SCRN Anatomy, Physiology, and Pathophysiology of Stroke 4 — Questions and Answers
Question 1: A patient presents with pure motor hemiplegia affecting the face, arm, and leg equally with no cortical signs. Which location is the infarct most likely in?
- Cortex of the middle cerebral artery territory
- Posterior limb of the internal capsule (Correct answer)
- Thalamus
- Occipital lobe
Correct answer: Posterior limb of the internal capsule
A lacunar infarct in the posterior limb of the internal capsule, where corticospinal fibers are densely packed, causes pure motor hemiplegia affecting face, arm, and leg equally without cortical (aphasia, neglect, visual) signs.
Question 2: Cerebral amyloid angiopathy (CAA) most commonly causes hemorrhage in which location?
- Basal ganglia and thalamus
- Pons
- Cerebellum
- Lobar (cortical and subcortical) regions (Correct answer)
Correct answer: Lobar (cortical and subcortical) regions
CAA results from amyloid-beta deposition in cortical and leptomeningeal vessels, predisposing elderly patients to lobar hemorrhages in parietal, occipital, and frontal regions.
Question 3: Which cranial nerve is responsible for the gag reflex and is commonly affected in lateral medullary (Wallenberg) syndrome?
- CN VII (facial)
- CN IX (glossopharyngeal) and CN X (vagus) (Correct answer)
- CN XI (accessory)
- CN XII (hypoglossal)
Correct answer: CN IX (glossopharyngeal) and CN X (vagus)
CN IX and CN X nuclei in the lateral medulla mediate the gag reflex; lateral medullary infarcts damage these nuclei, causing dysphagia and absent gag reflex.
Question 4: Which pathophysiological process converts an ischemic infarct into a hemorrhagic transformation?
- Vasogenic edema leading to vessel rupture
- Reperfusion injury causing breakdown of damaged endothelium and BBB (Correct answer)
- Activation of the coagulation cascade within the infarct core
- Hypertensive crisis causing de novo vessel rupture
Correct answer: Reperfusion injury causing breakdown of damaged endothelium and BBB
Reperfusion of ischemia-damaged vessels causes blood to leak through the disrupted blood-brain barrier, resulting in hemorrhagic transformation, most commonly petechial (HI1/HI2) or parenchymal hematoma (PH1/PH2).
Question 5: In a stroke patient, which finding on diffusion-weighted MRI (DWI) indicates irreversible infarction?
- Hyperintense signal with corresponding ADC restriction (dark on ADC map) (Correct answer)
- Hyperintense signal with elevated ADC values
- Hypointense signal on DWI with bright ADC
- No DWI change within 24 hours of symptom onset
Correct answer: Hyperintense signal with corresponding ADC restriction (dark on ADC map)
Restricted diffusion (bright DWI, dark ADC map) indicates cytotoxic edema from acute ischemia, reflecting irreversible neuronal injury within minutes to hours of onset.
Question 6: What is the primary source of embolism in cardioembolic stroke associated with atrial fibrillation?
- Left ventricular mural thrombus
- Left atrial appendage thrombus (Correct answer)
- Mitral valve vegetation
- Pulmonary vein thrombus
Correct answer: Left atrial appendage thrombus
In atrial fibrillation, blood stasis in the left atrial appendage (LAA) promotes thrombus formation; embolization of LAA clots causes the majority of AF-related cardioembolic strokes.
Question 7: Which circle of Willis variant increases the risk of ischemic stroke when the ipsilateral internal carotid artery is occluded?
- Bilateral fetal posterior cerebral arteries
- Absent or hypoplastic anterior communicating artery (Correct answer)
- Duplicate basilar artery
- Persistent trigeminal artery
Correct answer: Absent or hypoplastic anterior communicating artery
An absent or hypoplastic anterior communicating artery prevents collateral blood flow from the contralateral hemisphere when the ipsilateral ICA is occluded, increasing infarct risk.
SCRN Anatomy, Physiology, and Pathophysiology of Stroke 4
A patient presents with pure motor hemiplegia affecting the face, arm, and leg equally with no cortical signs.
Which location is the infarct most likely in?