CORE - Neuro Flashcards
Location of central sulcus relative to pars marginalis
central sulcus is just anterior to pars marginalis
Innervation of “inverted omega”
motor function of the hand; posteriorly-directed knob arising from the precentral gyrus
Sulci intersecting the pre-central and post-central sulci
superior frontal sulcus intersects the pre-central sulcus; intraparietal sulcus intersects the post-central sulcus
Layers of cerebral cortex and hippocampus
6 and 3, respectively; 4 layers of cortex in lissencephaly
Dilated Virchow-Robins spaces
age-related atrophy, cryptococcus, mucopolysaccharidoses; lower basal ganglia, centrum semiovale, and midbrain most commonly
Posterior fossa mass DDx (adult)
hemangioblastoma, subependymoma, choroid plexus papilloma, desmoplastic medulloblastoma, mets, Lhermitte-Duclos, glioblastoma (uncommon)
Posterior fossa mass DDx (peds)
ependymoma, medulloblastoma, JPA, brainstem glioma, ATRT, ganglioglioma
Cystic space above 3rd ventricle and below fornices
cavum velum interpositum; extension of quadrigeminal plate cisterm to the foramen of Monro
T1 bright substances on MRI
blood (met-Hgb), fat, gad, protein, mineralization, melanin, slow flow
Fat and water content of immature myelin
high water, low fat => T1 dark and T2 bright white matter
Best MR sequence(s) to assess myelination in an infant/toddler
T1 <6 months, T2 from 6-18 months
Progression of myelination
inferior to superior, posterior to anterior, central to peripheral, sensory before motor
Last part of brain to myelinate
subcortical white matter
Normally myelinated areas at birth
brainstem, posterior limb of internal capsule
Last part of corpus callosum to form
rostrum
Order of paranasal sinus formation
maxillary => ethmoid => sphenoid => frontal
Crossing extra-axial vessels are seen in what space?
subarachnoid space; if fluid collection without crossing vessels (bridging veins) => consider subdural collection
Leptomeningeal layers
pia and arachnoid layers
Absent semicircular canals
CHARGE syndrome
Mondini triad
1.5 turns of cochlea (normal is 2.5), enlarged vestibule, enlarged vestibular aqueduct; SCCs are normal; assoc. with CHARGE
Location of trigeminal ganglion
Meckel’s cave
Contents of foramen ovale and spinosum
ovale contains CN V3 and accessory meningeal artery; spinosum contains middle meningeal artery
Contents of Dorello’s canal
CN 6
Contents of pars nervosa vs. pars vascularis
pars nervosa contains CN 9, Jacobson’s nerve, and inferior petrosal sinus; pars vascularis contains CN 10, CN 11, and jugular vein
Intra-temporal branches of facial nerve
chorda tympani, stapedial nerve, greater (superficial) petrosal nerve
Arnold’s nerve
auricular branch of CN 10 (vagus n.)
Most medial cranial nerve in cavernous sinus
CN 6; runs along the caverous portion of the ICA
Structures separating nerves in the IAC
falciform crest separates superior and inferior nerves; Bill’s bar separates CN 7 from superior vestibular nerve
Vessel giving rise to middle meningeal artery
maxillary artery (off ECA)
Nervus intermedius
a.k.a. nerve of Wrisberg; part of CN 7; runs with facial nerve in anterior-superior IAC; joins with CN 7 at geniculate ganglion
Complications of cervical ICA dissection
partial Horner’s syndrome (ptosis, miosis), MCA stroke
Aneurysm with origin at the dural ring
buzzword (phrase) for supraclinoid ICA aneurysm
Petrolingual ligament
forms proximal dural ring; marks beginning of C4 segment of ICA (cavernous)
Vessels above and below CN 3
PCA above, SCA below
Relationship of P-comm to CN 3 in fetal PCA
P-comm is superior-lateral to CN 3; normally P-comm is superior-medial to CN 3
Persistent carotid-vetebrobasilar anastomoses
persistent trigeminal a., persistent otic a., persistent hypoglossal a., persistent proatlantal a. (type 1 = from ICA, type 2 = from ECA)
Causes of pulsatile tinnitus
idiopathic intracranial hypertension, aberrant ICA, persistent stapedial a., glomus jugulare or tympanicum, dural AVF (when involving sigmoid sinus)
Causes of pulsatile exophthalmos
carotid-cavernous fistula, sphenoid wing dysplasia
Vessels that form aberrant ICA
inferior tympanic a. (from ascending pharyngeal a.) and caroticotympanic a. (from petrous ICA); due to failure in formation of cervical ICA
Aberrant ICA association
persistent stapedial a. (30% of the time)
Absent foramen spinosum
persistent stapedial a.; gives rise to middle meningeal a.; enlargement of anterior tympanic segment of facial n. canal
Venous drainage of cavernous sinus
superior petrosal sinus (to transverse sinus) and inferior petrosal sinus (to extracranial IJV)
Vein coursing along the roof of the 3rd ventricle
internal cerebral veins (paired); originate at foramen of Monro; drain to great vein of Galen
Vein coursing through the ambient cisterns
basal veins of Rosenthal (paired); originate along medial temporal lobes; drain to great vein of Galen; course is similar to PCA and CN 4
Drainage of veins of Trolard and Labbe
Trolard drains to superior sagittal sinus; Labbe drains to transverse sinus
Superficial middle cerebral vein
a.k.a. Sylvian vein; runs along Sylvian fissure; drains to cavernous sinus, as well as veins of Trolard and Labbe
Treatment of venous gas introduced during IV placement
none; should resolve within 48 hours
Causes of CN 3 palsy
P-comm aneurysm, uncal herniation; pupil is “down & out”, ptosis
Enhancement of multiple cranial nerves DDx
Lyme disease, mets (CSF spread), MS, ADEM
First sign of hydrocephalus
temporal horns dilate first
Causes of pachymeningeal enhancement
intracranial hypotension, post-op/post-LP/post-shunting, granulomatous disease, neoplasm (focal)
Causes of leptomeningeal enhancement
meningitis, leptomeningeal carcinomatosis, neurosarcoidosis, viral encephalitis, lymphoma, slow vascular flow
Findings in intracranial hypotension
pachymeningeal thickening/enhancement, sagging of brainstem and tonsils, distended veins/sinuses, +/- subdural hygromas/hematomas
Idiopathic intracranial hypertension associations
hypothyroidism, Cushing’s, vitamin A toxicity; slit-like ventricles, empty sella, tortuous optic nerves with dilated sheaths, flattening of posterior globes
Causes of non-obstructive communicating hydrocephalus
choroid plexus papilloma, NPH, ex vacuo dilitation
Causes of obstructive communicating hydrocephalus
SAH, meningitis, leptomeningeal carcinomatosis
Treatment for NPH
shunting; “ventricular size out of proportion to atrophy”
Blood-brain barrier in cytotoxic vs. vasogenic edema
cytotoxic = intact BBB (failure of Na/K pump); vasogenic = disrupted BBB (increased capillary permeability)
Complication of subfalacine herniation
ACA compression => ACA infarct
Effacement of ipsilateral suprasellar cistern
uncal herniation (a.k.a. downward transtentorial); uncus and hippocampus herniate through tentorial incisura
Duret hemorrhages
seen in downward transtentorial herniation; due to compression of basilar artery perforators
Large infarct with ipsilateral hemiparesis
uncal herniation => compression of contralateral peduncle/midbrain on tentorium => ipsilateral hemiparesis
Signs of ascending transtentorial herniation
flattening of quadrigeminal cistern (“smile”), severe hydrocephalus, “spinning top” sign (bilateral posterior midbrain compression)
Size criteria for tonsillar herniation
> 5 mm for single tonsil, or both tonsils >3 mm
Symmetric parietoccipital white matter edema
PRES; does not restrict; due to acute HTN, chemo, eclampsia, sepsis
Radiation-induced demyelination
T2 bright (edema) => atrophy; chemo can do the same thing; may see mineralizing microangiopathy in kids
What vitamin is thiamine?
vitamin B1; thiamine deficiency => Wernicke encephalopathy; involves mammillary bodies, medial thalamus, periaqueductal gray
Optic nerve atrophy + putaminal hemorrhage
methanol poisoning; may also see subcortical white matter necrosis
Stuff alcoholics get…
cerebral atrophy (especially vermal), Wernicke’s, Marchiafava-Bignami
T2 bright basal ganglia DDx
CO poisoning, Japanese encephalitis, CJD, Leigh syndrome, NF1 (FASI), osmotic demyelination
T2 bright basal ganglia + cortex DDx
hypoglycemia, hypoxic-ischemic, CJD
T1 bright basal ganglia DDx
hepatic encephalopathy, hyperalimentation, hypothyroidism, Fahr disease
Disseminated necrotizing leukoencephalopathy
seen in leukemia patients undergoing chemoradiation; severe white matter changes with ring enhancement
Preserved motor strip on FDG-PET
seen in dementia
Dementia with hippocampal atrophy
Alzheimer’s; temporal horn atrophy >3 mm
Most common cause of dementia + 2nd most common cause
Alzheimer’s > multi-infarct dementia
Binswanger disease
chronic small vessel ischemic disease + dementia; spares subcortical U-fibers; strongly assoc. with HTN
Most common TORCH infection
CMV > toxoplasmosis
Findings in CMV (TORCH)
periventricular calcifications +/- cysts, polymicrogyria, schizencephaly, cerebellar hypoplasia
HSV type in TORCH infection
HSV-2; hemorrhagic infarction => encephalomalacia
Most common opportunistic CNS infection in AIDS
toxoplasmosis; cryptococcus is the most common fungal CNS infection in AIDS
HIV patient with symmetric T2 WM abnormality sparing U-fibers
HIV encephalitis; CD4 <200; T1 signal is normal; may see assoc. brain atrophy
HIV patient with asymmetric T2 WM abnormality involving U-fibers
PML (JC virus); CD4 <50; corresponding low T1 signal
White cerebellum sign (CT)
hypoxic-ischemic encephalopathy
Ependymal enhancement in HIV patient
consider CMV; may also see atrophy and periventricular hypodensity/high T2 signal
T1 dark, T2 bright lesion with ring enhancement in cryptococcus
cryptococcoma; dilated perivascular spaces (filled with gelatinous material) are also T1 dark, T2 bright but should not enhance
Characteristics distinguishing toxoplasmosis from lymphoma (3)
toxo does NOT restrict, has decreased CBV, and is PET/thallium cold; lymphoma is the opposite for all of them
Basilar meningitis DDx
TB, cryptococcus, neurosarcoid, neurosyphilis, lymphoma, pyogenic infections
Basilar meningitis + hydrocephalus
TB
Limbic encephalitis association
small cell lung cancer commonly (paraneoplastic syndrome); next step is check for lung cancer
West Nile encephalitis findings
high T2 signal in basal ganglia and thalamus; corresponding restricted diffusion
Etiology of majority of CJD cases
sporadic; findings include gyriform diffusion restriction, pulvinar sign, and rapidly progressive atrophy
Neurocysticercosis stages
vesicular (T1 dark/T2 bright with dot) => colloid (T1/T2 bright + edema) => granular (thicker wall, less edema) => nodular (calcified)
Complications of meningitis
venous thrombosis, vasospasm, empyema, ventriculitis, hydrocephalus, cerebritis, abscess; sterile subdural collections (infants)
Common causes of ventriculitis
shunt placement, intra-thecal chemo; septa may develop => hydrocephalus; intraventricular extension of abscess is pre-terminal
Most common CNS met in peds
neuroblastoma; to orbit, bone, or dura (not usually brain parenchyma)
Primary CNS neoplasms that “seed”
medulloblastoma, ependymoma, GBM, oligodendroglioma
Most common location for oligodendroglioma
frontal lobe; expands cortex; 1p19q deletion assoc. with better outcome
Cortical-based mass with calcification
oligodendroglioma, ganglioglioma
CNS neoplasms associated with seizures in kids
PXA, ganglioglioma, DNET
PXA in an infant
desmoplastic infantile ganglioglioma (DIG)
4th ventricle mass in an adult DDx
choroid plexus papilloma, subependymoma
Supratentorial ependymoma
often >4 cm at presentation; may be extraventricular (cerebral hemisphere > 3rd vent. > lateral vent.); large, heterogeneous, cystic and solid; often with calcification and/or hemorrhage
Medulloblastoma + dural calcifications
Gorlin syndrome; also keratocysts, basal cell cancers, cardiac fibromas
Medulloblastoma associations
Gorlin syndrome, Turcot syndrome (GBMs also)
Choroid plexus carcinoma association
Li-Fraumeni syndrome
Most common location of intraventricular mets
trigone of lateral ventricle; most common primary is lung or renal
Causes of multiple meningiomas
NF2, radiation to head (may also cause capillary telangiectasias)
Most common location for a dermoid
suprasellar > posterior fossa
T1 hyperintensity in IAC
IAC lipoma; will dropout on fat sat; assoc. with sensorineural hearing loss
Most common supratentorial mass
mets
Primary CNS lymphoma
solidly enhancing in immunocompetent patients, ring-enhancing (necrosis) in immunocompromised
Infant with rapidly increasing head circumference
consider DIG
Subgaleal space
between periosteum and scalp aponeurosis
Most common location for chordoma
sacrococcygeal > clivus > C-spine; often crosses disc space to involve adjacent vertebral body
Dural-based mass DDx
meningioma, mets (breast most commonly), hemangiopericytoma, lymphoma, neurosarcoid
First consideration for any suprasellar lesion
could it be an aneurysm?
Intrasellar mass (within pituitary) DDx
microadenoma, macroadenoma, Rathke cleft cyst, craniopharyngioma (completely intrasellar is rare), pars intermedia cyst
Most common suprasellar mass (adults)
macroadenoma with suprasellar extension; arises from adenohypophysis; >1 cm by definition
Suprasellar mass with carotid encasement (no narrowing)
macroadenoma; suprasellar meningiomas may cause carotid narrowing
Findings in pituitary apoplexy
fluid level or increased T1 signal representing hemorrhage; causes include Sheehan syndrome and bromocriptine; acute syndrome with headache, visual impairment, and panhypopituitarism; most often occurs in an existing adenoma or peri-/postpartum
Rathke cleft cyst with small enhancing nodule
craniopharyngioma; Rathke cleft cysts do not enhance (may see enhancing rim of compressed pituitary tissue)
Midline suprasellar mass with restricted diffusion
epidermoid cyst
Differences between types of craniopharyngioma
adamantinomatous = cystic areas, calcs, recur more often; papillary = no cystic areas, no calcs, recur less often
Most common location of germinoma
pineal > suprasellar; 10-19 y/o most commonly, almost only in boys; restrict diffusion, enhancing
Enhancement pattern of hypothalamic hamartoma
do NOT enhance (consider alternative diagnosis if enhancement); gelastic seizure, precocious puberty
Pineal mass with exploded calcifications
pineoblastoma (2nd decade, invasive) vs. pineocytoma (4th-5th decade, non-invasive)
Increased FLAIR signal in subarachnoid space DDx
subarachnoid hemorrhage, meningitis, leptomeningeal carcinomatosis, recent oxygen or propofol, residual contrast
Multiple areas of susceptibility in brain parenchyma DDx
hypertensive microhemorrhages, CAA, familial cavernomas, DAI, hemorrhagic mets
Dysplastic cerebellar gangliocytoma
a.k.a. Lhermitte-Duclos; assoc. with Cowden syndrome
Recurrent laryngeal nerve course
right recurs around the right subclavian, left recurs at the AP window
Appearance of cerebral contusion
may appear as small patchy hyperdense foci of hemorrhage or larger coalescent hemorrhage (hematoma)
Most sensitive sequence for SAH
FLAIR; most common cause of SAH is trauma (not aneurysm rupture); vasospasm at 4-14 days typically
Fracture locations in LeFort system
1 = lateral nasal aperture; 2 = medial orbital rim + orbital floor; 3 = lateral orbital rim/wall + zygomatic arch; always pterygoid process
Timing of stages of blood
hyperacute = 0-6 hours; acute = 6-72 hours; early subacute = 3-7 days; late subacute = 1 week to months; chronic is old
Swirl sign (CT)
active bleeding; low attenuation blood is hyperacute and non-clotted
Airless expanded sinus
mucocele; often T1 bright with thin rim enhancement
Most common type of temporal bone fracture
longitudinal
Most common type of temporal bone fracture to involve ossicles
longitudinal; results in conductive hearing loss
Sequelae of transverse temporal bone fractures
sensorineural hearing loss, facial nerve and/or vascular injury
Symptoms of superficial siderosis
sensorineural hearing loss, ataxia
Most common location for hypertensive hemorrhage
basal ganglia > pons and cerebellum
Treatment of non-hemorrhagic stroke
IV tPA within 3 hours or IA tPA within 6 hours (from symptom onset); must be no hemorrhagic transformation and the area of hypodensity must be <1/3 of MCA territory
Watershed infarcts in a kid
moyamoya
Patients at increased risk for hemorrhagic transformation of infarct
on anticoagulation, received tPA, large embolic infarcts, venous infarcts
Patients at increased risk for venous thrombosis/infarction
dehydration (babies), mastoiditis (kids), coagulopathies, OCPs
Patients at increased risk for intracranial aneurysm formation
smokers, ADPKD, Marfan’s, Ehlers-Danlos, aortic coarctation, AVMs
Most common location for intracranial aneurysm
anterior circulation > posterior; A-comm in anterior circulation; basilar tip > PICA in posterior circulation
Increased risk of aneurysm rupture
increased size, posterior location, prior SAH, smokers, females
Fusiform intracranial aneurysm associations
PAN, connective tissue diseases, syphilis; most commonly affect posterior circulation
Pedicle aneurysm
found on artery feeding an AVM; majority of AVM-assoc. aneurysms occur within the nidus; high bleeding risk
Blister aneurysm
broad-based; located at a non-branch point (supraclinoid ICA most commonly)
Size limit for P-comm infundibulum
≤3 mm
Increased bleeding risk in AVMs
smaller size, single draining vein, intranidal or perinidal aneurysm, basal ganglia/thalamic/periventricular location
Increased bleeding risk in dural AVFs
direct cortical venous drainage; dural AVFs are acquired due to dural venous thrombosis, seen in 50-60 y/o
Low flow vascular lesions (intracranial)
cavernoma, DVA, capillary telangiectasia
Vascular lesions occult on angiography
cavernoma, capillary telangiectasia
Risk factors for vasospasm in SAH
SAH >1 mm in thickness, intraventricular or parenchymal extension of hemorrhage; occurs 4-14 days after SAH
Causes of vasospasm
SAH, meningitis, PRES, migraines; smooth, long stenoses; often involves multiple vascular territories; may cause infarction
MR sequence for carotid dissection
T1 fat sat (crescent of bright blood)
Most common vasculitis to involve CNS
PAN; all vasculitides demonstrate a beaded appearance with multifocal areas or narrowing
Most common collagen vascular disease to involve CNS
SLE
Moyamoya associations
sickle cell disease, NF1, prior radiation, Down syndrome; may cause watershed infarction (peds) or hemorrhage (adults)
Thunderclap headache with multifocal narrowing on CTA (no SAH)
consider reversible cerebral vasoconstriction syndrome (RCVS); may result in infarction
CADASIL
frontal and temporal white matter disease (high T2); h/o migraines and/or strokes/TIAs; may progress to dementia
NASCET criteria for measuring carotid stenosis
maximum ICA stenosis compared to a parallel (non-curved) segment of the distal cervical ICA; (1-(A/B))*100
Colpocephaly associations
anything assoc. with callosal dysgenesis (pericallosal lipoma, Chiari II, Dandy-Walker, holoprosencephaly)
Iniencephaly
“star-gazing fetus”; deficit of occipital bones, enlarged foramen magnum
Arhinencephaly
no olfactory bulbs or tracts; assoc. with Kallman syndrome
Rhombencephalosynapsis
vermal aplasia with fused cerebellar hemispheres (“single-lobed cerebellum”)
Joubert syndrome associations
retinal dysplasia, MCDK; molar tooth malformation + hepatic fibrosis = COACH syndrome
Dandy-Walker (classic) findings
cystic dilation of 4th ventricle, enlarged posterior fossa, torcular-lambdoid inversion, vermal hypoplasia; often with hydrocephalus
Dandy-Walker spectrum variants
ventriculocele = large 4th erodes occipital bone; variant = normal-sized PF, variable vermian hypoplasia, no or small cyst; blake pouch cyst = normal-sized PF, open 4th communicates with cyst; MCM = enlarged PF, retrocerebellar CSF space >10 mm
Direction of cerebral cleavage
posterior to anterior (think of holoprosencephaly)
Absent septum pellucidum associations
septo-optic dysplasia, schizencephaly, holoprosencephaly
Holoprosencephaly associated findings
cyclops eye, pyriform aperture stenosis, mega-incisor
Enlarged cerebral hemisphere + enlarged ventricle
hemimegalencephaly; “hamartomatous overgrowth”; may have pachygyria, polymicrogyria, heterotopia
Number of layers of cortex in lissencephaly
4 layers
Type of lissencephaly associated with band heterotopia
type 1 (classic)
Most common gray matter heterotopia
subependymal
Schizencephaly associations + most common type
optic nerve hypoplasia, absent septum pellucidum, epilepsy; most common type is open lip (80%); lined by gray matter
Cortical mantle + falx present
hydrocephalus; if no falx => holoprosencephaly
Cephalocele
generic term for herniation of brain contents; may represent an encephalocele or meningocele
Chiari I association
syrinx, Klippel-Feil syndrome, hydrocephalus; tonsilar herniation >5 mm, “peg-like” morphology
Chiari II associations
myelomeningocele, syrinx, callosal dysgenesis, lacunar skull; hydrocephalus seen in 90%
Most common craniosynostosis
scaphocephaly (dolicocephaly)
Brachycephaly + Wormian bones + absent clavicles
cleidocranial dysostosis
Brachycephaly + syndactyly + facial hypoplasia
Apert syndrome
Brachycephaly + maxillary/mandibular hypoplasia + exophthalmos
Crouzon syndrome
Sinus pericranii
low flow communication between a dural venous sinus and extracranial veins (via emissary veins); osseous defect present
Most common cause of macrocephaly
BESSI; resolves without treatment within 2 years; assoc. with increased risk of subdural bleed
Choanal atresia associations
CHARGE, Crouzon’s, DiGeorge syndrome, Treacher-Collins, fetal alcohol syndrome; unilateral > bilateral; bony > membranous
MELAS (acronym)
mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes; increased lactate, decreased NAA
Most common leukodystrophy
metachromatic
Leukodystrophies with big heads
Alexander disease, Canavan disease
Adrenoleukodystrophy gender predilection
only in boys (sex-linked); 5-10 y/o (other leukodystrophies are generally <5 y/o)
Three normal peaks in MR spectroscopy
Choline, Creatine, and N-acetyl aspartate; form Hunter’s angle (plane taking off)
MR spect: decreased NAA, increased lactate
MELAS
MR spect: elevated NAA peak (higher than normal)
Canavan disease
MR spect: elevated alanine
meningioma
MR spect: elevated glutamine
hepatic encephalopathy
MR spect: significance of Cho and lactate
Cho is a non-specific marker for cell turnover (tumor, infarction, or inflammation); lactate is seen with anaerobic metabolism (necrotic tumors, radiation necrosis, abscess)
MR spect: decreased Cho, decreased NAA, elevated lactate
radiation necrosis
MR spect: elevated Cho, decreased NAA, elevated lactate
high-grade malignancy (e.g. GBM)
Most common primary petrous apex lesion
cholesterol granuloma; most common symptom is hearing loss; may require surgery if rapidly growing
Petrous apex cholesteatoma - congenital or acquired
congenital
Petrous apex lesion with smooth expansile bony change
cholesterol granuloma or cholesteatoma
Complication of petrous apicitis extending into Dorello’s canal
Gradenigo syndrome; petrous apicitis + facial pain (trigeminal neuropathy) + lateral rectus palsy; involves Meckel’s cave and Dorello’s canal
Petrous apicitis is a complication of…
otomastoiditis; may progress to skull base osteomyelitis, ICA vasospasm, meningitis, venous sinus thrombosis
Endolymphatic sac tumor MR characteristics
T2 bright, avid enhancement, +/- flow voids; amorphous calcifications on CT; tumor blush on angiography; assoc. with VHL
Most common presenting symptom of paraganglioma
hoarseness (from vagal nerve compression); “salt-and-pepper”; often hereditary and multiple
Most common cause of congenital sensorineural hearing loss
enlarged vestibular aqueduct; hearing loss is progressive, often bilateral; assoc. with Mondini triad and absence of bony modiolus
Enhancement in cochlea and/or semicircular canals
labyrinthitis; viral cause most often
Labrynthitis ossificans findings
increased density (CT) or low T2 signal in labyrinthine structures; healing response to prior infection or trauma
Fenestral otosclerosis - conductive or sensorineural hearing loss?
conductive; fenestral otosclerosis occurs at fissula ante fenestram
Retrofenestral otosclerosis - conductive or sensorineural hearing loss?
conductive + sensorineural; retrofenestral type is almost always bilateral
Patients at increased risk for otitis media
children, Down syndrome; due to horizontal orientation of eustachian tubes; >6 weeks = chronic
Complications of otitis media
coalescent mastoiditis, facial nerve palsy, dural sinus thrombosis, meningitis, labyrinthitis
Bezold abscess
complication of otomastoiditis; infection erodes through bone to form an abscess deep to the sternocleidomastoid
Order of destruction in cholesteatoma
scutum => long process of incus (+/- other ossicles) => LSCC (may result in labrynthine fistula)
Most common type of cholesteatoma (middle ear)
pars flaccida > pars tensa; flaccida is flimsy and at the top; tensa is tough and at the bottom; may be congenital or acquired
Noise-induced vertigo
a.k.a. Tulio’s phenomenon; seen in dehisence of the superior SCC
Michel aplasia
complete labyrinthine aplasia; absence of inner ear structures
Necrotizing (malignant) external otitis associations
almost always in diabetics; Pseudomonas (98%); soft tissue swelling, bony destruction, +/- abscesses
Non-enhancing segments of facial nerve
cisternal, canalicular, and labyrinthine; tympanic and mastoid segments normally enhance (perineural venous plexus)
Enhancing facial nerve DDx
Bell’s palsy, Lyme disease, Ramsay Hunt syndrome (VZV), perineural spread of malignancy (parotid), schwannoma
Ramsay Hunt syndrome
due to VZV infection; CN 7 palsy (facial paralysis), sensorineural hearing loss, vesicular rash of external ear
Enhancing lesion in geniculate ganglion area with bony spicules
facial nerve venous malformation (or hemangioma); facial paralysis (CN 7 palsy)
Nerve involvement in Lyme disease
CN 7 > CN 3 and CN 5; multiple enhancing cranial nerves, periventricular/spinal cord white matter lesions (high T2)
EAC exostoses
due to cold water exposure (surfers classically); always bilateral; most common symptom is conductive hearing loss
Enhancing lesion in geniculate ganglion area
facial nerve schwannoma, facial nerve cavernous malformation
Location of glomus tympanicum
cochlear promontory; arises from Jacobson’s nerve
Intracranial complications of Paget disease
hearing loss, CN palsies, secondary osteosarcoma, basilar impression (may compress brainstem or cause hydrocephalus)
Basilar impression (acquired) DDx
RA, Paget’s, ankylosing spondylitis, osteomalacia/rickets, osteogenesis imperfecta, mucopolysaccharidoses
Basilar invagination (developmental) DDx
Chiari I, Chiari II, Klippel-Feil, atlanto-occipital assimilation, achondroplasia, Down syndrome
Nasal mass with nose bleeds
JNA; originates in sphenopalatine fossa, spreads to PPF and nasopharynx; bone remodeling +/- destruction
Widened maxillary ostium
buzzword for antrochoanal polyp; peripheral enhancement with NO central enhancement, smooth bony remodeling; teenagers
Cerebriform enhancement
inverted papilloma; originates at middle meatus, may extend into maxillary sinus; bony remodeling; 40-70 y/o; risk of malignant transformation to SCC (look for bony destruction and/or necrosis)
Nasopharyngeal mass that is hot on octreotide
esthesioneuroblastoma; intracranial posterior cyst is classic; 2nd and 6th decades (bimodal)
Most common location for SNUC
arises from ethmoids most commonly; highly aggressive malignancy of paranasal sinus
Most common etiology of epistaxis
bleeding from anterior septum (Kiesselbach plexus); posterior sources are less common, but more difficult to treat (sphenopalatine a.)
Ranulas arise in what space?
sublingual space; “plunging” = beyond mylohyoid muscle (through or around)
Sialolithiasis most common in which duct?
Wharton’s duct (submandibular); may lead to sialoadenitis (acute) or fatty atrophy of gland (chronic)
Determinant of spread of odontogenic infection
attachment of mylohyoid muscle to inner mandible; infection above = sublingual spread; infection below = submandibular spread (includes 2nd/3rd molars)
Most common masticator space mass (adult)
odontogenic abscess
Causes of mandibular osteonecrosis
prior radiation, bisphosphonates
Cyst associated with the crown of an unerupted tooth
dentigerous cyst (a.k.a. follicular cyst); displace and resorb adjacent teeth
Odontogenic keratocyst characteristics
expands longitudinally in mandible; expansile, solitary, unilocular (most commonly); assoc. with Gorlin syndrome
Ameloblastoma characteristics
expansile, multiloculated, “soap bubbly”; may see enhancing mural nodule or septa; typically assoc. with unerupted tooth
Most common salivary gland tumor (major and minor glands)
benign mixed tumor (a.k.a. pleomorphic adenoma); in parotid, 90% are in superficial lobe; treatment is excision
Warthin’s tumor association
smokers; may be bilateral, only occurs in parotid; hot on pertechnetate and PET
Most common primary parotid gland malignancy
mucoepidermoid carcinoma; assoc. with prior radiation
Most common primary submandibular and sublingual gland malignancy
adenoid cystic carcinoma; perineural spread (CN palsies and paresthesias)
Multiple parotid masses DDx
mets, lymphoma (NHL), Warthin tumors, benign mixed tumors (seeding from post-op spillage), Sjogren’s, HIV lymphoepithelial lesions, sarcoidosis
Complication of Sjogren’s (parotid)
lymphoma (MALT-type NHL); Sjogren’s is most commony seen in middle-aged females
Painless parotid swelling
benign lymphoepithelial lesions, sarcoidosis; as opposed to parotitis which is presents as painful swelling
Uveoparotid fever
bilateral uveitis, parotid enlargement, facial nerve palsy; considered pathognomonic for sarcoidosis
Three classic tumors arising in the post-styloid parapharyngeal space
a.k.a. carotid space; paraganglioma, schwannoma, neurofibroma
Axial level carotid body tumor vs. glomus vagale
carotid body tumor occurs at the level of the floor of the mouth; glomus vagale occurs at the level of the nasopharynx or palate
Suprahyoid neck compartments in which a schwannoma can arise
carotid space (CN 9/10/11/12), parotid space (CN 7), masticator space (CN V3), parapharyngeal space (CN V3 branches)
Nodes of Rouviere
retropharyngeal, off-midline, at the level of the nasopharynx; suppurative nodes may appear cystic
Thick rim-enhancing cervical nodes with central necrosis
tuberculous cervical lymphadenitis (scrofula); +/- nodal calcification; neck is most common extra-thoracic site for TB nodes
Low density lesion DDx (neck)
SCC nodal mets, suppurative lymph nodes, 2nd branchial cleft cyst, lymphatic malformation, TB nodal involvement, thyroid cancer mets, thyroglossal duct cyst
Grisel syndrome
torticollis (atlantoaxial rotatory subluxation) related to respiratory infection or ENT surgery
Roles of muscles of mastication
lateral pterygoid opens mouth, medial pterygoid, temporalis, and masteter close mouth
Boundaries of oropharynx, hypopharynx, and larynx
oropharynx = palate to hyoid; hypopharynx = hyoid to esophagus; larynx = hyoid to trachea
Boundaries of lymph node level IIA
anterior = posterior submandibular gland; posterior = posterior margin of IJV; inferior = inferior margin of hyoid bone
Boundaries of lymph node level III
posterior = posterior margin of SCM; superior = inferior margin of hyoid bone; inferior = inferior margin of cricoid cartilage
Suspected 2nd branch cleft cyst
must consider could this be metastatic SCC
Most common location for nasopharyngeal SCC
fossa of Rosenmuller; mucosal elevation just anterior is the torus tubarius; SCC may present as a unilateral mastoid effusion
Most common location for laryngeal SCC
glottic (also the type with the best prognosis)
Fixation of vocal cords (T-stage in SCC)
at least T3
Tumor on both sides of cricoid cartilage (laryngeal SCC)
compatible with cricoid invasion => contraindication to laryngeal conservation surgery
Causes of laryngocele
SCC (ipsilateral), glass-blowing, wind instrument players, chronic coughers; may be air or fluid-filled
Findings in vocal cord paralysis
paramedian true cord, ballooning of ipsilateral ventricle, enlarged ipsilateral pyriform sinus
Findings in chronic allergic fungal sinusitis
central hyperdensity/low T2 signal with peripherally enhancing mucosa; expanded sinus
Patient at risk for acute invasive fungal sinusitis
diabetics, immunocompromised patients; look for bony destruction and extension of enhancement outside of sinus
Coloboma associations
CHARGE (especially if bilateral), trisomy 13, trisomy 18, VATER
Microphthalmia + increased density of vitreous DDx
Coat disease vs. PHPV; both may lead to retinal detachment; Coat disease is seen in boys
Bilateral microphthalmia + intraocular calcifications
retinopathy of prematurity; may also have increased density of vitreous; seen in premature infants on prolonged oxygen; bilateral
MR characteristics of orbital pseudotumor
low T2 signal, enhancing; painful proptosis; involves lateral rectus most commonly
Tolosa-Hunt syndrome
essentially orbital pseudotumor involving the cavernous sinus; presents with multiple cranial nerve palsies
Most common benign and malignant orbital masses (peds)
dermoid and rhabdomyosarcoma, respectively
Ill-defined orbital mass DDx
orbital cellulitis, pseudotumor, infantile hemangioma, lymphatic malformation, plexiform neurofibroma, lymphoma, sarcoid, Wegener’s, rhabdomyosarcoma
Orbital lymphoma association
Chlamydia Psittaci (MALT-type); painless proptosis (downward)
Orbital mass with fluid-fluid levels
lymphatic malformation; peds usually; extraconal most commonly
Most common cause of spontaneous orbital hemorrhage
orbital varix; distend with provocative maneuvers; may thrombose => pain
Round rim-enhancing lesion in lacrimal fossa
dacryocystitis
Treatment for subperiosteal abscess (orbit)
surgical emergency for any concerning symptoms (e.g. visual impairment, pain/pressure)
Most common orbital mass (adult)
orbital cavernous venous malformation (a.k.a. hemangioma); intraconal most commonly; T2 bright, enhancing
Balo and Marburg MS variants
Balo (concentric) = younger patients, alternating concentric bands; Marburg = fulminant form of MS, death within months
Origin of artery of Ademkiewicz
originates from the aorta (on the left) at T8-T11; “hairpin” turn on DSA
Exiting nerve root at C4-5
exiting = C5 root
Exiting nerve root at L4-5
exiting = L4 root (descending root is L5)
Cause of epidural lipomatosis
corticosteroids
Medications to hold prior to LP (and duration)
moderate bleeding risk (see SIR tables)
Complications of spine surgery
residual disk, epidural fibrosis, arachnoiditis, conjoined nerve roots; nerve root enhancement >6 weeks post-op is abnormal
Most common type of odontoid fracture
type 2; both type 2 and 3 are unstable
Os odontoideum association
Morquio’s syndrome; prone to subluxation and instability; orthotopic = on top of dens; dystopic = fused to clivus
Anterior cord syndrome
impaired motor function and pain/temperature sensation; proprioception and vibration are intact (dorsal columns)
Normal atlanto-dental (atlanto-axial) and basion-dental intervals
atlanto-dental <2.5 mm (or <5 mm in peds); basion-dental interval <12 mm
Atlanto-axial instability associations
JIA, Down syndrome, Klippel-Feil, achondroplasia, os odontoideum, fracture; may result in rotatory subluxation with head stuck in a torticollis-like position
Spinal cord syndrome: upper extremity deficit worse than lower
central cord syndrome
Most common level for pars interaticularis defects
L5-S1 (90%); results in spondylolisthesis
Open spinal dysraphism
a.k.a. spina bifida aperta or cystica; myelomeningocele (98%) or myelocele; NO skin covering
Open spinal dysraphism (myelomeningocele) associations
Chiari II, diastematomyelia, kyphoscoliosis, syrinx
Closed spinal dysraphism
dorsal dermal sinus, lipomyelomeningocele, diastematomyelia, terminal myelocystocele, thickened filum, intradural lipoma, meningocele; skin covering present
Tethered cord associations
caudal regression syndrome, VACTERL, most open or closed spinal dysraphisms
Thickened filum terminale
> 2 mm at L5-S1, low-lying conus; may be assoc. with fibrolipoma (fatty filum) or terminal lipoma; clinical syndrome is tethered cord
Lipomyelomeningocele
cord tethered to a dorsal lipoma (often blends with dorsal subcutaneous fat)
Terminal myelocystocele
hydromelic tethered cord traversing dorsal meningocele to terminate in dilated terminal ventricle cyst
Dermal sinus association
epidermoid or dermoid; dermal sinus extends inward from skin surface; epithelium-lined
Most common type of spinal arteriovenous lesion
type 1 (dural AVF)
Type 2 arteriovenous lesion (AVM)
intramedullary nidus of AVM from anterior or posterior spinal artery; assoc. with HHT and Klippel-Trenaunay-Weber
Foix Alajouanine syndrome
myelopathy assoc. with dural AVF (due to venous hypertension); lower extremity weakness and sensory deficits
Most common pathogen in osteomyelitis
S. aureus; phlegmon enhances, abscess contents does not
Brucellosis osteomyelitis (spine)
favors L-spine and SI joints, can spare disc similar to TB; from cow’s milk or farm exposure
Long segment cord myelopathy
transverse myelitis, NMO, cord infarct; MS and ADEM usually involve a shorter area; must consider tumor
Causes of transverse myelitis
post-infectious, post-vaccination, SLE, Sjogren’s, paraneoplastic, AVMs; ‘acute partial’ type (<2 segments) is more likely to develop MS
Increased T2 signal in dorsal columns
subacute combined degeneration (B12 deficiency), HIV vacuolar myelopathy
“Owl eye” appearance of cord
anterior cord infarct; cord infarcts are typically >2 segments
Lateral meningocele associations
NF1, connective tissue diseases (e.g. Marfan’s)
Empty thecal sac sign
ararchnoiditis; may also see nerve root clumping
Enhancing nerve roots (spine) DDx
Guillain-Barre syndrome, CIDP, Charcot-Marie-Tooth (inherited); CIDP and CMT demonstrate nerve root thickening and develop over a longer period of time (>8 weeks)
Most commonly affected cranial nerve in GBS
CN 7; assoc. with Campylobacter; may also be post-viral or post-vaccination; ascending flaccid paralysis
Intradural-extramedullary lesions
schwannoma, neurofibroma, meningioma, dermoid cyst, epidermoid cyst, drop mets (e.g. medulloblastoma)
Intramedullary lesion with T2 dark cap
ependymoma; T2 dark cap represents hemorrhage; assoc. with NF2 (especially if in a child)
Most common cause of intramedullary mets (spine)
lung cancer
Treatment of spinal schwannomas vs. neurofibromas
schwannoma may be resected with a nerve-sparing approach; neurofibroma requires nerve resection
Lytic sacral lesion DDx (adult)
mets, chordoma, lymphoma, GCT, ABC, myeloma, chondrosarcoma, Paget’s, insufficiency fracture
Child with seizures, hemiparesis, and port-wine stain nevus
Sturge-Weber; pial angiomatosis, cortical calcifications, cortical atrophy, ipsilateral enlarged choroid plexus
Duct draining sublingual glands
duct of Rivinus
Duct draining parotid glands
Stensen’s duct
Accessory parotid gland location
anterior to parotid gland, superficial to masseter m.; commonly bilateral
Sinonasal polyposis
extensive remodeling and erosion of the nasal cavity and paranasal sinuses; assoc. with Samter’s triad (nasal polyposis, aspirin intolerance, asthma)
Nerve involvement in vocal cord paralysis
recurrent laryngeal n. > superior laryngeal n.
Features of vocal cord paralysis
thyroarytenoid m. and posterior cricoarytenoid m. atrophy, ipsilateral paramedian vocal cord, ipsilateral enlarged laryngeal ventricle/pyriform sinus; left > right, bilateral > unilateral
Laryngocele
ipsilateral and fluid-filled if related to neoplastic obstruction
Most common nerve schwannoma arises from
superior vestibular nerve (CN 8)
Size of a giant cerebral aneurysm
> 2.5 cm
TOF technique - head vs. neck
3D GRE TOF in the head, 2D GRE TOF in the neck
Innervation of the digastric muscle
anterior belly innervated by CN5, posterior belly innervated by CN7 (“Heinz 57”)
Pendred syndrome
enlarged vestibular aqueduct, absence of bony modeolus, +/- Mondini malformation; assoc. with thyroid goiter
Tributaries of the internal cerebral veins
choroidal vein and thalamostriate vein combine to form each internal cerebral vein
Most medial cranial nerve
CN6 (not including CN3)
Pathologic basal ganglia calcification
Fahr disease, hyperparathyroidism, hypoparathyroidism (also pseudo- and pseudopseudo-), Fabry disease
DDx for Tornwaldt cyst
mucous retention cyst, adenoidal hyperplasia
Causes of trigeminal neuralgia
compression of CN5 by a vessel, schwannoma, meningioma, or epidermoid
Enhancement of microadenoma vs. macroadenoma (pituitary)
microadenomas enhance more slowly than pituitary gland; macroadenomas are heterogeneously hyperenhancing
Broca’s area
inferior frontal gyrus, a.k.a. pars opercularis
Locations without choroid plexus
frontal horns, occipital horns, cerebral aqueduct
