The effects of subconcussive impacts on white matter integrity in the corpus callosum and corticospinal tracts

Abstract

Over the course of a football season the athletes are subject to a large number of impacts ranging in magnitude. With these impacts failing to cause any clinical signs of concussion, they often get disregarded as non-injurious. Recent evidence shows that the cumulative effects of these impacts may cause microstructural damage within the brain. This study set out to examine the effects of these subconcussive impacts on two specific white matter tracts in the brain: the corpus callosum (CC) and the corticospinal tract (CST). 20 Canadian Univeristy level football players were followed for one season. These players were examined using diffusion tensor imaging at three time points: prior to any team sessions (preseason), following training camp (post-training camp), and following the last session of the season (post-season). Four DTI measures were analyzed: fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD), in order to asses white matter integrity. Players were separated into two groups based on impact exposure throughout the season. Results showed that the high exposure group had significantly lower FA (main effect of Group) in the CC and the bottom-left section of the CST. There was a significant decrease in FA over time in the top section of the left CST. There were no observed changes in MD, AD or RD. The changes found in this study indicate that despite no outward symptoms of injury (SRC), “silent” changes are occurring within the brain’s microstructures as a result of receiving numerous subconcussive impacts during a season of football.