A 44 year-old man presents with double vision. The diplopia began 2 months ago and has not changed since that time. It is binocular, vertical, and the same at both distance and near. He denies pain. His past medical history is only significant for gastroesophageal reflux disease for which he is taking Omeprazole. His past surgical history is notable for an appendectomy at age 20. Family history and social history are noncontributory.