[1] Hosp Sick Children, Div Pediat Neurosurg, Toronto, ON M5G 1X8, Canada
[2] Hosp Sick Children, Div Pediat Neurol, Toronto, ON M5G 1X8, Canada
[3] Hosp Sick Children, Div Neuroradiol, Toronto, ON M5G 1X8, Canada
[4] Univ Toronto, Fac Med, Toronto, ON, Canada