1. Department of Neurosurgery, Medical Corporation Shokokai San-ai Hospital, Saitama, Japan
2. Department of Neurosurgery, Saitama Medical Center, Saitama Medical University, Saitama, Japan
3. Department of Neurosurgery, Teikyo University School of Medicine, Tokyo, Japan
4. Department of Neurosurgery, Saitama Medical Center, Jichi Medical University, Saitama, Japan