Clinical reasoning: a 42-year-old man who developed blurred vision and dropped his iPod while jogging.

A 42-year-old man noted sudden onset of blurriness in his left eye and dropped his iPod from his right hand while jogging. In the emergency room, it was noted that visual blurring resolved with right eye closure, but his ophthalmologic examination was otherwise normal. He had subtle right nasolabial fold flattening and right arm pronator drift. His examination was otherwise normal. He reported no headache, neck pain, prior trauma, prior transient neurologic deficit, or palpitations. He took no medications and did not smoke, drink alcohol, or use illicit drugs.