A 52-year-old patient developed an eye movement disorder first resembling a left 
internuclear ophthalmoplegia and subsequently a "one-and-a-half syndrome" as the 
presenting symptoms of ocular myasthenia gravis. No accompanying myasthenic 
features were present except for the fluctuation in the amplitude of dissociated 
nystagmus. This patient shows that an oculomotor disorder considered a typical 
pontine lesion may instead be caused by myasthenia gravis, even in the absence 
of other clinical and electrophysiologic features of neuromuscular deficit.