This study demonstrates persistent neurometabolic and microstructural alterations in female athletes suffering a sports-related concussion.

Concussion is an injury affecting millions of individuals annually that can be associated with long-term sequelae. Recent studies have reported long-term abnormalities in the white matter (WM) tracts of male athletes. The corpus callosum (CC) and corticospinal tract (CST) have been shown to be particularly vulnerable to concussion, which may be related to abnormal interhemispheric functional connectivity and motor impairments. These anatomical pathways, however, have not been investigated in female athletes despite the functional significance of the CC and CST to adequate sports performance. In the present study, 8 healthy, unconcussed female athletes (soccer, hockey) were compared with 10 female athletes (soccer, hockey, water polo) 6 months post-concussion. Diffusion tensor imaging (DTI) of the CC and CST was conducted in a 3T magnetic resonance imaging (MRI) scanner. DTI analysis showed no significant differences between groups within the CST but revealed differences between groups in the CC. The concussed group had lower mean diffusivity (t = 2.14; p = 0.048) and lower radial diffusivity (t = 2.91; p = 0.010) in the region of the CC projecting to the prefrontal cortex. A lower volume of WM fibers was found in the region projecting to the premotor and supplementary motor areas (t = 2.14; p = 0.048). Finally, lower axial diffusivity (AD) was observed in the CC area projecting mainly to the parietal and temporal area (t = 2.23; p = 0.041). Long-term alterations in the CC of female athletes appear to affect mostly the anterior part of the CC projecting to the prefrontal and premotor areas. Further studies are needed to determine whether these alterations are associated with a higher risk of sustaining a subsequent concussive injury.

Object Despite negative neuroimaging findings using traditional neuroimaging methods such as MRI and CT, sports-related concussions have been shown to cause neurometabolic changes in both the acute and subacute phases of head injury. However, no prospective clinical study has used an independent physician-observer design in the monitoring of these changes. The objective of this study was to evaluate the effects of repetitive concussive and sub-concussive head impacts on neurometabolic concentrations in a prospective study of two Canadian Interuniversity Sports (CIS) ice hockey teams using MR spectroscopy (MRS). Methods Forty-five ice hockey players (25 men and 20 women) participated in this study. All participants underwent pre- and postseason MRI, including spectroscopy imaging, using a 3-T MRI machine. The linear combination model was used to quantify the following ratios: glutamate/creatine-phosphocreatine (Cr), myoinositol/Cr, and N-acetylaspartate (NAA)/Cr. Individuals sustaining a medically diagnosed concussion were sent for MRI at 72 hours, 2 weeks, and 2 months after injury. Results No statistically significant differences were observed between athletes who were diagnosed with a concussion and athletes who were not clinically diagnosed as sustaining a concussion. Although no statistically significant longitudinal metabolic changes were observed among athletes who were diagnosed with a concussion, the results demonstrated a predictable pattern of initial impairment, followed by a gradual return to ratios that were similar to, but lower than, baseline ratios. No significant pre- to postseason changes were demonstrated among men who were not observed to sustain a concussion. However, a substantively significant decrease in the NAA/Cr ratio was noted among the female hockey players (t(13) = 2.58, p = 0.02, η2 = 0.34). Conclusions A key finding in this study, from the standpoint of future research design, is the demonstration of substantively significant metabolic changes among the players who were not diagnosed with a concussion. In addition, it may explain why there are few statistically significant differences demonstrated between players who were diagnosed with a concussion and players who were not diagnosed with a concussion (that is, the potency of the independent variable was diminished by the fact that the group of players not diagnosed with a concussion might be better described as a subgroup of the players who may have sustained a concussion but were not observed and diagnosed with a concussion). This result suggests that definitions of concussion may need to be revisited within sports with high levels of repetitive subconcussive head impacts. Future analysis of these data will examine the relationships between the modes of MRI (diffusion tensor imaging, MRS, and susceptibility-weighted MR imaging) used in this study, along with other more sensitive evaluative techniques. This type of intermodal comparison may improve the identification of concussions that were previously dependent on the unreliable self-reporting of recognized concussion symptomatology by the athlete or on poorly validated neuropsychological tests.

While MRI and CT are generally unrevealing, advanced neuroimaging techniques demonstrated neurometabolic, microstructural, and functional alterations following SRC in athletes younger than 19 years of age in the acute, subacute, and chronic phases of recovery. However, more studies are needed to fully understand the impact of SRC on the developing brain in children and adolescents.