1. Department of Pediatrics, Juntendo University Faculty of Medicine, 3-1-3 Hongo, Bunkyo, Tokyo 113-8431, Japan
2. Department of Neurosurgery, Juntendo University Faculty of Medicine, 3-1-3 Hongo, Bunkyo, Tokyo 113-8431, Japan
3. Department of Neurosurgery, International University of Health and Welfare Narita Hospital, 852 Hatakeda Narita, Chiba 286-0124, Japan