A concussion is a temporary change in brain function after a head injury without any signs of brain damage visible on imaging tests, such as computed tomography (CT) or magnetic resonance imaging (MRI).
Sports that involve high-speed collisions (for example, football, rugby, ice hockey, and lacrosse) have the highest rates of concussion, but few sports, including cheerleading, are free of risk. Almost 20% of contact sports participants have a concussion over the course of a season. Estimates of the number of sports-related concussions vary from 200,000 per year to 3.8 million per year. Estimates vary so much because getting an accurate count is difficult when people are not evaluated in a hospital.
Concussions probably do not occur more often in athletes than they have in the past, but they are being recognized more often. The increased recognition is because people are more aware that repeated concussions can have serious consequences.
Unlike with other causes of concussion, such as car crashes and falls, sports participants are continually at risk of concussion. Thus, repeat injury is more likely. Athletes are particularly susceptible if another head injury occurs before they have fully recovered from a previous concussion. And even after recovery, athletes who continue participating are two to four times more likely to have another concussion than if they had never had one. Also, repeat concussions can be caused by an impact less severe than the impact that caused the first one.
Although people eventually recover fully from a single concussion, about 3% of those who had several (even apparently minor) concussions develop long-term brain damage. This damage is termed chronic traumatic encephalopathy (CTE) and was first described in boxers (and termed dementia pugilistica). However, CTE can happen in anyone who has had several concussions. People with CTE have evidence of brain damage on CT or MRI and have symptoms that are similar to those of dementia. Such symptoms include the following:
Several prominent retired athletes who had multiple concussions have committed suicide, possibly caused, at least partly, by CTE.
People with a concussion may or may not lose consciousness, but they have symptoms of brain dysfunction. Symptoms include
Confusion: Appearing dazed or stunned, being unsure of opponent or score, and/or answering slowly
Memory loss: Not remembering plays or assignment and/or not recalling events just before the injury or just afterward
Vision disturbance: Double vision
Sensitivity to light
Dizziness, clumsy movements, and impaired balance
Nausea and vomiting
Ringing in the ears (tinnitus)
Loss of smell or taste
Certain symptoms may be present for a few days to weeks after a concussion. People may have
In teenagers, many postconcussion symptoms, particularly irritability, fatigue, and inability to concentrate, may mistakenly be attributed to normal adolescence.
Athletes with symptoms of a concussion should be evaluated by a doctor experienced in evaluation and treatment of this type of injury. Sometimes such doctors are on site at high-level athletic events. When they are not, sideline staff should be trained in how to recognize concussion, how to evaluate affected athletes, and when to refer them for further evaluation.
Tools such as Sports Concussion Assessment Tool 2 (SCAT2), SCAT3, or SCAT5 can help coaching staff, trainers, and others evaluate athletes on site. SCAT2 and SCAT3 are available free online and can be downloaded to handheld devices. SCAT5 is the latest version and is available free online. The Centers for Disease Control and Prevention (CDC) also has tools and training information for sideline staff (CDC "Heads Up" programs).
Doctors and sideline staff should be aware that athletes may deny or understate symptoms resulting from concussion so that they can continue playing.
Imaging tests such as computed tomography (CT) are done if doctors suspect a more serious injury, such as accumulation of blood within the brain or between the brain and skull (intracranial hematomas) or bruises (contusions) of the brain.
In some programs, all athletes undergo neurocognitive testing (testing of certain brain functions) before sports participation. Then, if a concussion is suspected, doctors can retest the athlete and determine whether brain function has deteriorated.
Treatment of sports-related concussions is similar to that of other people who have concussion. People should rest and take acetaminophen as needed for headache. School and work activities, driving, alcohol, and excessive brain stimulation (for example, using computers, television, video games) should be avoided.
Family members should take the athlete to a hospital if symptoms worsen.
Returning to sports activities is not recommended until several steps have been completed. Once symptoms of concussion have resolved, people may begin light aerobic exercise and then advance through sport-specific training, noncontact drills, full-contact drills, and finally competitive play. Athletes should not move to the next stage until all symptoms at the prior stage have resolved.
Even if symptoms improve quickly, athletes should probably not return to full competitive play until all symptoms have resolved for at least a week.
A person who had a severe concussion (for example, being unconscious for more than 5 minutes or losing memory of events that occurred more than 24 hours before or after the injury) should wait at least a month before resuming full competitive play.
A person who has had multiple concussions in one season needs to understand the risks of continued participation. The person (or the parents if the person is a child) should discuss these risks with a doctor who has experience with brain injuries.