1. Department of Critical Care and Emergency Medicine, Okayama University Hospital;
2. Department of Surgery, National Hospital Organization Mito Medical Center, Ibaraki; and
3. Department of Health Science, College of Life Science, Kurashiki University of Science and The Arts;
4. Spinal Cord Treatment Center, Shin Komonji Hospital, Fukuoka, Japan
5. Department of Neurological Surgery, Okayama University Graduate School of Medicine, Okayama;