A 70-year-old woman is brought to urgent care with acute onset left facial droop and weakness of the left arm after waking up. Which historical finding would most likely explain this presentation?

• A. Atrial fibrillation
• B. Hypertension
• C. Diabetes mellitus
• D. Hyperlipidemia

Answer: (A)

The main idea here is that sudden facial droop with arm weakness points to an ischemic stroke caused by an embolus. Atrial fibrillation creates stasis of blood in the left atrium, leading to thrombus formation in the left atrial appendage. If a piece breaks off, it can travel to the brain and block a cerebral artery, causing abrupt focal neurologic deficits like facial droop and arm weakness. This embolic mechanism fits the waking-stroke pattern well, since the event likely occurred during sleep and was noticed on waking. Among the listed risk factors, atrial fibrillation most directly explains an embolic stroke, whereas hypertension, diabetes, and hyperlipidemia contribute to stroke risk mainly through other pathways (like chronic small-vessel disease or atherosclerosis) and don’t as neatly account for the sudden, focal presentation.