[1] Hokkaido Univ Hosp, Dept Neurosurg, Sapporo, Hokkaido, Japan
[2] Kohnan Hosp, Dept Neurosurg, Sendai, Miyagi, Japan
[3] Niigata Univ Med & Dent Hosp, Dept Orthopaed Surg, Niigata, Japan
[4] Dokkyo Med Univ Hosp, Dept Neurosurg, Mibu, Tochigi, Japan
[5] Gunma Univ Hosp, Dept Neurosurg, Gunma, Japan
[6] Japanese Red Cross Narita Hosp, Dept Orthopaed Surg, Chiba, Japan
[7] Univ Tokyo Hosp, Dept Neurosurg, Tokyo, Japan
[8] Tokyo Metropolitan Neurol Hosp, Dept Neurosurg, Tokyo, Japan
[9] Yokohama City Univ Med, Dept Neurosurg, Yokohama, Kanagawa, Japan
[10] Nagoya Univ Hosp, Dept Neurosurg, Nagoya, Aichi, Japan
[11] Osaka City Univ, Dept Neurosurg, Grad Sch Med, Osaka, Japan
[12] Osaka Univ, Dept Neurosurg, Grad Sch Med, Osaka, Japan
[13] Okayama Univ, Dept Neurosurg, Grad Sch Med, Okayama, Japan
[14] Ota Mem Hosp, Brain Attack Ctr, Dept Spinal Surg, Hiroshima, Japan
[15] Hiroshima Univ Hosp, Dept Neurosurg, Hiroshima, Japan
[16] Ehime Univ Hosp, Dept Neurosurg, Toon, Ehime, Japan
[17] Kurume Univ Hosp, Dept Neurosurg, Fukuoka, Japan
[18] Kagoshima Univ Hosp, Dept Neurosurg, Kagoshima, Japan