1. Department of Neurosurgery, Shimane Prefectural Central Hospital, Izumo, Shimane, Japan
2. Department of Neurosurgery, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Hiroshima, Japan
3. Department of Cerebrovascular Medicine, National Cerebral and Cardiovascular Center, Suita, Osaka, Japan
4. Shimane University School of Medicine, Izumo, Shimane, Japan
5. Hospital Bureau of Shimane Prefecture, Izumo, Shimane, Japan