[1] SUNY Stony Brook, Dept Neurol, Stony Brook, NY 11794 USA
[2] Univ Toronto, St Michaels Hosp, Toronto, ON, Canada
[3] Copenhagen Univ Hosp, Danish Multiple Sclerosis Ctr, Dept Neurol, Copenhagen, Denmark
[4] Univ Complutense Madrid, IdISSC, Hosp Clin San Carlos, Madrid, Spain
[5] Harvard Med Sch, Brigham & Womens Hosp, Brookline, MA USA