Methodology of the INVestigating traIning assoCiated blasT pAthology (INVICTA) study.

BACKGROUND: Subconcussive blast exposure during military training has been the subject of both anecdotal concerns and reports in the medical literature, but prior studies have often been small and have used inconsistent methods. METHODS: This paper presents the methodology employed in INVestigating traIning assoCiated blasT pAthology (INVICTA) to assess a wide range of aspects of brain function, including immediate and delayed recall, gait and balance, audiologic and oculomotor function, cerebral blood flow, brain electrical activity and neuroimaging and blood biomarkers. RESULTS: A number of the methods employed in INVICTA are relatively easy to reproducibly utilize, and can be completed efficiently, while other measures require greater technical expertise, take longer to complete, or may have logistical challenges. CONCLUSIONS: This presentation of methods used to assess the impact of blast exposure on the brain is intended to facilitate greater uniformity of data collection in this setting, which would enable comparison between different types of blast exposure and environmental circumstances, as well as to facilitate meta-analyses and syntheses across studies.

Mitigating the Consequences of Subconcussive Head Injuries.

Subconcussive head injury represents a pathophysiology that spans the expertise of both clinical neurology and biomechanical engineering. From both viewpoints, the terms injury and damage, presented without qualifiers, are synonymously taken to mean a tissue alteration that may be recoverable. For clinicians, concussion is evolving from a purely clinical diagnosis to one that requires objective measurement, to be achieved by biomedical engineers. Subconcussive injury is defined as subclinical pathophysiology in which underlying cellular- or tissue-level damage (here, to the brain) is not severe enough to present readily observable symptoms. Our concern is not whether an individual has a (clinically diagnosed) concussion, but rather, how much accumulative damage an individual can tolerate before they will experience long-term deficit(s) in neurological health. This concern leads us to look for the history of damage-inducing events, while evaluating multiple approaches for avoiding injury through reduction or prevention of the associated mechanically induced damage.

Effects of Fish Oil on Biomarkers of Axonal Injury and Inflammation in American Football Players: A Placebo-Controlled Randomized Controlled Trial.

There are limited studies on neuroprotection from repeated subconcussive head impacts (RSHI) following docosahexaenoic acid (DHA) + eicosapentaenoic acid (EPA) supplementation in contact sports athletes. We performed a randomized, placebo-controlled, double-blinded, parallel-group design trial to determine the impact of 26 weeks of DHA+EPA supplementation (n = 12) vs. placebo (high-oleic safflower oil) (n = 17) on serum concentrations of neurofilament light (NfL), a biomarker of axonal injury, and inflammatory cytokines (interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-a)) in National Collegiate Athletic Association Division I American football athletes. DHA+EPA supplementation increased (p < 0.01) plasma DHA and EPA concentrations throughout the treatment period. NfL concentrations increased from baseline to week 26 in both groups (treatment (<0.001); placebo (p < 0.05)), with starting players (vs. non-starters) showing significant higher circulating concentrations at week 26 (p < 0.01). Fish oil (DHA+EPA) supplementation did not mitigate the adverse effects of RSHI, as measured by NfL levels; however, participants with the highest plasma DHA+EPA concentrations tended to have lower NfL levels. DHA+EPA supplementation had no effects on inflammatory cytokine levels at any of the timepoints tested. These findings emphasize the need for effective strategies to protect American football participants from the effects of RSHI.

Heading in the Right Direction: A Critical Review of Studies Examining the Effects of Heading in Soccer Players.

The practice of heading in soccer has become a public concern because of the potential for subconcussive impacts to cause cumulative concussive-like effects; however, experimental evidence for this hypothesis has been mixed. This systematic review used pre-defined search parameters to assess primary literature that examined changes in cognitive, behavioral, structural, and/or biological processes after acute heading exposure in youth and young adult soccer players. The findings were synthesized into a concise and comprehensive summary of the research following the preferred reporting items for systematic reviews and meta-analyses (PRISMA) format, and suggestions for standardization of acute heading protocols are described. A total of 1189 articles were considered for this review, with 19 articles meeting all of the inclusion criteria for full analysis. An attempt was made to identify methods with significant sensitivity and reliability by grouping studies based on their outcome measures. Because of lack of standardization across intervention types and data collection protocols, no sensitive and reliable methods could be identified conclusively to assess the effects of acute heading exposure in soccer players. Based on this review, there is not enough evidence to either support or refute the potential of effects of subconcussive events from acute soccer heading exposure. Recommendations for standardization of acute heading exposure studies based on the included literature are discussed. Standardization is required to better understand the impact of acute heading exposure in soccer players, while allowing for the development of guidelines that mitigate any potential risks and allowing athletes to remain active and develop their skills.

Accumulation of high magnitude acceleration events predicts cerebrovascular reactivity changes in female high school soccer athletes.

Mitigating the effects of repetitive exposure to head trauma has become a major concern for the general population, given the growing body of evidence that even asymptomatic exposure to head accelerations is linked with increased risk for negative life outcomes and that risk increases as exposure is prolonged over many years. Among women's sports, soccer currently exhibits the highest growth in participation and reports the largest number of mild traumatic brain injuries annually, making female soccer athletes a relevant population in assessing the effects of repetitive exposure to head trauma. Cerebrovascular biomarkers may be useful in assessing the effects of repetitive head trauma, as these are thought to contribute directly to neurocognitive symptoms associated with mild traumatic brain injury. Here we use fMRI paired with a hypercapnic breath hold task along with monitoring of head acceleration events, to assess the relationship between cerebrovascular brain changes and exposure to repetitive head trauma over a season of play in female high school soccer athletes. We identified longitudinal changes in cerebrovascular reactivity that were significantly associated with prolonged accumulation to high magnitude (> 75th percentile) head acceleration events. Findings argue for active monitoring of athletes during periods of exposure to head acceleration events, illustrate the importance of collecting baseline (i.e., pre-exposure) measurements, and suggest modeling as a means of guiding policy to mitigate the effects of repetitive head trauma.

Dependence on subconcussive impacts of brain metabolism in collision sport athletes: an MR spectroscopic study.

Long term neurological impairments due to repetitive head trauma are a growing concern for collision sport athletes. American Football has the highest rate of reported concussions among male high school athletes, a position held by soccer for female high school athletes. Recent research has shown that subconcussive events experienced by collision sport athletes can be a further significant source of accrued damage. Collision sport athletes experience hundreds of subconcussive events in a single season, and these largely go uninvestigated as they produce no overt clinical symptoms. Continued participation by these seemingly uninjured athletes is hypothesized to increase susceptibility to diagnoseable brain injury. This study paired magnetic resonance spectroscopy with head impact monitoring to quantify the relationship between metabolic changes and head acceleration event characteristics in high school-aged male football and female soccer collision sport athletes. During the period of exposure to subconcussive events, asymptomatic male (football) collision sport athletes exhibited statistically significant changes in concentrations of glutamate+glutamine (Glx) and total choline containing compounds (tCho) in dorsolateral prefrontal cortex, and female (soccer) collision sport athletes exhibited changes in glutamate+glutamine (Glx) in primary motor cortex. Neurometabolic alterations observed in football athletes during the second half of the season were found to be significantly associated with the average acceleration per head acceleration events, being best predicted by the accumulation of events exceeding 50 g. These marked deviations in neurometabolism, in the absence of overt symptoms, raise concern about the neural health of adolescent collision-sport athletes and suggest limiting exposure to head acceleration events may help to ameliorate the risk of subsequent cognitive impairment.

Every hit matters: White matter diffusivity changes in high school football athletes are correlated with repetitive head acceleration event exposure.

Recent evidence of short-term alterations in brain physiology associated with repeated exposure to moderate intensity subconcussive head acceleration events (HAEs), prompts the question whether these alterations represent an underlying neural injury. A retrospective analysis combining counts of experienced HAEs and longitudinal diffusion-weighted imaging explored whether greater exposure to incident mechanical forces was associated with traditional diffusion-based measures of neural injury-reduced fractional anisotropy (FA) and increased mean diffusivity (MD). Brains of high school athletes (N = 61) participating in American football exhibited greater spatial extents (or volumes) experiencing substantial changes (increases and decreases) in both FA and MD than brains of peers who do not participate in collision-based sports (N = 15). Further, the spatial extents of the football athlete brain exhibiting traditional diffusion-based markers of neural injury were found to be significantly correlated with the cumulative exposure to HAEs having peak translational acceleration exceeding 20 g. This finding demonstrates that subconcussive HAEs induce low-level neurotrauma, with prolonged exposure producing greater accumulation of neural damage. The duration and extent of recovery associated with periods in which athletes do not experience subconcussive HAEs now represents a priority for future study, such that appropriate participation and training schedules may be developed to minimize the risk of long-term neurological dysfunction.