Brain Quickie Flashcards
What does the labyrinthine branch of AICA supply?
Vestibulo-cochlear and facial nerves
Clinical clue to differentiate AICA from PICA infarct?
Hearing loss
Horner syndrome includes…
- ptosis (drooping eyelid),
- miosis (constricted pupils)
- anhidrosis (ipsilateral decreased sweating) from sympathetic dysfunction.
Clinical presentation of SCA infarction includes…
dysarthria, ipsilateral ataxia, and Horner syndrome
Brain imaging features of Carbon Monoxide poisoning
bilateral, symmetric globi pallidi cytotoxic edema
also seen toxic etiology (illicit drug use)
Corpus callosum (CC) agenesis classic imaging findings
- colpocephaly—lateral ventricular “tear drop” appearance (with a parallel orientation)
- radiating pattern of the central gyri (sagittal view)
Focal nodules along the subependymal lining of the lateral ventricles, differentials?
tuberous sclerosis, heterotopic gray matter (HGM), and metastasis.
Lissencephaly—type I classic features and what must be ruled out for diagnoses
hourglass configuration with smooth cortical surface, shallow sylvian fissures with lateral displacement of the middle cerebral vessels. Subcortical gray matter and thick band heterotopia.
*correlate with gestational age to rule out normal immature brain
A well defined, non-enhancing, hypodense (CSF density) unilocular cystic lesion with no surrounding edema.
Differentials
perivascular space, porencephalic cyst,
neuroglial cyst,
cerebral hydatid cyst
if enhances > consider tumor/infection
Perivascular spaces (PVS) are also known as
Virchow-Robin spaces
Congenital CMV CT features
periventricular calcifications, cortical malformations (agyria, focal cortical dysplasia, schizencephaly)
Schizencephaly
rare cortical malformation that manifests as a grey matter lined cleft extending from the ependyma to the pia mater, separated with CSF
Open vs closed lip
Bilateral vs unilateral
Ring Enhancing Lesions
D: demyelinating disease (incomplete rim enhancement)
R: radiation necrosis
M: metastasis
A: abscess, (bacterial or fungal)
G: glioblastoma
I: infarct (subacute phase), inflammatory - neurocysticercosis (NCC), tuberculoma.
C: contusion, resolving hematoma
A: AIDS, i.e. Toxoplasmosis, Cryptococcus.
L: lymphoma (common in immunocompromised).
Common site for hematogenous seeding in brain
anterior circulation at the gray-white junction
Herpes encephalitis commonly involved sites
- medial temporal lobes
- insular cortex
- inferior frontal lobes
may be bilateral but asymmetric
Clinical signs for uncal herniation
Ipsilateral mass effect of CN 3:
- ipsilateral pupil dilation, unresponsive to light
- ipsilateral eye deviation “down and out”
-compression of the reticular activating system of midbrain > altered conscious state
-motor deficits
usually contralateral hemiparesis
in ~25% ipsilateral hemiparesis due to Kernohan phenomenon
Uncal herniation CT clues
Effacement of suprasellar and prepontine cisterns
Common CNS metastases
- Breast
- Lung
- Melanoma
Classic CT finding for cavernous malformation
calcified “popcorn” lesion on non-contrast CT with NO surrounding vasogenic edema unless haemorrhage is present
Hypertensive haemorrhage common sites
- basal ganglia
- subcortical white matter
- thalamus
- pons
- cerebellum
Blood supply basal ganglia
ACA branches of A1 segment (medial lenticulostriate artery)- anterior inferior parts of basal nuclei and anterior limb of internal capsule
MCA branches of MI (lateral lenticulostriate artery)- superior parts of caudate, most of lentiform and posterior limb of internal capsule
3 basic components of AVM
- enlarged arterial feeders
- compact nidus
- dilated draining vessels
Direct CT signs for CVT
- hyperdense thromboses vein (“cord sign”)
- lack of luminal enhancement in sagittal sinus (“empty delta sign”) on CTV
*indirect: intense contrast enhancement of falx and tentorium
can lead to venous infarct (pattern not consistent with arterial territory)/hemorrhage
Causes for lobar haemorrhages
- cerebral amyloid angiopathy (elderly)
- AVM (young)
- tumors
- bleeding disorders/antigoagulation
- CVT
- cerebral aneurysm
-hypertension (primary/secondary)
PCA supplies
Occipital lobes Temporal lobes thalamus hypothalamus posterior limb of internal capsule
infarction of the medial occipital lobes causes
Homonymous hemianopia (visual defect of either the right or left halves of the visual field)
Bilateral watershed zone infarct etiology
Usually secondary to hypotension
What procedure can be lethal in cerebral empyema?
Lumbar puncture
Cephalohematoma
Subperiosteal hematoma bound by sutures
if crosses midline, consider caput seccundum or subgaleal hematoma
Supracellar mass differentials:
- Craniopharyngioma
- pituitary macroadenoma ( micro adenomas are typically hormonally active , unlike macro)
- Rathke cleft cyst (female predominance)
- thrombosed aneurysm (CTA or MRA)
- dermoid/epidermoid cyst
Common site for arachnoid cyst
Middle fossa
Differentials for prominent extra-axial spaces in infants
- enlarged subarachnoid space
- hematoma (ensure to ask for trauma)
- communicating hydrocephalus
- brain atrophy
Does SAH require further work up?
Yes, vascular imaging in order to exclude aneurysm or AVM
Intracranial giant aneurysms
- larger than 25mm
- exhibit peripheral calcifications
- Heterogenous contrast enhancement
- connects to arterial origin
Colloid cyst
- benign
- spherical focal high attenuated structure
- 99% within the foramen of Monro/anterior third ventricle
- always check for hydrocephalus/ventricle asymmetry
Choroid plexus tumors
occur most commonly in younger children and are the most common brain tumor under 1 year of age.
differential diagnosis for a mass at the cerebellopontine angle includes
meningioma,
epidermoid cyst,
schwannoma.
Vestibular schwannomas (VS) are the most common cerebellopontine angle (CPA) mass.
CNS Hemangioblastoma: common location and CT features
- Crebellum (40-70%), then spinal cord and medulla
- Cystic lesion with mural nodular enhancement
what is PRES?
Posterior reversible Encephalopathy Syndrome:
a transient neurotoxic state may be secondary to HTN, pre/eclampsia, immune suppression, shock/sepsis
bilateral and symmetric distribution
vasogenic edema pattern
common in parietal and occipital lobes
Holoprosencephaly
a rare congenital brain malformation resulting from incomplete separation of the two hemispheres.
alobar
semilobar
lobar
absent septum pellucidum and mono ventricle seen within whole spectrum
Pseudosubarachnoid hemorrhage
Describes an apparent increased attenuation within the basal cisterns simulating true subarachnoid hemorrhage. It is usually due to cerebral edema.
Toxoplasmosis commonly involved site
Treatment
Basal ganglia
pyrimethamine (requires folinic acidity for toxicity) and sulfadiazine for about 6weeks
Wilson disease
autosomal recessive disease with impairment of copper transport leading to copper deposition in organs and cellular damage
Primary CNS lymphoma enhancement pattern
intense enhancement in immunocompetent individuals
ring enhancement in immunocompromised individuals
Differentials for a well circumscribed tumor in the temporal lobe
- ganglioglioma (*common neoplastic cause for temporal epilepsy)
- pilocytic astrocytoma
- oligodendrioglioma (50-65% in frontal lobe)
- pleomorphic xanthoastrocytoma
Heterogenous hemispheric mass with malignant features in a child
Gliobalstoma multiforme (predilection for the cerebral hemispheres)
primitive neuroectodermal tumor (PNET)»_space; CSF seeding common, so image spine
atypical teratoid rhabdoid tumor
choroid plexus carcinoma with significant parenchymal invasion
Metastases prone to hemorrhage
"Mr CT" melanoma Renal Cell Choriocarcinoma Thyroid
Differential bilateral thalamic hypodensity
artery of Percheron infarct
DVT
Wernickes encephalopathy (form of thiamine -B1 deficiency) -
basilar tip infarction
Structures supplied by distal basilar artery
midbrain, thalami, PCA distribution
*effects: visual, oculomotor deficits, somnolence or behavioural changes
Heterogenous enhancement of extra axial lesions ddx
meningioma
metastases
hemangiopericytoma
Intracranial aneurysms
commonly saccular, occur at bifurcations
Normal pressure hydrocephalus classic triad
gait disturbance
dementia
urinary incontinence
What do the 5 point star of the supra cellar cistern represent
fissures between:
- between the two frontal lobes (1)
- between frontal and temporal lobe (2)
- between temporal lobe and brainstem (2)
Common Subarachnoid Hemorrhage patterns
diffuse: likely from ACA or carotid aneurysm
unilateral in region of Sylvian fissure: MCA bifurcation
Prepontine or cerebello-pontine region: basilar tip or PCA
Subdural Hematomas usual causes
often NOT associated with trauma
patients with increased CSF space (from atrophy or dehydration) are at risk from rotational acceleration/deceleration»_space; as veins are fixed at the skull but can rotate with the cortex
Secondary clues and differentials to skull fractures
clues:
jagged and sharp lines
step off along skull surface
adjacent subgaleal hematomas and subcutaneous air
differentials to exclude- suture lines (main/accessory/variants), vascular impressions
In the setting of trauma, small hyperdense foci noted within parenchyma, differential
blood from a SAH may accumulate within sulci making distinguishing SAH from parenchymal bleed difficult
*parenchymal bleed may have surrounding edema
What is the risk with blood within the Ventricles?
CSF obstruction with impaired CSF reabsorption(at arachnoid granulations) likely leading to non-communicating hydrocephalus
Density (HU) of acute hemorrhage vs brain parenchyma
Acute bleed: 50-80HU (hyper acute, ie within an hour, may be isointense)
Brain: 30-40HU
Non-pathological calcifications commonly seen in
- choroid plexus
- pineal gland
- falx and tentorium
- basal ganglia
when reporting intraparenchymal hemorrhage, what must you include?
- size of hemorrhage
- location
- wether it extends to the ventricles
- if there is hydrocephalus
- if there is mass effect (sulcal, loss of basal cisterns, hernation >midline shift, uncal, foramen magnum)
Diffuse Axonal Injury
Results from shearing forces of axons
MRI more sensitve (black spots on SWI)
when present on CT: scattered small round foci of hemorrhage along grey-white matter junction, corpus callous and in basal ganglia.
Common location to watch out for Epidural hematoma
Along the squamous portion of temporal bone»_space; Pterion (H-shaped formation of sutures)
Middle meningeal artery commonly injured causing epidural bleed
What does basal cisterns effacement suggest?
important finding !!!
Transtentorial/uncal herniation
How do you differentiate arachnoid granulations from venous thrombus?
arachnid G- appear as round defect
thrombus -linear filling defect
ALSO»_space; thrombus is usually hyper dense on non-contrast CT whereas arachnoid Gs are CSF density
what nerves may be compressed with PCA and SCA aneurysm?
Oculomotor and Trochlear Nerves (midbrain)
Artery of Percheron infarct feautures:
Super rare as this is anatomic variant!
- bilateral paramedian thalamic and midbrain infarction (most common)
- isolated bilateral paramedian thalamic infarction
- bilateral paramedian thalamic and anterior thalamic infarction
- bilateral paramedian thalamic, anterior thalamic and midbrain infarction (least common)
What is Superficial siderosis?
Cause: chronic SAH, and source of bleeding is found in less than 50% of patients
A RARE disorder characterized by deposition of hemosiderin in leptomeninges covering cerebrum, cerebellum, brain stem, cranial nerves and spinal cord
Clinical Triad: sesorineural hearing loss, cerebellar ataxia, and pyramidal signs along with hemorrhagic or xanthochromic CSF
CT/MRI
Identify the pathology and it’s features
Optic nerve sheath meningioma
These benign tumors arise in middle-aged patients (slight female predominance) from the dural sheath around the optic nerve.
Has an association with neurofibromatosis type 2
Clinical: proptosis, progressive visual loss, color vision defects and afferent pupillary defect (sluggish reaction to light)
CT features:
- usually isoattenuating
- calcifications seen in 20-50% cases
- tram tracking: enhancing tumour surrounding the non-enhancing optic nerve (axial/sagittal)
- doughnut: cuff of enhancing tumour around a central non-enhancing dot (optic nerve)
Most common intramedullary (spine) tumors
- ependymoma (most common in adults).»_space;usually well circumscribed
- astrocytoma (most common in
children) .»_space; infiltrative pathology - hemangioblastoma
- paraganglioma
- metastasis
Common hemorrhagic mets to the brain
- Renal
- thyroid
- melanoma
- choriocarcinoma
