1. Department of Neurological Surgery, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama, Okayama, Japan
2. Department of Neurological Surgery, Sumitomo Besshi Hospital, Niihama, Ehime, Japan
3. Department of Neurosurgery, Japanese Red Cross Society Himeji Hospital, Himeji, Hyogo, Japan
4. Department of Diagnostic Pathology, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama, Okayama, Japan