1. Department of Neurosurgery, Showa General Hospital, Tokyo, Japan
2. Department of Neurosurgery, Tokyo University Hospital, Tokyo, Japan
3. Department of Neurosurgery, Tokyo Metropolitan Fuchu Hospital, Tokyo, Japan
4. Department of Neurosurgery, Kyorin School of Medicine Hospital, Tokyo, Japan
5. Department of Neurosurgery, Tokyo Metropolitan Bokuto Hospital, Tokyo, Japan