Introduction to brain imaging Flashcards
basal cisterns include
quadrigeminal plate and suprasellar cistern
basal cistern that appears like a symmetric smile in axial plane
quadrigeminal cistern
basal cistern that looks like a pentagon, Jewish star or the Hindu Shatkona
suprasellar cistern
5 corners of suprasellar cistern
anterior- interhemispheric fissure
anterolateral- Sylvian fissure
posterolateral- ambient cisterns
6th point of the suprasellar cistern
posterior-interpeduncular fossa
what to look at in the brain on a first cursory look
midline, symmetry, basal cisterns, ventricles
emergency cranial CT checklist
is the middle of the brain in the middle of the head?
Do the 2 sides of the brain look alike?
Can you see the smile and the pentagon or Jewish star/Shatkona?
IS the 4th ventricle in the midline and more or less symmetrical?
Are the lateral ventricles huge, with effaced sulci?
anterior cerebral arteries travel in what fissure
interhemispheric fissure
cranial nerve that travels in parallel with the posterior communicating artery
3rd cranial nerve
marks the anterior lip of foramen magnum
inferior edge of clivus
posterior lip of foramen magnum is marked by
cortical margin of occipital bone
cerebellar tonsils should project no more than ___ mm below a line drawn between the anterior and posterior lips of the foramen magnum
5 mm
most posterior projection of the dorsal medullar that should lie above the imaginary line drawn between the anterior and posterior lips of the foramen magnum
obex
only structures visible in the craniocervical junction
cervical medullary junction and a tiny bit of cerebellar tonsillar tissue
these scans are useful in certain specialized settings, such as medically refractory epilepsy, movement disorders and dementia
nuclear medicine, PET scans
if the onset of neurologic symptoms is within 24-48 hours, imaging preferred is
CT
MRI is recommended if neurologic symptoms are older than how many days
2 days
best for screening of AVMs
MRA
best for problem solving and aneurysm treatment planning
CTA
if the CT or MR fails to demonstrate an acute infarct and the symptoms suggest a transient ischemic attack or stroke, do a
carotid Doppler US, or MRA or CTA
shows the distribution of brain metabolities based by the chemical shift of protons within themm which is a property determined by the chemical environment of the protons in question
proton MR spectroscopy
marker for cell membranes and hence a marker for cellular turnover
choline
compound found in neurons and therefore a marker of neuronal density
N-acetyl aspartate
this is evenly distributed in many types of cells and serves as a reference standard
creatine
helps distinguish radiation necrosis from recurrent tumor or infection
elevation of choline-to-creatine ratio
if choline peak is sky high, think of
meningioma, demyelinating processes such as MS
decrease in NAA-to-creatine ratio are associated with
neuronal death
focally decreased NAA is seen in
mesial temporal sclerosis and infarcts
global depletion of NAA can be seen in
MS, Alzheimer disease
elevated myoinositol is seen in
Alzheimer disease
abscesses and metastatic lesions will have low or high NAA-to-creatine ratio
lower
markedly elevated NAA levels are seen in
Canavan disease, due to a specific defect in the enzyme that metabolizes NAA
Amino acid peaks can be seen in
intracranial infections
characteristic doublet peak of lactic acid can help make the diagnosis of
ischemia
sagittal MIP in CTA is useful in
carotid ophthalmic aneurysm, Pcomm and PICA
coronal MIP in CTA is useful in
Acomm, carotid “T” and basilar tip
axial MIP in CTA is useful in
Acomm and Pcomm
this tool, exploits the fact that within the elongated cell processes such as axons, water can diffuse more freely “down the tube” than “sideways”, allowing for reconstruction of white matter tracts or “tractography”
diffusion tensor imaging
in acute stroke patient, a delay of time to peak that is greater than __ seconds strongly suggest ischemia in MR perfusion technique
6 seconds
refers to studies of the brain using blood exygen level-dependent imaging
Functional MR imaging
imaging study of choice from chronic headache
MR without contrast
imaging study of choice for dementia
MR without contrast
imaging study of choice for coma patients
CT without contrast
True or false: loss of gray/white distinction, low attenuation in basal ganglia, poor definition of insula on CT may contraindicate thrombolytic therapy
true
acute stroke questions
Are there signs of an acute infarct? How big?
Is there acute blood?
Is there a hyperdense artery, for example, MCA, suggesting a large vessel clot?
diffusion-perfusion mismatch can be calculated to identify the penumbra of potentially salvageable brain thru
subtracting the volume of abnormal diffusion from the volume of abormal perfusion
freq indication for imaging of the brain
Headache
recognized by the displacement of normal structures away from the abnormality
mass
recognized by widening of the ipsilateral sulci or enlargement of the ventricle adjacent to the lesion
atrophy or volume loss
shift ipsilateral to an atrophic lesions is very unusual and is only seen commonly in
congenital hemiatrophy
3 common causes of reversible atrophy
dehydration and starvation, Addison disease, High-dose steroid therapy
may also occasionally result in reversible atrophy but its neurotoxic effects are not reversible
alcoholism
most reliable sign of an extra-axial mass in the posterior fossa
widening of the ipsilateral subarachnoid space
common pattern of enhancement of extra-axial masses
homogeneous enhancement
common pattern of enhancement of intra-axial masses
ring-like of irregular fashion
True or false: intra-axial masses have more surrounding edema than extra-axial masses of same size
true
lesions involving the gray matter are usually of
infarct, trauma or encephalitis
this form of edema results from disturbances in tight capillary junctions that occur in association with cerebral tumors, abscesses or hematomas
vasogenic edema
edema that results from increased tissue water content following the neuropathologic response to cell death. in these cases, infarct, trauma, or encephalitis should be considered
cytotoxic edema
if ischemia of the deep gray matter structures bilaterally are involved, what can be considered
pure anoxia owing to carbon monoxide poisoning or respiratory arrest
traumatic lesions tend to occur at what areas in acceleration/deceleration injuries
orbital and frontal polar regions, temporal poles and occipital poles
this disease spreads from the oral and nasal mucosa to the trigeminal and olfactory ganglion cells and then transdurally to the brain. most common location are medial temporal lobes, adjacent to the trigeminal ganglia and orbital frontal regions adjacent to the olfactory bulbs
Herpes simplex encephalitis
Mass lesion questions
Intra or extra-axial? solitary or multiple? Gray matter or white matter? pattern of contrast enhancement SI or attenuation pattern in MRI
