1. Department of Neurosurgery, Tokyo University School of Medicine
2. Department of Neurosurgery, Kameda General Hospital, Chiba
3. Department of Neurosurgery, Teraoka Memorial Hospital, Hiroshima
4. Department of Neurosurgery, Bokuto Metropolitan Hospital, Tokyo
5. Department of Neurosurgery, Suwa Chuo Hospital, Nagano, Japan