Clinical Reasoning: A 41-Year-Old Man With Steroid-Responsive Hemiparesis.

A 41-year-old, left-handed man was admitted to the hospital for workup of a 3-week history of headache, constant vertigo, diplopia, and left hemiparesis. An initial diagnosis was made, and the patient was treated with symptomatic improvement. He was discharged and then presented a few weeks later with recurrence of his symptoms which required additional diagnostic workup. This ultimately led to a diagnosis of a rare disorder. In this case report, we outline his clinical course and our reasoning at each step which led to our eventual definitive diagnosis.