1. Department of Neurology, Itoigawa General Hospital, 457-1, Takehana, Itoigawa 945-0006, Japan
2. Department of Neurosurgery, Itoigawa General Hospital, 457-1, Takehana, Itoigawa 945-0006, Japan
3. Department of Neurosurgery, Hamamatsu University School of Medicine, 1-20-1, Handayama, Hamamatsu 431-3192, Japan