A 75-year-old man presents to the emergency department after an episode of left arm weakness and slurred speech that occurred yesterday evening, lasted around 20 minutes, and resolved completely. This is his first such episode. He denies headache or visual changes. He has a history of hypertension, dyslipidemia, and coronary artery disease. He underwent percutaneous coronary intervention with a stent five years ago after a myocardial infarction. He is on lisinopril, metoprolol, and atorvastatin. He is a 40-pack-year smoker who quit 10 years ago. He is right-handed. Head CT shows some scattered old lacunar infarctions bilaterally.