1. National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
2. Departments of Neurology and Psychiatry, Uniformed Services University of the Health Sciences, Bethesda, MD, USA
3. Department of Neurology, Hospital for Special Surgery, Weill Cornell School of Medicine, New York, NY, USA
4. Department of Neurology, University of Florida, Gainesville, FL, USA
5. Healey Center for ALS at Mass General, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA, and
6. Department of Neurology, Columbia University Irving Medical Center, New York, NY, USA