1. Division of Emergency Medicine, Boston Children's Hospital, Boston, Massachusetts, USA.
2. Department of Neurology, Boston Children's Hospital, Boston, Massachusetts, USA.
3. Harvard Medical School, Boston, Massachusetts, USA.
4. Department of Surgery, Boston Children's Hospital, Boston, Massachusetts, USA.
5. The Micheli Center for Sports Injury Prevention, Boston, Massachusetts, USA.
6. Sports Concussion Clinic, Boston Children's Hospital, Boston, Massachusetts, USA.