“Differences arise at every level of the organ’s astonishingly intricate architecture; the human brain contains 100 billion neurons, which come in thousands of types and collectively form an estimate of more than 100 trillion interconnections. These differences, in turn, lead to variances in the ways that we think, learn, and behave and in our propensity for mental illness.” (Gage FH, Muotri AR. What makes each brain unique. Sci. Am. 2012; 306(3):26–31).
The complex issues concerning sport-related concussion recently have drawn national attention. Disability and forced retirement among high-profile professional athletes, emergence of chronic traumatic encephalopathy as a possibly significant health concern for football players and other athletes experiencing multiple subconcussive head impacts, and an alarming number of disabling brain injuries and deaths occurring among athletes at all competitive levels have been reported extensively by the news media, creating a high level of public awareness. Congressional committees have held hearings soliciting testimony from medical experts and National Football League officials.
The level of concern has resulted in the issuance of “concussion policies” by various sport leagues and associations and the passage of “concussion legislation” by well-intentioned state and local legislators who, unfortunately, often lack expertise concerning concussion science and the realities of sports competition at different levels existing in local communities. Unforeseen results of these policies and laws may create new threats to competitive athletes and sports event organizers that may result in failure to report head injuries when they occur and loss of opportunity for athletes related to fears of tort liability. Additionally complex incident reporting requirements and “one approach fits all” management mandates that are impossible to fulfill causes confusion and additional expense, especially for high school and community-based junior league sponsors.
Herein we consider the important question of “when to approve athletes to return to play (RTP) following a sport-related concussion” (or minimal traumatic brain injury (mTBI)). Discussion of the chronic effects of subconcussive head impacts not resulting in diagnosed concussion that have been suggested as causing degenerative brain disease (chronic traumatic encephalopathy) many years later (15) will not be undertaken as the results from pertinent scientific studies are still too fragmentary for firm conclusions to be reached.
For many years, various grading systems for the severity of mTBI were utilized to recommend RTP guidelines. These were discarded gradually with the most recent international concussion expert consensus conference recommending that the simplest grading system (simple vs. complex concussion) be abandoned “as the panel felt that the terminology itself did not fully describe the entities” (13).
While concussion was defined recently (13) as “a complex pathophysiological process affecting the brain, induced by traumatic biomechanical forces,” this phrase may be translated more simply as “a brain injury resulting from a head incident.” Many physicians who treat sport-related mTBI believe that the term “concussion” is a rather neutral-sounding expression that diminishes the medical significance of the occurrence. We believe that brain injury is a more appropriate term to describe the entity. By using this term, we hope to alert athletes, parents, coaches, and administrators that a concussion is not “just a ding” but rather a significant injury requiring thoughtful care and management.
The answer to the question posed above (“when to approve an athlete to RTP following a sport-related concussion?”) is straightforward. No definite evidence exists to support a specific decision.
Factors contributing to this lack of certainty include the following:
- 1. A concussed athlete is not a laboratory animal with uniform genetic, age, gender, diet, medication, and environmental background features and identical trauma history and experience. Therefore every brain-injured individual differs from all others in many ways that are not apparent to the treating clinician. Genetic factors include variants of the ApoE gene, present in some people, which may predispose to brain injury or more severe consequences of injury (19). Younger athletes (8) and females (7) seem to be more affected severely by concussions. Football players with diagnosed learning disability seem to fare worse than others (2). In addition, 2% to 4% of collegiate athletes are treated with amphetamines for attention deficit disorder, 10% to 20% frequently consume alcohol by binge drinking (14), and 20% to 30% smoke marijuana regularly (10). These confounders affecting brain function influence response to brain injury in unpredictable and as yet poorly understood ways. Finally many athletes already have experienced prior diagnosed concussions, sometimes multiple, before entering college, and many others, suffering their first episode in college, will volunteer that they had similar prior undiagnosed episodes in high school or junior league competition.
- 2. No simple and accurate test exists to confirm that a given “head incident” has resulted in a concussion. The diagnosis depends upon the clinical interpretation of consequent symptoms and signs by a responsible medical professional.
- 3. Serial computerized neuropsychological testing at “baseline” and at intervals following a concussion has been utilized for 10 years in an attempt to provide a simple and available “concussion test” for all injured athletes. While judicious application of neuropsychological testing may inform concerning the effects of mTBI on individual athletes, this approach unfortunately has failed tests of accuracy and validity (9,18) and cannot be used to determine the interval for RTP since psychometric measures do not correlate with measurements of persistent brain injury.
- 4. Additionally every treating clinician differs from others relative to knowledge base, experience, and individual biases toward illness, injury, and the significance of the sport experience. He or she also may be exposed to differing pressures from athletes, parents, coaches, and administrators.
- 5. The time required for healing of the brain injury postconcussion is currently undefined. This issue will be considered further below.
For several decades, athletes were allowed to RTP postconcussion when they felt able to participate. With this management paradigm, it was reported that 15% of National Football League players returned to play “immediately” after a diagnosed concussion, 32% returned during the same game, while more than 90% returned to compete within 7 d (16). This practice apparently reflected the athletes’ tolerance for unpleasant symptoms and the pressures to RTP, both self-imposed and externally imposed by coaches and peers. During this period, it also became customary for high school and college athletes to RTP within 7 d. Not surprisingly, this interval coincided with the next scheduled football game. In my experience, many coaches, athletes, and administrators still expect that a concussed athlete should return to full play in 1 wk.
While this management paradigm lacks scientific validity, experience has shown that, for many concussed athletes, most symptoms have resolved by 7 d postinjury, and that upon RTP, they are able to perform their sport adequately. Since we know that many athletes are able to “function” on the field within 1 wk following injury, it follows that widely used functional performance tests (i.e., balance, neuropsychological, exercise stress, and reaction times) probably normalize within a similar interval, and they do (11). However a normal result on performance testing does not equate with healing of a brain injury.
Pertaining to this issue, unfortunately, no simple, affordable, and widely available tests exist to answer the critical question of time of healing after a brain injury. Nevertheless complex tests available mainly in research settings have been developed and utilized to evaluate sport-related brain injury and to estimate its duration. These techniques include electronic recordings of evoked brain wave activity (4,5,17), multitask effects on balance (22), transcranial magnetic spectroscopic measurements of brain metabolites (6,21,20), positron emission tomographic measurements of energy metabolism (1), and functional magnetic resonance imaging and diffusion tensor imaging of injured brain regions (3,6). Without a lengthy consideration of the complexities of these procedures, their results when summarized indicate that healing of brain damage is generally not complete within 4 wk after concussive injury.
The divide between the RTP time interval of 7 d resulting from “usual and customary” application of consensus guidelines that largely are based on symptoms resolution and functional tests and the evidence from the various measurements of brain healing cited above that injury effects persist for four or more weeks is disturbing. Both clinical and experimental evidence has shown that the risk of experiencing a second concussion and the consequences of a second episode are greatest within the 2 wk following a first episode. These consequences can include rapid uncontrolled brain swelling resulting in death (second impact syndrome) (12). Although occurring very rarely, the result is catastrophic. No responsible medical practitioner advocates returning a brain-injured patient to a situation involving significant risk of another brain injury prior to healing of the original trauma. Nevertheless this is precisely the circumstance existing when the most recent consensus RTP guidelines are followed.
With the absent current accessible and affordable technology to determine precisely the time of postconcussion injury healing in individual athletes, we believe that all of the methods for determining extent and persistence of brain injury cited above should be utilized to study different injured cohorts (by age, gender, sport, injury history, etc.) to determine mean and standard deviation intervals for healing of postconcussive brain injury. These results then could be used to provide informed counseling to the vastly larger injured population currently without access to these studies and evidence-based RTP advice to the individual athletes that we serve. Until a stronger evidence base justifying the current practice of starting earlier physical activity progression and RTP after concussion becomes available, adoption of a more conservative approach allowing for longer recovery intervals of 4 to 6 wk appears to be indicated.
The authors declare no conflict of interest and do not have any financial disclosures.
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