1. Department of Neurosurgery, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima 890-8520, Japan
2. Department of Cardiovascular, Respiratory and Metabolic Medicine, Graduate School of Medicine, Kagoshima University, Kagoshima 890-8520, Japan
3. Department of Neurosurgery, Graduate School of Biomedical Science, Hiroshima University, Hiroshima 734-8551, Japan