Hemiplegic migraine is a condition associated with vascular alteration of the central nervous system and transient neurologic deficits. Permanent morphine-induced motor dysfunction has been reported after spinal ischemia. We report a persisting central neurological deficit after single-dose spinal administration of 400 microg of morphine in a patient with no previous neurological condition. Hemiplegic migraine was thought to be present when the patient emerged from anesthesia. Weakness in the left quadriceps and saddle anesthesia of the perineum and urinary retention of central origin remained present 3 yr later. Over the 3 postoperative years, the patient was admitted to a neurological unit 5 times because of acute headache associated with complete left-sided hemiplegia. These symptoms resolved within 24 h of onset. Hemiplegic migraine was thought to be the most likely diagnosis of these recurrent attacks. We hypothesize that the patient's persistent deficits were caused by a combination of spinal morphine and spinal cord vascular dysfunction associated with hemiplegic migraine.