[1] Univ British Columbia, Vancouver Gen Hosp & Hlth Sci Ctr, Div Neurol, Vancouver, BC V5Z 1M9, Canada
[2] Univ British Columbia, Vancouver Gen Hosp & Hlth Sci Ctr, Dept Radiol, Vancouver, BC V5Z 1M9, Canada
[3] Univ British Columbia, Vancouver Gen Hosp & Hlth Sci Ctr, Dept Med, Vancouver, BC V5Z 1M9, Canada