Abstract: 78-year-old male with history of left middle cerebral artery (MCA) distribution infarct now presents after a syncopal episode. An echocardiogram (ECG) and cardiac enzymes are negative. A head computed tomography (CT) is ordered for further evaluation.
Question Text
What is the most likely etiology of the salient finding? (The left MCA distribution infarct is old and does not represent the finding of interest.)