SCRN Anatomy, Physiology, and Pathophysiology of Stroke 3 — Questions and Answers
Question 1: Cerebral autoregulation maintains constant cerebral blood flow across which range of mean arterial pressure (MAP)?
- 40–60 mmHg
- 50–150 mmHg (Correct answer)
- 70–120 mmHg
- 100–200 mmHg
Correct answer: 50–150 mmHg
Normal cerebral autoregulation maintains constant cerebral blood flow when MAP ranges from approximately 50–150 mmHg; outside this range, CBF becomes pressure-passive.
Question 2: Which area of the brain is most sensitive to ischemia and will undergo infarction after the shortest duration of ischemia?
- Cerebral cortex neurons
- CA1 region of the hippocampus (Correct answer)
- Purkinje cells of the cerebellum
- Brainstem neurons
Correct answer: CA1 region of the hippocampus
CA1 hippocampal neurons are selectively vulnerable and begin to die within 3–5 minutes of complete ischemia, contributing to memory deficits after global hypoxia.
Question 3: Cytotoxic edema in the ischemic brain is primarily caused by:
- Disruption of the blood-brain barrier allowing protein leakage
- Failure of Na⁺/K⁺-ATPase causing intracellular water accumulation (Correct answer)
- Increased hydrostatic pressure from arterial hypertension
- Inflammatory cytokine-mediated endothelial disruption
Correct answer: Failure of Na⁺/K⁺-ATPase causing intracellular water accumulation
Cytotoxic edema results from energy failure and Na⁺/K⁺-ATPase pump dysfunction, causing sodium and water to accumulate within neurons and astrocytes without BBB breakdown.
Question 4: Which neurotransmitter is primarily responsible for excitotoxic neuronal death in acute ischemia?
- GABA
- Dopamine
- Glutamate (Correct answer)
- Serotonin
Correct answer: Glutamate
Massive glutamate release during ischemia activates NMDA and AMPA receptors, causing calcium influx and triggering excitotoxic neuronal death.
Question 5: In a patient with subarachnoid hemorrhage, cerebral vasospasm most commonly occurs at which time interval after the initial bleed?
- Immediately (within 6 hours)
- 24–48 hours
- 4–14 days (Correct answer)
- 3–4 weeks
Correct answer: 4–14 days
Cerebral vasospasm after SAH typically peaks between days 4–14, with the highest risk around days 7–10, due to oxyhemoglobin degradation products irritating vessel walls.
Question 6: The blood-brain barrier (BBB) is primarily maintained by which cell type?
- Microglia
- Oligodendrocytes
- Astrocyte end-feet and tight junction endothelial cells (Correct answer)
- Neurons
Correct answer: Astrocyte end-feet and tight junction endothelial cells
Tight junctions between cerebral endothelial cells, supported by astrocyte end-feet, pericytes, and the basement membrane, form the structural basis of the BBB.
Question 7: Which type of cerebral herniation occurs when the uncus of the temporal lobe displaces through the tentorium cerebelli, compressing cranial nerve III?
- Central (transtentorial) herniation
- Uncal herniation (Correct answer)
- Tonsillar herniation
- Subfalcine herniation
Correct answer: Uncal herniation
Uncal herniation occurs when the medial temporal lobe (uncus) herniates over the tentorial edge, compressing CN III and causing ipsilateral pupil dilation and contralateral hemiparesis.
SCRN Anatomy, Physiology, and Pathophysiology of Stroke 3
Cerebral autoregulation maintains constant cerebral blood flow across which range of mean arterial pressure (MAP)?