Introduction to brain imaging

Question 1

basal cisterns include

Answer 1

quadrigeminal plate and suprasellar cistern

Question 2

basal cistern that appears like a symmetric smile in axial plane

Answer 2

quadrigeminal cistern

Question 3

basal cistern that looks like a pentagon, Jewish star or the Hindu Shatkona

Answer 3

suprasellar cistern

Question 4

5 corners of suprasellar cistern

Answer 4

anterior- interhemispheric fissure
anterolateral- Sylvian fissure
posterolateral- ambient cisterns

Question 5

6th point of the suprasellar cistern

Answer 5

posterior-interpeduncular fossa

Question 6

what to look at in the brain on a first cursory look

Answer 6

midline, symmetry, basal cisterns, ventricles

Question 7

emergency cranial CT checklist

Answer 7

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?

Question 8

anterior cerebral arteries travel in what fissure

Answer 8

interhemispheric fissure

Question 9

cranial nerve that travels in parallel with the posterior communicating artery

Answer 9

3rd cranial nerve

Question 10

marks the anterior lip of foramen magnum

Answer 10

inferior edge of clivus

Question 11

posterior lip of foramen magnum is marked by

Answer 11

cortical margin of occipital bone

Question 12

cerebellar tonsils should project no more than ___ mm below a line drawn between the anterior and posterior lips of the foramen magnum

Answer 12

5 mm

Question 13

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

Answer 13

obex

Question 14

only structures visible in the craniocervical junction

Answer 14

cervical medullary junction and a tiny bit of cerebellar tonsillar tissue

Question 15

these scans are useful in certain specialized settings, such as medically refractory epilepsy, movement disorders and dementia

Answer 15

nuclear medicine, PET scans

Question 16

if the onset of neurologic symptoms is within 24-48 hours, imaging preferred is

Answer 16

CT

Question 17

MRI is recommended if neurologic symptoms are older than how many days

Answer 17

2 days

Question 18

best for screening of AVMs

Answer 18

MRA

Question 19

best for problem solving and aneurysm treatment planning

Answer 19

CTA

Question 20

if the CT or MR fails to demonstrate an acute infarct and the symptoms suggest a transient ischemic attack or stroke, do a

Answer 20

carotid Doppler US, or MRA or CTA

Question 21

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

Answer 21

proton MR spectroscopy

Question 22

marker for cell membranes and hence a marker for cellular turnover

Answer 22

choline

Question 23

compound found in neurons and therefore a marker of neuronal density

Answer 23

N-acetyl aspartate

Question 24

this is evenly distributed in many types of cells and serves as a reference standard

Answer 24

creatine

Question 25

helps distinguish radiation necrosis from recurrent tumor or infection

Answer 25

elevation of choline-to-creatine ratio

Question 26

if choline peak is sky high, think of

Answer 26

meningioma, demyelinating processes such as MS

Question 27

decrease in NAA-to-creatine ratio are associated with

Answer 27

neuronal death

Question 28

focally decreased NAA is seen in

Answer 28

mesial temporal sclerosis and infarcts

Question 29

global depletion of NAA can be seen in

Answer 29

MS, Alzheimer disease

Question 30

elevated myoinositol is seen in

Answer 30

Alzheimer disease

Question 31

abscesses and metastatic lesions will have low or high NAA-to-creatine ratio

Answer 31

lower

Question 32

markedly elevated NAA levels are seen in

Answer 32

Canavan disease, due to a specific defect in the enzyme that metabolizes NAA

Question 33

Amino acid peaks can be seen in

Answer 33

intracranial infections

Question 34

characteristic doublet peak of lactic acid can help make the diagnosis of

Answer 34

ischemia

Question 35

sagittal MIP in CTA is useful in

Answer 35

carotid ophthalmic aneurysm, Pcomm and PICA

Question 36

coronal MIP in CTA is useful in

Answer 36

Acomm, carotid "T" and basilar tip

Question 37

axial MIP in CTA is useful in

Answer 37

Acomm and Pcomm

Question 38

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"

Answer 38

diffusion tensor imaging

Question 39

in acute stroke patient, a delay of time to peak that is greater than __ seconds strongly suggest ischemia in MR perfusion technique

Answer 39

6 seconds

Question 40

refers to studies of the brain using blood exygen level-dependent imaging

Answer 40

Functional MR imaging

Question 41

imaging study of choice from chronic headache

Answer 41

MR without contrast

Question 42

imaging study of choice for dementia

Answer 42

MR without contrast

Question 43

imaging study of choice for coma patients

Answer 43

CT without contrast

Question 44

True or false: loss of gray/white distinction, low attenuation in basal ganglia, poor definition of insula on CT may contraindicate thrombolytic therapy

Answer 44

true

Question 45

acute stroke questions

Answer 45

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?

Question 46

diffusion-perfusion mismatch can be calculated to identify the penumbra of potentially salvageable brain thru

Answer 46

subtracting the volume of abnormal diffusion from the volume of abormal perfusion

Question 47

freq indication for imaging of the brain

Answer 47

Headache

Question 48

recognized by the displacement of normal structures away from the abnormality

Answer 48

mass

Question 49

recognized by widening of the ipsilateral sulci or enlargement of the ventricle adjacent to the lesion

Answer 49

atrophy or volume loss

Question 50

shift ipsilateral to an atrophic lesions is very unusual and is only seen commonly in

Answer 50

congenital hemiatrophy

Question 51

3 common causes of reversible atrophy

Answer 51

dehydration and starvation, Addison disease, High-dose steroid therapy

Question 52

may also occasionally result in reversible atrophy but its neurotoxic effects are not reversible

Answer 52

alcoholism

Question 53

most reliable sign of an extra-axial mass in the posterior fossa

Answer 53

widening of the ipsilateral subarachnoid space

Question 54

common pattern of enhancement of extra-axial masses

Answer 54

homogeneous enhancement

Question 55

common pattern of enhancement of intra-axial masses

Answer 55

ring-like of irregular fashion

Question 56

True or false: intra-axial masses have more surrounding edema than extra-axial masses of same size

Answer 56

true

Question 57

lesions involving the gray matter are usually of

Answer 57

infarct, trauma or encephalitis

Question 58

this form of edema results from disturbances in tight capillary junctions that occur in association with cerebral tumors, abscesses or hematomas

Answer 58

vasogenic edema

Question 59

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

Answer 59

cytotoxic edema

Question 60

if ischemia of the deep gray matter structures bilaterally are involved, what can be considered

Answer 60

pure anoxia owing to carbon monoxide poisoning or respiratory arrest

Question 61

traumatic lesions tend to occur at what areas in acceleration/deceleration injuries

Answer 61

orbital and frontal polar regions, temporal poles and occipital poles

Question 62

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

Answer 62

Herpes simplex encephalitis

Question 63

Mass lesion questions

Answer 63

``` Intra or extra-axial? solitary or multiple? Gray matter or white matter? pattern of contrast enhancement SI or attenuation pattern in MRI ```