[1] Miyagi Childrens Hosp, Dept Neurosurg, Aoba Ku, 4-3-17 Ochiai, Sendai 9893126, Japan
[2] Sendai City Hosp, Dept Neurosurg, Sendai, Japan
[3] Miyagi Childrens, Dept Neurosurg, Sendai, Japan
[4] Tohoku Med & Pharmaceut Univ, Div Publ Hlth Hyg & Epidemiol, Sendai, Miyagi, Japan
[5] Tohoku Univ, Dept Neurosurg, Grad Sch Med, Sendai, Miyagi, Japan