1. Department of Neurosurgery, Miyagi Children’s Hospital, Sendai, Japan (T.H., T.K., R.S.).
2. Department of Neurosurgery, Sendai City Hospital, Japan (H.K.).
3. Department of Neurosurgery (T.S.), Tohoku Medical and Pharmaceutical University, Sendai, Japan.
4. Division of Public Health, Hygiene and Epidemiology (H.M.), Tohoku Medical and Pharmaceutical University, Sendai, Japan.
5. Department of Neurosurgery, Tohoku University Graduate School of Medicine, Sendai, Japan (T.T.).