Investigating the effect of subconcussive impact exposure on white matter integrity in collegiate football players

Abstract

Background: Recently, there has been growing concern around subconcussive impacts (SCI) in football and the potential implications on neurologic health. Of particular interest are athletes who undergo repeated exposure to SCI over a single football season. This form of neurotrauma is often overlooked due to lack of observable symptomatology, however previous work has shown evidence of microstructural damage to white matter (WM). Methods: 22 Canadian Collegiate varsity football players were studied over a single competitive season using accelerometers and diffusion tensor imaging (DTI). Accelerometers were used to assess impacts received by each player throughout the season. Imaging was conducted at 3 timepoints (PRE-season; PRE, post-training camp; PTC, POST-season; POST) and probabilistic tractography was used to delineate WM tracts of interest. Changes in WM microstructure were assessed at each time point and between exposure groups (high exposure; HE, low exposure; LE, based on impacts over the season) using the diffusion metrics fractional anisotropy (FA) and mean diffusivity (MD). Results: The HE group had significantly lower FA in the left and right corticospinal tracts (CST), left anterior thalamic radiation (ATR), and left superior thalamic radiation (STR), and higher MD in the left and right CST, left ATR, and left inferior fronto-occipital fasciculus (IFO) compared to the LE group. FA was found to decrease in the LE group from PRE and PTC to POST timepoints in the right posterior thalamic radiation (PTR) and right CST respectively. The HE group had decreased FA from PTC to POST in forceps minor (FMI). MD was found to be significantly decreased from PRE to PTC in the right superior longitudinal fasciculus (SLF) in the HE group. Conclusions: Our findings indicate changes to WM microstructure occurs silently due to repetitive SCI exposure which may persist beyond a single football season.