A 45-year-old woman developed acute diplopia on looking down or to the right. She had a history of migraine with aura, prior Hodgkin lymphoma treated with thoracic irradiation 26 years earlier, epilepsy, smoking, hypertension, hyperlipidemia, and a left middle cerebral artery territory transient ischemic attack 5 years earlier. She previously had surgery, chemotherapy, and radiotherapy for recurrent breast carcinoma. She was taking 200 mg of carbamazepine slow-release formulation daily, 150 mg of aspirin daily, 10 mg of amlodipine daily, 2.5 mg of bendrofluazide daily, 20 mg of tamoxifen daily, and 50 μg of thyroxine daily.