Yasunaru Kawashima1,2. 1. National Cerebral and Cardiovascular Center, Fujishiro-dai 5-7-1, Suita, Osaka, 565-8565, Japan. ykawashi@mgt.ncvc.go.jp. 2. Department of Surgery, Osaka University School of Medicine, Yamadaoka 2-15, Suita, Osaka, 565-0871, Japan. ykawashi@mgt.ncvc.go.jp.