1. Department of Neuroscience, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
2. Department of Neurology, Medical College of Wisconsin, Milwaukee, WI, USA
3. Department of Neurology, University of Miami, Miami, FL, USA
4. ALS Department, Hospital Carlos III-La Paz, Madrid, Spain
5. Department of Rehabilitation, Elson S. Floyd College of Medicine, Washington State University, Spokane, WA, USA
6. Department of Neurology, Washington University, St. Louis, MO, USA
7. Department of Neurology, Temple Health, Philadelphia, PA, USA
8. Department of Neurology, Duke University, Durham, NC, USA
9. Duke University, Durham, NC, USA
10. Department of Neuroscience, University of Sheffield, Sheffield, South Yorkshire, UK
11. Department of Neurology, University of Nebraska Medical Center, Omaha, NE, USA
12. Tulane University, New Orleans, LA, USA
13. Independent Consultant, Lichfield, UK, and
14. Department of Neurology, University of California, Los Angeles, CA, USA