Taylor Twellman is donating his brain to science. Hopefully, the 31-year-old won’t be giving it up any time soon. Twellman is one of 300 professional athletes participating in a Boston University Medical School program to study the long-term effects of repeated concussions.¹ Twellman, considered by many to be one of the best Major League Soccer players ever, sustained seven concussions during his 10-year career. Ongoing medical problems related to concussions forced him to announce his retirement in November 2010. “When you’re told if you want to live your life and be healthy, then soccer needs to stop,” Twellman said at his farewell news conference. “The decision is made for you.”¹

For decades athletes considered “getting your bell rung” to be a normal part of sports. Coaches and athletes alike minimized concussion symptoms so athletes would return to the game as soon as possible instead of being assessed by healthcare providers. Today, researchers are ringing bells of their own — alarm bells — pointing out the mounting evidence that concussions can cause long-term problems and permanent brain injury, including cognitive impairment, learning disabilities, personality changes and even dementia. Professional sports organizations and their university and high school counterparts are getting the message and looking at ways to avoid and manage sports-related concussions. For example, in December 2009, the National Football League issued a more stringent policy regarding when concussed players may return to play.

The actual number of concussions is difficult to ascertain. Many sources report 300,000 a year, but that generally counts only concussions with loss of consciousness, or LOC.² A more realistic estimate that does not narrowly define concussions by LOC is about 3.8 million a year.² The large variance may be due to the lack of a uniform surveillance tool in youth sports and the fact that many people do not seek care for what is seen as a relatively minor injury.²

Few studies have focused on sports-related concussion in younger children, yet sports is the most common cause of concussion in children and adolescents.³ One study looked at 502,000 ED visits for concussion and found that about half related to sports activities.⁴ The study found that ED visits among 8- to 13-year-olds with organized sports-related concussions had doubled during a 10-year period and more than doubled in 14- to 19-year-olds.⁴

Another study of ED visits for pediatric concussion found that 28% of patients were discharged without specific instructions to follow up with their healthcare providers after discharge.³ Clearly, healthcare providers, coaches, trainers, parents and athletes could benefit by further education when it comes to preventing and managing sports-related concussions. 

Defining Concussion

Clinicians have not yet reached a clear consensus on the definition of concussion.^5,6 An injury described as a concussion may be viewed as less serious than when described as a mild traumatic brain injury; those who are “only” concussed may be allowed to return to school and sports activities prematurely.² A concussion is part of the spectrum of traumatic brain injury, which ranges from the mildest of symptoms to coma and death. (This module covers sports-related concussions only. For information on traumatic brain injury, see the CE module “Traumatic Brain Injury.”)

A concussion results from a direct blow to the head, neck or body in which impulsive forces are transmitted to the brain. A concussion is a closed head injury that may or may not result in loss of consciousness and causes functional rather than structural damage to the brain.² Injury is due to acceleration-deceleration and rotational forces to the brain.² The brain slams into the skull (acceleration) and then “bounces” off the opposite side of the skull (deceleration). It also may rotate inside the skull, causing further damage.

Forces applied to the brain can be dramatic. In a not-yet-published study, investigators inserted sensors into the helmets of 21 high school football players.⁷ Researchers were startled to find helmet hits of 100 Gs or more — 100 times the force of gravity.⁷ By comparison, “heading” a soccer ball produces around 20 Gs.^{7 (Level B)}

Concussions generally do not show structural damage when they are imaged, making it difficult to understand what happens on a cellular level in a living brain. Animal studies provide a model of the pathophysiology of concussion; it is not clear how the findings can be applied to human concussion, however.²

Animal studies of the concussed brain show an initial disruption of the neuronal membrane, causing the efflux of potassium to the extracellular space. This in turns leads to release of glutamine, an excitatory amino acid. Glutamine causes further loss of potassium, resulting in cell depolarization and suppression of neuronal activity. This cascade of sequelae continues, leading to the accumulation of lactate and decreased cerebral blood flow. Large amounts of calcium collect in cells, resulting in cell death. The concussed area enters a hypometabolic state that may persist up to four weeks following injury.²

A study of 12 concussed and 12 nonconcussed athletes noted a significant reduction in N-acetylaspartate (NAA, a key marker for neuronal integrity) in the primary motor cortex and the dorsolateral prefrontal cortex (an area associated with higher executive functions, such as planning and monitoring of behavior) in the concussed athletes only.^{5 (Level B)} Researchers found the changes using magnetic resonance spectroscopy (or proton MR spectroscopy), which is capable of detecting several brain metabolites in the living subject.⁵ While this specialized testing is not widely available, some researchers suggest that measuring NAA could prove to be an important method of monitoring concussion recovery.⁶

Symptoms

Many people equate concussion with LOC, but LOC occurs less than 10% of the time.² However, LOC and amnesia may be indicators of more severe injury needing further study.² Athletes may not recognize or report concussion symptoms, and some symptoms may not become evident until several hours after the event. The common signs and symptoms of concussion can be divided into four categories:²

• Physical: headache, nausea, vomiting, balance problems, visual problems, fatigue, sensitivity to light or noise, dazed, stunned
• Cognitive: feeling mentally foggy or slowed down, difficulty concentrating and remembering, forgets recent information, confused about recent events, answers questions slowly, repeats questions
• Emotional: irritability, sadness, overly emotional, nervousness
• Sleep: drowsiness, sleeping more or less than usual, difficulty falling asleep.

Long-term effects of concussions can occur in athletes of any age and are a cause for concern. Athletes with three or more concussions are more likely to experience LOC, amnesia and confusion with subsequent concussions.² Children 8 to 16 have been found with persistent deficits in processing complex visual stimuli for three months after a concussion.² Athletes with two or more concussions have also shown lower grade-point averages than their peers with no history of concussion.² Young athletes pose a challenge because their brains are still developing and may be more susceptible to the effects of a concussion.²

Post-concussion syndrome. Although the term “post-concussion syndrome” is often used, no widely accepted definition exists. Some authorities define it by the number of symptoms present and how long they persist.² A recently proposed definition of post-concussion syndrome is the presence of cognitive, physical or emotional symptoms after a concussion, lasting at least one to six weeks.² The Mayo Clinic says that most symptoms of concussion dissipate within three months but may last a year or more in those with post-concussion syndrome.⁸

Second-impact syndrome is a very rare but often fatal condition that may occur when an athlete sustains a second concussion before fully recovering from the first. Second-impact syndrome may happen hours, days or weeks after the first event.^2,9 The second impact may cause cerebral vascular congestion leading to diffuse cerebral edema, brainstem herniation and death, which may occur within minutes.^2,9 For unknown reasons, young athletes are at greatest risk; all cases have been reported in people under 20.²

Chronic traumatic encephalopathy has long been recognized in boxers who receive repeated blows to the head over several years.¹⁰ More recently, the pathological changes associated with chronic traumatic encephalopathy have been found in other athletes, such as football and soccer players.¹⁰ Chronic traumatic encephalopathy is a progressive neurological disorder that includes abnormalities of tau proteins (proteins that stabilize microtubules that help form neuronal support structures), tangles of astrocytes and neurons throughout the frontal and temporal lobes, and amyloid plaques.¹⁰ Some experts suggest repetitive concussive and subconcussive injury is a risk factor for dementia, Alzheimer’s and Parkinson’s diseases, and ALS.^10,11

Hidden Danger

Athletes do not have to sustain a concussion to experience impairment. In the previously mentioned study of high-school football players, researchers identified players who had been diagnosed by a physician as having a concussion, those who received an unusually high number of head impacts (50 to 60 per week) and those who received a single unusually hard impact.⁷ Half of the players who appeared to be uninjured exhibited changes in brain function demonstrated by neurocognitive testing and functional MRI.^{7 (Level B)} This is a new category of head injury that cannot be defined as concussion but that results in measurable impairment, especially in the dorsolateral prefrontal cortex.⁷ A danger associated with this phenomenon is that athletes with unrecognized symptoms may return to play too soon and sustain subsequent injuries with worse sequelae.⁷

Sports-related concussions may affect the sexes in different ways. For example, a study to be published in the Journal of Athletic Training finds that while headaches are the most frequently reported symptom of concussions in both girls and boys, boys report being confused and disoriented and having amnesia far more often after concussions than girls do.^{12 (Level B)} Girls report feeling more drowsy and being more sensitive to noise than boys do after a concussion.¹² Recovery times in both sexes averaged three days, and many athletes returned to play within six days of injury.¹² Also, girls are reported to have a higher rate of concussion than boys in similar sports.² One explanation is that boys may be more reluctant to report injuries for fear of being removed from the game; this may result in under-reporting of concussions in boys.² In addition, girls have weaker neck muscles and a smaller head mass than boys do, making it more likely that they will sustain a concussion under comparable conditions.² In some sports, such as ice hockey, body checking (knocking another player down or against the boards) is allowed on boys’ teams but not girls’ teams. Girls may therefore be less prepared to protect themselves from a head injury with an accidental collision than boys are.¹³

What sports are the most dangerous for different age groups? Speakers at a Mayo Clinic conference on concussion found that the concussion rate for women’s ice hockey is the highest of all sports in the National Collegiate Athletic Association; the rate for women’s ice hockey was 2.72 per 1,000 player hours, 2.34 for NCAA football and 1.47 for men’s ice hockey.¹³

A study of slightly younger ice hockey players (average age 18.2) found the sport far more dangerous than previously reported.¹⁴ Physicians observed 52 ice hockey games and found the concussion rate to be 3.3 times higher than the highest rate previously reported in the literature.¹⁴ In addition, the rate of return to play after concussion was higher than previously measured, suggesting that some athletes may be returning to play earlier than they should.^{15 (Level B)}

An analysis of high school sports ranked concussions as most frequent in football, followed by girls’ soccer, boys’ lacrosse, boys’ soccer, girls’ basketball, wrestling, girls’ lacrosse, softball and boys’ basketball.² And while a study of more than 4 million basketball injuries in children and adolescents showed that injuries overall are down, concussion and other brain injuries increased 70% between 1997 and 2007.^{16 (Level B)}

Among 8- to 13-year-old children, the greatest number of ED visits for sports-related concussions result from football, basketball, baseball, soccer and ice hockey.⁴ A study of Canadian ice hockey players ages 11 and 12 compared concussions on teams that allowed body checking with those that didn’t.¹⁷ Children playing in games that allowed body checking had 300% more injuries, including mild and severe concussions.¹⁷ More studies are needed of the youngest athletes, such as those on pee-wee football, Little League and T-ball teams.

Assessment

All athletes who have sustained a head or neck trauma should be immediately evaluated on the field for airway, breathing, circulation (ABCs) and cervical spine injury. Next, a brief assessment of the athlete’s condition is usually performed using one of several “sideline assessment tools” for concussion, such as the Sports Concussion Assessment Tool (SCAT or SCAT2).² The simpler form can be administered in moments; it measures symptoms such as LOC or seizure and problems with memory or cognition, and includes a brief neurological screening. Outcomes range from immediate in-hospital assessment to return to play the following day. Other common concussion assessment tools are the Colorado Medical Society guidelines, the American Academy of Neurology guidelines and the Cantu guidelines, named after Robert Cantu, MD, a sports concussion specialist. However, these grading systems focus on concussion symptoms such as LOC and amnesia. Because 90% of concussions don’t cause LOC, important signs of concussion can be missed. As science has developed a better understanding of concussion, sophisticated postconcussion neuropsychological testing is being used more often.²

Many of these neuropsychological tests are computerized and may be administered more than once during recovery from concussion. A study of nearly 550 concussions among high school athletes showed that those who received neuropsychological testing were less likely to return to play within a week of their injury, suggesting that such testing may prevent premature return to sports activities.^{18 (Level B)}

One widely used proprietary neuropsychological test is called imPACT (Immediate Post-Concussion Assessment and Cognitive Testing). This 20-minute computerized test can be administered by healthcare workers, team coaches and others with appropriate training at schools or in clinics. Components include description of current symptoms and injury; measurement of word and visual memory; cognitive processing speed; matching symbols, letters, colors and numbers; attention span; and reaction time.^2,19 Some sports organizations are performing preseason baseline screening so that if an athlete has a concussion, the results can be measured against baseline results to more accurately monitor recovery.¹⁹

Diagnosis, Treatment

Because concussions are largely functional rather than structural brain injuries, routine postconcussion CT or MRI imaging adds little to evaluation and management.² Symptoms that would suggest the need for such imaging include severe headache, seizures, focal neurological deficits, repeated emesis, significant irritability or drowsiness, slurred speech, LOC longer than 30 seconds and poor orientation to person, place or time.² Although rare, findings could include skull fracture or any of the four types of intracranial hemorrhage.²

Methods under study to diagnose concussion include using magnetic resonance spectroscopy to test for NAA, a marker for neuronal integrity (discussed earlier); PET scans; and single-photon emission CT.² Just as the injured myocardium spills markers such as troponin into the bloodstream, so does the injured brain. Researchers are studying two proteins known as SBDP145 and SBDP120 that enter the blood when neurons are damaged in traumatic brain injury.²⁰ The U.S. Army is studying these biomarkers in patients with concussions. Measurement of these biomarkers has the potential for early and accurate diagnosis of concussive injury.

The cornerstones of concussion treatment are physical and cognitive rest.² Most people understand physical rest, but cognitive rest is a lesser-known concept. It includes avoiding TV, gaming and reading and may mean staying home from school or attending fewer hours.² Concussion rehabilitation is a six-step program that starts with complete physical and cognitive rest, and proceeds to return to play.² No evidence-based research exists on the use of medication to treat concussion. In fact, experts usually recommend that patients avoid NSAIDs after head injury for fear of intracranial bleeding.²

The Next Steps

Sports-related concussions are now receiving the attention they deserve. A search for concussion at www.clinicaltrials.gov shows nearly three dozen trials involving concussions. Researchers are developing new helmets; some include air bladders that inflate to better fit the head. Helmets with sensors record the severity of impacts. Studies are needed to ascertain which helmets protect athletes best.

Education about unrecognized concussion is important for healthcare providers, families, coaches, trainers and athletes. But some experts believe sports culture itself needs to change. An article in Time magazine about professional football summarized it succinctly:²¹

1. Change the rules: Take the purposeful helmet hit out of football. Institute a penalty box for egregious head hits.
2. Change the equipment and training: Continue to develop better helmets. Consider eliminating repetitious off-season training that unnecessarily results in head injuries.
3. Change youth football: Train all youth coaches in a concussion-management program. Coaches should use a concussion assessment card and rethink techniques taught to children.
4. Change the culture: Teach players about the dangers of concussion and encourage them to report it. Many young athletes are victims of their own bravado and machismo.

Schools, counties, states and athletic organizations are paying attention to the dangers of concussions and taking steps to mitigate them. A bill titled The Concussion Treatment and Care Tools Act of 2010 was introduced in Congress last year, but did not become law.²² The bill would have set up a conference of experts to establish guidelines to help prevent and treat concussions in children and teens and develop return-to-play standards.²²

Determining when an athlete returns to play after a concussion should follow an individualized course; each athlete will recover at a different pace. “When in doubt, sit them out” is paramount in the management of a pediatric or adolescent concussion.³ Sports-related concussions are not inevitable, and healthcare providers can do much to inform the public and patients about their dangers.

Further Resources

• American College of Sports Medicine
• Brain Trauma Foundation
• CDC Concussion in Sports Information
• North American Brain Injury Society

Gannett Education guarantees this educational activity is free from bias.