1. Department of Neurosurgery, Atsugi City Hospital, 1-16-36, Mizuhiki, Atsugi, Kanagawa 243-8588, Japan
2. Department of Neurosurgery, The Jikei University School of Medicine Tokyo, 3-25-8, Nishi-Shinbashi, Minato-ku, Tokyo 105-8461, Japan
3. Department of Neurosurgery, The Jikei University Daisan Hospital, 4-11-1, Izumi-honcho, Komae City, Tokyo 201-8601, Japan