A diagnosis of exclusion

A 26-year-old woman was brought to the emergency department following several episodes of seizures. The patient’s friend witnessed several 15-minute episodes of sudden jerks and tremors of her right arm during which the patient bit her tongue, had word-finding difficulty, had horizontal eye deviation, and was incontinent of urine. She became unresponsive during the episodes, with incomplete recovery of consciousness between attacks. She was afebrile. Her neurologic exam 4 hours after several seizures revealed word-finding difficulty and right arm weakness. A complete blood count, chemistry panel including renal and liver function tests, urine toxicology screen, and computed tomography (CT) of the head were normal. After a loading dose of fosphenytoin, the patient did not experience further seizures and was discharged on a maintenance dose of phenytoin. Over the next week, the patient continued to note a sensation of heaviness in her right arm and felt fatigued. The patient’s mother brought her back to the emergency department after witnessing a similar seizure episode that persisted for an hour. On arrival, the patient was no longer seizing.