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Concussion Research: Why We Should Back Up Before We Move Forward!

Gammons, Matthew MD

doi: 10.1249/JSR.0000000000000347
Invited Commentaries

Sports Concussion Program, Vermont Orthopaedic Clinic, Rutland Regional Medical Center, Rutland, VT

Address for correspondence: Matthew Gammons, MD, Vermont Orthopaedic Clinic, 3 Albert Cree Drive, Rutland, VT 05701; E-mail:

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Concussions and head injuries continue to be of great concern to athletes and to the general public. A steady stream of research articles flows out of the journal pipeline monthly causing a frenzied response from the media who report their often incomplete interpretation of the findings. While concussion research is extremely important, this mass of information has created confusion amongst health care providers, athletes, parents, and coaches. Any quick Internet search provides a wide variety of sources with significant variation in recommendations and information about head injuries and concussions. Recommendations about baseline testing and post injury rest, for example, have gone back and forth in recent guidelines, highlighting our lack of overall progress on the identification, management, and treatment of concussion (4,5,8,9).

We, the sports medicine community, may have swung the pendulum too far in our approach to athletes with suspected concussion injuries. Why did this happen? Going back more than 100 yr physicians knew that putting a player back into a game with signs of concussion was not a good idea. By the middle of the last century, we had somehow forgotten our past. Fortunately, the sports medicine community woke up and realized again that we should not allow athletes back into competition until they have recovered from their concussions. We also began to once again educate coaches, players, and athletes on the potential dangers of concussion.

As we reengaged the athletic community, we found resistance to the idea of denying athletes the opportunity to play based on a “ding,” which we had allowed before our reawakening. In response to the resistance, we started to yell louder and push harder, creating guidelines and pushing legislation to protect our young athletes. Couple that with an explosion in technology and communication; a “crisis” was created, leading Hollywood to join the party. While one might think all this attention to the potential short- and long-term risk associated with head injuries would be positive, and some of it is, there is the cost of creating unnecessary anxiety, rules and regulation, lawsuits, and confusing, and perhaps unrealistic, recommendations (2,12). This anxiety has even led to the tragedy of a professional athlete taking his own life because of concerns of chronic traumatic encephalopathy (13). Within this swirl of confusion, concussion has become a “not miss” condition. Health care providers are quick to diagnose the condition and warn of its potential complications, often without understanding the true evidence we have for diagnosis, treatment, and outcomes.

The pathophysiology of concussion is a classic example of information being taken as good science when the reality is quite different. In a recent review article addressing concussion, a majority of the referenced articles that described the pathophysiology were based on either animal models or moderate to severe brain injury patients (1). Additionally, most of the animal models use a drop or impact test to create a “concussive injury.” Given our current understanding that impact (i.e., linear forces) may play less of a role in concussive injuries than acceleration/deceleration forces put these models in doubt. This, coupled with the lack of correlation between force measurements and concussive injuries, makes it difficult to know if we are truly imparting the same injury on the animals that we are trying to diagnose and treat in humans. Given the wide variation of concussion presentation and recovery, it may be that among brain injured athletes some may conform to the current model, while others may not.

Confounding injuries also pose a large problem in the diagnosis and management of concussion. Most confusing is the acute post-traumatic headache that is reportedly the most common symptom of concussion (5,8,9). Because brain cells do not contain nociceptors and nontraumatic headaches are common, it would seem odd that we consider this a primary sign of brain injury. One could argue that in concussion the brain may not interpret the signal correctly, but the brain cells still cannot be the primary pain generator. Given that many post-traumatic headaches meet criteria for migraine it is highly likely that at times we are confusing brain injury with post-traumatic migraine (3,7,11). Additionally, whiplash injuries occur with similar forces, and the symptoms have significant overlap with those commonly associated with concussion (2).

So how do we move forward? We can only move ahead by first taking a step back. Rather than relying on our clinical definition of concussion with no criterion standard for diagnosis, we need to operationalize our definition of concussion utilizing standardized research evaluation of concussion (12). This change would allow us to better understand what “truly” constitutes trauma to the brain. In addition, a standardized research evaluation may allow us to also assess what injuries within the scope of brain trauma constitute higher risk and account for other conditions that may mimic or copresent with concussion. Because most current concussion research does not use well-defined inclusion criteria to determine who has sustained a concussion, our ability to interpret results from even methodologically sound studies is suspect.

Studies also have shown that recall alone is not adequate to determine an accurate concussion history and while these studies focused mostly on underreporting, the likelihood of overreporting is equally high given the complexities associated with the diagnosis of concussion (6,10). Given much of our early cornerstone research relied on recall along with the large variation in study populations, there is significant potential that our baseline assumptions about these brain injuries are incorrect.

This research will take time so what do we do clinically for our patients to bridge this knowledge gap?

  • We should advise athletes to remove themselves from activity for symptoms that could be a concussion and to make sure they recover fully from a concussive injury before returning to high-risk activities.
  • We should acknowledge that there are real limitations in our ability to definitively diagnose these injuries and communicate well with athletes, parents, and coaches why we are taking our current approach.
  • We should inform athletes and the public that by using the above plan that most individuals will recover well without short-term or long-term consequences.
  • We should not be afraid to treat an athlete conservatively without labeling him or her with a concussion when the diagnosis is not clear, understanding that there are consequences to overdiagnosis as well.
  • We should do our best to identify other injuries/conditions that may present like concussion or with concussion.
  • We should direct treatment at these injuries knowing this will likely remain an imperfect science with risks of both overdiagnoses and underdiagnoses, even with more research.

Finally, and most importantly, we should treat each athlete with a suspected or diagnosed concussion individually; evaluating all of the variables when formulating a treatment plan to maximize the chance of a correct diagnosis and good outcome while minimizing the risks associated with underdiagnosis and overdiagnosis.

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