[1] Stanford Univ, Dept Neurol, Sch Med, Stanford, CA 94305 USA
[2] Nova Southeastern Univ, Phys Therapy Dept, Ft Lauderdale, FL 33314 USA
[3] George Washington Univ, Sch Med & Hlth Sci, Dept Hlth Human Funct & Rehabil Sci, Washington, DC 20052 USA
[4] Univ Texas Southwestern Med Ctr Dallas, Dept Phys Therapy, Dallas, TX 75390 USA
[5] Washington Univ, Dept Neurol, St Louis, MO 63110 USA
[6] Univ Calif Davis Hlth, Dept Phys Med & Rehabil, Sacramento, CA USA
[7] Childrens Natl Med Ctr, Dept Biostat, Washington, DC 20010 USA
[8] Cooperat Int Neuromuscular Res Grp CINRG, Washington, DC USA