1. Vanderbilt Sports Concussion Center, Vanderbilt University Medical Center, Nashville, TN, USA
2. Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, TN, USA
3. Department of Exercise and Sport Science, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
4. Department of Epidemiology, Colorado School of Public Health, University of Colorado Anschutz, Aurora, CO, USA
5. Department of Neurological Surgery, Oregon Health and Sciences University, Portland, OR, USA
6. Department of Neurological Surgery, Stanford University, Stanford, CA, USA