Acute and Chronic Changes in Diffusivity Measures after Sports Concussion

Abstract

Despite negative neuroimaging findings in concussed athletes, studies indicate that the acceleration and deceleration of the brain after concussive impacts result in metabolic and electrophysiological alterations that may be attributable to changes in white matter resulting from biomechanical strain. In the present study we investigated the effects of sports concussion on white matter using three different diffusion tensor imaging (DTI) measures: fractional anisotropy (FA), mean diffusivity (MD), and axial diffusivity (AD). We compared a group of 10 non-concussed athletes with a group of 18 concussed athletes of the same age (mean age 22.5 years) and education (mean 16 years) using a voxel-based approach (VBA) in both the acute and chronic post-injury phases. All concussed athletes were scanned 1-6 days post-concussion and again 6 months later in a 3T Siemens Trio(™) MRI. Three 2×2 repeated-measures analyses of variance (ANOVAs) were conducted, one for each measure of DTI used in the current study. There was a main group effect of FA, which was increased in dorsal regions of both corticospinal tracts (CST) and in the corpus callosum in concussed athletes at both time points. There was a main group effect of AD in the right CST, where concussed athletes showed elevated values relative to controls at both time points. MD values were decreased in concussed athletes, in whom analyses revealed significant group differences in the CST and corpus callosum at both time points. Although the use of VBA does limit the analyses to large tracts, and it has clinical limitations with regard to individual analyses, our results nevertheless indicate that sports concussions do result in changes in diffusivity in the corpus callosum and CST that are not detected using conventional neuroimaging techniques.

Sex matters: repetitive mild traumatic brain injury in adolescent rats

“…While many of these findings were sex‐dependent and are discussed further in the next section, DTI metrics revealed a significant effect of injury in the contralateral CC with RmTBI rats having significantly lower AD and ADC than shams regardless of sex. Reduced ADC has been observed in the CC of adolescents with mTBI,48 and in university students including concussed male49 and female50 athletes. In the latter study, and consistent with our results here, concussed athletes also had reduced AD in the CC.…”

A Longitudinal Diffusion Tensor Imaging Study Assessing White Matter Fiber Tracts after Sports-Related Concussion

“…78 In discussing these findings, other researchers 68 suggest the possibility that contact sport athletes represent a distinct population because of their continued exposure to subconcussive hits leading to constant WM injury and recovery cycles and therefore might present a different recovery profile from the civilian, non-contact-sport population suffering a single mTBI episode. It must be noted that at least one study on SRC 79 showed significantly higher FA, AD, and lower MD (as compared to noncontact controls) values at two time points: *81 hours (on average) and 6 months postinjury, suggesting no significant recovery in diffusion measures during that time interval. Future work is needed to address these observed differences of diffusion metrics during recovery after SRC.…”

Sports Concussion: A Clinical Overview

“…In 2012, a systematic review of the DTI and concussion literature [65] reported on eight studies and raised concern in the literature at the time that there was so much variability in the methodology bringing together the findings of the diverse range of work and attempting to interpret the results was challenging. A more recent DTI and concussion systematic review [49] suggested that the most consistent findings were decreased mean diffusivity and/or an increase in fractional anisotropy in white matter within 6 months post-concussion [66][67][68][69][70], but these findings are not universal (i.e., the opposite patterns have also been reported in other studies) [56,62,71]. In addition, reduced radial diffusivity has been reported [68,[72][73][74], but increase and decrease in axial diffusivity have been described [68,69].…”