[1] Univ Calif San Francisco, Dept Neurol, UCSF Weill Inst Neurosci, 675 Nelson Rising Lane, San Francisco, CA 94143 USA
[2] Univ Toronto, Dept Med, St Michaels Hosp, Div Neurol, Toronto, ON, Canada
[3] St Michaels Hosp, Li Ka Shing Knowledge Inst, Toronto, ON, Canada
[4] Univ British Columbia, Dept Med, Div Neurol, Vancouver, BC, Canada
[5] Univ British Columbia, Dept Med Genet, Vancouver, BC, Canada
[6] Harvard Med Sch, Brigham & Womens Hosp, Dept Neurol, Partners MS Ctr, Boston, MA 02115 USA