What is a Concussion?
A concussion (a.k.a., mild traumatic brain injury; MTBI) is a common injury in amateur and professional athletics, particularly in contact sports.This injury can be very distressing for the athlete, his or her family, coaches, and school personnel. Making return to play decisions is difficult and often requires the input from a physician and neuropsychologist. Neuropsychologists possess the background knowledge and training to understand brain-behaviour relationships and are specialists in the identification and treatment of cognitive impairment. Neuropsychologists are uniquely qualified to objectively evaluate the neurocognitive and psychological effects of concussion. Neuropsychologists interpreting neuropsychological test data assist athletes by identifying and tracking post-concussion symptoms and sequelae, lending valuable information for managing return to play decisions, and focusing on the best interests of the athlete.
Concussions are common injuries in athletics
The Centers for Disease Control and Prevention (CDCP) reported that at least 300,000 athletes per year suffer concussions within the context of sports in the United States alone. This incidence rate is conservative and likely seriously under-estimates the true incidence because: (a) the CDCP based its statistics only on those athletes who lost consciousness, and (b) players and coaches tend to lack awareness or minimize symptoms of concussion. Typically, concussions do not cause a loss of consciousness (LOC). In fact, approximately 90% of concussions in sports occur without LOC. A recent study found that 70% and 63% of football and soccer players, respectively, reported symptoms consistent with concussion, although only 23% and 20% realized they had, in fact, sustained a concussion. This partially explains why some injuries appear to go unrecognized or unreported by the athlete. However, on a confidential survey regarding their concussion histories 40% of high school football players believed that they were concussed but deliberately did not reveal this information for fear of losing playing time.
Concussion rates in high school and college football have ranged from approximately 3–4% to 7–9%. A systematic review of published literature revealed that hockey had the highest incidence of concussion compared to football, soccer, and taekwondo/boxing for high school, college, and amateur adult males. However, out of all high school sports, football has been found to have the highest inherent risk among males, and soccer the highest inherent risk among females.
Concussions result in physical, psychological, and cognitive symptoms
A concussive injury to the brain follows a blow to the skull or an action that generates abrupt acceleration and deceleration of the brain within the skull. The acceleration/deceleration forces may lead to linear and/or rotational movement of the brain whereby brain tissue moves against itself inside the skull, increasing the risk for neurocognitive and neurobehavioral deficits. Under the vast majority of circumstances, concussions in sports do not result in damage to the brain that is visible with static neuroimaging techniques, such as CT or MRI. However, structural damage can occur, especially in sports such as equestrian and auto racing.
The vast majority of concussions in athletes fall at the mild end of the mild traumatic brain injury severity continuum. Loss of consciousness typically is not present, and post-traumatic amnesia is typically brief. This injury is likely associated with low levels of axonal stretch resulting in temporary changes in neurophysiology.
The most common symptoms of sports-related concussion include headache, dizziness, confusion, nausea, memory difficulties, “mental fogginess,” fatigue, balance problems, attention and concentration difficulties, sleep disturbances, and “nervousness”. Many athletes with concussions have neurocognitive decrements detectable using traditional paper–pencil or computerized neuropsychological tests in the initial hours, days, and potentially weeks post-injury. In group studies, athletes tend to recover in terms of perceived symptoms and neuropsychological test performance within 2–14 days. It is important to note, however, that a minority of athletes who remain symptomatic at more than one or two weeks post-injury can be obscured in group analyses. The majority of athletes appear to recover fully within one-month post-injury, but some athletes can have lingering problems.
Baseline and post-injury neuropsychological testing is preferred
Neuropsychological testing provides unique information that can be invaluable not only in diagnosing the injury but also in tracking recovery over time. Neuropsychological testing of athletes is standard practice in the management of concussions in U.S. college and professional sports (e.g., NFL and NHL). The standard use of neuropsychological testing in high school athletes is being debated within high levels of government in the U.S.
The model of neuropsychological assessment utilized in sports is distinctly different from more traditional models of neuropsychological evaluation that utilize extensive, time-consuming test batteries. Sports concussion assessment and management models are designed to promote the screening of large numbers of athletes in order to establish an individual standard for each athlete. The baseline evaluation is not meant to represent a comprehensive assessment but is targeted to assess cognitive domains that are most often affected by concussion, such as memory, attention, speed of mental processing, and reaction time. Baseline neuropsychological testing is usually conducted prior to the sports season. If an athlete is concussed, serial evaluations are conducted post-injury to determine the point at which neurocognitive deficits and clinical symptoms are no longer present. It is considered standard practice that an athlete’s neurocognitive performance must return to baseline or better before returning to play, in order to avoid the possibility of more serious, cumulative injury during the vulnerable recovery period. Although there is variability across sports concussion management programs regarding the administration of neuropsychological tests, the interpretation of neuropsychological test data should only be conducted by a clinical neuropsychologist who is the only healthcare professional that is uniquely qualified to translate the test data into recommendations for clinical management.
Most athletes recover from a concussion within one month
There is accumulating and converging evidence that isolated concussions in sports are often self-limiting injuries that are not associated with long-term cognitive or neurobehavioral problems. The pathophysiology of concussion appears to be predominately neurometabolic and reversible, although under certain circumstances a small number of cells might degenerate and die. It is reasonable, however, to assume that the vast majority of neurometabolic pathophysiology will undergo dynamic restoration in the hours and days following the injury. This dynamic restoration proposed in animal models seems to fit the recovery curves that have been reported repeatedly in studies with athletes.
There is some research that suggests that professional football players recover more quickly than younger athletes. In a large-scale prospective study, the vast majority of college football players recovered within seven days. There is evidence suggesting that high school football players take longer to recover than university and professional athletes. The majority of high school football players appear to recover within one month post-injury. Although the recovery rate for most athletes is reasonably well understood, much additional research is needed to identify reliable predictors of rapid versus slow recovery and to better appreciate the effects of multiple injuries.
Concussions should be managed conservatively and individually
Consensus guidelines for general management and return to play have been available for several years. First, the athlete should be asymptomatic at rest. Then, the athlete is progressed through increasing non-contact physical exertion, until he or she has demonstrated asymptomatic status with non-contact physical exertion and non-contact sport-specific training. The athlete should demonstrate full recovery of neurocognitive function as measured by neuropsychological testing prior to returning to play. Neurocognitive recovery is inferred when the athlete’s performance either returns to baseline levels or, in the absence of a baseline, is consistent with pre-injury estimates of functioning when the test data are compared to normative values. Although the preferred interpretation of post-injury test scores involves a comparison to baseline test scores, it is important to underscore that neuropsychological testing may be quite useful in the absence of baseline test data, particularly in the case of protracted or unusually severe symptoms.
Children may need to be managed differently
Some researchers have reported slower and differential recovery patterns for high school athletes as compared to college-aged and professional athletes. Although the mechanisms are poorly understood, there is reason to be concerned that more severe forms of concussion could have lasting effects on complex neurochemical and anatomical events that are occurring in the developing brain. Unfortunately, there is limited research on concussion in young athletes, with very little research extending to pre-high school years. Treatment of concussion and knowledge of return-to-play guidelines for young athletes appears to be limited.
In one retrospective study, 70% of concussed youth visiting the emergency room received inappropriate discharge instructions. One study found medical practitioners correctly identified specific return to play criteria in only 8–56% of hypothetical cases. In spite of the vulnerability of this population, individuals caring for concussed youth athletes are not uniformly familiar with guidelines for identification, treatment, and management of concussions. Moreover, youth athletic contests represent the venue least likely to have qualified medical professionals or paraprofessionals in attendance.
Concussions carry some risk for cumulative effects
Once concussed, an athlete is at a statistically increased risk for a future concussion. The reasons for the increased risk are unclear. Previously concussed athletes are four to six times more likely to experience a second concussion, even if the second blow is relatively mild. In a more recent two-year prospective study of high school and collegiate football players, there was a six times greater relative risk for individuals with a history of concussion than for individuals with no history. Results of research on professional football players reveal mixed results, although Canadian Football League (CFL) players with a history of concussion were found to have increased risk of future concussion.
Athletes, their families, coaches, athletic trainers, and sports medicine professionals are concerned about possible lingering effects, or permanent brain damage, resulting from multiple concussions. The literature regarding the persistent effects of two previous concussions is mixed. With regard to possible long-term effects, some researchers have reported statistically significant adverse effects, and others have not. In a large-scale study, athletes with one or two previous concussions did not differ on neuropsychological testing or symptom reporting from athletes with no previous concussion on baseline, preseason testing. Research on the effects of prior concussion on recovery time from an athlete’s next concussion also has revealed mixed results. Some studies have found that some athletes with two previous concussions have slower recovery times whereas other studies found that concussion history was unrelated to recovery time in high school athletes.
There is accumulating evidence that a history of three or more concussions is associated with changes in neurophysiology, subjective symptoms, and neuropsychological test performance in some athletes. Furthermore, some athletes with three or more concussions are likely at increased risk of sustaining future concussions, experiencing worse on-field presentations of their next concussion, having a greater likelihood of slowed recovery, and experiencing more severe, acute changes in memory performance on neuropsychological testing. More research is needed to examine recovery rate in relation to concussion history.
An extraordinarily rare and tragic outcome of concussion can be catastrophic brain swelling leading to severe disability or death. This has been described as second impact syndrome, and over the past 20 years a number of cases have been reported. In theory, sustaining a second brain injury during a period of increased vulnerability, while the athlete is recovering from the first injury, has been linked to second impact syndrome. The pathophysiology of second impact syndrome is thought to be cerebrovascular congestion or a loss of cerebrovascular autoregulation leading to considerable brain swelling. Most cases of second impact syndrome have been reported in children or adolescents.
Adapted from the National Academy of Neuropsychology Position Paper “Neuropsychological evaluation in the diagnosis and management of sports-related concussion”, Archives of Clinical Neuropsychology 22 (2007) 909–916
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