[Myoclonus of the abdominal muscles originated in spinal vascular malformation]

We studied segmental spinal myoclonus of abdominal muscles observed in a 62-year-old man. The myoclonus consisted of continuous rhythmic contractions of the bilateral abdominal muscles at T8-T10 segments at a rate of 3 to 4 c/s. It was observed with the patient was in supine position and almost exclusively during the expiratory phase, and it disappeared during sleep. The myoclonus decreased in amplitude or disappeared during physical exercise, and intensified for a few minutes after physical exercise including breath-holding by Valsalva's maneuver. Myelography showed spinal vascular malformation at the level of T9-T11 vertebrae. Electromyography showed neurogenic change of the paravertebral muscles at T5-T11 segments on the right side and T7-T9 segments on the left side. Hypoalgesic zone contained those segments. The myoclonus disappeared for a short period after lumbar puncture and improved by administration of clonazepam.