“PUT ME BACK IN COACH” THE DANGER OF THE REPEAT CONCUSSION

By Rahul Barra and Ashley Chen

Incidence rates of mild traumatic brain injury (mTBI) — namely concussions — remain severely underreported within exclusive reliance on emergency department statistics, due to a litany of factors ranging from poor pediatric diagnosis and delayed symptom onset to medical hesitancy in cases of abuse and occupational injury. Even so, it is estimated that over 2 million mild TBI’s occur annually in the United States alone. With studies increasingly implicating activities with greater frequency or severity of concussions as a significant risk factor for neurodegenerative pathologies, efforts to mitigate the long-term burden of concussions now increasingly center on one particular facet: the timecourse of recovery and potential for re-injury within it.

A concussion describes the phenomenon wherein an external impact or rapid deceleration of the skull results in slight movement of the brain within the surrounding calvaria. Not only can this cause focal bruising of the brain, but the shearing forces produced from this internal rotation is capable of tearing axons from nerve cell bodies, releasing toxic concentrations of neurotransmitters and reactive oxygen species that leave surrounding brain tissue vulnerable to further damage. Symptoms associated with a concussion can vary significantly in degree and type: including such things as acute loss of consciousness, persistent headaches, nausea, light sensitivity, sleep disruption, and balance issues. Accordingly, concussions are generally classified into categories of severity ranging from grade 1 to 3 based on symptom presentation and duration. Importantly, concussions are considered a separate designation from the more acutely dangerous moderate and severe TBI, which often present with abnormal CT structural imaging and significant swelling in the brain. In contrast, concussions are characteristically undetectable by standard CT imaging, with microscopic white matter tract lesions only occasionally picked up by advanced MRI. This is a fact that contributes significantly to the high levels of under-diagnosis associated with the injury, as patients who are relatively symptom-free or have delayed symptom onset underestimate their condition and may re-engage with activities capable of inducing a second, more harmful concussion.

By age group, children and adolescents aged 5 to 24 maintain the largest burden of concussions in the U.S. by a significant margin, and annual concussion rates for adolescents have shown a substantial rise over the last 20 years. This age stratification is partially a result of recreation and sports being among the largest contributing factors for initial and repeat mild TBI at the amateur, collegiate, and pro level. It is estimated that anywhere between 300,000 and 3 million sports-related concussions occur in the U.S. annually, with bicycling, football, basketball, and soccer accounting for the largest percentage of these brain injuries. The potential for repeat concussions is not solely a risk factor associated with athletics, however. Military service, domestic violence, compounding diseases with associated fall risks, and substance abuse have all also shown significant correlation with repeat head injury. However, particular focus has been placed on brain injuries in athletics for its outsized role in re-injury potential and seemingly greater capacity for substantial reform.

While an initial concussion can be dangerous by itself in potentially contributing to prolonged issues with cognition and focus past the typical recovery period of 16-29 days, subsequent follow-up concussions have been linked to significantly worse prognosis in both the short and long-term — particularly when a second concussion occurs before the prior recovery period is finished. Multiple studies have now shown that athletes and other individuals with a history of past concussions present more symptoms and have longer recovery times following each new concussion, regardless of time since prior injury. For even minor second head injuries sustained before symptoms from a previous concussion subside, a generally fatal condition known as Second Impact Syndrome (SIS) can occasionally occur due to rapid brain swelling. In the long-term, suffering multiple concussions in early life has increasingly been shown to be associated with persistent deficits in memory, concentration, balance, and chronic traumatic encephalopathy (CTE). It should be noted that the evidence is still not definitive on the role of repetitive sub-concussive events (impacts that do not meet the criteria of a full concus- sion) in long-term issues like CTE. Nonetheless, the comparative danger of multiple concussions over a single concussive event in life is now largely irrefutable - with particular concern in situations where initial concussions may go undiagnosed and untreated. Efforts to improve brain injury safety among athletes have shifted to focus largely on two specific areas in recent years: more robust prevention protocols and more rapid diagnostic abilities. From a preventative standpoint, programs like the Center for Disease Control’s HEADS UP initiative, in conjunction with schools and professional leagues, have focused on improvements in such things as protective equipment design, player-to-player contact protocols, and education of coaches and players. Moreover, all 50 states have now passed concussion legislation focusing on head injury education, removing athletes from same-day play following head impacts, and requiring clearance from a healthcare professional trained in concussion management for players to return. From the diagnostic point of view, one particularly exciting new advancement in the field has been the development of hand-held, rapid blood tests for detecting TBI on-site. Such tests rely on detection of specific protein markers associated with TBI in the blood, and have shown surprisingly few false negative results in clinical trials. Used in tandem with more traditional systems of diagnosis like patient questioning and visual exam, these advancements have the potential to dramatically increase rates of identifying concussions in a player that otherwise would have gone undiagnosed. In doing so, the long-term and acute risks associated with repeat concussions can be partially mitigated by ensuring athletes do not return to play while recovering from even a mild prior concussion.

An at-times simultaneously controversial, widely prevalent, and under-discussed issue, continuing to confront mild traumatic brain injuries - and specifically, unnecessary cases of repeat concussion - in the areas of daily life where they most occur via new preventative, diagnostic, and therapeutic techniques, is thus an effort both littered with many hurdles and replete with extraordinary necessity.

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What does concussion do to the brain? (1525844700). https://qbi.uq.edu.au/ blog/2018/05/what-does-concussiondo-brain

What happens to the brain during a concussion? (n.d.). Scientific American. from https://www.scientificamerican.com/article/what-happens-to-thebrain/

Albano, A. W., Jr, Senter, C., Adler, R. H., Herring, S. A., & Asif, I. M. (2016). The Legal Landscape of Concussion Sports Medicine Providers.