Background: Little is known about the effect of repetitive head impact exposure (RHIE) on adolescents, who are in a period of tremendous brain maturation and for whom neuronal damage during development might be deleterious. While imaging and blood-based biomarkers provide insight into the mechanistic underpinnings of brain function after RHIE, they are not feasible for repeated monitoring. More accessible metrics are needed. Oculomotor and autonomic biomarkers have shown sensitivity to RHIE however there are limited data on youth and when present, are limited mostly to football. Hypothesis: Oculomotor/autonomic measures of neurofunction would be sensitive to elevated RHIE in male high school lacrosse players. Methods: A prospective observational study of a male varsity high school lacrosse team was conducted. Players wore the Prevent Biometrics impact monitoring mouthguard (IMM) during six competitive games over 20 days. Weekly and at the beginning/end of the study, players were assessed via a pupillometer measuring the pupillary light reflex (PLR) and a visio-vestibular exam (VVE) measuring oculomotor and vestibular function. Each game was filmed with 2+ cameras, time-synchronized with the IMM data. For periods of live play, the players on the field were recorded, to time-window the IMM data and classify head acceleration events (HAE). HAEs per player hour were calculated for each player, and players were categorized into 4 quartiles according to impact count. The change in PLR and VVE outcomes from pre-study to post-study were examined for each HAE quartile. Results: Sixteen high school lacrosse players were enrolled in the study. Sixty-four HAEs were recorded from 87 athlete-exposures (34.17 player-hours) for a rate of 1.87 HAEs per player-hour. The mean (standard deviation) for peak linear acceleration, angular velocity and angular acceleration were 11.0 (6.1) g, 804 (699) rad/s2 and 5.3 (3.9) rad/s, respectively. Data from an exemplar game (Fig 1) are shown below. Post study, more athletes trended towards an abnormal near point of convergence (NPC) (6/14 vs 2/14 pre-study) and a slowed pupillary dilation velocity (Table 1), however these deficits did not correlate with HAE count quartile. Conclusion: This study suggests subtle changes in oculomotor and autonomic function are present after a concentrated period of lacrosse games. The lack of correlation with HAE count quartile suggests further study is needed using more complex impact exposure measures (i.e. cumulative severity).
Arbogast et al. (Mon,) studied this question.