1. Department of Neurosurgery, Jikei University School of Medicine, Kashiwa Hospital, Chiba, Japan
2. Department of Neurosurgery, Jikei University School of Medicine, Tokyo, Japan
3. Department of Neurosurgery, Japanese Red Cross Medical Center, Tokyo, Japan
4. Department of Neurosurgery, National Center for Global Health and Medicine, Kohnodai Hospital, Chiba, Japan