1. Department of Neurosurgery, Graduate School of Medical Sciences, Kyushu University, Fukuoka;
2. Department of Clinical Trials and Research, National Hospital Organization, Nagoya Medical Center, Nagoya;
3. Department of Neurosurgery, Iwate Medical University, Morioka;
4. Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka;
5. Department of Neurosurgery, Kobe City Medical Centre General Hospital, Kobe;
6. Department of Neurology, Kumamoto City Hospital, Kumamoto;
7. Department of Neurosurgery, Kyorin University School of Medicine, Mitaka;
8. Department of Neurosurgery, Aichi Medical University, Nagakute;
9. Department of Neurosurgery, University of Tsukuba, Tsukuba;
10. Department of Neurosurgery, Gifu University Graduate School of Medicine, Gifu;
11. Department of Neurosurgery, Tohoku University School of Medicine, Sendai;
12. Department of Preventive Medicine and Epidemiology, National Cerebral and Cardiovascular Center, Suita;
13. Department of Neurosurgery, Juntendo University School of Medicine, Tokyo; and
14. Department of Neurosurgery, Kyoto University Graduate School of Medicine, Kyoto, Japan