concussion2Hundreds, if not thousands, of times a year a young athlete takes a hard blow to the head in the course of a high school, college, or an amateur sporting event. When this occurs, how do trainers and coaches determine if the athlete has received a concussion? If he or she has a concussion, is it cause for concern? And how is a decision made to return an athlete to playing contact sports? Over the past several years, a number of studies have shown that many different factors need to be considered in assessing sports-related concussions at all levels, from young children involved in Little League to professional athletes.

Concussion: A Form of Mild Head Injury
Although to athletes, parents, and the general public, a concussion is not necessarily considered a serious head injury, research suggests that concussions are in fact a form of traumatic brain injury. This categorization seems much more believable in light of recent evidence indicating that repeated concussions in amateur and professional athletes can lead to measurable deficits in planning abilities, memory, and other cognitive activities. In addition, concussions can also increase an athlete’s risk for second impact syndrome. This rare, but life-threatening situation can occur when an athlete receives two, sometimes fairly minor, blows to the head within a short period of time. These clinical findings indicate that it is critical for coaches and trainers to be able to safely determine whether a player has sustained a concussion, and to consider carefully when and if these athletes can continue their sports activities.

Effects of Concussion on the Brain

Single Concussion
Historical definitions of concussion often included a brief or prolonged loss of consciousness. However, some professional groups, such as the American Orthopaedic Society for Sports Medicine, have recently redefined concussion to include all changes of “cerebral function caused by a direct or indirect (rotation) force transmitted to the head” that lead to one or more characteristic symptoms (see Table 1).

Immediate symptoms Later onset symptoms
Headache Memory problems/amnesia
Dizziness Difficulty concentrating
Confusion Irritability
Vision problems Sleep problems
Nausea and/or vomiting Emotional changes
Tinnitus or other auditory problems Personality changes
Loss of consciousness Fatigue

Table 1
In terms of diagnosing a concussion, it is initially important to gather as much information as possible about the kinds of obvious symptoms that are listed above. However, the presence of one or more of these symptoms usually means that, at some level, microscopic damage to the brain tissue has occurred.

Case Study: The Effects of Concussion on a Cellular Level
Researchers and clinicians are still working to understand all of the cellular changes that take place following a concussion, but a great deal of information is already known. For example, imagine a college football player has his face mask grabbed by another player during a tackle and both players fall to the ground. The first player receives a concussion caused by the rapid spin of his head as his face mask was pulled and rotated, or by his head hitting the ground, or both. As the player’s brain moves rapidly back and forth in its bath of cerebrospinal fluid, some small number of axons and capillaries may be damaged while others may be completely pulled apart as a result of shearing forces that pass through the brain tissue. Other neurons that are not damaged by shearing may be subjected to dramatic changes in their surroundings, including fluctuations in the levels of ions, neurotransmitters, and free radicals that are necessary for normal neuronal function. Some damaged neurons may fill with calcium, which activates many intracellular processes — some destructive and some beneficial. Potassium levels surrounding some neurons may increase, causing the neighboring glial cells to swell as they try to buffer the chemical changes. Electrical signals passing along axons are disrupted, as some excitatory neurotransmitters are dumped out at toxic levels. As the vulnerability of the damaged neurons increases, they are in desperate need for more glucose, the sugar that fuels their function. However, some neurons’ needs go unmet, as one of the other global effects of the player’s injury is a decrease in the flow of blood to the damaged areas of his brain. In this player’s case, the cellular effects of his concussion were diffuse and affected many different brain functions. He loses consciousness for several minutes as the electrical signals from his brain stem to his cerebral cortices are temporarily disrupted. When he awakes several minutes after his injury, he has a headache as well as some confusion and amnesia. These effects may be the result of minor damage to regions of his brain such as his frontal and temporal lobes. Over the next few days, the player may lose a small number of neurons throughout his brain — those that were damaged beyond repair when his initial injury occurred. However, most of the damaged neurons eventually survive thanks in part to glial cells that have helped return the levels of ions and neurotransmitters to a normal state and have scavenged bits of neuronal debris from the otherwise healthy tissue. As his brain tissue recovers, he begins to feel better and goes on to play in another game several weeks later.

Multiple Concussions and Cumulative Chronic Brain Injury
It is not surprising, given that a single concussion qualifies as a traumatic brain injury, that multiple concussions — even multiple impacts to the brain that do not qualify as concussions — can contribute to a permanent change in a person’s cognitive abilities. Most of us have seen the rigidity, tremor, and speech impairment experienced by former boxer Mohammed Ali. In his case, cumulative injuries to his brain have probably led to the development of an encephalopathy, which is similar to that which occurs in Parkinson’s disease, and exhibits some features of Alzheimer’s. Cumulative damage to brain as a result of involvement in sports is most widely associated with boxing, but this type of damage can also occur with other sports that involve repeated major or minor blows to the head, including soccer and horseracing.

Second Impact Syndrome
Although in most cases, a single concussion is a fairly minor injury and could hardly be considered a life-threatening condition, the rare second-impact syndrome draws attention to the importance of careful evaluation of concussions in all athletes. Second impact syndrome is believed to occur when neurons that have already been placed in a vulnerable state by an initial concussion are exposed to a second, sometimes extremely minor, insult. The second impact appears to cause the affected region of the brain to lose complete control of its ability to regulate the pressure in the brain’s blood vessels. Massive, and typically irreversible, brain swelling and death usually result. Although extremely rare, the risks of second impact syndrome require that any athlete with post-concussive symptoms be carefully protected from further head injury while he/she is still experiencing these symptoms.

Effects of Concussions on Higher Brain Function
In light of the stresses that a concussion places on neurons at the cellular level, it is not hard to imagine that these changes could have a downstream effect on thought processing and other cognitive abilities. However, relatively few studies have assessed these relationships, particularly in amateur and/or young athletes. It is a positive step, then, that several recent studies have examined the relationship between concussions and more minor head trauma on brain function. The outcomes of these studies, and the fact that they were conducted with amateur athletes, provide some important insights that have been needed in the field of sports medicine for some time.

In the first study, Dr. Michael Collins and a number of his colleagues from around the country examined the effects of concussion on neuropsychological performance in college football players from 1997 to 1999. Players’ cognitive abilities were assessed on a number of standard psychological tests at the beginning of the fall season, and those who sustained one or more concussions during the season were tested again following their injury. Post-injury testing confirmed that a history of multiple concussions can be correlated with lowered scores on cognitive tests, particularly those that examine executive functioning and the ability to process information rapidly. Although this finding in itself is not welcome news to young football players and their families, this study uncovered an even more troubling relationship between concussions and cognitive performance in players with a prior history of learning disability . Based on the findings from this study, it appears as though there may be an additive effect of learning disabilities and head injuries on subsequent thought processing. This interpretation is based on the finding that players with prior problems with learning and multiple concussions fared substantially worse on some aspects of testing as did players with concussions and no prior diagnosis of learning disability. If this relationship is substantiated by further research, a “red flag” should be raised with parents whose sons or daughters may be interested in becoming involved in contact sports. The participation of kids and young adults in these activities after they have been diagnosed with a learning disorder will involve some difficult decision-making, given the potential long-term impact of this participation on their cognitive abilities.

The second study was published in 1999 by Erik Matser of St. Anna Hospital in the Netherlands and several collaborators at other institutions in both the Netherlands and the United States. In this study, the cognitive performance of amateur soccer players was examined in an attempt to learn if concussions and other more minor blows to the head (from “heading” the ball) could lead to chronic traumatic brain injury and subsequent problems with cognitive tasks. On a very basic level, the results of this research suggest that the standard activities involved in soccer do appear to impact a player’s mental function, particularly on tasks involving planning abilities and memory. Furthermore, the cognitive performance of players with multiple concussions appeared to be inversely related to the number of concussions they had sustained, i.e. the more concussions, the worse the performance. These findings suggest that athletes in general should be advised that all blows to the head, however minor, may contribute to the cumulative damage that their brains sustain. Whether these findings are also applicable to much younger soccer players is not known; however, it would be prudent to assume that at least some of these relationships probably hold true for athletes of all ages.

Returning Players to the Game
Deciding when it is safe to return to play is one of the most difficult judgements that sports physicians and athletic trainers routinely make. An incorrect judgment on their part could result in a permanent change in a player’s cognitive status or a life-threatening secondary injury. How are these decisions made? Do the current systems provide enough protection for the players?

Over the last 25 to 30 years, a number of systems have been developed to provide coaches, doctors, and trainers with guidelines to assess the level of brain injury. They must be aware that concussions can be caused by both a direct impact to the head or helmet or a sudden movement of the head — such as a whiplash injury. Once head injury has been determined without damage to the neck or spine, standard procedure involves issuing a brief battery of cognitive tests to the player. Some questions and tests may be administered on the field, while others may be given a few minutes later on the sidelines. Initial questions are often designed to evaluate the player’s knowledge of his/her immediate surroundings, for example asking for the date, month, the current score in the game, or the circumstances that caused the player’s injury. Additional questions regarding events earlier that day may help determine if the player has retrograde amnesia. Subsequent testing may include asking the player to recall three words at 0 and 5 minute intervals and to perform concentration tasks such as repeating the months of the year or short strings of numbers backwards. The evaluation would also include questions about symptoms such as dizziness and headache, as well as a short neurological exam.

The outcome of this evaluation, given immediately after the injury, and again some time later, should determine how long a player will be restricted from play. Many sports physicians disagree about standards of evaluating the severity of a player’s injury. Some believe that a player with short-term amnesia can potentially return to the game or practice the same day if the symptoms subside. Others recommend that any period of amnesia should prevent an athlete from returning to contact sports for one week after the injury. Fortunately, work is underway to standardize these practice guidelines into a single concise format that will be accepted and used by trainers and sports physicians at all levels.

There is little question that concussions, whether manifested in a few minor symptoms or a number of serious consequences, are a form of traumatic brain injury, and should be taken seriously by players, parents, and health professionals. Although the effects of concussions in many sports and many age groups have not been fully investigated, it is clear that they can have a long-lasting, and sometimes permanent, impact on a person’s mental function. Unfortunately, people with learning disabilities may be particularly susceptible to these effects. The standardization of guidelines that can be followed by sports personnel on the field will likely help the difficulties surrounding decision-making when a concussion occurs. However, it is the adherence to these guidelines, and an appreciation of the potential seriousness of concussions, that will ensure the best possible outcomes for athletes of all ages.