1. Department of Neurosurgery, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima;
2. Department of Neurosurgery and Neuro-Endovascular Therapy, Hiroshima Prefectural Hospital, Hiroshima; and
3. Department of Neurosurgery, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan