A 70-year-old woman with long-term tobacco use presented with 2 weeks of bilateral ptosis and binocular horizontal diplopia. She denied weakness, difficulty swallowing, or breathing. On initial examination, she had a normal mental status, no pupillary abnormalities, normal visual acuity, and full visual fields. She had moderate exotropia, severe bilateral ptosis, impaired bilateral adduction and vertical ductions, and impaired convergence. Her abduction and vertical oculocephalic reflexes were intact. She had full strength and normal sensation and reflexes but had a slightly wide-based and unsteady gait. Over the subsequent weeks, she experienced worsening gait, falls, inattention, and short-term memory loss.