1. Department of Neurological Surgery, Nippon Medical School, Tokyo 113-8603, Japan
2. Department of Neurological Surgery, Nippon Medical School Musashikosugi Hospital, Kanagawa 211-8233, Japan
3. Department of Anatomy and Neurobiology, Graduate School of Medicine, Nippon Medical School, Tokyo 113-8602, Japan
4. Department of Neurosurgery, Juntendo University School of Medicine, Tokyo 113-8431, Japan
5. Department of Pathology, Tokai University School of Medicine, Kanagawa 259-1143, Japan
6. Department of Pathology, Nippon Koukan Hospital, Kanagawa 210-0852, Japan