1. Kennedy Krieger Institute, Baltimore, MD, USA
2. Department of Physical Medicine and Rehabilitation, Johns Hopkins University School of Medicine, Baltimore, MD, USA
3. Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, USA
4. VA Maryland Health Care System, Baltimore Medical Center, Baltimore, MD, USA
5. Department of Physical Medicine and Rehabilitation, University of Utah School of Medicine, UT, USA
6. Department of Physical Medicine and Rehabilitation, The Children's Hospital, Denver, CO, USA