1. Department of Neurosurgery, Tokyo Rosai Hospital, 4-13-21 Omori-minami, Ota-city, Tokyo 143-0013, Japan
2. Department of Neurosurgery, Blue–sky Matsui Hospital, 739 Muraguro-cho, Kanonji-shi, Kagawa-ken 768-0013, Japan
3. Department of Neurosurgery, Narita Tomisato Tokusyukai Hospital, 1-1-1 Hiyoshidai, Tomisato-shi, Chiba-ken 286–0201, Japan
4. Department of Neurosurgery, Koshigaya Neurosurgical Clinic, 5–7 Gamoukotobuki-cho, Koshigaya-shi, Saitama-ken 343-0836, Japan