The Relationship Between Repeated Subclinical Head Impacts and Electrophysiological Indices of Brain Function

Abstract

Background Concussions occur at a rate of seven million annually within high school athletics, where football is responsible for the largest proportion of these injuries among all sports. Literature suggests that both concussion history and exposure to repeated subclinical head impacts may lead to long term declines in brain function. The length of exposure to result in these effects has mostly been observed in adult athletes using very large (e.g. lifetime) windows of exposure. Objective The objective of the current study is to investigate changes in ERP components across the course of a season of exposure in contact and non-contact groups of high school athletes. The relationship between any potential changes measures in ERP components and repeated subclinical head impacts within the contact sport group will also be elucidated. Methods 24 athletes were included in the study (Twelve football and twelve non-contact athletes). Athletes underwent testing prior to the season, at mid-season and at the end of the season. Eventrelated potential components were calculated during an auditory Go/NoGo task while participants were equipped with a 256 electrode EEG. Football athletes were also equipped with helmets which recorded the magnitude and frequency of impacts over the course of a season. Results Changes in N2 and P3 latency between each athlete type were seen across the course of the season. N2 latency for both athlete types was significantly influenced by the number of previous diagnosed concussions. Within the football athletes, linear impact density was shown to significantly influence changes in P3b that occurred across the season. This measure may help classify contact sport athlete sensitivity to incur concussive injuries. Conclusion The results from this study indicate that contact and non-contact athletes show differential changes in brain components over the course of a season of exposure. Changes within the contact group may be explained in part by the magnitude of head impact metrics incurred over that time.