1. Department of Neurosurgery, Kawasaki Medical School, Okayama, Japan.
2. Department of Neurosurgery, Brain Research Institute, University of Niigata, Niigata, Japan.
3. Department of Neurosurgery, Gifu University, Gifu City, Japan.
4. Department of Neurosurgery, University of Yamanashi, Yamanashi, Japan.
5. Department of Neurosurgery, Nara Medical University, Nara, Japan.
6. Department of Neurosurgery, Shiga University of Medical Science, Shiga, Japan.
7. Department of Neurosurgery, Hirosaki University, Aomori, Japan.
8. Department of Neurosurgery, Miyakonojo Medical Association Hospital, Miyazaki, Japan.
9. Department of Neurosurgery, Miyazaki University, Miyazaki, Japan
10. The Clinical Research Institute, Kurashiki Central Hospital, Okayama, Japan.
11. Department of Neurosurgery, Gunma University, Maebashi, Japan.