Pseudopartial Third Nerve Palsy as the Presenting Sign of Ocular Myasthenia Gravis

SIGNIFICANCE This case emphasizes the high degree of suspicion necessary for a timely diagnosis of myasthenia gravis. PURPOSE This report discusses a case of ocular myasthenia gravis presenting as a pseudo-third nerve palsy with ptosis. The pathogenesis, treatment, and management of ocular myasthenia gravis are discussed. CASE REPORT A 68-year-old white man presented to our clinic after noticing a new right eyelid droop for several days and experiencing horizontal double vision for the past 3 weeks. A pupil-sparing partial third nerve palsy was diagnosed, and MRI and laboratory work were ordered to assist with diagnosis. Laboratory results demonstrated highly positive acetylcholinesterase antibodies, confirming a diagnosis of ocular myasthenia gravis. CONCLUSIONS Myasthenia gravis commonly presents with ocular signs and symptoms. Because ocular myasthenia gravis can mimic other causes of diplopia, heightened awareness and suspicion are necessary to make a timely diagnosis.