1. Department of Neurosurgery, Ishikiri-seiki Hospital, Higashiosaka, Osaka, Japan
2. Department of Neurosurgery, Japan Community Health Care Organization, Hoshigaoka Medical Center, Hirakata, Osaka, Japan
3. Department of Neurosurgery, Osaka City University Graduate School of Medicine, Osaka, Osaka, Japan
4. Department of Neurosurgery, Shimada Municipal Hospital, Shimada, Shizuoka, Japan