1. Department of Clinical Neurosciences, University of Calgary, Calgary, AB, Canada
2. Department of Neurology, MS Center Amsterdam, Amsterdam University Medical Center, Amsterdam, The Netherlands
3. Department of Neurology, Rijnstate Hospital, Arnhem, The Netherlands
4. Department of Neurology, Columbia University Irving Medical Center, New York, NY, USA
5. Multiple Sclerosis Center, Swedish Neuroscience Institute, Seattle, WA, USA
6. Department of Medicine, Neurology Service, Hôpital de la Cité-de-la-Santé, Laval, QC, Canada
7. Department of Biostatistics, The University of Alabama at Birmingham, Birmingham, AL, USA