1 Department of Neurosurgery, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-Ku, Tokyo, 160-8582, Japan.
2 Department of Neurosurgery, The Jikei University School, of Medicine Kashiwa Hospital, 163-1 Kashiwashita, Kashiwa-shi, Chiba, 277-8567, Japan. ttanaka@jikei.ac.jp.
3 Department of Neurosurgery, The Jikei University School of Medicine, 3-25-8 Nishi-Shinbashi, Minato-Ku, Tokyo, 105-8461, Japan. ttanaka@jikei.ac.jp.
4 Department of Pathology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-Ku, Tokyo, 160-8582, Japan.
5 Department of Neurosurgery, The Jikei University School of Medicine Daisan Hospital, 4-11-1 Izumi-Motomachi, Komae-Shi, Tokyo, 201-8601, Japan.
6 Department of Neurosurgery, The Jikei University School of Medicine Katsushika Medical Center, 6-41-2 Aoto, Katsushika-Ku, Tokyo, 125-8506, Japan.
7 Department of Neurosurgery, The Jikei University School of Medicine, 3-25-8 Nishi-Shinbashi, Minato-Ku, Tokyo, 105-8461, Japan.
8 Department of Neurological Surgery, Faculty of medicine, Kagawa University Graduate School of Medicine, 1750-1 Miki-Choho, Ikenobe, Kita-Gun, Kagawa, 761-0793, Japan.
9 Department of Neurosurgery, Tokyo Dental College Ichikawa General Hospital, 5-11-13 Sugano, Ichikawa-Shi, Chiba, 272-8513, Japan.