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Haemodynamic TIAs – Low-Flow Mechanism — SCE Neurology MCQ

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ModerateCerebrovascular DiseaseHaemodynamic TIAs – Low-Flow MechanismSCE Neurology

A 70-year-old man with a known right internal carotid artery occlusion develops episodes of transient left arm weakness lasting 2–3 minutes, occurring when he stands up quickly from sitting. The episodes are stereotyped and reproducible with postural change. Between episodes, his neurological examination is normal. What mechanism is causing his symptoms?

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Correct answer: C — Haemodynamic (low-flow) TIAs due to impaired cerebral autoregulation distal to the carotid occlusion

Haemodynamic (low-flow) TIAs occur when cerebral perfusion drops below the compensatory capacity of collateral circulation, typically distal to a severe stenosis or occlusion. They are characterised by: stereotyped, brief events, triggered by postural changes (orthostatic), exercise, or other causes of systemic hypotension. The clinical features correspond to the watershed territory between the ACA and MCA (proximal arm more than hand or face). Treatment focuses on optimising blood pressure (avoiding aggressive lowering), hydration, and maximising collateral flow. Anticoagulation or revascularisation may be considered. A: The positional trigger and stereotypy argue against epilepsy. C: Cardioembolic TIAs are random, not postural. D: Migraine aura lasts 20–60 minutes. E: The ICA occlusion provides a structural basis.

Reference: RCP Stroke Guidelines