Diaphragmatic myoclonus: diagnosis by fluoroscopy and electromyography with response to phenytoin.

A 40-year-old woman presented a 6-week history of "fluttering" in her chest. A diagnosis of bilateral diaphragmatic myoclonus was made by fluoroscopy and electromyography of both hemidiaphragms. No central or peripheral cause was identified, but treatment with intravenous phenytoin had an immediate effect. With therapy, she has been symptom free for 12 months.