Myasthenic "oculomotor" palsy

A patient is described who presented with an abrupt onset of diplopia in association with a drooping lid. The motility pattern was consistent with a pupil sparing oculomotor nerve palsy. In addition, the behavior of the palpebral fissure was characteristic of aberrant regeneration. Intravenous Tensilon resulted in a prompt elevation of the lid and improvement in eye movements. The differential diagnosis of a pupil sparing third nerve palsy should include myasthenia gravis.