Skull & Brain Flashcards
By what age do the anterior and mastoid fontanelles typically close?
Approx. 2 yrs
By what age do the posterior and sphenoid fontanelles typically close?
Approx 1-3 months
What is the weakest part of the skull and what is a complication from fx to this area?
Pterion; middle meningeal artery sits right below this area and fx to this area can result in rupture and an epidural hematoma.
By what age does the metopic suture typically fuse and early fusion results in which type of craniosynostosis?
Usually fuses by 9 months;
Trigonocephaly.
a) Which foramen does the middle meningeal artery travel through?
b) Which foramen does the mandibular division of CNV travel through?
c) Which foramen does the maxillary division of CNV travel through?
a) Foramen spinosum
b) Foramen ovale
c) Foramen rotundum
Which embryological anatomy gives rise to the peripheral nerves, roots and ganglia of the ANS?
Neural crest
What are the 5 divisions of the brain after ventral induction?
Prosencephalon (forebrain) -- telencephalon -- diencephalon Mesencephalon (midbrain) Rhombencephalon (hindbrain) -- metencephalon -- myelencephalon
What are the 6 stages of neurogenesis?
1) Dorsal induction
2) Ventral induction
3) Proliferation
4) Migration
5) Organization
6) Myelination
Which embryological division makes up the cerebrum? Which makes up the cerebellum?
Cerebrum –> telencephalon
Cerebellum –> metencephalon
List 4 locations where the blood-brain barrier is not continuous.
1) Portions of hypothalamus – where hormones enter the systemic circulation
2) Posterior lobe pituitary gland – where ADH and oxytocin are released
3) Pineal gland – pineal secretions
4) Choroid plexus – ependymal cells maintain the blood-CSF barriar
What is the M/C/C and 2nd M/C/C of congenital CNS infection?
1st = CMV 2nd = Toxoplasmosis
Where do CNS toxoplasmosis like to affect?
- basal ganglia
- parenchyma (peripheral corticomedullary junction)
- periventricular (sparsely)
Does CNS toxoplasmosis like to calcify?
Yes (71%)
What is the enhancing pattern in adult toxoplasmosis?
Ring-enhancing
What clinical finding is common to both toxiplasmosis & CMV?
chorioretinitis
Which congenital infection has a high risk for miscarriage and birth defects?
Rubella
What are the clinical features of CMV?
- chorioretinitis
- CNS involvement (50%)
- microencephaly (10%)
- hepatosplenomegaly (10%)
- petechial rash (10%)
What are the radiographic findings associated with CNS CMV?
- parenchymal & periventricular Ca++ (50%)
- Schizencephaly
- ventricular dilation
- cerebellar hypoplasia
What % of children will develop CMV if present in their mothers?
40%
How do neonates acquire herpes simple infection?
Through contact with infected mother’s cervix or vagina during birth.
What is the M/C/C for an epidural abscess?
Direct extension from infection in mastoids, paranasal sinuses or calvarium.
Can also be post-surgical.
What is a subdural empyema and how does it form?
Purulent collection collected within the potential subdural space by disruption of arachnoid meningeal barrier.
What enhances in a subdural empyema?
The granulation tissue that forms over time adjacent to the infection.
What is the M/C/C of a pyogenic brain (cerebral abscess)?
Hematogenous dissemination (33%) from a primary infectious site. Eg. AV shunts, cardiac, drug abuse, pulmonary infection, sepsis.
Other than timing (days vs. 1-2 weeks), what is the difference btwn early and late cerebritis?
Early: May or may not be detected on CT; patchy enhancement.
Late: Central necrosis (hypodense) in with irregular ring enhancement.
What is the difference btwn the early capsule vs. late capsule stage in a cerebral abscess?
Early capsule: well-defined rim enhancing with surrounding vasogenic edema (double rim sign)
Late capsule: thickened capsule
What are the 4 stages of cerebritis?
a) Early cerebritis
b) Late cerebritis
c) Early capsule formation
d) Late capsule formation
What is the ddx for ring enhancing lesions?
MAGIC DR: Mets Abscess Glioblastoma multiform Infarct Contusion Demyelinating Radiation necrosis
(Toxoplasmosis can also present like this.)
What is commonly the cause of death with infectious cerebritis?
Herniation of infection into the ventricles (the medial wall of the capsule is often less thick, allowing for easier rupture).
What is the M/C organism to cause stroke from infective endocarditis?
Staph aureus
What is the M/C location for a cerebral abscess?
Frontal & parietal lobe (distribution of MCA)
What is the M/C etiology for meningitis?
What is the 2nd M/C?
1st = hematogenous dissemination from distant infectious focus 2nd = direct geographic extension from sinusitis, otitis or mastoiditis
What is the M/C form of CNS infection?
Meningitis
What is the M/C organism to cause acute pyogenic meningitis in a neonate?
In kids?
In adults?
In the elderly?
Neonates = Group B streptococcus Kids = N. meningitidis Adults = Strep pneumonia Elderly = Listeria; Strep pneumonia; N. meningitidis
What is the imaging appearance of meningitis on MRI?
- exudates in the cisterns (do not suppress on FLAIR like CSF)
What is the M/C/C of acute lymphocytic meningitis? What is its prognosis?
Viral origin (50-80% enterovirus); benign and self-limiting.
What is the M/C/C for chronic meningitis?
Tuberculosis (or granulomatous origin)
In encephalitis, what part of the cerebrum is M/C affected?
Gray matter
Herpes varicella zoster virus presents with small vessel vasculitis (and hence CNS involvement) in which pop’n?
Immuno-compromised patients (eg. lymphoma, AIDS)
What is the preferred intracranial site for herpes simplex encephalitis?
Temporal lobes & insular cortex
Infectious mononucleosis (from an Epstein-Barr virus) has a predilection for which intracranial regions in children?
Brain stem & cerebellum
The “giant panda sign” is associated with which condition?
Which MSK condition is it also classically seen in?
Japanese encephalitis
(high signal in tegmentum but spares red nucleus and corticospinal tract)
Also seen in Wilson’s disease.
What % of TB cases have CNS involvement?
5-10%
What is the M/C form of TB CNS?
What is the 2nd M/C form?
1st = Tuberculous meningitis 2nd = Tuberculoma
Where do tuberculomas M/C like to occur?
brain stem
What is the pathomechanism for tuberculous meningitis?
Ruptured tuberculoma into the subarachnoid space –> discharges necrotic debris –> causes meningitis
Which granulomatous disease likes to affect the CN7?
Sarcoidosis
What CNS locations does sarcoidosis like to involve?
Hypothalamus, pituitary stalk, optic nerve and chiasm
What are 2 forms that CNS sarcoidosis can present as?
i) Chronic basilar leptomeningitis
ii) Parenchymal sarcoid nodule
A white matter disease (radiologically similar to MS & ADEM) in a patient from the midwest (eg. Minnesota/Wisconsin) who has a “target sign” on their skin, most likely has which condition?
Lyme disease
(It is also common in the New England area).
What is the M/C CNS parasitic disease?
Cysticercosis (called neurocysticercosis)
What is the classic imaging appearance of an old neurocysticerocsis infection?
Cyst with dot sign –> rim enhancing and dot enchancing
What is the M/C opportunistic infection in AIDS patients?
Toxoplasmosis
How is amebic meningoencephalitis acquired and manifested in the CNS?
Amebic enters nasal cavity and directly extends through the cribiform plate of ethmoid bone to brain.
What is an aka for Progressive Dementia Complex?
AIDS Encephalopathy
What are the imaging findings associated with AIDS encephalopathy?
- progressive volume loss
- bilateral, patchy confluent hypodensities in white matter (T2 periventricular hyperintensity)
- reduced gray matter
- no enhancement
What is a major differential for progressive dementia complex (AIDS encephalopathy)?
progressive multifocal leukoencephalopathy (PML)
What are other manifestations of HIV/AIDS?
a) Vasculopathy
b) HIV/AIDS bone marrow changes (eg. bright disc sign)
c) Benign lymphoepithelial lesions (=non-neoplastic cystic masses that enlarge salivary glands)
- - bilateral M/C
- - Parotid gland M/C
- - Imaging: multiple cysts w/ thin enhancing rim/hyper T2
What is the M/C opportunistic infection in HIV patients?
Toxoplasmosis
Sarcoidosis M/C involves which portion of the CNS?
meninges
Which cranial nerve is involved in sarcoidosis?
CN7 (facial palsy) & CN2 (optic neuritis)
What are the M/C cosmopolitan CNS fungal diseases?
a) aspergillosis
b) mucormycosis
c) candida
d) cryptococcus
What are the M/C geographically restricted CNS fungal diseases?
a) coccidioidomycosis
b) blastomycosis
c) histoplasmosis
What is the M/C CNS (fungal?) infection?
Cryptococcus
What is the 1st, 2nd and 3rd M/C CNS pathogen?
1st = HIV 2nd = toxoplasmosis 3rd = cryptococcus
Which fungal infection M/C infects the CNS when disseminated?
Aspergilosis
What is the clinical findings associated with CNS histoplasmosis infection?
Asymptomatic infection
Other than CNS, disseminated blastomycosis likes to involve which other body region?
Male genital tract
What is the difference between the locations involved in CNS toxoplasmosis and lymphoma?
Toxoplasmosis has a predilection for the basal ganglia and at the corticomedullary junction.
Lymphoma has a predilection for periventricular and subependymal regions.
Which region of the spine is most frequently involved in AIDS-associated myelopathy?
Thoracic spine
What is the difference btwn demyelinating and dysmyelinating disorders?
Demyelinating = inflammatory component that injures/destroys white matter
Dysmyelinating = intrinsic abnormalities of myelin formation or myelin maintenance (in pediatric/adolescence)
Is MS a primary or secondary demyelinating disease?
Primary
What are some secondary demyelinating disease?
a) Allergic – ADEM
b) Viral – HIV, encephalitis, progressive multifocal leukoencephalopathy
c) Vascular – Binswanger disease (small vessel dementia)
d) Toxic – alcohol, radiation
e) Traumatic – diffuse axonal injury
Optic neuritis is seen in what % of MS patients?
80%
What are 2 positive laboratory tests that are associated with MS?
IgG (70%) Oligoclonal bands (90%)
(Both are found in CSF)
What are the different clinical courses that can occur in MS and which is the M/C?
a) Relapsing remitting (M/C 85%) – exacerbations followed by remissions
b) Secondary progressive – progressive w/out much remission
c) Primary progressive (chronic progressive) – progressive from start
d) Progressive relapsing – progressive disease with clear acute relapses
MS likes to affect which location?
- periventricular (85%)
- callososeptal interface (50-90%)
- subcortical U-fibers
- brain stem
- spinal cord
What is the imaging appearance of MS in the brain?
- Multiple hyperintense T2 lesions
- thinned corpus callosum
- Dawson’s fingers
- Dot-dash sign
- Tumefactive (lesions >2cm) –> produce horseshoe-shaped ring enhancement
- horse-shoe enhancement
- ONLY enhances early in disease process when its active
What differentiates a tumefactive MS lesion from a tumor?
i) Perfusion in tumor increased, not in MS
ii) Veins displaced by neoplasm, they course through MS lesion
What does a MS lesion look like in the spinal cord?
- 90% MS lesions less than 2 VB lengths
- cervical region
What are some imaging differences between MS and ADEM?
ADEM
- favors subcortical & deep white matter regions
- no Dawson’s fingers
- cranial nerve enhancement
- usually at least one large dominant lesion
- no new lesions on MR 6 months from start of disease
- more symmetric in appearance
- DWI may show restriction (MS typically does not OR may show increased diffusion)
Most ADEM patients completely recover after what time period?
1-2 months (>50%)
What is the etiology of progressive multifocal leukeoencephalopathy (PML) and what does it specifically affect?
JC virus – infects oligodendrocyte
What is the main condition associated with PML?
AIDS
What’s an aka for Binswanger disease?
What is the pathology?
Subcortical arteriosclerotic encephalopathy
Small vessel dementia –> severe arteriosclerosis of the small vessels causing infarction.
How does Binswanger disease present on imaging?
CT: diffuse, symmetrical, hypodense white matter lesions
MR: high signal T2 lesion
What location does Binswanger disease affect?
- subcortical U-fibers (according to radiopedia BUT Neuroreq says these are spared b/c they have dual blood supply!!!)
- periventricular
- frontal lobe
- centrum semiovale
Which condition is radiographically identical to Binswanger disease except it affects the subcortical fibers? (This is according to Neurorequisite)
Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopahty (CADASIL)
What are vascular causes for white matter disease?
- Binswanger disease
- CADASIL
- Reversible posterior leukoencephalopathy
What are some dysmyelinating disease?
- Alexander disease
- Krabbe disease
- Canavan disease
- X-linked adrenoleukodystrophy
- Metachromatic leukodystrophy
A glasgow coma scale of which number is considered severe?
<8
Which bone and vascular structure is most commonly involved in an epidural hematoma?
Temporal (90%)
Middle meningeal artery (90%)
What is the deceiving clinical presentation in 50% of epidural hematoma cases and what is it called?
Lucid interval = brief loss of consciousness followed by asymptomatic period then onset of coma and/or neuro deficit.
Which extraaxial hematoma is M/C?
2nd M/C?
Subarachnoid hemorrhage
Subdural hematoma
Which vessels are affected in a subdural hematoma?
Bridging veins
What are the 2 subtypes of subdural hematomas?
a) Simple = w/out brain parenchymal injury
b) Complicated = w/ brain parenchymal injury (poorer prognosis)
Subdural effusion is usually a complication of which condition?
Meningitis (eg. hx of prior infection)
Subdural empyema is usually secondary to which condition(s)?
Sinusitis or mastoiditis
What are some non-traumatic causes of sudural hematoma?
- aneurysm
- amyloid
- Menkes disease
- post-shunt coagulopathy
What is a non-traumatic cause for epidural hematoma?
Post-operative
What is a subdural hygroma and what is its etiology?
Fluid collection with similar characteristics as CSF (but has more protein).
Etiology:
a) Tear in arachnoid membrane causing of leaking of CSF.
b) Chronic degradation of subdural hematoma
What is the M/C/C of intracranial subarachnoid hemorrhage?
Trauma
What is the M/C/C of a non-traumatic intracranial subarachnoid hemorrhage?
Ruptured basilar aneurysm (80%)
What is the M/C intraaxial injury?
Hemorrhagic contusion