1. Department of Neurosurgery, Yokohama Sakae Kyosai Hospital, Yokohama, Kanagawa, Japan
2. Department of Neurosurgery, Yokohama Rosai Hospital, Yokohama, Kanagawa, Japan
3. Department of Cardiovascular Surgery, Yokohama Sakae Kyosai Hospital, Yokohama, Kanagawa, Japan
4. Department of Neurosurgery, Kanto Rosai Hospital, Kawasaki, Kanagawa, Japan