1. Division of Medicine, Department of Neurosurgery, Faculty of Medical Sciences, University of Fukui, 23-3, Matsuokashimoaizuki, Eiheiji-cho, Yoshida-gun, Fukui 910-1193, Japan
2. Department of Neurosurgery, Fukui General Hospital, 58-16-1 Egami-cho, Fukui-shi, Fukui 910-8561, Japan
3. Department of Neurosurgery, Kaga Medical Center, Kaga, Ri 36, Sakumi-machi, Kaga-shi, Ishikawa 922-8522, Japan
4. Department of Frontier Fiber Technology and Science, Graduate School of Engineering, University of Fukui, 3-9-1, Bunkyo, Fukui-shi, Fukui 910-8507, Japan
5. Organization for Life Science Advancement Programs, University of Fukui, 3-9-1, Bunkyo, Fukui-shi, Fukui 910-8507, Japan