1. Harvard Medical School, Neurological Clinical Research Institute (NCRI), Massachusetts General Hospital165 Cambridge St, Suite 600, Boston Massachusetts02114 USA
2. Massachusetts General Hospital Biostatistics CenterBoston Massachusetts USA
3. Department of Management Science and EngineeringStanford UniversityStanford California USA
4. Department of NeurologyHouston Methodist Neurological Institute, Houston Methodist HospitalHouston Texas USA
5. Department of NeurologyEmory University School of MedicineAtlanta Georgia USA
6. Department of Neurology, Eleanor and Lou Gehrig MDA/ALS Research CenterColumbia University Medical CenterNew York New York USA
7. Department of NeurologyForbes Norris MDA/ALS Research Center, California Pacific Medical CenterSan Francisco California USA