[1] Univ Ottawa, Dept Surg, Div Neurosurg, Ottawa, ON, Canada
[2] Queens Univ, Sch Med, Kingston, ON, Canada
[3] Hop Sacre Coeur, Dept Surg, Div Neurosurg, Montreal, PQ, Canada
[4] Dept Med, Div Hematol, Ottawa, ON, Canada
[5] Ottawa Hosp Res Inst, Ottawa, ON, Canada