1. Department of Neurology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
2. Wellstone Muscular Dystrophy Cooperative Research Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
3. Department of Pediatrics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
4. Department of Anesthesiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
5. Department of Radiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.