[1] Queen Elizabeth II Hlth Sci Ctr, Div Neurosurg, Halifax, NS B3H 2Y9, Canada
[2] Univ Toronto, Hosp Sick Children, Div Neurosurg, Toronto, ON M5G 1X8, Canada
[3] Queen Elizabeth II Hlth Sci Ctr, Dept Pathol, Halifax, NS, Canada
[4] Nova Scotia Canc Ctr, Halifax, NS, Canada