1. Department of Neurology, Brain Attack Center Ota Memorial Hospital, Fukuyama, Hiroshima, Japan
2. Department of Neurosurgery, Brain Attack Center Ota Memorial Hospital, Fukuyama, Hiroshima, Japan
3. Department of Spinal Surgery, Brain Attack Center Ota Memorial Hospital, Fukuyama, Hiroshima, Japan
4. Department of Neurosurgery, Shimane University School of Medicine, Izumo, Shimane, Japan