A 63-year-old patient with atrial fibrillation who presents with sudden focal neurologic deficits; what is the most likely mechanism of stroke?

• A. Embolic occlusion from atrial fibrillation
• B. Hypertensive intracerebral hemorrhage
• C. Lacunar infarct from lipohyalinosis
• D. Venous sinus thrombosis

Answer: (A)

Atrial fibrillation promotes clot formation in the left atrium due to irregular, ineffective contractions, especially in the left atrial appendage. A piece of that clot can break off and travel to cerebral arteries, lodging and causing abrupt occlusion that leads to an ischemic stroke. This cardioembolic mechanism is the typical cause of sudden focal neurologic deficits in someone with AF, because a large artery in the brain can be blocked quickly by an embolus, producing focal signs corresponding to the territory supplied.

Hypertensive intracerebral hemorrhage would involve bleeding into brain tissue from ruptured small vessels, not an abrupt occlusion by an embolus. Lacunar infarcts from lipohyalinosis affect small penetrating vessels and usually produce small, deep brain strokes with more limited or stereotyped deficits. Venous sinus thrombosis presents differently, often with headache and signs of increased intracranial pressure or seizures, rather than a single abrupt focal deficit from arterial occlusion.