1. Department of Neurosurgery, Kawasaki Municipal Hospital, Shinkawa-Dori, Kawasaki-ku, Kawasaki-Shi, Kanagawa-Ken, Japan
2. Department of Respiratory Medicine, Kawasaki Municipal Hospital, Shinkawa-Dori, Kawasaki-ku, Kawasaki-Shi, Kanagawa-Ken, Japan
3. Department of Neurosurgery, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, Japan