Subjects presenting to one the nine participating Canadian pediatric hospitals (IWK Health Sciences Centre (NS), CHU Sainte-Justine (PQ), Montreal Children's Hospital (PQ), Children's Hospital of Eastern Ontario (ON), The Hospital for Sick Children (ON), Children's Hospital of Western Ontario (ON), Children's Hospital of Winnipeg (MB), Stollery Children's Hospital (AB) and Alberta Children's Hospital (AB)) EDs after sustaining a head injury.