1. Department of Neurosurgery, Tokyo Metropolitan Neurological Hospital, Tokyo;
2. Department of Neurosurgery, Kohnan Hospital, Sendai;
3. Department of Neurosurgery, Okayama University Graduate School of Medicine, Okayama;
4. Department of Neurosurgery, Hokkaido University Hospital, Sapporo;
5. Department of Orthopaedic Surgery, Niigata University Medical and Dental Hospital, Niigata;
6. Department of Neurosurgery, Dokkyo Medical University Hospital, Tochigi;
7. Department of Neurosurgery, Gunma University Hospital, Gunma;
8. Department of Orthopaedic Surgery, Japanese Red Cross Narita Hospital, Chiba;
9. Department of Neurosurgery, The University of Tokyo Hospital, Tokyo;
10. Department of Neurosurgery, Yokohama City University Hospital, Yokohama;
11. Department of Neurosurgery, Nagoya University Hospital, Nagoya;
12. Department of Neurosurgery, Osaka City University Graduate School of Medicine, Osaka;
13. Department of Neurosurgery, Osaka University Graduate School of Medicine, Osaka;
14. Department of Spinal Surgery, Brain Attack Center, Ota Memorial Hospital, Hiroshima;
15. Department of Neurosurgery, Hiroshima University Hospital, Hiroshima;
16. Department of Neurosurgery, Ehime University Hospital, Ehime;
17. Department of Neurosurgery, Kurume University Hospital, Fukuoka; and
18. Department of Neurosurgery, Kagoshima University Hospital, Kagoshima, Japan