[1] Univ British Columbia, Vancouver Gen Hosp, Div Neurosurg, Vancouver, BC V5Z 1M9, Canada
[2] Univ Toronto, Brain Vasc Malformat Study Grp, Toronto Western Hosp, Dept Med Imaging, Toronto, ON, Canada
[3] Univ Toronto, Toronto Gen Hosp, Inst Res, Dept Med, Toronto, ON, Canada