Abstract
Background: Previous research has shown evidence for transient neuronal loss after repetitive head impacts (RHI) as demonstrated by a decrease in N-acetylaspartate (NAA). However, few studies have investigated other neuro-metabolites that may be altered in the presence of RHI; furthermore, the relationship of neuro-metabolite changes to neurocognitive outcome and potential sex differences remain largely unknown.Objective: The aim of this study was to identify alterations in brain metabolites and their potential association with neurocognitive performance over time as well as to characterize sex-specific differences in response to RHI.Methods: 33 collegiate ice hockey players (17 males and 16 females) underwent 3T magnetic resonance spectroscopy (MRS) and neurocognitive evaluation before and after the Canadian Interuniversity Sports (CIS) ice hockey season 2011–2012. The MRS voxel was placed in the corpus callosum. Pre- and postseason neurocognitive performances were assessed using the Immediate Post-Concussion Assessment and Cognitive Test (ImPACT). Absolute neuro-metabolite concentrations were then compared between pre- and postseason MRS were (level of statistical significance after correction for multiple comparisons: p < 0.007) and correlated to ImPACT scores for both sexes.Results: A significant decrease in NAA was observed from preseason to postseason (p = 0.001). Furthermore, a trend toward a decrease in total choline (Cho) was observed (p = 0.044). Although no overall effect was observed for glutamate (Glu) over the season, a difference was observed with females showing a decrease in Glu and males showing an increase in Glu, though this was not statistically significant (p = 0.039). In both males and females, a negative correlation was observed between changes in Glu and changes in verbal memory (p = 0.008).Conclusion: The results of this study demonstrate changes in absolute concentrations of neuro-metabolites following exposure to RHI. Results suggest that changes in Glu are correlated with changes in verbal memory. Future studies need to investigate further the association between brain metabolites and clinical outcome as well as sex-specific differences in the brain's response to RHI.
Highlights
Concussions and head injuries in general are a frequent occurrence in contact sports, representing the most common injury in women’s ice hockey and the second most common injury in men’s ice hockey [1, 2]
NAA was found to be significantly lower at the end of the season compared to the beginning in both males and females, regardless of whether the players had a concussion during the season (Figure 2A)
A sex effect, was observed for Glu, though the difference was only of trend level significance, indicating that while males had an increase in Glu from pre- to postseason assessment, females had a decrease (Figure 2B)
Summary
Concussions and head injuries in general are a frequent occurrence in contact sports, representing the most common injury in women’s ice hockey and the second most common injury in men’s ice hockey [1, 2]. Ice hockey is a contact sport that predisposes players to concussive and subconcussive repetitive head impacts (RHI) based on the inherent nature of the sport. Previous research suggests that females generally have worse outcomes following concussion compared to males. The impact exposures in ice hockey in females are less frequent and of a lower magnitude compared to males [6]. Previous research has shown evidence for transient neuronal loss after repetitive head impacts (RHI) as demonstrated by a decrease in N-acetylaspartate (NAA). Few studies have investigated other neuro-metabolites that may be altered in the presence of RHI; the relationship of neuro-metabolite changes to neurocognitive outcome and potential sex differences remain largely unknown
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