1. Department of Neurosurgery, Yokohama Sakae Kyosai Hospital, Yokohama, Kanagawa, Japan
2. Department of Neurology, Yokohama Sakae Kyosai Hospital, Yokohama, Kanagawa, Japan
3. Department of Neurosurgery, Yokohama City University School of Medicine, Yokohama, Kanagawa, Japan