Hitachi General Hospital - Department of Emergency and Critical Care Medicine, University of Tsukuba - Department of Emergency and Critical Care Medicine, Hitachi General Hospital - Department of Emergency and Critical Care Medicine, Hitachi General Hospital - Department of Emergency and Critical Care Medicine, National Center for Global Health and Medicine - Department of Emergency Medicine and Critical Care, National Center for Global Health and Medicine - Department of Emergency Medicine and Critical Care, Teikyo University - Department of Emergency Medicine, TMG Asaka Medical Center - Neurointensive Care Unit, Neurosurgery, Stroke and Epilepsy Center, TMG Asaka Medical Center - Neurointensive Care Unit, Neurosurgery, Stroke and Epilepsy Center, Nippon Medical School Tama Nagayama Hospital - Department of Emergency and Critical Care Medicine, Nippon Medical School Tama Nagayama Hospital - Department of Emergency and Critical Care Medicine, Juntendo University - Department of Emergency and Critical Care Medicine, Jichi Medical University - Department of Emergency and Critical Care Medicine, Dokkyo Medical University - Emergency and Critical Care Medical Center, Dokkyo Medical University - Emergency and Critical Care Medical Center, University of Tsukuba - Department of Biostatistics, University of Tsukuba - Department of Biostatistics, University of Tsukuba Hospital/Ibaraki Prefectural Central Hospital - Epilepsy Center, University of Tsukuba - Departments of Neurosurgery, University of Tsukuba - Department of Emergency and Critical Care Medicine and Independent