1. Department of Neurosurgery, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo,
2. Department of Neurosurgery, Japanese Red Cross Ashikaga Hospital, 284-1 Yobe-cho, Ashikaga city, Tochigi,
3. Department of Neurosurgery, Kawasaki Municipal Hospital, 12-1 Shinkawadori, Kawasaki-ku, Kawasaki city, Kanagawa,
4. Department of Radiology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, Japan.