1. From the Department of Surgical Neurology (T.M., T.I.), Research Institute for Brain and Blood Vessels-Akita, Akita, Japan; the Department of Neurosurgery (K.K.), Teine Keijinkai Medical Center, Sapporo, Japan; and the Department of Neurosurgery (S.T.), Hokkaido University Graduate School of Medicine, Sapporo, Japan.