1. Department of Neurosurgery, Ichinomiya Neurosurgical Hospital, Hita, Japan.
2. Department of Neurosurgery, Uchikado Neuro-Spine Clinic, Fukuoka, Japan.
3. Department of Neurosurgery, Social Insurance Tagawa Hospital, Fukuoka, Japan.
4. Department of Neurosurgery, Yame General Hospital, Yame, Japan.