1. Department of Neurosurgery, Fukushima Medical University, Fukushima, Fukushima, Japan
2. Division of Neuroimaging and Intervention and New England Center for Stroke Research, Department of Radiology, University of Massachusettes Medical School, Worcester, USA
3. Department of Neurosurgery, University of the Ryukyus, Nishihara, Okinawa, Japan
4. Department of Neurosurgery, Dokkyo Medical University Koshigaya Hospital, Koshigaya, Saitama, Japan