Neuroscience (Approach to Stroke)

Question 1

State the differences between CT and MRI

Answer 1

CT to be used in emergency, MRI better still (if no emergency)

Question 2

State the 3 types of MRI

Answer 2

1. DWI - diffuse weighted imaging
2. ADC - apparent diffusion coefficient
3. T2 star sequence

Question 3

During low diffusion coefficient because of many cells (tumours/swollen cells due to infarction), state the appearance in DWI and ADC

Answer 3

DWI (diffuse weighted imaging) - hyperintensity (bright) due to less dispersion of signal

ADC (apparent diffusion coefficient) - hypointensity (darker) due to restriction

Question 4

State the use of T2 star sequencing

Answer 4

T2 Star Sequencing = microbleed

Question 5

State the contrasts used in CT and MRI.

Answer 5

CT - iodine (large molecules that has many electrons so appears hyperdense)
- CT angiograms - iodine

MRI - gadolinium (supramagnetic characteristics)
- MRI angiogram - no contrast

Contrasts do not usually pass through BBB unless there is pathology

Question 6

State the gold standard test for investigating stroke. Why?

Answer 6

CT SCAN without CONTRAST
- Fast
- Inexpensive
- Readily available
- No contrast as contrast can mimic blood because it is dense
- Used to exclude intracranial haemorrhage (hyperdense)

Question 7

State the density of grey and white matter on CT scan

Answer 7

grey matter = hyperdense (low fat content) = bright
white matter = hypodense (higher fat content) = dark

grey matter is brighter than white matter on ct scan

Question 8

State the presentation of … on CT scan
(1) Vascular oedema
(2) Cytotoxic oedema

Answer 8

(1) VASCULAR OEDEMA –> grey-white differentiation present, white matter more hypodense
- Pathology causes BBB to be leaky –> extravasation of fluids and proteins
- Grey matter usually brighter than white matter on CT

(2) CYTOTOXIC OEDEMA –> grey-white differentiation absent
- Pathology of astrocytes –> ion channels disrupted –> ions enter astrocytes and sodium and fluid leak out of astrocytes –> grey and white matter become hypodense

Question 9

State the presentation of ACUTE MCA INFARCTS on CT scan

Answer 9

ACUTE MCA INFARCTS
- loss of grey-white differentiation
- wedge-shaped hypodensities (due to swelling and dying tissues)
- sulcal effacement
- ‘insular ribbon’ sign

Question 10

State the presentation of CHRONIC MCA INFARCTS on CT scan

Answer 10

CHRONIC MCA INFARCTS
- liquefactive necorsis (hypodense)
- ventricles dilated

Question 11

State the common presentation of middle cerebral artery (MCA) occlusion

Answer 11

MIDDLE CEREBRAL ARTERY (MCA) OCCLUSION
- hemiparesis for UL
- aphasia (broca and wernicke’s area and auditory cortex lesioned)

Question 12

State the common presentation of anterior cerebral artery (ACA) occlusion

Answer 12

ANTERIOR CEREBRAL ARTERY (ACA) OCCLUSION
- bilateral leg weakness (LL)

Question 13

State the steps in acute management of stroke

Answer 13

rTPA (recombinant tissue plasminogen activator) within 4.5 hours of stroke onset
- Activates plasminogen to plasmin to break up clots

Question 14

State the use of MRI in stroke

Answer 14

Useful in confirming infarcts in the posterior fossa or small lacunar infarcts (hard to see on CT)

Question 15

State the pathogenesis of stroke

Answer 15

1. ATHEROSCLEROSIS (risk factors = smoking, DM, HTN, hypercholesterolemia)
2. CLOTTING –> occludes vessel (can be thromboemboli from heart from AF) –> insufficient blood supply to areas of the brain

Question 16

State the long term management of stroke

Answer 16

(1) Reduce risk factors leading to atherosclerosis
- Recap: Risk factors = smoking, HTN, DM, hypercholesterolemia
- Smokign cessation
- DM - HbA1c monitoring
- Hypercholesterolemia - lipid panel (start on statins)

(2) Blood thinners
- Antiplatelet agents - aspirin, clopidogrel, tricagrelor