Myasthenia gravis presenting as a unilateral abducens nerve palsy.

A 48-year-old man with no significant medical history presented to the emergency department of a large, urban, tertiary-care hospital complaining of double vision and unsteady gait. Physical examination was remarkable for an isolated, unilateral sixth nerve palsy. After comprehensive testing, a final diagnosis of myasthenia gravis was made. The patient's unsteady gait was a manifestation of sensory distortion from the diplopia and corrected when the patient closed his eyes. The presentation of myasthenia gravis as an isolated sixth nerve palsy is unprecedented in the emergency medicine literature.