1. Department of Endovascular Surgery, Tokyo Medical and Dental University, Tokyo, Japan;
2. Department of Clinical Biostatistics, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan;
3. Department of Neurosurgery, Tsuchiura Kyodo General Hospital, Ibaraki, Japan;
4. Department of Neurosurgery, National Hospital Organization Disaster Medical Center, Tokyo, Japan;
5. Department of Neurosurgery, Japanese Red Cross Musashino Hospital, Tokyo, Japan;
6. Department of Neurosurgery, Shuuwa General Hospital, Saitama, Japan;
7. Department of Neurosurgery, JA Toride Medical Center, Ibaraki, Japan;
8. Department of Neurosurgery, Ome Medical Center, Tokyo, Japan;
9. Department of Neurosurgery, Tokyo Kita Medical Center, Tokyo, Japan;
10. Department of Neurosurgery, Tokyo Metropolitan Toshima Hospital, Tokyo, Japan;
11. Department of Endovascular Surgery, Jichi Medical University Saitama Medical Center, Saitama, Japan;
12. Department of Neurosurgery, Kanto Rosai Hospital, Kanagawa, Japan;
13. Department of Neurosurgery, Tokyo Bay Urayasu Ichikawa Medical Center, Chiba, Japan;
14. Department of Neurosurgery, Fujiyoshida Municipal Hospital, Yamanashi, Japan