Bilateral pseudo-internuclear ophthalmoplegia in myasthenia gravis.

A 38-year-old male with bilateral pseudo-internuclear ophthalmoplegia (-INO) in myasthenia that could have been misdiagnosed as INO in multiple sclerosis is reported. He experienced fluctuating symptoms including double vision, imbalance, and tinnitus. His eye movements simulated bilateral INO, with a downshoot in abduction. After thymectomy, his eye movements became normal. From our case and a review of the literature, we propose that ptosis, downshoot, and fatigability are likely to be signs of pseudo-INO in myasthenia, whereas an impaired vertical smooth pursuit is unlikely. Dissociated nystagmus and monocular overshoot might be the results of central compensation.