1. Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA, Department of Neurology, VA Greater Los Angeles Health Care System, Los Angeles, CA, USA,
2. Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
3. Multiple Sclerosis Center of Excellence-East, Research and Neurology Services, VA Maryland Health Care System, Baltimore, MD, USA, Department of Neurology, University of Maryland School of Medicine, Baltimore, MD, USA
4. Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
5. Multiple Sclerosis Center of Excellence-West, VA Puget Sound Health Care System, Seattle, WA, USA, Department of Rehabilitation Medicine, University of Washington School of Medicine, Seattle, WA, USA, Departments of Epidemiology, University of Washington School of Medicine, Seattle, WA, USA
6. Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA, USA, Department of Medicine, VA Greater Los Angeles Health Care System, Los Angeles, CA, USA
7. Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA, Department of Neurology, VA Greater Los Angeles Health Care System, Los Angeles, CA, USA