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