1. Department of Neurosurgery, Faculty of Medicine, University of Tsukuba, Ibaraki, Japan
2. Department of Neurosurgery, Yokomhama City University Medical Center, Yokohama, Kanagawa, Japan
3. Division of Stroke Prevention and Treatment, Faculty of Medicine, University of Tsukuba, Ibaraki, Japan
4. Department of Neurosurgery, Dokkyo Medical University, Saitama Medical Center, Saitama, Japan
5. Department of Neuroendovascular Therapy, Toranomon Hospital, Tokyo, Japan
6. Department of Neurosurgery, Mito Medical Center Hospital, Ibaraki, Japan
7. Department of Neurosurgery, Tsukuba Medical Center Hospital, Ibaraki, Japan
8. Department of Neurosurgery, Yokomhama City University, Yokohama, Kanagawa, Japan