this could be a hing:
Erossions (scutum and ossicular chain):
Displacement of the ossicular chain:
Mastoids: poorlypneumatized
Middle Ear Opacification:Can completely
opacity
For the purpose of multiple choice this could be a hing:Thickened
mucosa
Erossions (scutum and ossicular chain):Rare (< 10%)
Displacement of the ossicular chain:NEVEr
Cholesteatoma
Mastoids:
Middle Ear Opacification:
For the purpose of multiple choice this could be a hing:
Erossions (scutum and ossicular chain):
Displacement of the ossicular chain:
Mastoids:poorlypneumatized
Middle Ear Opacification:Can completely
opacity
For the purpose of multiple choice this could be a hing:Non-
Dependent
Mass
Erossions (scutum and ossicular chain):Common
(75%)
Displacement of the ossicular chain:It can happen
L a b y rin th itis
This is an inflammation o f the
membranous labyrinth, probably most commonly the
result o f a viral respiratory track infection. Acute
otomastoiditis can also spread directly to the inner ear
(this is usually unilateral). Bacterial meningitis can
cause bilateral labyrinthitis.
L a b y rin th itis
classic look
The cochlea and semicircular canals
will be shown enhancing on Tl post contrast imaging.
the F a c ia l N e rv e (CN 7)
segments
• Intracranial (“Cisternal”) segment
• Meatal (“Canalicular”) segment - the part inside the
Internal Auditory Canal “IAC”).
• Labyrinthine segment (LS) - from the IAC to
geniculate ganglion (GG).
• Tympanic segment (TS) - GG to pyramidal eminence
• Mastoid segment (MS) - from pyramidal eminence
to stylomastoid foramen “SMF”
• Extratemporal segment - Distal to the SMF
the F a c ia l N e rv e (CN 7)
enhancement
The facial nerve is unique in that portions of it can enhance normally. The trick is which parts are normal and which parts arc NOT. Normal Enhancement: Tympanic & Mastoid Segments including the Geniculate Ganglia. The Labyrinthine segment can also sometimes. No normal enhancement = Cisternal, Canalicular, or Extratemporal
the F a c ia l N e rv e (CN 7)
IVhat
causes abnormal enhancement?
Big one is Bell’s Palsy. Lymes, Ramsay
Hunt, and Cancer can do it too.
the F a c ia l N e rv e (CN 7)
When do yo u think Cancer
Nodular Enhancement
the F a c ia l N e rv e (CN 7)
When do yo u damage the facial nerve
T-Bone fracture (transverse > longitudinal).
Axial CT- Level of I AC
-the bend at the GG =
anterior genu
Axial MR T2 - Cisternal Segment
-CN8 is posterior also
entering the IAC
Bells
Etiology is probably viral. Usually a
clinical diagnosis. Abnormal enhancement in
the Canalicular Segment (in the IAC) is
probably the most classic finding.
RH
Caused by reactivation varicella zoster
virus. Classic rash around ear. CN 5 is
usually also involved.
O to s c le ro s is (F e n e s tra l and R e tro fe n e s tra l):
A better term would actually be “otospongiosis,” as the bone becomes more lytic (instead of sclerotic).
When I say conductive hearing loss in an adult female, you say this
Fenestral
This is bony resorption anterior to the oval widow at the fissula ante fenestram.
If not addressed, the footplate will fuse to the oval window.
Retro-fenestral
This is a more severe form, which has progressed to have demineralization around
the cochlea. This form usually has a sensorineural component, and is bilateral and symmetric nearly
100% of the time.
to s c le ro s is (F e n e s tra l and R e tro fe n e s tra l):
treatment optoins
Early on (if the focus is small) dietary supplementation with Fluoride
may be useful. Although this is controversial - may or may not w o rk …
and may or may not be part o f a new world order David Icke Reptilian
conspiracy to lower IQs (Alex Jones has the documents).
Later on they might try a stapedectomy (partial removal o f the stapes
with implantation o f a prosthetic device) or a Cochlear implant
S u p e r io r S em ic ir cu la r Canal D e h is c e n c e
This is an Aunt Minnie. It’s supposedly from long standing elevated
ICP. The most likely way this will be asked is either (1) what is it? with
a picture or (2) “Noise Induced Vertigo” or “Tullio’s Phenomenon.”
Pietro Tullio
Mad scientist who drilled holes in the semicircular canals of pigeons then observed that they became off balance when he exposed them to loud sounds. He also created a “pigeon rat” like Hugo Simpson did in the 1996 Simpsons Halloween Special.
Large V e s tib u la r A q u ed u c t S y n d rom e
The vestibular aqueduct is a bony canal that connects the vestibule (inner ear) with the endolymphatic
sac. The enlargement of the aqueduct (> 1.5 mm) has an Aunt Minnie appearance. The classic
history is progressive sensorineural hearing loss. Supposedly the underlying etiology is a failure of
the endolymphatic sac to resorb endolymph, leading to endolymphatic hydrops and dilation.
Large V e s tib u la r A q u ed u c t S y n d rom e
trivia
«This is the most common cause of congenital sensorineural hearing loss
•The finding is often (usually) bilateral,
j l v ‘There is an association with cochlear deformity - near 100%
4y r l (absence o f the bony modiolus in more than 90%)
•Progressive Sensorineural Hearing Loss (they arc NOT bom deaf)
The normaI Vestibular Aqueduct (VA) is
NEVER
larger than the adjacent
Posterior Semicircular Canal (PSCC)
Congenital malformations o f the inner ear
Along those lines, we can discuss two disorders on opposite ends o f that severity spectrum
with the Michel’s Aplasia being the earliest and most severe, and the Classic Mondini’s
Malformation (incomplete partition II) being the latest and least severe
Mondini Malformation
Type o f cochlear hypoplasia where the basal turn is normal, but
the middle and apical turns fuse into a cystic apex. This is usually written as “only 1.5 turns” -
instead o f the normal 2.5. There is an association with an enlarged vestibule, and enlarged
vestibular aqueduct. They have sensorineural hearing loss, although high frequency sounds are
typically preserved (as the basal turn is normal).
Michel’s A p la sia
This is also referred to as complete labyrinthine aplasia or “CLA.” As
above, this represents the most severe o f the congenital abnormalities o f the inner ear - with
absence o f the cochlea, vestibule, and vestibular aqueduct. No surprise these kids are
completely deaf.
Michel’s A p la sia
associations
Anencephaly, Thalidomide Exposure
Michel’s A p la sia
gamesmanship
Some people think this looks like labyrinthitis ossificans. Look for the
absent vestibular aqueduct to help differentiate.
h i s vs THAT: Mondini vs Michel
mondine
Timing:
Severity:
Cochlea:
Vestibule:
Vestibular Aqueduct:
Frequency:
Timing:Late (7th Week
Severity:Some Preserved High Frequency Hearing
Cochlea:Cystic Apex (basilar turn is normal)
Vestibule:Sometimes Enlarged (can be normal)
Vestibular Aqueduct:Large
Frequency:Common
(relative to other malformations)
h i s vs THAT: Mondini vs Michel
michel
Timing:
Severity:
Cochlea:
Vestibule:
Vestibular Aqueduct:
Frequency:
Timing:Early (3rd Week)
Severity:Total Deafness
Cochlea:Absent
Vestibule:Absent
Vestibular Aqueduct:Absent
Frequency:Rare As Fuck
E n d o lym p h a tic S a c Tumor
Rare tumor o f the endolymphatic sac and duct. Although most are sporadic, when you see this
tumor you should immediately think Von-Hippel-Lindau.
E n d o lym p h a tic S a c Tumor
classic look
They almost always have internal amorphous calcifications on CT. There are
T2 bright, with intense enhancement. They are very vascular often with flow voids, and
tumor blush on angiography.
P a r a g a n g liom a
On occasion, paraganglioma o f the jugular fossa (glomus jugulare or jugulotympanic tumors)
can invade the occipital bone and adjacent petrous apex
P a r a g a n g liom a
trivia
»40% o f the time it’s hereditary, and they are multiple.
»The most common presenting symptom is hoarseness from vagal nerve compression.
A »They are very vascular masses and enhance avidly with a “salt and pepper”
appearance on post contrast MRI, with flow voids.
*They are FDG avid.
Petrous Apex - Anatomic Variations
A sym m e tr ic Marrow
Typically the petrous apex contains significant fat, closely
following the scalp and orbital fat (T1 and T2 bright). When it’s asymmetric you can have
two problems (1) falsely thinking y o u ’ve got an infiltrative process when you d o n ’t, and (2)
overlooking a T1 bright thing (cholesterol granuloma) thinking it’s fat. The key is to use
STIR or some other fat saturating sequence
Petrous Apex - Anatomic Variations
C e p h a lo c e le s
A cephalocoele describes a herniation o f CNS content through a defect
in the cranium. In the petrous apex they are a slightly different animal. They d o n ’t contain any
brain tissue, and simply represent cystic expansion and herniation o f the posterolateral portion
o f Meckel’s cave into the superomedial aspect o f the petrous apex. Describing it as a
herniation o f Meckel’s Cave would be more accurate. These are usually unilateral and are
classically described as “smoothly marginated lohulated cystic expansion o f the petrous
apex. ”
Petrous Apex - Anatomic Variations
Aberrant in te rn a l ca ro tid .
The classic history is pulsatile tinnitus (although other
things can cause that). This term is used to describe the situation where the Cl (cervical)
segment o f the ICA has involuted/underdeveloped, and middle ear collaterals develop
(enlarged caroticotympanic artery) to pick up the slack. The hypertrophied vessel runs
through the tympanic cavity and joins the horizontal carotid canal. The ENT exam will show a
vascular mass pulsing behind the ear drum (don’t expect them to make it that easy for you).
The oldest trick in the book is to try and fool you
into calling it a paraganglioma.
Look for the connection to the horizontal carotid
canal - that is the most classic way to show this.
DO NOT BIOPSY !
A p ica l P e tr o s itis
Infection o f the petrous apex is a rare complication o f infectious otomastoiditis. It can have
some bad complications if it progresses including osteomyelitis o f the skull base, vasospasm o f
the ICA (if it involves the carotid canal), subdural empyema, venous sinus thrombosis, temporal
lobe stroke, and full on meningitis.
In children, it can present as a primary process. In adults it’s usually in the setting o f chronic
otomastoiditis or recent mastoid surgery
G rad en ig o S yn d rom e
This is a complication o f apical petrositis, when Dorello’s canal
(CN 6) is involved. They will show you (or tell you) that the patient
has a lateral rectus palsy
G rad en ig o S yn d rom e
classic triad
• Otomastoiditis,
• Face pain (trigeminal
neuropathy), and
• Lateral Rectus Palsy
Dorello’s Canal
The most medial point of the pertrous ridge - between the pontine cistern and cavernous sinus
Petrous Apex - Inflammatory Lesions
C h o le s te r o l Granuloma
The most common primary petrous apex lesion. Mechanism is likely obstruction o f the air
cell, with repeated cycles o f hemorrhage and inflammation leading to expansion and bone
remodeling. The most common symptom is hearing loss.
Petrous Apex - Inflammatory Lesions
Choelsteatoma
This is basically an epidermoid (ectopic epithelial tissue). Unlike the ones in the middle ear,
these are congenital (not acquired) in the petrous apex. They are typically slow growing, and
produce bony changes similar to cholesterol granuloma.
The difference is their MRI findings; T l dark. T2 bright, and restricted diffusion
C h o le s te r o l Granuloma
imaging
On CT the margins will be sharply defined. On MRI it’s gonna be T l and T2 bright, with a T2 dark hemosiderin rim, and faint peripheral enhancement
C h o le s te r o l Granuloma
key point
Cholesterol Granuloma =
Tl and T2 Bright.
THIS vs THAT:
Cholesterol Granuloma Cholesteatoma
Cholesterol Granuloma Cholesteatoma
T l Bright Tl Dark
T2 Bright T2 Bright
Doesn’t Restrict Does Restrict
Smooth Expansile Bony Change Smooth Expansile Bony Change
R egu la r and N e c r o tiz in g O titis Externa
Otitis Externa - the so called “swimmers ear” is an infection (usually bacterial) o f the
external auditory canal. The more testable version Necrotizing Otitis Externa (also called
“Malignant” Otitis Externa - for the purpose o f fucking with you) is a more aggressive
version seen almost exclusively in diabetics.
You are going to see swollen EAC soft tissues, probably with a bunch o f small abscesses, and
adjacent bony destruction.
They always (95%) have diabetes and the causative agent is always (98%) Pseudomonas
E x te rn a l Auditory Canal E x o s t o s is (“Sw im m e r s Ear”)
This is an
overgrowth o f tissue in the ear canal, classically seen in Surfers who get repeated bouts o f ear
infections. It’s usually bilateral, and when chronic will look like bone. Unlike Necrotizing
Otitis, these patients are immunocompetent and non-diabetes (although they are dirty hippie
surfers).
E x te rn a l Auditory Canal O s te om a
This is a benign bone tumor, maybe best
thought o f as an overgrowth o f normal bone. They are usually incidental and unilateral
(,remember exostosis was bilateral) occurring near the junction o f cartilage and bone in the
ear canal.
E x te rn a l Auditory Canal A tr e sia
This is a developmental anomaly where the external
auditory canal (secondary crayon storage
compartment) doesn’t form. As you might imagine,
this results in a hearing deficit (conductive subtype).
There may or may not be a mashed up ossicular
chain.
E x te rn a l Auditory Canal A tr e sia
trivia
ENT will want to know: (1) if the tissue covering the normally open ear hole (atretic
plate) is soft tissue or bone, and (2) if there is an aberrant course o f the facial nerve.
Pagets
This is discussed in great depth in the MSK chapter. Having said that, I want to
remind you o f the Paget skull changes. You can have osteolysis as a well-defined large
radiolucent region favoring the frontal and occipital bones. Both the inner and outer table are
involved.
pagets buzzwork
osteolysis circumscripta.
pagets skull related complications
- Deafness is the most common complication
- Cranial Nerve Paresis
- Basilar Invagination -> Hydrocephalus -> Brainstem Compression
- Secondary (high grade) osteosarcoma.
Fibrous D y sp la s ia
The ground-glass lesion. If you are getting ready to call it Pagets,
stop and look at the age. Pagets is typically an older person (8% at 80), whereas fibrous
dysplasia is usually in someone less than 30.
Fibrous D y sp la s ia
findings
• Classically, fibrous dysplasia o f the skull spares the otic capsule
• McCune Albright Syndrome - Multifocal fibrous dysplasia, cafe-au-lait spots, and
precocious puberty.
• The outer table is favored (Pagets tends to favor in the inner table)
Sinus D isea se Strategy Intro
You will see C’T and MRI used in the evaluation of sinus
disease. It is useful to have some basic ideas as to why one modality might be preferred over the
other (for gamesmanship and distractor elimination). CT is typically used for orbital and sinus
infections. In particular it is useful to see if the spread of infection involves the anterior 2/3 of the
orbit. If you wanted to know if the patient has cavernous sinus involvement, or involvement of the
posterior 1/3 (orbital apex) MRI will be superior.
CT also has the ability to differentiate common benign disease
(inspissated secretion and allergic fungal sinusitis) from the more
rare sinus tumors. The trick being that a hyperdense opacified sinus
is nearly always benign (tumor will not be dense). In addition to
that CT is useful for characterization of anatomical variation
(justification of endoscopic nasal surgery for recurrent sinusitis).
MRI is going to be more valuable for tumor progression / extension (perineural spread, marrow
involvement etc..).
- Hyper Dense Sinus
• Blood
• Dense (inspissated)
Secretions
• Fungus
Fungal Sinusitis
This comes in two flavors; the good one (allergic) and the bad one (invasive). The chart below will
contrast the testable differences:
Allergic Fungal Sinusitis
Opacification of multiple sinuses, ususually bilateral
favoring the ethmoid and maxillary sinuses.
Normal Immune System (Asthma is common)
CT: Hyperdense centrally or with layers. Can
erode and remodel sinus walls if chronic.
MRI: T1-T2 Dark - because of the high protein
content / heavy metals. Can mimic an aerated sinus.
Inflamed (T2 bright) mucosa which will enhance.
The glob of fungus snot will not enhance (thats how
you know it is not a tumor).
Acute Invasive Fugal Sinusitis
Opacification of multiple sinuses. Stranding /
Extension into the fat around the sinuses in the key
finding.
Immunocompromised
- Neutropenic = Aspergillus
- Diabetic in DKA = Zygomycetes / Mucor
CT: Opacified Sinus with is NOT hyperdense. Fat
stranding in the orbit, masticator fat, pre-antral fat,
or PPF suggests invasion. This does NOT require
bone destruction.
MRI: Also can be T1/T2 Dark. However, the
mucosa may not enhance (suggesting it is necrotic).
The extension of disease out of the sinus will be
bright on STIR and enhance.
C h r o n ic In f lam m a to r y S in o n a s a l D i s e a s e
This is typically thought of as an inflammation of the paranasal sinuses
that lasts at least 12 weeks. The causes arc complex and people write
long boring papers about the various cytokines and T-Cell mediation
pathways are involved but from the Radiologist’s point of view the issue
is primarily anatomical patency of sinus Ostia
Infundibular
Pa tte rn .
O s tiom e a ta l U nit P a tte rn
Sinonasal Polyposis
P a tte rn .
Infundibular
Pa tte rn .
The most common pattern. In this pattern, disease is limited to the maxillary sinus and occurs from the obstruction at the ipsilateral ostium / infundibulum (star).
O s tiom e a ta l U nit P a tte rn
Second most common pattern. I’m not going to get into depth on the various subtypes - just think about this as more centered at the middle meatus (star) with disease involving the ipsilateral maxillary, frontal and ethmoid sinuses. The contributors to this pattern involve all the usually suspects (hypertrophied turbinates, anatomic variants - concha bullosa, middle turbinates which curl the wrong way “paradoxical”, and septal deviation).
Sinonasal Polyposis
P a tte rn .
The pattern is characterized by a combination of soft tissue nasal polyps (found throughout the nasal cavity) and variable degrees of sinus opacification. About half the time fluid levels will also be present. A key feature is the bony remodeling and erosion. In particular the “widening of the infiindibula” is the classic description. This erosion and remodeling is important to distinguish between the “expansion” o f the sinus - which is more classic for a mucocele. Testable associations include CF and Aspirin Sensitivity.
Mu co ce le
This is how I think about these things. You have an obstructed sinus.
Maybe you had trauma which fucked the drainage pathway or you’ve got
CF and the secretions just clog things up. Mucus continues to accumulate
in the sinus, but it can’t clear (because it’s obstructed). Over time the sinus
become totally filled and then starts to expand circumferentially. Hence the
buzzword “expanded airless sinus.” The frontal sinus is the most common
location. It won’t enhance centrally (it is not a tumor), but the periphery
may enhance from the adjacent inflamed mucosa
A n tro c h o a n a l Polyp
Seen in young adults (30s-40s), classically presenting with nasal congestion / obstruction symptoms. Arises
within the maxillary sinuses and passes through and enlarges the sinus ostium (or accessory ostium).
A n tro c h o a n a l Polyp
buzzword
“widening of the maxillary ostium/’
A n tro c h o a n a l Polyp
clasically
Classically, there is no associated bony destruction but instead smooth enlargement o f the sinus. The polyp
will extend into the nasopharynx. This thing is basically a monster inflammatory polyp with a thin stalk
arising from the maxillary sinus
J u v e n ile N a s a l A n g io fib rom a (JN A
Often you can get this one right just from the history - Male teenager with nose bleeds (obstruction is
actually a more common symptom in real life, but not so much on multiple choice).
J u v e n ile N a s a l A n g io fib rom a (JN A
things to know
- Location = Centered on the sphenopalatine foramen
- Bone Remodeling (not bone destruction)
- Extremely vascular (super enhancing) with intratumoral Flow Voids on MR
- Pre-surgical embolization is common (via internal maxillary & ascending pharyngeal artery)
In v e r te d P ap illom a :
This uncommon tumor has distinctive imaging features (which therefore make it testable). The classic
location is the lateral wall of the nasal cavity - most frequently related to the middle turbinate.
Impaired maxillary drainage is expected.
In v e r te d P ap illom a :
thinkgs to know
- A focal hyperostosis tends to occur at the tumor origin.
- Another high yield pearl is that 10% harbor a squamous cell CA.
- MRI “cerebriform pattern” - which sorta looks like brain on T1 and T2.
E s th e s io n e u ro b la s tom a :
This is a neuroblastoma o f olfactory cells so it’s gonna start at the cribiform plate. It classically has a
dumbbell appearance with growth up into the skull and growth down into the sinuses, with a waist at the
plate. There are often cysts in the mass. There is a bi-modal age distribution
E s th e s io n e u ro b la s tom a :
things to know
•Dumbbell shape with wasting at the cribiform plate is classic
.Intracranial posterior cyst is a “diagnostic” look
‘Octreotide scan will be positive - since it is o f neural crest origin
S q u am o u s C e ll I SNUC
Squamous cell is the most common head and neck cancer. The maxillary antrum is the most common
location. It’s highly cellular, and therefore low on T2. Relative to other sinus masses it enhances less.
SNUC (the undifferentiated squamer), is the monster steroided-up version o f a regular squamous cell. They
are massive and seen more in the ethmoids
Epistaxis (Nose Bleeds
This is usually idiopathic, although it can be iatrogenic (picking it too much - or not enough). They could
get sneaky and work this into a case of HHT (hereditary hemorrhagic telangiectasia). The most common
location is the anterior septal area (Kiesselbach plexus) - these tend to be easy to compress manually. The
posterior ones are less common (5%) but tend to be the ones that “bleed like stink” (need angio). Most
cases are given a trial o f nasal packing. When that fails, the N-IR team is activated.
Epistaxis (Nose Bleeds
what to know
The main supply to the posterior nose is the sphenopalatine artery (terminal internal maxillary
artery) and tends to be the first line target. Watch out for the variant anastomosis between the ECA
and ophthalmic artery (you don’t want to embolize the eye).
Nasal Septal Perforation
Typically involves the
anterior septal cartilaginous
area.
Nasal Septal Perforation
causes
• Surgery - Old school Septoplasty techniques - essentially resecting the thing (Killian submucous resection)
• Cocaine use (> 3 months)
• Too much nose picking (or perhaps not picking it enough)
• Granulomatosis with polyangiitis (Wegener granulomatosis) — Triad o f renal masses, sinus
mucosal thickening and nasal septal erosion, disease, and cavitary lung nodules / fibrosis. cANCA positive.
• Syphilis - affects the bony septum (most everything else effect the cartilaginous regions).
S ia lo lith ia s is
Stones in the salivary ducts. The
testable trivia includes: (1) Most commonly in the
submandibular gland duct (wharton’s),
(2) can lead to an infected gland “sialoadenitis”, and
(3) chronic obstruction can lead to gland fatty atrophy.
salivary gland ducst
Submandibular = Wharton Parotid = Stenson Sublingual = Rivinus
Odontogenic In fe c tio n
These can be dental or periodontal in origin. If I were writing
a question about this topic I would ask three things. The first would be that infection is more
common from an extracted tooth than an abscess involving an intact tooth.
The second would be that the attachment of the mylohyoid muscle to the mylohyoid ridge dictates the spread of infection to the sublingual and submandibular spaces. Above the mylohyoid line (anterior mandibular teeth) goes to the sublingual space, and below the mylohyoid line (second and third molars) goes to the submandibular space.
The third thing I would ask would be
that an odontogenic abscess is the
most common masticator space
“mass” in an adult.
Sublingual
Space
-Above the Mylohyoid Line
(Anterior Mandibular Teeth
Submandibular
Space
-Below the Mylohyoid Line
2nd and 3rd Molars
L u dw ig ’s Angina:
This is a super aggressive cellulitis in the floor o f the
mouth. If they show it, there will be gas everywhere
L u dw ig ’s Angina:
trivia
most cases start with an odontogenic infection
Torus Palatinus
This is a normal variant that looks scary. Because it looks scary some multiple choice writer may try and trick you into calling it cancer. It’s just a bony exostosis that comes off the hard palate in the midline. Classic History. “Grandma’s dentures won’t stay in.”
O s te o n e c ro s is of
th e M a n d ib le
The trivia is most likely gonna be etiology. Just remember it is related to prior radiation, licking a radium paint brush, or bisphosphonate treatment.
Ranula
This is a mucous retention cyst. They are typically lateral. There are two testable pieces o f trivia to know: (1) They arise from the sublingual gland / space. and (2) Use the word “plunging” once it’s under the mylohyoid muscle.
T h y ro g lo s s a l D u c t C y s t
This can occur anywhere between the foramen cecum (the
base o f the tongue) and the thyroid gland. They are usually found in the midline. It looks like a
thin-walled cyst. Further discussion in the endocrine & peds chapters.
Floor of Mouth Dermoid I Epidermoid
There isn’t a lot o f trivia about these other
than the buzzword and what they classically look like. The buzzword is “sack of marbles” -
fluid sack with globules o f fat. They are typically midline. Further discussion in the peds
chapter.
Head and neck cancer
Squamous cell is going to be the most common cancer o f the mouth (and head and
neck). In an older person think drinker and smoker.
In a younger person think HPV. HPV related SCCs tend to be present with large necrotic level
2a nodes (don’t call it a branchial cleft cyst!).
Head and neck cancer
trivia
Classic Scenario = Young adult with new level 1/ neck mass = HPV related SCC.
lesions of the Jaw
There are a BUNCH o f these and they all look pretty similar. Lesions in the jaw are broadly
grouped into either odontogenic (from a tooth) or non-odontogenic (not from a tooth). The
non-odontogenic stuff you see in the mandible is the same kind o f stuff you see in other bones
(ABCs, Simple Bone Cysts, Osteomyelitis, Myeloma / Plasmacytoma e tc …). I think if a test
writer is going to show a jaw lesion - they probably are going to go for odontogenic type.
Obviously your answer choices will help you decide what they are going for. The other tip is
that odontogenic lesions are usually associated with a tooth.
Pe ria p ic a l Cyst (R a d ic u la r Cys t)
D en tig e ro u s Cyst (F o llic u la r Cyst)
K e ra to g e n ic O d o n to g en ic T um or
Am e lo b la s tom a
Odontoma
Pe ria p ic a l Cyst (R a d ic u la r Cys t)
This is the most
common type o f odontogenic cyst. They are typically the result
o f inflammation from dental caries (less commonly trauma).
The inflammatory process results in a cystic degeneration
around the periodontal ligament.
e ria p ic a l Cyst (R a d ic u la r Cys t)
things to know
‘Located at the apex o f a non-vital tooth
‘ Round with a Well Corticated Border
• Usually < 2 cm
D en tig e ro u s Cyst (F o llic u la r Cyst)
This is a
cyst that forms around the crown o f an un-erupted tooth.
It’s best thought o f as a developmental cyst (peri-apicals
are acquired). These things like to displace and resorb
adjacent teeth - usually in an apical direction. This is the
kind o f cyst that will displace a tooth into the condylar regions o f the mandible or into the floor o f the orbit.
D en tig e ro u s Cyst (F o llic u la r Cyst)
things to know
‘ Located at the crown o f an un-erupted tooth
• Tend to displace the tooth
K e ra to g e n ic O d o n to g en ic T um o
(Odontogenic Keratocyst) - Unlike the prior two
lesions (which were basically fluid collections) this
is an actual tumor. They tend to occur at the
mandibular ramus or body. Although they can be
uni-locular the classic look is multi-locular
( “daughter cysts ”) and th at’s how I would expect
them to look on the test.
K e ra to g e n ic O d o n to g en ic T um o
things to know
- Body / Ramus Mandible
- They typically grow along the length o f the bone
- Without significant cortical expansion
- May have daughter cysts
- When multiple think Gorlin Syndrome
Am e lo b la s tom a
(Adamantinoma o f the
jaw) - This is another tumor (locally aggressive).
The appearance is variable but for the purpose o f
multiple choice I would expect the most classic
look - multi-cystic with solid components and
expansion o f the mandible.
Out o f the four I’ve discussed, this will be the
most aggressive-looking one. If they show you a
really aggressive-looking lesion, especially if it
has multiple “soap bubbles” - you should
consider this.
Am e lo b la s tom a
things to know
- Hallmark = Extensive Tooth Root Absorption
- Mandibular Expansion
- Solid component (shown on MR or CT) favors the Dx o f Ameloblastoma
- About 5% arise from Dentigerous Cysts
Odontoma
This is the easy one to pick out because it’s
most likely to be shown in it’s mature solid form (they start
out lucent). It’s actually the most common odontogenic
tumor o f the mandible. It’s basically a “tooth hamartoma.”
Odontoma
what to know
• Radiodense with a lucent rim
Suprahyoid neck
The suprahyoid neck is usually taught by using a “spaces” method. This is actually the best
way to learn it. What space is it? What is in that space? What pathology can occur as the
result o f what normal structures are there? Example: lymph nodes are there - thus you can get
lymphoma or a met.
Parotid Space
The parotid space is basically the parotid gland, and portions o f the facial nerve. You can 't see the facial nerve, but you can see the retromandibular vein (which runs ju st medial to the facial nerve). Another thing to know is that the parotid is the only salivary gland to have lymph nodes, so pathology involving the gland itself, and anything lymphatic related, is fair game.
Parotid Space contains
- The Parotid Gland
- Cranial Nerve 7 (Facial)
- Retro-mandibular Vein
Parotid Space Pathology
Pleomorphic A denoma (benign m ixed tum o r)
Warthins
M u coepide rm oid C a rc in om a
Lymphoma
Sjo gren s
Benign L ym p h o e p ith e lia l D is e ase
A c u te P a ro titis
Pleomorphic A denoma (benign m ixed tum o r)
This is the most common major (and minor) salivary gland
tumor. It occurs most commonly in the parotid, but can also
occur in the submandibular or sublingual glands. 90% o f
these tumors occur in the superficial lobe. They are
commonly T2 bright, with a rim o f low signal. They have a
small malignant potential and are treated surgically.
Pleomorphic A denoma (benign m ixed tum o r)
superficial vs deep
Involvement o f the superficial (lateral to the facial nerve) or deep
(medial to the facial nerve) lobe is critical to the surgical approach. A line is drawn
connecting the lateral surface o f the posterior belly o f the digastric muscle and the
lateral surface o f the mandibular ascending ramus to separate superficial from deep
Pleomorphic A denoma (benign m ixed tum o r)
resection
Apparently, if you resect these like a clown you can spill them, and they will have a
massive, ugly recurrence.
Major Salivary Glands:
- Parotid
- Submandibular
- Sublingual
Minor Salivary Glands
• Literally 100s of unnamed
minor glands
Warthins
This is the second most common benign tumor. This one ONLY occurs in the
parotid gland. This one is usually cystic, in a male, bilateral (15%), and in a smoker. As a
point o f total trivia, this tumor takes up pertechnetate (it’s basically the only tumor in the
parotid to do i t , ignoring the ultra rare parotid oncocytoma).
M u coepide rm oid C a rc in om a
This is the most common malignant tumor of minor
salivary glands. The general rule is - the smaller the gland, the more common the malignant
tumors; the bigger the gland, the more common the benign tumors. There is a variable
appearance based on the histologic grade. There is an association with radiation.
Adenoid Cys tic C a rc in om a
This is another malignant salivary gland tumor, which
favors minor glands but can be seen in the parotid. The number one thing to know is
perineural spread. This tumor likes perineural spread.
When I say adenoid cystic, you say
perineural spread
Adenoid Cys tic C a rc in om a
Pearl
I used to think that perineurial tumor spread would widen a neural foramen
(foramen ovale for example). It’s still m ight… but it’s been my experience that a nerve
sheath tumor (schwannoma) is much more likely to do that. Let’s ju st say for the purpose o f multiple choice that neural foramina widening is a schwannoma - unless
there is overwhelming evidence to the contrary
Lymphoma (parotid)
Because the parotid has lymph nodes (it’s the only salivary gland that does), you can get
lymphoma in the parotid (primary or secondary). If you see it and it’s bilateral, you should
think Sjogrens. Sjogrens patients have a big risk (like lOOOx) o f parotid lymphoma. Like
lymphoma is elsewhere in the body, the appearance is variable. You might see bilateral
homogeneous masses. For the purposes o f the exam, just knowing you can get it in the
parotid (primary or secondary) and the relationship with Sjogrens is probably all you
need.
Sjo gren s
Autoimmune lymphocyte-induced destruction o f the gland. “Dry Eyes and Dry Mouth.”
Typically seen in women in their 60s. Increased risk (like lOOOx) risk o f non-Hodgkins MALT
type lymphoma. There is a honeycombed appearance o f the gland.
Benign L ym p h o e p ith e lia l D is e ase :
You have bilateral mixed solid and cystic lesions with diffusely enlarged parotid glands. This
is seen in HIV. The condition is painless (unlike parotitis - which can enlarge the glands).
A c u te P a ro titis :
Obstruction o f flow o f secretions is the most common cause. They will likely show you a stone
(or stones) in Stensen’s duct, which will be dilated. The stones are calcium phosphate. Post
infectious parotitis is usually bacterial. Mumps would be the most common viral cause. As a
point o f trivia, sialography is contraindicated in the acute setting.
Parapharyngeal Space
overview
Also referred to as the “pre-styloid” parapharyngeal space - for the purpose of fucking with you. The primary utility o f the space is when it is displaced (discussed below).
Parapharyngeal Space
spread
Mets and infections can spread directly in a vertical direction through this space (squamous cell cancer from tonsils, tongue, and larynx).
Parapharyngeal Space
cystic mass
A cystic mass in this location could be an atypical 2nd Branchial Cleft Cyst (but is more likely a necrotic lymph node).
Parapharyngeal Space
borders
The parapharyngeal space is bordered on four sides by different spaces. If you have a mass dead in the middle, it can be challenging to tell where it’s coming from. Using the displacement o f fat, you can help problem solve. Much more important than that, this lends itself very well to multiple choice.
Parapharyngeal Fat (PPF) Displacement
Carotid
Space =
Anterior
Displacement
Parotid
Space =
Medial
Displacement
Masticator Space = Posterior Medial Displacement
Superficial Mucosal Space = Lateral Displacement
The parapharyngeal
space is primarily a
ball of fat with a few
branches of the
trigeminal nerves, and
the pterygoid veins
Carotid Space
overview
The carotid space is also sometimes called the
“post styloid” or “retro-styloid’’ parapharyngeal
space — for the purpose of fucking with you.
Although it is worth noting that this space is commonly involved in secondary spread of aggressive multi-spatial disease - such as infectious path (necrotizing otitis external) or malignant spread (nasopharyngeal, squamous cell etc..). Metastatic squamous cell is what you should think for nodal disease in this region
Carotid Space
3 classic tumors
1) Paraganglioma
(2) Schwannoma
(3) Ncurofibroma
Carotid Space
contains
" Carotid artery ■ Jugular vein ■ Portions o f CN 9, CN 10, CN 11 ■ Internal jugular chain lymph node
Carotid Space
paraganglioma
There are three different ones worth knowing about - based on location.
The imaging features are the same. They are hypervascular (intense tumor blush), with a
“Salt and Pepper” appearance on MRI from the flow voids. They can be multiple and
bilateral in familial conditions (10% bilateral, 10% malignant, etc.). ,n In-octreotide
accumulates in these tumors (receptors for somatostatin).
Carotid Space
schwannoma
Most commonly in this location we are talking about vagal nerve
(CN 10), but if the lesion is pretty high up near the skull base it
could also be involving CN 9, 11, or even 12. The typical MR
appearance is an oval mass, heterogenous (cystic and sold parts)
with heterogenous bright signal on T2.
These things enhance a ton (at least the solid parts anyway). They
enhance so much you might even think they were vascular.
Ironically, schwannomas are considered hypo vascular lesions and
the only reason they enhance is because o f extravascular leakage
(and poor venous drainage).
Carotid Space
neruofibroma
These are less common than the schwannoma. About 10% o f the time they are related to
NF-1 (in which case you should expect them to be bilateral and multiple). In contrast to
schwannomas they tend to be more homogenous, and demonstrate the classic target sign on
T2 with decreased central signal.
Carotid Space
paraganglioma
Carotid Body Tumor
Carotid
Bifurcation (Splaving ICA and
EC A)
Carotid Space
paraganglioma
Glomus Jugulare
Skull Base
(often with destruction o f jugular
fo ram en )
Middle Ear Floor Destroyed =
Glomus Jugulare
Carotid Space
paraganglioma
Glomus Vagale
Above Carotid
Bifurcation, but below the Jugular
Foramen
Carotid Space
paraganglioma
Glomus Tympanicum
Confined to the middle ear. Buzzword is “overlying the cochlear promontory. ” Middle Ear Floor Intact = Glomus Tympanum
Carotid space
Surgical
Planning Trivia
• Distance of Skull Base ( > 1 cm = Neck Dissection) • Degree of Vascularity (might need preembolization) • Relationship to the Carotid (Don’t Fuck with Big Red)
Neurofibroma
quick
Mildly Heterogenous Enhancement T2: Target Sign (bright rim, dark middle) NF-1 Association
Schwannoma
quick
Although they enhance intensely they are not vascular on Angio T2: Moderate to High Signal - Heterogenous NF-2 Association
Paraganglioma
quick
Hypervascular (tumor blush on angio) T2: Light Bulb Bright with Salt and Pepper (flow voids) ' "In-Octreotide avid
Lemierre’s Syndrome
This is a thrombophlebitis of the jugular veins with septic emboli in
the lung. It’s found in the setting of oropharyngeal infection (pharyngitis, tonsillitis, peritonsillar
abscess) or recent ENT surgery. Buzzword bacteria = “Fusobacterium Necrophorum”
Grisel’s Syndrome
Torticollis with atlanto-axial joint inflammation seen in H&N surgery or
retropharyngeal abscess
Pleomorphic A denoma (benign m ixed tum o r)
This is the most common major (and minor) salivary gland
tumor. It occurs most commonly in the parotid, but can also
occur in the submandibular or sublingual glands. 90% o f
these tumors occur in the superficial lobe. They are
commonly T2 bright, with a rim o f low signal. They have a
small malignant potential and are treated surgically.
Pleomorphic A denoma (benign m ixed tum o r)
superficial vs deep
Involvement o f the superficial (lateral to the facial nerve) or deep
(medial to the facial nerve) lobe is critical to the surgical approach. A line is drawn
connecting the lateral surface o f the posterior belly o f the digastric muscle and the
lateral surface o f the mandibular ascending ramus to separate superficial from deep
Pleomorphic A denoma (benign m ixed tum o r)
resection
Apparently, if you resect these like a clown you can spill them, and they will have a
massive, ugly recurrence.
Major Salivary Glands:
- Parotid
- Submandibular
- Sublingual
Minor Salivary Glands
• Literally 100s of unnamed
minor glands
Warthins
This is the second most common benign tumor. This one ONLY occurs in the
parotid gland. This one is usually cystic, in a male, bilateral (15%), and in a smoker. As a
point o f total trivia, this tumor takes up pertechnetate (it’s basically the only tumor in the
parotid to do i t , ignoring the ultra rare parotid oncocytoma).
M u coepide rm oid C a rc in om a
This is the most common malignant tumor of minor
salivary glands. The general rule is - the smaller the gland, the more common the malignant
tumors; the bigger the gland, the more common the benign tumors. There is a variable
appearance based on the histologic grade. There is an association with radiation.
Adenoid Cys tic C a rc in om a
This is another malignant salivary gland tumor, which
favors minor glands but can be seen in the parotid. The number one thing to know is
perineural spread. This tumor likes perineural spread.
N e rv e S h e a th Tumo rs
Masticator Space
Since you have a nerve, you can have a schwannoma or
neurofibroma of V3. Remember the schwannoma is more likely to cause the foramina expansion vs
perineural tumor spread.
Adenoid Cys tic C a rc in om a
Pearl
I used to think that perineurial tumor spread would widen a neural foramen
(foramen ovale for example). It’s still m ight… but it’s been my experience that a nerve
sheath tumor (schwannoma) is much more likely to do that. Let’s ju st say for the purpose o f multiple choice that neural foramina widening is a schwannoma - unless
there is overwhelming evidence to the contrary
Lymphoma (parotid)
Because the parotid has lymph nodes (it’s the only salivary gland that does), you can get
lymphoma in the parotid (primary or secondary). If you see it and it’s bilateral, you should
think Sjogrens. Sjogrens patients have a big risk (like lOOOx) o f parotid lymphoma. Like
lymphoma is elsewhere in the body, the appearance is variable. You might see bilateral
homogeneous masses. For the purposes o f the exam, just knowing you can get it in the
parotid (primary or secondary) and the relationship with Sjogrens is probably all you
need.
Sjo gren s
Autoimmune lymphocyte-induced destruction o f the gland. “Dry Eyes and Dry Mouth.”
Typically seen in women in their 60s. Increased risk (like lOOOx) risk o f non-Hodgkins MALT
type lymphoma. There is a honeycombed appearance o f the gland.
Benign L ym p h o e p ith e lia l D is e ase :
You have bilateral mixed solid and cystic lesions with diffusely enlarged parotid glands. This
is seen in HIV. The condition is painless (unlike parotitis - which can enlarge the glands).
A c u te P a ro titis :
Obstruction o f flow o f secretions is the most common cause. They will likely show you a stone
(or stones) in Stensen’s duct, which will be dilated. The stones are calcium phosphate. Post
infectious parotitis is usually bacterial. Mumps would be the most common viral cause. As a
point o f trivia, sialography is contraindicated in the acute setting.
Parapharyngeal Space
overview
Also referred to as the “pre-styloid” parapharyngeal space - for the purpose of fucking with you. The primary utility o f the space is when it is displaced (discussed below).
Parapharyngeal Space
spread
Mets and infections can spread directly in a vertical direction through this space (squamous cell cancer from tonsils, tongue, and larynx).
Parapharyngeal Space
cystic mass
A cystic mass in this location could be an atypical 2nd Branchial Cleft Cyst (but is more likely a necrotic lymph node).
Parapharyngeal Space
borders
The parapharyngeal space is bordered on four sides by different spaces. If you have a mass dead in the middle, it can be challenging to tell where it’s coming from. Using the displacement o f fat, you can help problem solve. Much more important than that, this lends itself very well to multiple choice.
Parapharyngeal Fat (PPF) Displacement
Carotid
Space =
Anterior
Displacement
Parotid
Space =
Medial
Displacement
Masticator Space = Posterior Medial Displacement
Superficial Mucosal Space = Lateral Displacement
The parapharyngeal
space is primarily a
ball of fat with a few
branches of the
trigeminal nerves, and
the pterygoid veins
Carotid Space
overview
The carotid space is also sometimes called the
“post styloid” or “retro-styloid’’ parapharyngeal
space — for the purpose of fucking with you.
Although it is worth noting that this space is commonly involved in secondary spread of aggressive multi-spatial disease - such as infectious path (necrotizing otitis external) or malignant spread (nasopharyngeal, squamous cell etc..). Metastatic squamous cell is what you should think for nodal disease in this region
Carotid Space
3 classic tumors
1) Paraganglioma
(2) Schwannoma
(3) Ncurofibroma
Carotid Space
contains
" Carotid artery ■ Jugular vein ■ Portions o f CN 9, CN 10, CN 11 ■ Internal jugular chain lymph node
Carotid Space
paraganglioma
There are three different ones worth knowing about - based on location.
The imaging features are the same. They are hypervascular (intense tumor blush), with a
“Salt and Pepper” appearance on MRI from the flow voids. They can be multiple and
bilateral in familial conditions (10% bilateral, 10% malignant, etc.). ,n In-octreotide
accumulates in these tumors (receptors for somatostatin).
Carotid Space
schwannoma
Most commonly in this location we are talking about vagal nerve
(CN 10), but if the lesion is pretty high up near the skull base it
could also be involving CN 9, 11, or even 12. The typical MR
appearance is an oval mass, heterogenous (cystic and sold parts)
with heterogenous bright signal on T2.
These things enhance a ton (at least the solid parts anyway). They
enhance so much you might even think they were vascular.
Ironically, schwannomas are considered hypo vascular lesions and
the only reason they enhance is because o f extravascular leakage
(and poor venous drainage).
Carotid Space
neruofibroma
These are less common than the schwannoma. About 10% o f the time they are related to
NF-1 (in which case you should expect them to be bilateral and multiple). In contrast to
schwannomas they tend to be more homogenous, and demonstrate the classic target sign on
T2 with decreased central signal.
Carotid Space
paraganglioma
Carotid Body Tumor
Carotid
Bifurcation (Splaving ICA and
EC A)
Carotid Space
paraganglioma
Glomus Jugulare
Skull Base
(often with destruction o f jugular
fo ram en )
Middle Ear Floor Destroyed =
Glomus Jugulare
Carotid Space
paraganglioma
Glomus Vagale
Above Carotid
Bifurcation, but below the Jugular
Foramen
V o c a l Cord P a ra ly s is
buzzword
“Hoarseness” - If you see “Hoarseness” in the question header, you need to
dkjpO think recurrent laryngeal nerve compression in the AP Window - either from a mass/node
or aortic path. *Hoarseness is also a classic Laryngeal CA buzzword (so look there too).
Carotid space
Surgical
Planning Trivia
• Distance of Skull Base ( > 1 cm = Neck Dissection) • Degree of Vascularity (might need preembolization) • Relationship to the Carotid (Don’t Fuck with Big Red)
Neurofibroma
quick
Mildly Heterogenous Enhancement T2: Target Sign (bright rim, dark middle) NF-1 Association
Schwannoma
quick
Although they enhance intensely they are not vascular on Angio T2: Moderate to High Signal - Heterogenous NF-2 Association
Paraganglioma
quick
Hypervascular (tumor blush on angio) T2: Light Bulb Bright with Salt and Pepper (flow voids) ' "In-Octreotide avid
Lemierre’s Syndrome
This is a thrombophlebitis of the jugular veins with septic emboli in
the lung. It’s found in the setting of oropharyngeal infection (pharyngitis, tonsillitis, peritonsillar
abscess) or recent ENT surgery. Buzzword bacteria = “Fusobacterium Necrophorum”
Grisel’s Syndrome
Torticollis with atlanto-axial joint inflammation seen in H&N surgery or
retropharyngeal abscess
Masticator Space
As the name implies this space contains the
muscles o f mastication (masticator,
temporalis, medial and lateral pterygoids).
Additionally, you have the angle and ramus
of the mandible, plus the inferior alveolar
nerve (branch o f V3).
A trick to be aware o f is that the space
extends superiorly along the side o f the skull
via the temporalis muscle. So, aggressive
neoplasm or infection may ride right up there
Masticator Space
lesions displace
the Parapharyngeal Fat
POSTERIOR and MEDIAL
Masticator Space:
key point
Congenital Stuff and
Aggressive Infection/
Cancer tends to be Trans-
Spatial.
Masticator Space
ddx
O d o n to g en ic In fe c tio n
S a rcom a s
C av e rnou s H em a n g iom a s
P e rin e u ra l S p re ad
N e rv e S h e a th Tumo rs
O d o n to g en ic In fe c tio n
Masticator Space
In an adult, this is the most common cause of a masticator space mass. If you see a mass here, the next
move should be to look at the mandible on bone windows. Just in general, you should be on the look
out for spread via the pterygopalatine fossa to the orbital apex and cavernous sinus. The relationship
with the mylohyoid makes for good trivia - as discussed above.
S a rcom a s
Masticator Space
In kids, you can run into nasty angry masses like Rhabdomyosarcomas,
from the bone of the mandible (chondrosarcoma favors the TMJ
C av e rnou s H em a n g iom a s
Masticator Space
These can also occur, and are given away by the presence of
phlcboliths. Venous or lymphatic malformations may involve multiple
compartments / spaces.
P e rin e u ra l S p re ad
Masticator Space
You can have perineural spread from a head and neck primary along V3.
When I say ‘‘perineural spread” you should think two things:
( 1) Adenoid Cystic Carcinoma of the minor salivary gland
(2) Melanoma
N e rv e S h e a th Tumo rs
Masticator Space
Since you have a nerve, you can have a schwannoma or
neurofibroma of V3. Remember the schwannoma is more likely to cause the foramina expansion vs
perineural tumor spread.
Retropharyngeal Space / Danger Space
The retropharyngeal space has some complex anatomy. Simplified, this is a midline space, deep
to the oral & nasal pharynx. The retropharyngeal space has an anterior “true” space which
extends caudal to around C6-C7, and a more posterior “danger space” - which is dangerous
because it listens to rap music and plays first person shooter video games - plus it extends into
the mediastinum - so you could potentially dump pus, or cancer, right into the mediastinum
Infectious behind this deep cervical fascia (the Prevertebral Space)
are different than the ones
discussed below in that they are not spread from the neck but instead the spine/disc (osteomyelitis
Retropharyngeal Space / Danger Space
In fe c tio n
Involvement o f the retropharyngeal
space most often occurs from spread from the tonsillar
tissue. You are going to have centrally low density
tissue and stranding in the space. You should evaluate
for spread o f infection into the mediastinum.
Don 'I Forget: Delays are often critical for differentiate phlegmon and drainable abscess
Retropharyngeal Space / Danger Space
N e c ro tic N ode s
(nodes o f Rouviere) - These things are located in the lateral retropharyngeal region. In kids you can see suppurative infection in these, but around age 4 they start to regress - so adults are actually much less to get infection in this region. Now, you can still get mets (squamous cell, papillary thyroid, etc..). Lymphoma can involve these nodes as well - but won’t be necrotic until treated.
SCC and infrahyoid neck
When you are talking about head and neck cancer, you are talking about squamous cell cancer.
Now, this is a big complex topic and requires a fellowship to truly understand / get good at.
Obviously, the purpose o f this book is to prepare you for multiple choice test questions not
teach you practical radiology. If you want to actually learn about head and neck cancer in a
practical sense you can try and find a copy o f Hamsberger’s original
Lymph node anatomy
testable trivia
Anterior Belly o f Digastric
separates 1A from 1B
Stylohyoid muscle
(posterior submandibular
gland) separates 1B from
2A
Jugular Vein (Spina!
Accessory Nerve) separates
2A from 2B *see below
Vertical borders:
2-3 = Lower Hyoid
3-4= lower cricoid
Lymph node anatomy
2A
Anterior, Medial, Lateral or Abutting the Posterior Internal Jugular
Lymph node anatomy
2B
Posterior to the Internal Jugular, with a clear fat plane between node and IJ
Floor o f th e M outh SCC
touched on this once already. Just remember smoker/drinker in an old person. HPV in a
young person. Necrotic level 2 nodes can be a presentation (not a branchial cleft cyst).
N a s o p h a ryn g e a l SCC:
This is more common in Asians and has a bi-modal distribution: • group 1 (15-30) typically Chinese • group 2 (> 40). Involvement o f the parapharyngeal space results in worse prognosis (compared to nasal cavity or oropharynx invasion).
Fossa of Rosenmuller
The FOR is the MOST COMMON location for
Nasopharyngeal Cancer
See a Unilateral Mastoid Effusion or See a Pathologic Retropharyngeal Node
Look
at the
FOR
“Earliest Sign ” o f nasopharyngeal SCC is
the effacement o f the fat within the FOR.
“Earliest Sign ” o f nasopharyngeal SCC is
the
“Earliest Sign ” o f nasopharyngeal SCC is
the effacement o f the fat within the FOR.
See a Pathologic
Retropharyngeal or
Supraclavicular Node
Look at the Clivus
About 30% o f the patients with nasopharyngeal tumors
have skull base erosion.
(MR1 ^ CT for skull base invasion)
Nodal mets are present in 90% o f
nasopharyngeal tumors, with the
retropharyngeal nodes usually the
first involved.
Nek anatomy page 153
go there now pictures on phone from 7/15/21
L a ry n g o c e le
When the laryngeal “saccule” dilates with air you call it a
laryngocele. If it is filled with fluid you still might call it a
larygocele (but if saccular cyst is a choice - consider that). If it
is filled with fluid and air you still might call it a larygocele
(but it laryngopyocele is a choice — and you have any hint of
infection - consider that
L a ry n g o c e le
what is a saccule
The “saccule” is the
appendix of the laryngeal ventricle (a blind ending sac that
extends anterior and upwards). It’s usually closed or
minimally filled with fluid (you don’t typically see it in
normal adults).
L a ry n g o c e le
why does a saccule dilate
Usually because it’s obstructed (ballvalve
mechanics at the neck of the saccule), and the testable
point is that 15% of the time that obstruction is a tumor.
You can also see them in forceful blowers (trumpet players,
glass blowers) — well maybe, this depends on what you
read. Simply read the mind of the question writer to know if
they are on team trumpet player laryngocele.
L a ry n g o c e le :
internal vs external
ointernal vs external version of this (based on
containment of violation of
the thyrohyoid membrane).
V o c a l Cord P a ra ly s is
The involved side will have an expanded ventricle (it’s the opposite side with a cancer). If you see
it on the left, a good “next step” question would be to look at the chest (for recurrent laryngeal nerve
involvement at the AP window).
V o c a l Cord P a ra ly s is
buzzword
“Hoarseness” - If you see “Hoarseness” in the question header, you need to
dkjpO think recurrent laryngeal nerve compression in the AP Window - either from a mass/node
or aortic path. *Hoarseness is also a classic Laryngeal CA buzzword (so look there too).
■gG4- Orbit
Lymphocytic
Hypophysitis:
This is histologically the same thing as orbital pseudotumor but instead involves the cavernous sinus. It is painful (just like pseudotumor), and presents with multiple cranial nerve palsies. It responds to steroids (just like pseudotumor).
laryngeal Cancer
Risk Factors
Smoking, Alcohol, Radiation, Laryngeal Keratosis, HPV, GERD, & Blasphemy against the correct religion (false religions are safe to talk shit about).
laryngeal Cancer
role
The role of the Radiologist is not to make the primary cancer diagnosis here, but to assist in staging.
Laryngeal cancers are subdivided into (a) supraglottic, (b) glottic, and (c) subglottic types.
“Transglottic” would refer to an aggressive cancer that crosses the laryngeal ventricle.
laryngeal Cancer
Supra-Glottic
-More Aggressive
-Early Lymph
Node Mets
-They do n ’t get
hoarseness
laryngeal Cancer
Supra-Glottic:
Epiglottic Centered
-Anterior
-Likes to Invade the Pre-
Epigolttic Space /Fat (which
is rich in lymphatics
laryngeal Cancer
Supra-Glottic:
False Cord / Fold
Centered
-Posterior Lateral
-Likes to Invade the Para-
Glottic Space /Fat (which
communicates superiorly
with the Pre-Epiglottic
Space
laryngeal Cancer
Glottic
-Most Common
-Best Outcome
-Grow Slowly
-Metastatic Disease
is Late
laryngeal Cancer
Sub-Glottic
-Least Common
-Often small
compared to nodal
burden
-Bilateral nodal
disease &
mediastinal
extension
laryngeal Cancer
Paraglottic space
involvement makes the
tumor
T3 and
“transglottic: ”
*Best seen in coronals.
laryngeal Cancer
Fixation of the cords
indicates at least a
T3 tumor - this is best assessed with a scope but can be suspected with disease in the cricoarytenoid joint.
laryngeal cancer
Invasion of the cricoid cartilage
is a contraindication to all types of laryngeal conservation surgery (cricoid cartilage is necessary for postoperative stability of the vocal cords).
Laryngeal cancer
The only reliable sign of
cricoid invasion is
tumor on both sides of
the cartilage (irregular
sclerotic cartilage can
be normal).
Retinob la stoma
This is the most common primary malignancy o f the globe. If you see
calcification in the globe of a child - this is the answer.
Retinob la stoma
globe size
The globe should be normal in size (or bigger), where Coats’ is usually smaller. It’s usually seen
before age 3 (rare after age 6). The trivia is gonna be where else it occurs. They can be bilateral
(both eyes - 30%), trilateral (both eyes and the pineal gland), and quadrilateral (both eyes,
pineal, and suprasellar).
Retinob la stoma
step 1
The step 1 question is RB suppressor gene (chromosome 13 — “unlucky 13”). That’s the same
chromosome osteosarcoma patients have issues with and why these guys are at increased risk o f
facial osteosarcoma after radiation
C o a ts ’ D is e a s e
The cause o f this is retinal telangiectasia which results
in leaky blood and subretinal exudate. It can lead to retinal detachment. It’s
seen in young boys and typically unilateral. The key detail is that it is NOT
CALCIFIED (retinoblastoma is).
C o a ts ’ D is e a s e
imaging
CT - Dense
T1 - Hyper
T2 - Hyper
Coats disease has a smaller globe. Retinoblastoma has a
normal sized globe.
P e rs is te n t H y p e rp la s tic P rim a ry V itre o u s (PH P V ) -
This is a failure o f the embryonic ocular blood supply to regress. It can lead to retinal
detachment. The classic look is a small eye (microphthalmia) with increased density of
the vitreous. No calcification
Retinal Detachment
This can occur
secondary to PHPV or Coats. It can also be
caused by trauma, sickle cell, or just old age.
The imaging finding is a “V” or “Y” shaped
appearance due to lifted up retinal leaves and
subretinal fluid.
Globe Size Comparison
- A Strategy’ for Eliminating Distractors
Retinoblastoma - Normal Size * PH P V - Small Size (Normal Birth Age) Toxocariasis - Normal Size * Retinopathy o f Prematurity - Bilateral Small Coats’ - Smaller Size
Orbit Melanoma
This is the most common intra-occular lesion in an adult. If you see an
enhancing soft tissue mass in the back o f an adult’s eye this is the answer.
Melanoma
questions
(1) show a picture - what is it?,
(2) ask what the most common intra-occular lesion in an adult is?
(3) ask the buzzword “collar button sh a p ed ’’ ? - which is related to
Bruch’s membrane,
(4) strong predilection for liver mets - next step Liver MR.
O p tic N e rv e Glioma
These almost always (90%)
occur under the age o f 20. You see expansion / enlargement
o f the entire nerve. If they are bilateral you think about
NF-1. They are most often WHO grade 1 Pilocytic
Astrocytomas. If they are sporadic they can be GBMs and
absolutely destroy you.
O p tic N e rv e S h e a th M en in g iom a
The buzzword
is “tram-track” calcifications. Another buzzword is
“doughnut” appearance, with circumferential enhancement
around the optic nerve.
Dermoid optic
This is the most common benign
congenital orbital mass.
It’s usually superior and lateral, arising from the
frontozygomatic suture, and presenting in the first
10 years o f life. It’s gonna have fat in it (like
Rhabdomyosarcoma orbital
Most common extra-occular orbital malignancy in children
(dermoid is most common benign orbital mass in child). Favors the superior-medial orbit and
classically has bone destruction. Just think “bulky orbital mass in a 7 year old.”
When they do occur - 40% o f the time it’s in the head and neck - and then most commonly it’s in
the orbit. It’s still rare as hell.
Stenosis sagittal view
vertebral body / spinal canal < 0.85
M e ta s ta tic N eu ro b la s tom a
This has a very classic appearance of “Raccoon Eyes” on
physical exam.
M e ta s ta tic N eu ro b la s tom a
classic location
The classic location is periorbital tumor infiltration
with associated proptosis. Don’t forget a basilar skull
fracture can also cause Raccoon Eyes… so clinical
correlation is advised. Neuroblastoma mets tend to be
more
M e ta s ta tic N eu ro b la s tom a
Worth mentioning
Another thing worth mentioning is the bony
involvement of the greater wing of the sphenoid.
Neuroblastoma is gonna be bilateral. Ewings favors
this location also - but will be unilateral.
M e ta s ta tic Scirrhous (fibrosing)
B re a s t C a n c e r -
This is classic gamesmanship here. The important point to
know is that unlike primary orbital tumors that are going to
cause proptosis, classically the breast cancer met causes a
desmoplastic reaction and enophthalmos (posterior
displacement o f the globe).
M e ta s ta tic Scirrhous (fibrosing)
B re a s t C a n c e r -
Trivia
Trivia: Mets are actually more common to the eye
relative to the orbit (like 8x more common).
Infiltrative retrobulbar mass +
enophthalmos
scirrhous carcinoma
of the breast
■gG4- Orbit
Orbital Pseudotumor
This is one of those IgG4 idiopathic inflammatory conditions that involves the extraoccular muscles. It looks like an expanded muscle. The things to remember are that this thing is painful, unilateral, it most commonly involves the lateral rectus and it does NOT spare the myotendinous insertions. Remember that Graves does not cause pain, and does spare the myotendinous insertions. It gets better with steroids. It’s classically T2 dark.
■gG4- Orbit
Tolosa Hunt Syndrome
This is histologically the same thing as orbital pseudotumor but instead involves the cavernous sinus. It is painful (just like pseudotumor), and presents with multiple cranial nerve palsies. It responds to steroids (just like pseudotumor).
■gG4- Orbit
Lymphocytic
Hypophysitis:
This is histologically the same thing as orbital pseudotumor but instead involves the cavernous sinus. It is painful (just like pseudotumor), and presents with multiple cranial nerve palsies. It responds to steroids (just like pseudotumor).
Thyroid Orbitopathy
This is seen in
1 /4th o f the Graves cases and is the most
common cause o f exophthalmos. The
antibodies that activate TSH receptors also
activate orbital fibroblasts and adipocytes.
Thyroid Orbitopathy
things to know
Things to know: Risk of compressive optic neuropathy • Enlargement o f ONLY MUSCLE BELLY (spares tendon) - different than pseudo tumor NOT Painful - different than pseudo tumor Order of Involvement: IR > MR > SR > LR > SO/IO Inferior, Middle, Superior, Lateral, Oblique
Thyroid Orbitopathy spares
tendon insertion
Orbital Vascular Malformations
Lymphangioma
These arc actually a mix of venous and lymphatic malfonnations. They arc illdefined and lack a capsule. The usual distribution is infiltrative (multi-spatial), involving, preseptal, post-septal, extraconal, and intraconal locations. Fluid-Fluid levels are the most classic finding , with regard to multiple choice. Do NOT distend with provocative maneuvers (valsalva).
Orbital Vascular Malformations
Varix
These occur secondary to weakness in the post-capillary venous wall (gives you massive dilation of the valvclcss orbital veins). Most likely question is going to pertain to the fact that they distend with provocative maneuvers (valsalva, hanging head, etc...). Another piece of trivia is that they are the most common cause o f spontaneous orbital hemorrhage. They can thrombose and present with pain.
Orbital Vascular Malformations
Carotid-Cavernous Fistula
These come in two flavors: (1) Direct - which is secondary to trauma, and (2) Indirect - which just occurs randomly in post menopausal women. The direct kind is a communication between the intracavemous ICA and cavernous sinus. The indirect kind is usually a dural shunt between meningeal branches of the ECA and the Cavernous Sinus. Buzzword: Pulsatile Exophthalmos *although this can also be a buzzword fo r NF-1 in the setting o f sphenoid wing dysplasia.
Intraconal
Space
is the
space inside the
rectus muscle
pyramid.
Extraconal
Space
is the
space outside
the rectus
muscle pyramid
Pre-SeptalI Post-Septal Cellulitis
As above, location of orbital infections are described by their relationship to the orbital septum. The
testable trivia is probably (1) that the orbital septum originates from the periosteum of the orbit and
inserts in the palpebral tissue along the tarsal plate, (2) that pre-septal infections usually start in
adjacent structures (likely teeth and the face), (3) post-septal infections are usually from paranasal
sinusitis, and (4) pre-septal infections are treated medically, post septal is surgical
Pre-SeptalI Post-Septal Cellulitis
trivia
Periorbital abscess can cause thrombosis of the ophthalmic veins or cavernous sinus (in
extreme examples infection — usually aspergillosis — can even cause a cavemous-carotid fistula).
Dacryocystitis
This is inflammation and dilation of the
lacrimal sac. It has an Aunt Minnie
look, with a well circumscribed, round
rim enhancing lesion centered in the
lacrimal fossa. The etiology is typically
obstruction followed by bacterial
infection (staph and strep).
Usually this is diagnosed clinically unless there is an associated peri-orbital cellulitis in which can
CT is needed to exclude post septal infection (treated surgically) from simple dacryocystitis
(treated non-surgically).
Orbital Subperiosteal Abscess
If you get inflammation under the periosteum
it can progress to abscess formation.
This is usually associated with ethmoid
sinusitis. This also has a very classic look
Optic Neuritis:
There will be enhancement of the optic
nerve, without enlargement of the nerve/
sheath complex. Usually (70%) unilateral,
and painful.
You will often see intracranial or spinal cord
demyelination - in the setting o f Devics
(neuromyelitis optica). 50% of patient’s with
acute optic neuritis will develop MS
If the optic nerve is enlarged, think
glioma… then think NF-1.
Papilledema:
This is really an eye exam thing.
Having said that you can sometimes see dilation/ swelling o f the optic nerve sheath.
Drusen
Mineralization at the
optic disc. Supposedly there is an
association with age-related
maculopathy
NOT Legit Indications for Fluoro Guided LP — all o f which I ’ve heard:
• “The patient is crazy”
• “The patient is crazy & violent”
• “The patient is crazy, violent, and has high viral load HIV…. and Hep C”
• “The patient recently escaped a locked mental institution for the extremely violent and criminally
insane, has both HIV and Hep C. He spits like a camel and has really terrible body odor.”
Ectopia Lentis (lens dislocation)
Causes include
Trauma, Marfans, and
Homocystinuria
Coloboma
This is a focal discontinuity o f the globe
(failure o f the choroid fissure to close).
They are usually posterior. If you see a
unilateral one - think sporadic.
If you see bilateral ones - think CHARGE
(coloboma, heart, GU, ears).
Cord Blood Supply
There is an anterior blood supply and a posterior blood supply to the cord.
These guys get taken out with different clinical syndromes
Anterior spinaI artery
arises bilaterally as two small branches at the level o f the termination of
the vertebral arteries. These two arteries join around the level o f the foramen magnum.
Artery o f Adamkiewicz
This is the most notable Anterior
reinforcer o f the anterior spinal artery. In 75%
of people it comes off the left side of the aorta
between T8 and Ti l . It supplies the lower 2/3
of the cord. This thing can get covered with the
placement of an endovascular stent graft for
aneurysm or dissection repair leading to spine
infarct.
Posterior Spinal Artery
Paired arteries which
arise either from the vertebral arteries or the
posterior inferior cerebellar artery. Unlike
anterior spinal artery this one is somewhat *
discontinuous and reinforced by\ multiple segmental or radiculopial branches.
Conus Medullaris
This is the terminal end of the spinal cord. It usually terminates at around L I.
Below the inferior endplate of the L2 / L3 body should make you think tethered cord (especially if
shown in a multiple choice setting).
Epidural Fat
The epidural fat is not evenly distributed. The epidural space in the cervical cord is
predominantly filled with venous plexus (as opposed to fat). In the lumbar spine there is fat both
anterior and posterior to the cord. “Epidural Lipomatosis ” = is a hypertrophy of this fat that only
occurs with patients on steroids (“on corticosteroids” would be a huge clue).
Stenos is
Stenos is : Spinal stenosis can be congenital (associated with short
pedicles) or be acquired. The Torg-Pavlov ratio can be used to call it
(cervical canal diameter to vertebral body width < 0.85).
Symptomatic stenosis is more common in the cervical spine (versus
the thoracic spine or lumbar spine). You can get some congenital
stenosis in the lumbar spine from short pedicles, but it’s generally not
symptomatic until middle age
Stenosis sagittal view
vertebral body / spinal canal < 0.85
Spondylosis Deformans
This is probably part of “normal aging” “Degenerative Change” or spine osteoarthritis. This is more rim / margin centered. Process is characterized by osteophyte formation.
Intervertebral Osteochondrosis
Pathologic (but
not necessarily
symptomatic
“Deteriorated Disc” - This process is more
centered in the disc space favoring the nucleus
pulposus & vertebral body endplates.
Osteophytes:
• More horizontal / oblique with a “claw” like appearance. • Formed also the vertebral margin. . Seen in “DJD” / Spondylosis
Syndesmophytes:
• More vertical symmetric, and thinner • Represent ossification of the annulus fibrosis. • Seen in Ankylosing Spondylitis.
En d p la te Changes: Commonly referred to as “Modic Changes
types
Type 1
“Edema”
T1 Dark,
T2 Bright
Type 2 “ Fat”
T1 Bright,
T2 Bright
Type 3
“Scar”
T1 Dark, T2 Dark
En d p la te Changes: Commonly referred to as “Modic Changes
overview
There is a progression in the MRI signal characteristics
that makes sense if you think about it. You start out with
degenerative changes causing irritation / inflammation
so there is edema (T2 bright). This progresses to chronic
inflammation which leads to some fatty change - just
like in the bowel o f an IBD patient - causing T1 bright
signal. Finally, the whole thing gets burned out and
fibrotic and it’s T1 and T2 dark. As a prominent factoid,
Type 1 changes look a lot like Osteomyelitis (clinical
correlation is recommended).
A n n u la r Fissure:
As the disc ages, it tends to dry out making it more friable and easily tom. “Tears” in the annulus (which are present in pretty much every degenerated disc) aren’t called “tears” but instead “fissures". People who write the papers on this stuff make a big fucking deal about that - with the idea being that “tear” implies pathology. Fissuring can be asymptomatic and part of the aging process. Even though fissures are present in basically every degenerated disc you don’t always see them on MRI. What you do see (some of the time) is a fluid signal gap in the annulus - which has been given the official vocabulary word “High Intensity Zone,” and anything with official vocabulary nomenclature should be respected as possible multiple choice fodder.
A n n u la r Fissure:
know this
•Annular fissures may be a source of pain
(radial pain fibers - trigger “discogenic pain”) but are also seen as incidentals.
»Fissures are found in all degenerative discs but are not all fissures are visualized as HIZs.
»Discography is more sensitive to fissures relative to MRI. but still not 100% sensitive.
*Also, Dude, “Tear” is not the preferred nomenclature - “Fissure.”
Schm orl Node:
Intravertebral Herniation
This is a herniation of disc material through a defect in the vertebral body endplate into the actual marrow. Common - like 75% of people have them. Classic look is to favor the inferior endplate of the lower thoracic / upper lumbar spine. When they are acute they can have edema on T2 and be dark on Tl - mimicking osteomyelitis. Chronic versions will have a sclerotic rim.
S c h e u e rm a n n ’s
This is multiple levels (at least 3) of wedged vertebral bodies with associated Schmorl’s nodes — Most classically the thoracic spine of a teenager, resulting in kyphotic deformity (40 degrees in thoracic or 30 degrees in thoracolumbar). 25% of patients have scoliosis
Limbus
V e r te b ra
This is a fracture mimic that is the result of herniated disc material between the nonfused apophysis and adjacent vertebral body.
Disc Nomenclature
Herniation
This is the approved verbiage for the
displacement of LESS THAN 25% of
disc material beyond the limits of the
disc space.
E x te n s io n T e a rd ro p
list
Distraction Injury
Stable in flexion (unstable in extension)
Hyperextension
Classic History “Hitfrom behind
Disc Nomenclature
Protrusion (subtype
of herniation)
Term used when the distance between the edge of the disc herniation is less than the distance between the edges of the base (base wider than herniation
Disc Nomenclature
Extrusion
(subtype of
herniation)
Term used when the edges of the disc are greater than the distance of the base (neck narrower than herniation).
Disc Nomenclature
Sequestration
Free (broken off)
disc fragment
Disc Nomenclature
Localization
Cranial
Caudal Plane
Disc Level
Suprapedicle Level
-Pedicle Level
- Infrapedicle Level
Disc Nomenclature
Localization
Axial Plane
Extra Foraminal Foraminal *Often symptomatic because o f the relationship to the Dorsal Root Ganglia Sub Articular *Most Common Location Central
Which Nerve is CompressedP
There are 31 pairs o f spinal nerves, with each pair corresponding to the adjacent
vertebra - the notable exception being the “C8” nerve. Cervical disc herniations are
less common than lumbar ones.
The question is most likely to take place in the lumbar spine (the same spot most disc
herniations occur). In fact more than 90% o f herniations occur at L4-L5, and L5-S1
A foraminal disc will smash the
exiting nerve
a central or subarticular disc will smash
the descending nerve
LP / Myelogram Technique
Absolute Contraindications
- Increased intracranial pressure or obstructed CSF flow
- Bleeding diathesis (hvpocoagulabilitv)
- Myelogram Specific — Iodinated contrast allergy
LP / Myelogram Technique
Prior to the LP
A CR-ASNR recommendations
STOP Coumadin 4-5 days STOP Plavix for 7 days Hold LMW Heparin for 12 hours Hold Heparin for 2-4 hours - document normal PTT Aspirin and NSAIDs are fine (not contraindicated)
LP / Myelogram Technique
Relative Contraindications
(vary per institution):
• Overlying infection, hematoma, or scarring
• Myelogram Specific - Recent myelogram (< 1 week)
• Myelogram Specific - History o f seizures
Legit Indications for Fluoro Guided LP:
• Advanced degenerative spondylosis,
• Post-surgical changes,
• Patient is so fat (“a person of size”), when Dracula sucked his/her blood, he got diabetes.
• Myelogram Specific - MRI contraindication
• Myelogram Specific - Geriatric Professor Emeritus of Neurosurgery wants it, and it is better than
doing the pneumoencephalogram he originally ordered.
NOT Legit Indications for Fluoro Guided LP — all o f which I ’ve heard:
• “The patient is crazy”
• “The patient is crazy & violent”
• “The patient is crazy, violent, and has high viral load HIV…. and Hep C”
• “The patient recently escaped a locked mental institution for the extremely violent and criminally
insane, has both HIV and Hep C. He spits like a camel and has really terrible body odor.”
LP / Myelogram Technique
technical overview
L2-L3 or L3-L4 are common entry points. A potential trick would be to show you imaging with a low lying conus (usually that thing stops at L1-L2). Remember you need to be below the conus - so you might need to adjust down, depending on how low it is
Target the inlerlaminar space, just off of midline. . Always aspirate before you inject anything.
The needle will naturally steer toward the sharper side and away from the bevel. So, if you are directing the needle, you’ll want the bevel side opposite the direction you are attempting to steer.
Myelogram Specific - Contrast should flow freely away from the needle tip, gradually filling the thecal
sac. The outlining of the cauda equina is another promising sign that you did it right. If contrast pools at
the needle tip or along the posterior or lateral thecal sac without free-flow, a subdural injection or
injection in the fat around the thecal sac should be suspected.
Technical Strategies to Reduce the Incidence of Post Dural Puncture Headache (PDPH):
’ Use a small needle (25 G), especially for epidural pain injections or myelography. You might have
to use a 22G for a diagnostic LP or you are going to struggle to get enough fluid for a sample, and
your opening pressures may not be accurate.
1 Non-cutting “atraumatic” needle (diamond shaped tip) reduce incidence o f PDPH
Replace the stylet before you withdraw the needle. This isn’t just for the 1 in a million chance that
you suck a nerve root up in the needle. This has also been shown to reduce incidence o f PDPH
Technical Strategies to Reduce the Incidence of Post Dural Puncture Headache (PDPH):
Direction o f the bevel: This actually matters
You want to run the bevel parallel with the fibers to push them apart, not cut them
perpendicular is wrong you are going to cut those fibers. Coming in at a crazy angle is not ideal for same reason
Blood Patch
Overview
Even a miniscule defect within the thecal sac post LP
can allow leakage of spinal fluid resulting in
intracranial hypotension and the dreaded chronic/
debilitating post dural puncture_headache.
Classic PDPHs are bilateral, better laying down, and
worse sitting up. They are also worse with coughing,
sneezing, or straining to push out a large turd (from
chronic opioid abuse).
The procedure involves injecting between 3-20cc of the
patients own blood into the epidural space near the
original puncture site with the hope of sealing the hole
Blood Patch
bulletts
. Most PDPHs start 24 hours after the puncture (between 24-48 hours) - larger leaks can present earlier. . Most people will wait 72 hours after the headache begins (“conservative therapy”) prior to attempting the patch. . Most people will try at least twice before calling neurosurgery to sew to hole you carved out of the dura (you fucking psycho) • Severe atypical symptoms should prompt a CT (to exclude a subdural from severe hypotension).
“Fa iled B a c k S u rg e ry S yn d rom e ” (FBSS)
Another entity invented by NEJM to take down the surgical subspecialties. Per the NEJM these
greedy surgeons generally go from a non-indicated spine surgery, to a non-indicated leg amputation,
to a non-indicated tonsillectomy on an innocent child.
Text books will define it as recurrent or residual low back pain in the patient after disk surgery. This
occurs about 40% of the time (probably more), since most back surgery is not indicated and done on
inappropriate candidates. Causes of FBSS are grouped into early and late for the purpose of multiple
choice test question writing:
Complications of Spine Surgery
Recurrent Residual Disk
Will lack enhancement (unlike a scar - which will enhance on delays)
Complications of Spine Surgery
Epidural Fibrosis
Scar, that is usually posterior, and enhances homogeneously
Complications of Spine Surgery
Arachnoiditis
Buzzwords are “clumped nerve roots ” and “empty thecal sac ”,
Enhancement for 6 weeks post op is considered normal. After 6 weeks
may be infectious or inflammatory.
Complications of Spine Surgery
12,000 Square Foot
Mansion Syndrome
As spine surgeons perform more and more unnecessary surgeries they
need something to spend all that money on.
THIS v.s THAT: Sca r v.v Residual Disc
Tl Pre Contrast they will look the same… like a bunch of mushy crap.
Tl Post Contrast the disc will still look like mushy crap, but the scar will enhance
Conjoined N e rv e Roots
Two adjacent nerve roots sharing an enlarged common sleeve - at a point during their exit from the
thecal sac. This can be a source of FBSS if it is the source of pain instead of a disc. Alternatively it
could be misidentified as a disc preoperatively. In both cases, the Radiologist will be cast in the roll
of “Scapegoat” during the malpractice suit.
Odontoid F ra c tu re
C la s s ific a tio n
type 1
(rare)
Fracture at upper part of Odontoid (related to avulsion o f the alar ligament) May be Stable
Odontoid F ra c tu re
C la s s ific a tio n
type 2
most common
Fracture at the base (high nonunion rate) Unstable
Odontoid F ra c tu re
C la s s ific a tio n
Type 3
best prognosis for healing
Fracture through dens into the body ofC2. Unstable
J e ffe rs o n F ra c tu re
This is an axial loading injury (jumping into a
shallow pool) - with the blow typically to the
top of the head.
The anterior and
posterior arches blow
out laterally.
• About 30% will also have a C2 Fracture
• Neurologic (cord) damage is rare, because
all the force is directed into the bones.
Could be shown on a plain
film open mouth odontoid
view.
Remember the C 1 lateral
masses shouldn’t slide off
laterally.
Os Od o n to id eum I Os T e rm in a le
These variants can mimic a type 1 Odontoid fracture. In both cases, you have an ossicle located at the
position of the odontoid tip (the orthotopic position). The primary difference is that with an
Os Odontoideum the base of the dens is usually hypoplastic
Anterior Cord Syndrome (The Really Bad One):
The anterior portion of the cord is jacked. Motor function and anterior column sensations (pain and
temperature) are history. The dorsal column sensations (proprioception and vibration) are still intact.
This is the reason FLEXION injuries are so bad.
H an gm a n ’s F ra c tu re
Seen most commonly when the chin hits the dashboard in an MVA
(“direct blow to the face”). The fracture is through the bilateral pars at
C2 (or the pedicles - which is less likely). You will have anterior
subluxation of C2 on C3 (> 2mm). Cord damage is actually uncommon
with these, as the acquired pars defect allows for canal widening. There is
often an associated fracture of the anterior inferior comer at C2 - from
avulsion of the anterior longitudinal ligament. Traction is
contraindicated.
Flex ion Te a rdrop
overview
This represents a teardrop shaped fracture
fragment at the anterior-inferior vertebral body.
Flexion injury is bad because it is associated
with anterior cord syndrome (85% o f patients
have deficits). This is an unstable fracture,
associated with posterior subluxation of the
vertebral body.
Flex ion Te a rdrop
list
Impaction Injury
Extremelv Unstable
Hyperflexion
Classic History: “Ran into wall
E x te n s io n T e a rd ro p
overview
Another anterior inferior teardrop
shaped fragment with avulsion o f the
anterior longitudinal ligament. This is
less serious than the flexion type
E x te n s io n T e a rd ro p
list
Distraction Injury
Stable in flexion (unstable in extension)
Hyperextension
Classic History “Hitfrom behind
C la y -S h o v e le r’s F ra c tu re
This is an avulsion injury o f a
lower cervical / upper thoracic spinous process (usually C7). It is
the result o f a forceful hyperflexion movement (like shoveling).
The “ghost sign” describes a double spinous process at C6-C7 on
AP radiograph.
C h an c e F ra c tu re
These are flexion-distraction fractures that are
classically associated with a lap-band seatbelt.
There are 3 column (unstable) fractures.
Most commonly seen at the upper lumbar levels &
thoracolumbar junction.
High association with solid organ trauma
F a c e t D is lo c a tio n
unilaterl
If you have unilateral locked facet (usually from hyperflexion and rotation) the
superior facet slides over the inferior facet and gets locked. The unilateral is a stable injury.
You will have the inverted hamburger sign on axial imaging on the dislocated side.
F a c e t D is lo c a tio n
bilateral
This is the result o f severe hyperflexion
You are going to have disruption o f the posterior
ligament complex. When this is full on, you are
going to have the dislocated vertebra displaced
forward one - h a lf the AP diameter o f the vertebral
body. This is highly unstable, and strongly
associated with cord injury.
F a c e t D is lo c a tio n
bilateral
This is a spectrum: Subluxed facets -> Perched -> Locked.
A tla n to a x ia l In s ta b ility
The articulation between Cl and C2 allows for lateral movement (shaking your head no). The
transverse cruciform ligament straps the dens to the anterior arch o f C l . The distance between
the anterior arch and dens shouldn’t be more than 5 mm. The thing to know is the association
with Down syndrome and juvenile RA.
Rotary subluxation can occur in children without a
fracture, with the kid stuck in a “cock-robin”
position - which looks like torticollis. Actually
differentiating from torticollis is difficult and may
require dynamic maneuvers on the scanner.
This never, ever, ever happens in the absence o f a
fracture in an adult (who doesn’t have Downs or
RA). Having said that, people over call this all the
time in adults who have their heads turned in the
scanner.
Pars In te ra r tic u la r is D e fe c t (S po ndy lo ly sis or A d u lt Is thm ic
S p o n d y lo lis th e s is )
the adult version. Defects in the pars interarticuaris are
usually caused by repetitive micro-trauma (related to hyper-extension). It is nearly
always at L5-S1 (90%). Pain is typically a L5 radiculopathy caused by foraminal
stenosis at L5 -S1. The term “pseudo-disc” is sometimes used to describe the
deformed annular fibers seen in the setting o f a related anterolithesis (forward
slippage).
Instability
trauma overview
For the purpose of multiple choice you will see the words “stable ” or “unstable ” associated with
specific fracture types. There are also some radiologic “definitions” of instability which seem to
vary depending on who you ask. In general, if you have acute segmental kyphosis greater than 11
degrees, acute anterolisthesis greater than 3-4 mm, or gross motion on flexion / extension imaging
it is probably an unstable fracture. You will also hear people talk about a “power ratio” for
occipitocervical instability, and a spinal column theory for the thoracolumbar injury.
Instability
definition
ou will read different definitions of “instability” as it relates to spinal trauma. The one I prefer
is something along the lines of “lost capacity to withstand even a normal physiologic load
without: potential damage to the spinal cord, nerve roots, or developing an incapacitating
deformity that forces one to seek employment in a cathedral bell tower. ”
Occipitocervical Instability
This can be traumatic (in which case the patient rarely lives because they rip their brainstem in half), or congenital (classically seen with Down Syndrome). Two popular methods for evaluating this:
Occipitocervical Instability
powers ratio
= C-D: A-B Ratio is greater than 1.0 = Ligamentous Instability
Transverse Myelitis
This is a focal inflammation of the cord. The causes are
numerous (infectious, post vaccination - classic rabies, SLE, Sjogren’s,
Paraneoplastic, AV-malformations). You typically have at least 2/3 of the cross
sectional area of the cord involved, and focal enlargement of the cord. Splitters will
use the terms “Acute partial” for lesions less than two segments, and “acute
complete” for lesions more than two segments. The factoid to know is that the
“Acute partials” are at higher risk for developing MS.
Denis 3 Spinal Column Concept
Most often you will see this idea applied to
thoracolumbar spinal fractures, although
technically it has some validity in the lower
cervical segments as well.
The idea is to divide the vertebral column into 3
vertical parallel columns , with instability
suggested when all 3 or 2 contiguous columns
(anterior and middle column or middle and
posterior column) arc disrupted.
Denis 3 Spinal Column Concept
anterior
• Anterior Longitudinal Ligament • Anterior 2/3 Vertebral Body
Denis 3 Spinal Column Concept
middle
• Posterior Longitudinal Ligament • Posterior 1/3 Vertebral Body
Denis 3 Spinal Column Concept
posterior
• Posterior Ligaments • Pedicles, Facets, Lamina, Spinous Process
When Does a “Trauma” Indicate Imaging P
Canadian C-Spine Rule
Age >65 years • Paresthesias in extremities • Dangerous mechanism • Fall >3 ft or 5 stairs • Axial load to the head (empty swimming pool diving, piano fell on head - while chasing a road runner High Speed MVA, • Pedestrian vs Car • Hulk Smash
When Does a “Trauma” Indicate Imaging P
Nexus Criteria:
focal neurological deficie Nexus Criteria: Midline spinal tenderness Altered level o f consciousness Intoxication (you c an ’t clear a drunk guys/girls c-spine while they are Distracting injury
Unstable
Vertebral Overriding > 3mm (“Subluxation”)
Angulation > 11 Degrees
Flexion Tear Drop
Bilateral Facet Dislocation “Double-Locked”
Odontoid Fracture Type 2 and 3
(most sources will say Type 2 & 3 or deploy the word
“usually”, but for sure if there is lateral displacement)
Two Contiguous Thoracolumbar Columns
(anterior & middle or middle & posterior)
Three Thoracolumbar Columns
(Chance Fracture, Etc…)
Jefferson Fracture
Flangman Fracture
Atlanto-Occipital and Atlanto-Axial Dislocations
Stable
Extension Tear Drop (At least in Flexion)
Unilateral Facet Dislocation
Odontoid Fracture Type 1
I (usually stable - flex/extension films still usually done
\ to exclude atlantooccipital instability )
| Isolated Single Thoracolumbar Column Fracture
Clay Shoveler’s Fracture
Transverse Process Fracture
Named Spine Fractures quick
Jefferson
Burst Fracture of Cl Axial Loading
Named Spine Fractures quick
Hangman
Bilateral Pedicle or Pars Fracture of C2 Hyperextension
Named Spine Fractures quick
Teardrop
Can be flexion or extension Flexion (more common
Named Spine Fractures quick
Clay-Shoveler’s
Avulsion of spinous process at C7 or T1 Hyperflexion
Named Spine Fractures quick
Chance
Horizontal Fracture through thoracolumbar spine “Seatbelt
most important factor for outcome is the presence o f a
hemorrhagic spinal cord injury
they do bad
Spinal Cord Syndromes
Central Cord
Old lady with spondylosis or young person with bad extension injury. Upper Extremity Deficit is worse than lower (corticospinal tracts are lateral in lower extremity)
Spinal Cord Syndromes
Anterior Cord
Flexion Injury Immediate Paralysis
Spinal Cord Syndromes
Brown Sequard
Rotation injury or
penetrating trauma
One side motor, other
side sensory deficits
Spinal Cord Syndromes
Posterior Cord
Uncommon - but
sometimes seen with hyperextension
Proprioception gone
Anterior Cord Syndrome (The Really Bad One):
The anterior portion of the cord is jacked. Motor function and anterior column sensations (pain and
temperature) are history. The dorsal column sensations (proprioception and vibration) are still intact.
This is the reason FLEXION injuries are so bad.
Spinal AVM / AVFs
overview
There are 4 types. Type 1 is by far the most common (85%). It is a Dural AVF; the result
o f a fistula between the dorsal radiculomedullary arteries and radiculomedullary vein /
coronal sinus - with the dural nerve sleeve. It is acquired and seen in older patients who
present with progressive radiculomyelopathy. The most common location is the thoracic
spine. If anyone asks, the “gold standard for diagnosis is angiography” , although CTA or
MRA will get the job done. You will have T2 high signal in the central cord (which will be
swollen), with serpentine perimedullary flow voids (which are usually dorsal).
Spinal AVM / AVFs
type 1
Most Common Type (85%). Dural AVF - with a single coiled vessel
Spinal AVM / AVFs
type 2
Intramedullary Nidus from anterior spinal artery or posterior spinal artery. Can
have aneurysms, and can bleed. Most common presentation is SAH. Associated
with HHT and KTS (other vascular syndromes).
Spinal AVM / AVFs
type 3
Juvenile, very rare, often complex and with a terrible prognosis
Spinal AVM / AVFs
type 4
Intradural perimedullary with subtypes depending on single vs multiple arterial
supply. These tend to occur near the conus.
Foix A la jo u an in e Syndrome
This is a congestive myelopathy associated with a Dural AVF. The classic history
is a 45 year old male with lower extremity weakness and sensory deficits.
You have increased T2 signal (either at the conus or lower thoracic spine), with
associated prominent vessels (flow voids). The underlying pathophysiology is
venous hypertension - secondary to the vascular malformation.
Foix A la jo u an in e Syndrome
key finding
The vascular malformation flow voids are
- punctate, serpiginous, and serpentine.
They are NOT blob like
- sorta like what you see with CSF pulsation signal loss.
Swollen High Signal
Cord with Serpentine
flow voids along the
surface of cord
Syrinx
Also known as “a hole in the cord”. People use the word “syrinx” for all those fancy
French / Latin words (hydromyelia, syringomyelia, hydrosyringomyelia, syringohydromyelia,
syringobulbia etc. . They usually do this because they
don’t know what those words mean.
Syrinx
simple version
• Hydromyelia = Lined by ependyma.
• Syringomyelia = NOT lined by ependyma
These is zero difference clinically - which is why
everyone just says “syrinx.” The distinction is strictly
academic (i.e. multiple choice trivia).
Syrinx
acquired vs congenital
Most (90%) cord dilations (healthy and sick ones) are congenital, and associated with Chiari I and II,
as well as Dandy-Walker, Klippel-Feil, and Myelomeningoceles. The other 10% are acquired either
by trauma, tumor, or vascular insufficiency.
Syrinx
clinical practice
normal cord I call it “central cord dilation” or “benign central cord dilation.” If there is the same
thing but the cord around the dilation looks “sick” - grayish / high signal, or the cord is atrophic, then
I use the word “myelopathy” or “myelopathic changes.” Myelopathy is a word for a diseased cord -
usually from disc/osteophyte compression. Although, you can have myelopathy for any number of
neoplastic, post traumatic, or inflammatory processes.
Spinal Cord In fa rc t:
Cord infarct / ischemia can have a variety o f causes. The most
common cause is “ idiopathic,” although I ’d expect the most common multiple choice scenario
to revolve around treating an aneurysm with a stent graft, or embolizing a bronchial artery.
Impairment involving the anterior spinal artery distribution is most common. With anterior
spinal artery involvement you are going to have central cord / anterior horn cell high signal on
T2 (because gray matter is more vulnerable to ischemia).
The “owl’s eye” sign
o f anterior spinal cord infarct is a buzzword
Spinal Cord In fa rc t:
length
It’s usually a long segment, (more than 2 vertebral body segments). Diffusion using single
shot fast spin echo or line scan can be used with high sensitivity (to compensate for artifacts
from spinal fluid movement).
.Demyelinating (T2 / FLAIR Hyperintense
cord
Broadly you can think of cord pathology in 5 categories: Demyelinating, Tumor, Vascular, Inflammatory,
and Infectious.
In the real world, the answer is almost always MS - which is by far the most common cause. The other
three things it could be are Neuromyelitis Optica (NMO), acute disseminating encephalomyelitis
(ADEM) or Transverse Myelitis (TM).
MS in the Cord
“Multiple lesions, over space and time.” The lesions in the spine are typically
short segment (< 2 vertebral segments), usually only affect half / part of the cord. The cervical cord is
the most common location. There are usually lesions in the brain, if you have lesions in the cord
(isolated cord lesions occur about 10% of the time). The lesions can enhance when acute - but this is
less common than in the brain. You can sometimes see cord atrophy if the lesion burden is large.
Transverse Myelitis
This is a focal inflammation of the cord. The causes are
numerous (infectious, post vaccination - classic rabies, SLE, Sjogren’s,
Paraneoplastic, AV-malformations). You typically have at least 2/3 of the cross
sectional area of the cord involved, and focal enlargement of the cord. Splitters will
use the terms “Acute partial” for lesions less than two segments, and “acute
complete” for lesions more than two segments. The factoid to know is that the
“Acute partials” are at higher risk for developing MS.
ADEM in the cord
As described in the brain section, this is usually seen after a viral illness or infection
typically in a child or young adult. The lesions favor the dorsal white matter (but can involve grey
matter). As a pearl, the presence of cranial nerve enhancement is suggestive of ADEM. The step 1
trivia, is that the “anti-MOG IgG” test is positive in 50% of cases. Just like MS there are usually brain
lesions (although ADEM lesions can occur in the basal ganglia and pons - which is unusual in MS).
NMO (Neuromyelitis Optica): in the cord
This is also sometimes called Devics. It can
be monophasic or relapsing, and favors the optic nerves and cervical cord. Tends
to be longer segment than MS, and involve the full transverse diameter of the cord
(mild swelling). Brain lesions can occur (more commonly in Asians) and are
usually periventricular. If any PhDs ask, the reason the periventricular location
occurs is that the antibody (NMO IgG) attacks the Aquaporin 4 channels - which
are found in highest concentration around the ventricles.
Subacute Combined Degeneration
This is a fancy way of describing the
effects of a Vitamin B12 deficiency. The classic look is bilateral, symmetrically
increased T2 signal in the dorsal columns, without enhancement. The
appearance has been described as an “inverted V sign.” The signal change
typically begins in the upper thoracic region with ascending or descending
progression.
HIV Vacuolar Myelopathy:
This is the most common cause of spinal cord
dysfunction in untreated AIDS. Key word there is “untreated” - this is a late
finding. Atrophy is the most common finding (thoracic is most common). The T2
high signal will be very similar to B12 (subacute combined degeneration) -
symmetrically involving the posterior columns. It can only be shown 2 ways - (a)
by telling you the patient has AIDS or risk factors such as unprotected anal sex at
a truck stop with a man “bear” with a thick mustache while sharing IV drug
needles, (b) not including B 12 as an answer choice.
MS cord maging
Lesions favor the white matter of the cervical region.
They tend to be random and asymmetric
“Owl’s Eye”
-Classic for Ischemia
(Anterior)
-Also seen in Polio
-Ischemia big
- More extensive
anterior involvement.
-Also seen in NMO,
TM, or MS
Vitamin B12 (SCD) HIV
Posterior. Can look
like an inverted “V”
MS cord quick
Usually Short Segment Usually Part of the Cord Not swollen, or Less Swollen Can Enhance/ Restrict when Acute
tm cord quick
Usually Long Segment Usually involves both sides of the cord Expanded, Swollen Cord Can Enhance
nmo cord quick
Usually Long Segment Usually involves both sides of the cord Optic Nerves Involved
adem cord quick
Not swollen, or
Less Swollen
infarct cord quick
Usually Long
Segment
Restricted
Diffusion
tumor cord quick
Expanded,
Swollen Cord Can Enhance
A ra c h n o id itis cord
This is a general term for inflammation o f the subarachnoid space. It can
be infectious but can also be post-surgical. It actually occurs about 10-15% o f the time
after spine surgery, and can be a source of persistent pain / failed back.
A ra c h n o id itis cord
Empty Thecal Sa c S ig n
Nerve roots are
adherent peripherally, giving the appearance o f an
empty sac.
A ra c h n o id itis cord
Central Nerve Ro o t Clumping
This can range in
severity from a few nerves clumping together, to all
o f them fused into a single central scarred band.
G u illa in B a rre S yndrom e (GBS)
Also known as “Acute inflammatory demyelinating polyneuropathy” (AIDP). One o f those weird
auto-immune disorders that causes ascending flaccid paralysis. The step 1 trivia was
Campylobacter, but you can also see it after surgery, or in patients with lymphoma or SLE.
G u illa in B a rre S yndrom e (GBS)
thing to know
The thing to know is enhancement of the nerve roots o f the cauda equina.
G u illa in B a rre S yndrom e (GBS)
trivia
Other pieces o f trivia that are less likely to be asked are that the facial nerve is the most
common cranial nerve affected, and that the anterior spinal roots enhance more than the
posterior ones
Chronic In flam m a to ry
D em y lin a tin g
P o lyn eu ro p a th y (CIDP)
The chronic counterpart to GBS. Clinically this has a gradual and protracted weakness (GBS improves in 8 weeks, CIDP does not). The buzzword is thickened, enhancing, “onion bulb” nerve roots. “Dreadlocks,” “Locs,” “Jata" some people call them.
CIDP =
Diffuse Thickening o f the Nerve Roots
Tumor
overview
The classic teaching with spinal cord tumors is to first describe the location o f the tumor, as
either (1) Intramedullary, (2) Extramedullary Intradural, or (3) Extradural. This is often easier
said than done. Differentials are based on the location.
Tumor
Intramedullary ddx
A stro cy tom a ,
E p en d ym om a ,
H em a n g io b la stom a
Tumor
Extramedullary
Intradural
ddx
S chw an n om a ,
M en in g iom a ,
N e u ro fib rom a ,
Drop Mets
Tumor
Extradural ddx
Disc D ise a se (most common) B o n e T um o rs, Mets, L ym p h om a
Cord Intramedullary:
A s tro c y tom a
This is the most common
intramedullary tumor in peds. It favors the
upper thoracic spine. There will be fusiform
dilation o f the cord over multiple segments.
They are eccentric, dark on T l, bright on T2,
and they enhance. They may be associated
with rostral or caudal cysts which are usually
benign syrinx(es).
Cord Intramedullary:
Astrocytoma list
Most common in child
Eccentric
Heterogenous
Enhancement
Cord Intramedullary:
Ependymoma list
Most common in Adults Central Homogenous Enhancement More Often Hemorrhagic
Cord Intramedullary:
Epend ymoma
This is the most common primary
cord tumor o f the lower spinal cord and conus / filum
terminale. You can see them in the cervical cord as well.
This is the most common intramedullary mass in adults.
The “myxopapillary form” is exclusively found in the
conus /filum locations. They can be hemorrhagic, and
have a dark cap on T2. They have tumoral cysts about %
o f the time. They are a typically long segment (averaging
4 segments).
Cord Intramedullary:
Epend ymoma
Myxopapillary
Most commonly located in the Lumbar spine (conus/filum location)
Cord Intramedullary:
H em a n g io b la s tom a
These are associated with Von Hippel Lindau (30%).
The thoracic level is favored (second most common is
cervical).
The classic look is a wide cord with considerable edema.
Adjacent serpinginous draining meningeal varicosities can
be seen.
Cord Intramedullary:
In tram e d u lla ry M e ts
This is very very rare, but when it does happen it is usually lung (70%).
Cord Extramedullary Intradural
S chw an n om a
This is the most common tumor to occur in the Extramedullary
Intradural location. They are benign, usually solitary, usually arise from the dorsal nerve
roots. They can be multiple in the setting o f NF-2 and the Carney Complex. The appearance
is variable, but the classic look is a dumbbell with the skinny handle being the intraforaminal
component. They are T1 dark, T2 bright, and will enhance. They look a lot like
neurofibromas. If they have central necrosis or hemorrhage, that favors a schwannoma.
Cord Extramedullary Intradural
S chw an n om a list
Does NOT envelop the adjacent nerve root
Solitary
Multiple makes you think NF-2
Cystic change / Hemorrhage
Cord Extramedullary Intradural
N eu ro fib rom a
This is another benign nerve tumor (composed o f all parts o f the nerve:
nerve + sheath), that is also usually solitary. There are two flavors: solitary and plexiform.
The plexiform is a multilevel bulky nerve enlargement that is pathognomonic for NF-1.
Their lifetime risk for malignant degeneration is around 5-10%. Think about malignant
degeneration in the setting o f rapid growth. They look a lot like schwannomas. If they have
a hyperintense T2 rim with a central area o f low signal - “target sign” that makes you favor
neurofibroma.
Cord Extramedullary Intradural
N e u ro fib rom a list
Does envelop the adjacent nerve root
(usually a dorsal sensory root)
Solitary
Associated with NF -1 (even when single)
T2 bright rim, T2 dark center “target sign”
Plexiform = Pathognomonic for NF-1
Cord Extramedullary Intradural
M enin gioma
These guys adhere to but do not originate from the dura. They are more
common in women (70%). They favor the posterior lateral thoracic spine, and the anterior
cervical spine. They enhance brightly and homogeneously. They are often T1 iso to hypo,
and slightly T2 bright. They can have calcifications.
Cord Extramedullary Intradural
Drop Mets
Medulloblastoma is the most common primary tumor to drop. Breast cancer
is the most common systemic tumor to drop (followed by lung and melanoma). The cancer
may coat the cord or nerve root, leading to a fine layer o f enhancement (“zuckerguss”).
Cord Extradural
V e r te b ra l H em a n g iom a
These are very common - seen in about 10% o f the
population. They classically have thickened trabeculae appearing as parallel linear densities
“jail bar” or “corduroy” appearance. In the vertebral body they are T1 and T2 bright,
although the extraosseuous components typically lack fat and are isointense on T 1 .
Cord Extradural
Os teoid O s teom a :
This is also covered in the MSK. chapter, but as a brief review
focusing on the spine, they love to involve the posterior elements (75%), and are rare after
age 30. They tend to have a nidus and surrounding sclerosis. The nidus is T2 bright and will
enhance. The classic story is night pain, improved with aspirin. Radiofrequency ablation can
treat them (under certain conditions).
Cord Extradural
O s te o b la s tom a :
This is similar to an Osteoid osteoma but larger than 1.5 cm. Again,
very often in the posterior elements - usually o f the cervical spine.
Cord Extradural
A n e u ry sm a l Bone Cyst
These guys are also covered in the MSK chapter. They also
like the posterior elements and are usually seen in the first two decades o f life. They are
expansile (as the name implies) and can have multiple fluid levels on T2. They can get big
and look aggressive.
Cord Extradural
G ian t Cell Tumor
These guys are also covered in the MSK chapter. These are common
in the sacrum, although rare anywhere else in the spine. You do n ’t see them in young kids.
If they show this, it’s going to be a lytic expansile lesion in the sacrum with no rim of
sclerosis
Cord Extradural
Chordoma
This is most common in the sacrum (they will want you to say clivus - that
is actually number 2). The thing to know is that a vertebral primary tends to be more
aggressive / malignant than its counter parts in the clivus or sacrum. The classic story in the
vertebral column is “involvement o f two or more adjacent vertebral bodies with the
intervening disc. ” Most are very T2 bright
Cord Extradural
Leu k em ia
They love to show it in the spine. You have loss o f the normal fatty marrow -
so it’s going to be homogeneously dark on T1. More on this in the MSK chapter
Cord Extradural
M e ts
The classic offenders are prostate,
breast, lung, lymphoma, and myeloma.
Think multiple lesions with low T1
signal. Cortical breakthrough or adjacent
paravertebral components are also helpful
V e r t e b r a P la n a :
The pancake flat vertebral body.
Just say Eosinophilic Granuloma in a ^ 3
kid (could be neuroblastoma met), and
Mets / Myeloma in an adult.
VHL Associations
• Pheochromocytoma •CNS Hemangioblastoma (cerebellum 75%, spine 25%) •Endolymphatic Sac Tumor •Pancreatic Cysts •Pancreatic Islet Cell Tumors •Clear Cell RCC
