1. Department of Neurosurgery, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Fukuoka, Japan
2. Department of Neurosurgery, Kyushu Central Hospital of the Mutual Aid Association of Public School Teachers, Fukuoka, Fukuoka, Japan
3. Department of Neurosurgery, Iizuka Hospital, Iizuka, Fukuoka, Japan