Page 16 Flashcards
5 corners of the pentagon of the suprasellar cistern?
- interhemispheric fissure - anteriorly 2-3. sylvian cisterns - anterolaterally 4-5. ambient cisterns - posterolaterally
6th point of the Jewish star or Hindu Shatkona of the supracellar cistern?
interpeduncular fossa
What does a small lucency frequently seen in the midbrain tegmentum represent?
decussation of the superior cerebellar peduncle
What is the most posterior projection of the dorsal medulla?
obex
The cerebellar tonsils should project no more than __ mm below a line drawing between the anterior and posterior lips of the foramen magnum.
5 mm
Follow-up question: Histologic grade correlates with choline-to-creatine ratio but there are exceptions. What disease should you think of if the choline peak is sky high?
there are exceptions. What disease should you think of if the choline peak is sky high?
meningioma (**also, demyelinating processes can present with elevated choline peaks)
-marker for cellular turnover?
choline (since it is a marker for cell membranes; it may be considered a tumor marker)
In what conditions do you see focally decreased NAA?
mesial temporal sclerosis and infarcts
-marker of neuronal density?
NAA (found only in neurons)
-marker of anaerobic metabolism?
lactate - ??? di ko alam kung interchangeable iyong lactate at lipid?
In what conditions do you see global depletion of NAA?
MS and dementia
Since they tend to infiltrate rather than replace brain, which conditions will have
lower NAA-to-creatine rations compared to primary brain tumors?
abscesses and mets
-serves as a “reference standard” metabolite since it is evenly distributed in many cell types?
creatine
NAA (found only in neurons)NAA (found only in neurons)
-Follow-up question: A characteristic doublet peak of lactic acid can help make the diagnosis of?
ischemia
Ulrich’s (older) classification of temporal bone fractures according to their orientation to the long axis of the petrous bone:
longitudinal (MC), transverse, mixed
Which conditions show nonspecific lipid necrosis peak?
malignant tumors, infections, and some ACTIVE DEMYELINATING lesions
-marker of necrosis?
lipids
How do you differentiate radiation necrosis from recurrent tumor on MRS?
radiation necrosis - elevated lactate; tumors - elevated choline and depressed NAA (which are not seen in radiation necrosis
What is the most reliable sign of an extra-axial mass in the posterior fossa?
widening of the ipsilateral subarachnoid space
Compare the hearing loss seen as a complication in longitudinal and in transverse temporal bone fractures
longitudinal - conductive (sensorineural is uncommon); transverse - sensorineural
What findings on cranial CT for trauma should raise suspicion for temporal bone
fracture?
Opacification of mastoid air cells, fluid in middle ear cavity, pneumocephalus, pneumolabyrinth
What are some signs that can point to an isodense subacute SDH (instead of atrophy)?
Sulcal effacement, white matter buckling, thick gray matter mantle, distorted ventricles, midline shift
How can you differentiate convexal SAH from SDH?
SAH extends into adjacent sulci, may also have sulcal effacement
What biochemical state of Hb is responsible for the MRI appearance of a subacute hematoma?
methemoglobin (intracellular pag early, extracellular pag subacute)
What artery may be infarcted in tonsillar herniation?
PICA
What is the peak time for hemorrhagic transformation?
1-2 weeks post infarction (same sa gyral enhancement)
What normal variant pertains to one pericallosal branch of ACA supplying both hemispheres?
azygous ACA (occlusion will affect both hemispheres)
Most sensitive places to look for SAH on CT
interpeduncular fossa, posterior Sylvian fissure, far posterior aspects of the occipital horns
What gyrus is displaced in subfalcine herniation?
cingulate gyrus (another term for subfalcine is cingulate herniation)
Le Fort fractures (fractures of the midface):
Le Fort I - floating palate - horizontal fracture through the maxillary sinuses, extending throught the nasal septum and walls of the maxillary sinuses into the inferior aspect of the pterygoid plates Le Fort II - pyramidal - fracture beginning at the bridge of the nose and extending in a pyramidal fashion through the nasal septum, frontal process of the maxillar, medial wall of the orbit, inferior orbital rim, superior, latera and posterior walls of the maxillary antrum, and midportion of the pterygoid plates Le Fort III - craniofacial dysjunction - horizontally oriented fracture through the orbits
What injury demonstrates association of subdural hematomas and retinal hemorrhages in chiildren with metaphyseal long bone fractures?
whiplash skaken injur
When does intravascular enhancement on MR resolve?
10 days
What term represents injury causing coma, subdural hematomas, and primary brain injury in child abuse?
shaken impact injury
When does gyral enhancement resolve?
3 months
Common locations of perivascular spaces
medial temporal lobes, inferior 1/3 of the putamen, thalamus
Rule of 3s regarding MR parenchymal enhancement:
peaks at 3 days to 3 weeks and resolves by 3 months
What size does an intracranial aneurysm pose risk for rupture?
3-5mm
Osborn: What size of saccular aneurysm poses increased risk of rupture?
> or = 5mm
What is the hallmark of uncal herniation?
effacement of the ambient cistern and contralateral hydrocephalus
How far is a significant general midline shift?
3mm or >
What neoplasms that metastasize to the brain often bleed?
bronchogenic, thyroid, melanoma, choriocarcinoma, RCC
pilocytic astrocytoma
Grade I
diffuse astrocytoma (Osborn)
Grade II
oligodendroglioma
Grade II
-subependymal giant cell astrocytoma
Grade I
-fibrillary astrocytoma
Grade II
-pleomorphic xanthoastrocytoma (located along meningocerebral interface)
Grade II
germistocytic astrocytoma and protoplasmic astrocytroma (rare variants of
fibrillary)
anaplastic astrocytomas
III
dysembryoplastic neuroepithelial tumor
Grade I
GBM
IV
-ependymoma
Grade II
medulloblastoma
IV
-atypical teratoid/rhabdoid tumor (ATRT)
IV
choroid plexus papilloma
Grade I
subependymoma
Grade I
-choroid plexus ca
III
-central neurocytoma
III (sa Osborn, II)
What are the 2 entities that commonly have bihemispheric spread through the corpus callosum with involvemenet of both frontal lobes?
GBM and CNS lymphoma
-pineoblastoma
IV
Usual hyperdense neoplasms?
lymphoma, pineablastoma, neuroblastoma, medulloblastoma
What are the calcified glial tumors in order of frequency?
oligodendroglioma, ependymoma, astrocytoma, GBM (Old Elephants Age Gracefully)
How can you differentiate medulloblastoma from astrocytoma on noncontrast CT?
astrocytoma - usually hypodense; medulloblastoma - almost never hypodense
Which malignancy is linked with the combination of falcine calcification and medulloblastoma?
nevoid basal cell ca
Which malignancy has a predilection to metastasize to the posterior fossa?
RCC
(Osborn) What syndrome should the patient be evaluated for if dense tentorial or
falcine calcifications are present together with medulloblastoma?
basal cell nevus (Gorlin) syndrome
Causative agent of subacute sclerosing panencephalitis (SSPE)?
measles
What is the likely diagnosis if a calcified pineal mass is seen in a female? male?
female - pineocytoma; male - germinoma
What is the size of microadenomas?
1 cm or less
What is the size of a pathologic pineal calcification?
1 cm
What viruses are associated with acute necrotizing encephalitis in children?
Influenza A and B
CD4 count in AIDS patients with toxoplasmosis?
<200
Causative agent of PML?
JC polyomavirus (reactivation)
CD4 count in AIDS patients with progressive multifocal leukoencephalopathy (PML)?
<200
diseases What are the areas of predilection of HSV type 1?
temporal lobes (hippocampus), insular cortex, subfrontal area, and cingulate gyri; spares the putamen
What disease refers to supraclinoid obliterative arteriopathy?
moyamoya disease
Characteristic locations of CSF obstruction in the following neoplasms:
What structure connects the third and fourth ventricles?
cerebral aqueduct
-colloid cyst
anterior third ventricle
-pineal tumors and tectal gliomas
aqueduct
ependymoma and medulloblastoma
fourth
Classic clinical triad of normal pressure hydroceph?
dementia, gait disturbance, urinary incontinence
What toxin may result in signal abnormalities in the globus pallidus?
CO
What toxin may result in signal abnormalities in the putamen?
methanol
Radiation leukoencephalitis usually follows a cumulative dose in excess of __ Gy delivered to the brain and occurs 6 to 9 months after treatment.
40
What age does T1 demonstrate an adult pattern?
8 mos (so sa 1st yr of life, best ang T1 for evaluating myelination)
What age is the adult gyral pattern established?
38 weeks
corpus callosum anatomy and development
1) rostrum, 2) genu, 3) body, and 4) splenium (development: 2->4 and then 1)
What age does T2 demonstrate an adult pattern?
18 mos (8-18 mos, most useful ang T2 for myelination)
What conditions do typically cause hemorrhages at gray-white matter interface?
mets, septic emboli, and fungal
T1 myelination milestones
3 months anterior limb of the internal capsule
4 months splenium
6 months genu
Most severe malformation resulting from an arrest of neuronal migration
lissencephalies
Which lobes are usually most severely affected in type 1 classic
licencephalies/agyria-pachygyria complex?
parieto-occipital lobes
What has probably the highest rate of infiltration of the meninges among the non-CNS tumors?
leukemia
What size should a saccular aneurysm be for it to be called a giant aneurysm
2.5 cm or > (sa table 2 cm)
Direction of vermian development?
from top to bottom (so pag hypogenetic iyong vermis, may mga kulang na folia sa inferior vermis)
What intracranial hemorrhage is a common association with intracranial hypotension?
subdural hematoma
How many components do the the circle of Willis have?
10
What artifact is the major imaging mimic of classic superficial siderosis?
bounce point artifact
What Zabramski type is the classic CCM appearing as a popcorn ball?
Zabramski type II (pag multiple microhemorrhages iyong appearance, type IV)
What is the size of a giant cerebral cavernous malformation (CCM)?
> 6 cm
What is the only CN that lies inside the cavernous sinus itself?
abducens (CN VI)
2010 McDonald criteria for MS:
Dissemination in space - >or= 1 T2 hyperiontense lesion(s) in at least 2 of these 4 areas
(periventricular, juxtacortical, infratentorial, spinal cord Dissemination in time - new lesion on follow-up; or simultaneous presence of asymptomatic enhancing and non-enhancing lesions at any time
In MS lesions especially large tumefactive lesions, where does the “open” nonenhancing segment of the horseshoe enhancement face?
face the cortex
