Top Five Issues in Sports Neurology

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Sports neurology remains an evolving field with wide-reaching implications for multiple medical disciplines. Arguably, no subspecialty is more topical to ongoing debates within the realms of neurology and popular culture. Despite recent strides made within the field, much remains unknown. With a plethora of issues currently being debated in the field of sports neurology, I provide you my top 5.

1. Youth sports
An emerging body of research suggests that repetitive, subconcussive head impacts play a larger role than concussive injury itself in risk of neurocognitive dysfunction later in life.^1-3 Out of concern for these repetitive head traumas and subsequent risk of chronic neurocognitive impairment, all college power-5 football conferences and the majority of state high school athletic associations now have legislated limits on full-contact practices. Two-a-day practices, once a staple of American football, are now a rarity. These formal mandates extend beyond high level sports and into youth leagues.

No fewer than 4 state legislatures have submitted bills banning tackle football for children aged younger than 14 years. This paradigm shift occurs on the backdrop of US Soccer’s 2016 total ban on heading for players aged younger than 11 as well as a partial ban for those in U-12 and U-13 programs. Not surprisingly, this has sparked an emotional debate from detractors on both sides of the contact-exposure issue. Regardless of viewpoint, the ripple effect is now reaching youth sports in earnest, and will continue to do so well beyond 2018.

2. Chronic traumatic encephalopathy
A list of top issues within sports neurology would certainly not be complete without a reference to chronic traumatic encephalopathy. Players-both active and potential-continue to steer away from participation in collision sports. Rule changes, as those referenced above, continue to be enacted to decrease exposure to repetitive head impacts, a presumed precursor to chronic traumatic encephalopathy.

In late 2017, researchers published the first case of the degenerative brain disease being identified in a living person.⁴ Specifically, [F-18]FDDNP-PET binding levels correlated with brain tau deposition within regions later confirmed upon neuropathologic examination at autopsy. Despite the excitement created from this discovery, future studies are warranted to determine whether this specialized imaging may be valid and reliable in establishing a diagnosis of chronic traumatic encephalopathy in at-risk patients. Until then, sports medicine personnel must remain diligent in clearly communicating the risks and benefits to those participating in high risk sports.

3. Impending effect of CGRP receptor antibodies
2018 is sure to be an exciting time in the world of migraine with 3 CGRP receptor antibodies having recently completed phase 3 studies. All 3 have subsequently submitted their formal New Drug Application to the FDA. As these compounds approach formal FDA approval and clearance for use in the US, the treatment of migraine with anti-CGRP antibodies may also provide a viable off-label approach in the setting of acute post-traumatic headache.

There remains very little evidence to support specific medical management in sport-related concussion, including the treatment of associated post-traumatic headache. There are no available data from RCTs evaluating specific medical interventions or their therapeutic efficacy in the treatment of post-traumatic headache (in athletes or otherwise). In these new migraine-derived compounds, might we discover the first athlete cohort in which a specific treatment intervention definitively reduces risk of refractory symptoms attributed to sport-related concussion? Ultimately, time will tell; however, rest assured, researchers anxiously await the opportunity to explore this next frontier of sports neurology.

4. Concussion protocols
The 2017-18 NFL season allowed for further media scrutiny on certain cases of suspected “concussion protocol” breaches. This media spotlight reached critical mass with the cases of Tom Savage and Russell Wilson. However, one must look at the larger picture in its entirety when dealing with an ever-changing injury such as sport-related concussion. The NFL’s Chief Medical Officer, Alan Sills, reported that over 600 concussion screens were performed during the 2017-2018 regular season.⁵ Of these, 3 (or fewer than .005%) came under formal review by the league office. The league should be credited for having what is arguably the most transparent protocol on public record, available for all to see and provide feedback.⁶

Sideline protocols for injury triage, however, are but one component of concussion rehabilitation and return-to-play progression. The graduated return-to-play progression remains the hallmark of concussion management in the days to weeks following injury. Notable studies have identified increased risks of lower extremity injury following return to play after sport-related concussion.^7,8 Might functional movement screens, performed pre-clearance, one day be incorporated into formal return-to-play protocols? If further studies confirm the risk of lower extremity injury, this could potentially be another paradigm shift that occurs in the active management of sport-related concussion.

Lay media reports recently portrayed-inaccurately-the newly approved testing of serum biomarkers following traumatic brain injury.⁹ Specifically, the proteins GFP and UCHL1 are now commercially available to screen for the likelihood of blood being present on neuroimaging following head trauma. To be clear, this is not a test for concussion; but rather, a test to rule out other clinical entities beyond the clinical syndrome of concussion. Regardless of its intended use at present, could the monitoring of such biomarkers one day play a formal role in the return-to-play progression? Although immediate use of these measures in sideline decision making is unlikely, this remains another area of active concussion management sure to evolve in upcoming years.

5. Weight-cutting in combat sports
Combat sports-medicine physicians remain gravely concerned over the increased occurrence and popularity of weight-cutting. In an attempt to obtain a competitive advantage within their respective weight class, many participants acutely reduce body mass and weight through a process known as “weight-cutting.” This potentially provides an advantage by being the larger and stronger combatant while competing against lighter, weaker, and smaller opponents. In response to such situations and an overriding concern for fighter health and safety, the California State Athletic Commission in April of 2017 proposed an ambitious plan to address these concerns.

In addition to recognized cardiac and renal consequences, the concern for acute and chronic brain injury is also heightened in the context of acute dehydration. Neurologic implications within rapid weight loss are multiple, including compensatory brain atrophy, psychomotor slowing, and possible increased risk of concussion.¹⁰ Unfortunately, negative effects of weight-cutting tactics can significantly skew the accuracy of clinical concussion assessments.

Furthermore, much like other realms of sports concussion research, there is a tremendous paucity of data showing a causative link of acute dehydration and increased risk of concussive injury. Clearly more information is needed to definitively establish an evidence-based association; however, until such data are available, clinicians should continue to utilize best-practice medicines, and operate under the assumption of acute dehydration lowering the threshold for concussion.

Conclusion
Dedication from all practitioners is necessary for the consummate protection of the central and peripheral nervous systems in athletes. This context extends far beyond sports concussion, although this remains the most prominent injury. It is reported that 103 million viewers tuned in to this year’s Super Bowl.¹¹ There is no doubt that many of the viewers were aware of the ongoing debate of head trauma within contact and collision sports.¹¹ As the popularity of other sports continues to grow, so does our role as sideline, training room, and traditional outpatient care providers.

References:

1. Talavage T, Nauman E, Breedlove E, et al. Functionally-detected cognitive impairment in high school football players without clinically-diagnosed concussion. J Neurotrauma. 2014;31:327-338.
2. Abbas K, Shenk TE, Poole VN, et al. Effect of repetitive sub-concussive brain injury on the functional connectivity of default mode network in high school football athletes. Develop Neuropsych. 2015;40:51-56.
3. Tagge CA, Fisher AM, Minaeva OV, et al. Concussion, microvascular injury, and early tauopathy in young athletes after impact head injury and an impact concussion mouse model. Brain. 2018;141:422-458.
4. Omalu B, Small GW, Bailes J, et al. Postmortem autopsy-confirmation of antemortem [F-18] FDDNP-PET scans in a football player with chronic traumatic encephalopathy. Neurosurg. 2017;82:237-246.
5. Seifert, K. NFL to have four independent concussion specialists at Super Bowl. http://www.espn.com/nfl/story/_/id/22268031/nfl-four-independent-concussion-specialists-super-bowl. Accessed March 8, 2018.
6. NFL Head, Neck and Spine Committee. Concussion diagnosis and management protocol. https://www.playsmartplaysafe.com/wp-content/uploads/2017/06/2017-nfl-concussion-protocol.pdf. Accessed March 8, 2018.
7. Lynall RC, Mauntel TC, Padua DA, et al. Acute lower extremity injury rates increase after concussion in college athletes. Med Sci Sports Exercise. 2015;47:2487-2492.
8. Gilbert FC, Burdette GT, Joyner AB, et al. Association between concussion and lower extremity injuries in collegiate athletes. Sports Health. 2016;8:561-567.
9. Kaplan S, Belson K. Concussions can be detected with new blood test approved by FDA. https://www.nytimes.com/2018/02/14/health/concussion-fda-bloodtest.html. Accessed March 8, 2018.
10. Seifert TD. Neurologic health in combat sports. Neurol Clin. 2017;35:523-535.
11. Pallota F. Super Bowl ratings are down, but 103 million people watched. http://money.cnn.com/2018/02/05/media/super-bowl-ratings/index.html. Accessed March 8, 2018.