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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, as 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 (for more serious brain injuries, see Traumatic Brain Injury). 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.
Estimates of the incidence of sports-related concussion in the US vary from 200,000/yr up to 3.8 million/yr; 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 traumatic brain injury 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 is free of risk, including cheerleading. An estimated 19% of participants in contact sports have a concussive injury over the course of a season.
Unlike with other causes of concussion (eg, vehicular crashes, falls), which are usually isolated events, sports participants are continually exposed to risk of concussion. Thus, repeat injury is common. Athletes are particularly vulnerable if the repeat injury occurs before they have fully recovered from a previous concussion, but even after recovery, athletes who have suffered one concussion are 2 to 4 times more likely to suffer another concussion at some point. Also, repeat concussions may occur following a less severe impact.
Furthermore, although most athletes eventually recover fully from a single concussion, about 3% of those who had multiple (even apparently minor) concussions develop chronic traumatic encephalopathy (CTE, initially described in boxers and termed dementia pugilistica). In CTE, patients have structural neurodegenerative changes, including cortical atrophy, somewhat similar to changes present in patients with Alzheimer disease. Symptoms can include memory problems, impaired judgment and decision making, personality change (eg, irascibility, volatility), and parkinsonism. Several prominent retired athletes who had sustained recurrent TBI have committed suicide.
The most obvious disturbance of brain function with a concussion is
However, many patients do not lose consciousness but instead manifest symptoms and signs such as
Confusion: Appears dazed or stunned, unsure of opponent or score, answers slowly
Memory loss: Does not know plays or assignment, does not recall events before the injury (retrograde amnesia) or afterward (anterograde amnesia)
Vision disturbance: Double vision, light sensitivity
Dizziness, clumsy movements, impaired balance
Postconcussive symptoms are cognitive and/or behavioral manifestations that may be present for a few days to weeks following concussion, including
Postconcussive symptoms typically resolve in a few days to several weeks.
Athletes with possible concussion should be evaluated by a clinician with experience in evaluation and management of concussions. Sometimes such clinicians are on site at high-level athletic events; otherwise, sideline staff should have training in recognizing concussive symptoms and protocols for referring patients for evaluation. Diagnostic tools, such as the Standardized Assessment of Concussion (SAC), Sports Concussion Assessment Tool 2 (SCAT2), or SCAT3 can help coaching staff, trainers, and inexperienced clinicians screen athletes on site. SCAT2 and SCAT3 are available free online (SCAT2, SCAT3) and can also be downloaded to handheld devices. The CDC has tools and training information for nonclinicians (CDC "Heads Up" programs).
Neuroimaging is not helpful to diagnose concussion itself but is done if there is suspicion of more serious brain injury (eg, hematoma, contusion). Typically, patients should have CT scan if they had loss of consciousness, have Glasgow Coma Score (GCS) < 15 ( Glasgow Coma Scale*), have focal neurologic deficit, have persistently altered mental status, or appear to be deteriorating (see Traumatic Brain Injury : Neuroimaging).
Formal neurocognitive testing would likely show abnormalities on symptomatic patients but is not typically done unless postconcussive symptoms last longer than expected or the individual is manifesting profound cognitive issues. However, some athletic programs do baseline neurocognitive tests on all participants and repeat them following concussion so that more subtle abnormalities can be identified and further participation deferred until the person returns to baseline. One of the more commonly used tests is a commercial computer-based tool called ImPACT (ImPACT).
Patients who had any concussive symptoms or signs should not return to play that day and are advised to rest. School and work activities, driving, and alcohol and excessive brain stimulation (eg, using computers, television, video games) should be avoided. No drugs have been shown to improve recovery from concussion, but specific symptoms can be treated with appropriate drugs (eg, acetaminophen or NSAIDs for headache). Family members are advised to watch for signs of deterioration (see Traumatic Brain Injury : Mild injury) and take the person to the hospital should they occur.
Typically, a graduated approach is recommended. Athletes should refrain from athletic activities until they are completely asymptomatic and require no medication. Then they may begin light aerobic exercise and advance through sport-specific training, non-contact drills, full-contact drills, and finally competitive play. Patients who remain asymptomatic at one level can be advanced to the next. But however quickly they improve, patients are typically not advised to return to full play until they have been asymptomatic for 1 wk. Those who had severe symptoms (eg, unconsciousness for > 5 min, > 24 h of amnesia) should wait at least 1 mo. Athletes who have had multiple concussions in one season need to be fully advised of the risks versus benefits of continued participation. Parents of school-aged children should be involved in these discussions as well.
Concussion involves transient, traumatic brain dysfunction; consciousness may be lost but sometimes patients manifest only confusion, memory loss, and gait or balance difficulties.
Symptoms may resolve quickly or persist for up to several weeks.
Athletes with possible concussion should be removed from play and evaluated; screening tools such as SCAT2 may be helpful.
Neuroimaging is done if there is loss of consciousness, GCS < 15, focal neurologic deficit, persistently altered mental status, or clinical deterioration.
After concussion, patients are more susceptible to repeat concussion for a period of time and must refrain from sports activities until they have been asymptomatic for 1 wk or more (depending on severity of injury).
Athletic activities are resumed gradually.
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