1. From Department of Neurosurgery (S.K., Y.I.), Hokkaido University Graduate School of Medicine, Sapporo, Japan; Department of Neurosurgery (N.H.), Kyoto University Graduate School of Medicine, Kyoto, Japan; Department of Neurosurgery (T.Y.), Tohoku University Graduate School of Medicine, Sendai, Japan and The Research Committee on Moyamoya Disease in Japan.