Examination of head impacts and abnormal imagery in young football players in consecutive seasons




Imaging data from two football athlete subjects showing a comparison between the season’s abnormal voxels with the highest 50th percentile of impacts per training session and the season’s abnormal voxels with the lowest 50th percentile of impacts per workout. The season with the lowest impact frequency in training sessions was associated with fewer abnormal voxels compared to the season with higher impact frequency in training sessions for both athletes. Credit: Copyright 2021 AANS.

In this longitudinal study, researchers at the Wake Forest School of Medicine and the University of Texas Southwestern in Dallas, Texas, examined the frequency and severity of head impacts experienced by young football players and how the exposure to head impacts changes from year to year in returning players. The researchers then compared the data obtained with the results of neuroimaging studies obtained in consecutive years in the same athletes. The comparison demonstrated a significant positive association between changes in head impact exposure (HIE) parameters and changes in abnormal results on brain imaging studies. Full details of this study can be found in the article “Analysis of Longitudinal Head Impact Exposure and White Matter Integrity in Young Returning Football Players” by Mireille E. Kelley , PhD, and colleagues, published today (June 15, 2021) in the Journal of Neurosurgery: Pediatrics.

Illustrating the considerable variability in head impacts among soccer players, Kelley et al. inform us that during a football season, young football players (10-13 years old) can suffer between 26 and 1003 hits to the head, and high school players can take between 129 and 1258 hits to the head . Fortunately, most of these impacts do not result in concussions. In fact, most of these sub-concussion impacts do not produce any acute signs or symptoms attributed to concussions.

Nonetheless, there is concern that over time, repetitive sub-concussion impacts could damage the brains of contact sports athletes. This is of particular concern when we are talking about young athletes, who have many years ahead of them in their sport and in their life.

To examine changes in Head Impact Exposure (HIE) from year to year, the researchers focused on a group of 47 athletes who participated in youth football for two or more consecutive years. between 2012 and 2017. The athletes played in various teams. All wore football helmets equipped with the Riddell Head Impact Telemetry System â„¢, which measures the linear and rotational accelerations of the head that occur during a head impact. The fitted helmets were worn during all football sessions, both practices and matches. Biomechanical head impact data was transmitted in real time via radio waves to a marginal data collection field unit for further analysis. In total, the data covered 109 seasons of football athletes with 41,148 head hits. Despite the large number of head impacts, none of the 47 young athletes suffered a clinically diagnosed concussion during the study period.

Kelley et al. examined a variety of HIE parameters: number of head hits, 50th percentile of hits per football session (game, practice and both); Maximum linear and rotational accelerations at the 95th percentile measured by the Head Impact Telemetry System â„¢; and cumulative risk-weighted exposure, a measure summarizing the frequency and magnitude of head impacts experienced by the athlete in a single season. The researchers found that variations in HIE measurements differed from year to year and between athletes. For example, in a review of data from three consecutive seasons, some young people suffered more impacts in their second year of play than in their first, while other young people suffered less impacts in their second year of play. last years of play.

Although trends of increasing average number of match impacts, the average 50th percentile of impacts per football session, and the average 50th percentile of impacts per match session were identified over three seasons, the differences between the averages were not statistically significant. The researchers noted “significant variability in several HIE metrics between teams,” but that was not the focus of this study.

In 19 of the 47 young football athletes, brain images were obtained before and after the season for two consecutive football seasons. This was done using diffusion tensor imaging (DTI), a type of magnetic resonance imaging that can be used to assess the integrity of the brain’s white matter, indicating possible sites of injury. Using this technique, the researchers assessed the changes in the following scalar metrics: fractional anisotropy; medium diffusivity; and the linear, planar and spherical anisotropy coefficients.

A group of 16 young athletes who participated in non-contact sports (e.g. swimming, tennis, track and field) underwent two DTI (baseline and follow-up studies, four months apart) and served control group. Abnormal white matter voxels (small three-dimensional areas) on brain images of young football players were defined as voxels in which DTI scalar values ​​increased or decreased significantly throughout the football season (two standard deviations higher or lower than the mean values ​​in the control group).

Similar to the HIE model, the researchers found “both increases and decreases in the number of abnormal voxels between season 1 and season 2” in young football athletes.

Linear regression analyzes were performed to assess the relationships between changes in HIE metrics and changes in DTI scalar metrics from year to year. There was a significant positive correlation between changes in the number of head impacts per workout and each DTI scalar metric. In addition, significant positive correlations were determined between changes in the 50th percentile impacts per training session and the 50th percentile impacts per football session (including training and play sessions) and the various metrics. DTI scalars.

In summary, the main conclusions of this longitudinal study are as follows:

  • HIE varies among individual athletes from season to season. Increases and decreases in the HIE over three consecutive seasons among young football players have been observed; the changes were not significant from season to season.
  • Trends in DTI imaging changes varied between individual athletes from season to season. Increases and decreases in the number of anomalous voxels on DTI from season one to season two have been identified in individual players.
  • The amount of HIE that an athlete experienced in football, especially in practice, was associated with the amount of change in neuroimaging metrics. Positive associations between abnormal voxel changes on DTI and number of head impacts per workout, 50th percentile impacts per workout, and 50th percentile impacts per overall session (including training and play) between consecutive seasons (seasons 1 and 2) were found.

Because of the significant positive correlations between changes in HIE metrics and changes in the number of anomalous voxels on DTI between consecutive seasons, the authors support efforts to reduce the number and frequency of head hits, in particular those that occur during workouts, when the majority of head impacts occur. They believe that this action may reduce the number of abnormal imaging results in young football athletes from one football season to the next.

Asked about the results of the study, Dr. Jillian Urban, assistant professor at the Wake Forest School of Medicine, responded: “Our results further support ongoing efforts to reduce the number of head impacts in health care practices. soccer. In an upcoming study, we plan to engage stakeholders in the youth football community to develop and test practical solutions informed by the biomechanical data we collect in the field to reduce head impacts in practice.

Reference: “Analysis of Longitudinal Head Impact Exposure and White Matter Integrity in Young Returning Football Players” by Kelley, ME, Urban JE, Jones DA, Davenport EM, Miller LE , Snively BM, Powers AK, Whitlow CT, Maldjian JA, Stitzel JD, June 15, 2021, Journal of Neurosurgery: Pediatrics.
DOI: 10.3171 / 2021.1.PEDS20586

Drs. Kelley, Urban, Jones, Miller, and Stitzel are affiliated with both the Wake Forest School of Medicine and the Virginia Tech-Wake Forest School of Biomedical Engineering and Sciences in Winston-Salem, North Carolina. Drs. Snively, Powers, and Whitlow are affiliated with the Wake Forest School of Medicine. Drs. Davenport and Maldjian are affiliated with the University of Texas Southwestern in Dallas, Texas.

Disclosure: The authors report no conflicts of interest regarding the materials or methods used in this study or the results specified in this article.

Grant: Three grants from the National Institutes of Health, namely grants R01NS094410 and R01NS082453 from the National Institute of Neurological Disorders and Stroke, and grant KL2TR001421 from the National Center for Advancing Translational Sciences.



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