1. Department of Neurosurgery, Institute of Brain and Blood Vessels, Mihara Memorial Hospital, Isesaki, Gunma, Japan
2. Department of Neurosurgery, Saitama Medical University, Iruma-gun, Saitama, Japan
3. Department of Neurosurgery, Gunma University, Gunma, Japan
4. Department of Neurology, Institute of Brain and Blood Vessels, Mihara Memorial Hospital, Isesaki, Gunma, Japan