A prospective study of physician-observed concussion during a varsity university hockey season: metabolic changes in ice hockey players. Part 4 of 4

Abstract

<jats:sec> <jats:title>Object</jats:title> <jats:p>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).</jats:p></jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p>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 <jats:italic>N</jats:italic>-acetylaspartate (NAA)/Cr. Individuals sustaining a medically diagnosed concussion were sent for MRI at 72 hours, 2 weeks, and 2 months after injury.</jats:p></jats:sec> <jats:sec> <jats:title>Results</jats:title> <jats:p>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<jats:sub>(13)</jats:sub> = 2.58, p = 0.02, η<jats:sup>2</jats:sup> = 0.34).</jats:p></jats:sec> <jats:sec> <jats:title>Conclusions</jats:title> <jats:p>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.</jats:p></jats:sec>

A Systematic Review of Proton Magnetic Resonance Spectroscopy Findings in Sport-Related Concussion

“…51,53,57 Repeated or follow-up MRS was conducted in five of the 11 identified studies. 51,53,54,57,58 Three of five of these studies reported significantly decreased levels of NAA in the DLPFC and M1, 50 and the frontal cortical-subcortical juncture, 53,57 and decreased Glu and mI in the M1. 50 More specifically, Henry and coworkers 51 reported persisting decreases in NAA:Cr levels in the DLPFC over time (6 month post-injury follow-up), decreased levels of Glu:Cr in the M1 in the acute phase but recovery in the chronic phase, and equivalent mI:Cr levels in the acute phase but significant differences emerged over time.…”

“…49 Two of 11 studies involved only male samples, 50,51 2 studies did not report on sex, 49,52 and 1 did not report on sex for the control group. 53 Of the seven studies that included a mixture of both exess, five reported on the sex split in athletes 54 and controls, [55][56][57] whereas the other two studies reported on the overall sample only. 53,58 In total, of the studies identifying sex, 219 males and 95 females were represented in the overall sample.…”

“…51 One study, however, detected no metabolic change across groups, 58 and another found no metabolic changes between concussed versus non-concussed athletes. 54 In these two studies, Chamard and colleagues 54 studied the corpus callosum while Maugans and associates 58 studied three separate brain regions (anterior cingulate gyrus, left dorsolateral prefrontal white matter, and left thalamus). Other studies detected statistically significant changes in a variety of neuroanatomical regions, including frontal white matter, [50][51][52][53]57 primary motor cortex (M1), 50,51 genu and splenium of the corpus callosum, 55,56 and the lentiform nucleus (putamen and globus pallidus).…”

“…Aside from one study, 54 possible sex differences were not fully explored, however. In terms of the sports represented, two studies involved boxers, 49,52 one used ice hockey players, 54 and one used American footballer players. 51 Four studies included a mixed sample of contact sport athletes, 53,57,58 and the remaining three did not report the sports in which athletes participated.…”

A Historical Perspective on Sports Concussion: Where We Have Been and Where We Are Going

“…Reductions in NAA have been reported within 72 h of a head injury, with complete recovery noted by day 30 [23]. NAA reductions have also been identified in female collegiate hockey players over the course of the season, with no such similarities in the male group [24]. Longterm changes in brain chemistry have also been identified in a group of former college athletes with a known history of concussion [25].…”