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.
