Sports activities are a common cause of concussion, a form of mild traumatic brain injury. Symptoms include loss of consciousness, confusion, memory difficulties, and other signs of brain dysfunction. Diagnosis is clinical with neuroimaging done as needed. Neuroimaging is not mandatory because there is rarely any evidence of structural brain injury. Early return to competition can be harmful; once symptoms are resolved, athletes can gradually resume athletic activity.
Concussion is a transient disturbance in brain function caused by head injury, usually a blow. By definition, there are no structural brain abnormalities visible directly or on imaging studies, in contrast to more serious brain injuries (traumatic brain injuries [TBIs]).
Pathophysiology is still being clarified, but brain dysfunction is thought to involve excitotoxicity, which is neuronal damage caused by excessive release of excitatory neurotransmitters, particularly glutamate. For additional information, see Concussions: What a neurosurgeon should know about current scientific evidence and management strategies.
Estimates of the incidence of sports-related concussion in the US vary from 200,000 a year up to 3.8 million a year; the highest numbers include rough estimates of injuries that are not evaluated in a hospital or otherwise reported. The awareness and thus reporting of concussions has risen significantly in the past decade—the incidence of serious and fatal sports-related TBI has not increased similarly. Sports that routinely involve high-speed collision (eg, football, rugby, ice hockey, lacrosse) have the highest rates of concussion, but no sport, including cheerleading, is free of risk. An estimated 19% of participants in contact sports have a concussive injury over the course of a season.
