Luke C. Henry

Acute and Chronic Changes in Diffusivity Measures after Sports Concussion

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.

Neurometabolic Changes in the Acute Phase after Sports Concussions Correlate with Symptom Severity

Sports concussion is a major problem that affects thousands of people in North America every year. Despite negative neuroimaging findings, many athletes display neurophysiological alterations and post-concussion symptoms such as headaches and sensitivity to light and noise. It is suspected that neurometabolic changes may underlie these changes. In this study we investigated the effects of sports concussion on brain metabolism using (1)H-MR spectroscopy by comparing a group of 12 non-concussed athletes with a group of 12 concussed athletes of the same age (mean 22.5 years) and education (mean 16 years). All athletes were scanned 1-6 days post-concussion in a 3T Siemens MRI, and were administered a symptom scale to evaluate post-concussion symptomatology. Participants also completed a neuropsychological test battery to assess verbal memory, visual memory, information processing speed, and reaction time, and no group differences were detected relative to controls. Concussed athletes showed a higher number of symptoms than non-concussed athletes, and they also showed a significant decrease in glutamate in the primary motor cortex (M1), as well as significant decreases in N-acetylaspartate in the prefrontal and primary motor cortices. No changes were observed in the hippocampus. Furthermore, the metabolic changes in M1 correlated with self-reported symptom severity despite equivalent neuropsychological performance. These results confirm cortical neurometabolic changes in the acute post-concussion phase, and demonstrate for the first time a correlation between subjective self-reported symptoms and objective physical changes that may be related to increased vulnerability of the concussed brain.

A Revised Factor Structure for the Post-Concussion Symptom Scale Baseline and Postconcussion Factors

Background: Symptom reports play a critical role in the assessment and management of concussions. Symptoms are often conceptualized as factors comprising several related symptoms (eg, somatic factor = headache, nausea, vomiting). Previous research examining the factor structure of the 22-item Post-Concussion Symptom Scale (PCSS) has been limited to small samples and has not adequately evaluated factor loadings at both baseline and postconcussion for male and female athletes at the high school and collegiate levels. Purpose: To examine the factor structure of the 22-item PCSS in independent samples of high school and collegiate athletes reported at baseline and postconcussion, and to evaluate sex and age differences in the resulting baseline and postconcussion symptom factor scores. Study Design: Case series; Level of evidence, 4. Methods: Exploratory factor analytic (EFA) methods were applied to 2 separate samples of athletes who completed the PCSS at baseline (n = 30,455) and 1 to 7 days after a sport-related concussion (n = 1438). The baseline sample (mean ± standard deviation) was 15.74 ± 1.78 years, with a range of 13 to 22 years, and the postconcussion sample was 17.14 ± 2.25 years, with a range of 13 to 24 years. Results: A 4-factor solution accounting for 49.1% of the variance at baseline included a cognitive-sensory, sleep-arousal, vestibular-somatic, and affective factor structure. A 4-factor solution that included cognitive-fatigue-migraine, affective, somatic, and sleep was revealed for the postconcussion EFA. High school athletes reported higher baseline levels of the cognitive-sensory and vestibular-somatic symptom factors and lower levels of the sleep-arousal factor than college athletes. Female participants reported higher symptoms on all postconcussion factors than male participants. Conclusion: The current findings reveal different symptom factors at baseline and postinjury and several age and sex differences on the symptom factors. At postconcussion, symptoms aggregated into a global concussion factor including cognitive, fatigue, and migraine symptoms. Symptoms reported at baseline are not the same as those reported after injury. The presence of a global postconcussion symptom comprising the fatigue factor highlights the importance of physical and cognitive rest during the first week after a concussion. Although headache was the most commonly reported symptom, it was not the greatest contributor to the global postconcussion symptom factor.

Advances in sport concussion assessment: from behavioral to brain imaging measures.

Given that the incidence of sports-related concussion is considered to have reached epidemic proportions, in the past 15 years we have witnessed an explosion of research in this field. The purpose of the current review is to compare the results provided by the different assessment tools used in the scientific literature in order to gain a better understanding of the sequelae and recovery following a concussion. Until recently, the bulk of the has literature focused on the immediate outcome in the hours and days post-injury as a means to plan the safest return-to-play strategy. This has led to the development of several assessment batteries that are relatively easy and rapid to administer and that allow for multiple testing sessions. The main conclusion derived from that literature is that cognitive symptoms tend to resolve within 1 week. However, accumulating evidence indicates that cognitive testing should be viewed as one of several complementary tools necessary for a comprehensive assessment of concussion. Including an objective measure of postural stability increases the sensitivity of the return-to-play decision-making process and minimizes the consequences of mitigating factors (e.g., practice effects and motivation) on neuropsychological test results. This is consistent with findings that symptom severity, neuropsychological function, and postural stability do not appear to be related or affected to the same degree after a concussion. Furthermore, recent evidence from brain imaging, including event-related potentials and functional and metabolic imaging, suggest abnormalities in the electrical responses, metabolic balance, and oxygen consumption of neurons that persist several months after the incident. We explain this apparent discrepancy in recovery by suggesting an initial and rapid phase of functional recovery driven by compensatory mechanisms and brain plasticity, which is followed by a prolonged neuronal recovery period during which subtle deficits in brain functioning are present but not apparent to standard clinical assessment tools.

Metabolic changes in concussed American football players during the acute and chronic post-injury phases

BackgroundDespite negative neuroimaging findings many athletes display neurophysiological alterations and post-concussion symptoms that may be attributable to neurometabolic alterations.MethodsThe present study investigated the effects of sports concussion on brain metabolism using 1H-MR Spectroscopy by comparing a group of 10 non-concussed athletes with a group of 10 concussed athletes of the same age (mean: 22.5 years) and education (mean: 16 years) within both the acute and chronic post-injury phases. All athletes were scanned 1-6 days post-concussion and again 6-months later in a 3T Siemens MRI.ResultsConcussed athletes demonstrated neurometabolic impairment in prefrontal and motor (M1) cortices in the acute phase where NAA:Cr levels remained depressed relative to controls. There was some recovery observed in the chronic phase where Glu:Cr levels returned to those of control athletes; however, there was a pathological increase of m-I:Cr levels in M1 that was only present in the chronic phase.ConclusionsThese results confirm cortical neurometabolic changes in the acute post-concussion phase as well as recovery and continued metabolic abnormalities in the chronic phase. The results indicate that complex pathophysiological processes differ depending on the post-injury phase and the neurometabolite in question.

Sports Concussions and Aging: A Neuroimaging Investigation

Recent epidemiological and experimental studies suggest a link between cognitive decline in late adulthood and sports concussions sustained in early adulthood. In order to provide the first in vivo neuroanatomical evidence of this relation, the present study probes the neuroimaging profile of former athletes with concussions in relation to cognition. Former athletes who sustained their last sports concussion >3 decades prior to testing were compared with those with no history of traumatic brain injury. Participants underwent quantitative neuroimaging (optimized voxel-based morphometry [VBM], hippocampal volume, and cortical thickness), proton magnetic resonance spectroscopy ((1)H MRS; medial temporal lobes and prefrontal cortices), and neuropsychological testing, and they were genotyped for APOE polymorphisms. Relative to controls, former athletes with concussions exhibited: 1) Abnormal enlargement of the lateral ventricles, 2) cortical thinning in regions more vulnerable to the aging process, 3) various neurometabolic anomalies found across regions of interest, 4) episodic memory and verbal fluency decline. The cognitive deficits correlated with neuroimaging findings in concussed participants. This study unveiled brain anomalies in otherwise healthy former athletes with concussions and associated those manifestations to the long-term detrimental effects of sports concussion on cognitive function. Findings from this study highlight patterns of decline often associated with abnormal aging.

Removal from play after concussion and recovery time

OBJECTIVE: Despite increases in education and awareness, many athletes continue to play with signs and symptoms of a sport-related concussion (SRC). The impact that continuing to play has on recovery is unknown. This study compared recovery time and related outcomes between athletes who were immediately removed from play and athletes who continued to play with an SRC. METHODS: A prospective, repeated measures design was used to compare neurocognitive performance, symptoms, and recovery time between 35 athletes (mean ± SD age, 15.61 ± 1.65 years) immediately removed after an SRC (REMOVED group) compared with 34 athletes (mean ± SD age, 15.35 ± 1.73 years) who continued to play (PLAYED group) with SRC. Neurocognitive and symptom data were obtained at baseline and at 1 to 7 days and 8 to 30 days after an SRC. RESULTS: The PLAYED group took longer to recover than the REMOVED group (44.4 ± 36.0 vs 22.0 ± 18.7 days; P = .003) and were 8.80 times more likely to demonstrate protracted recovery (≥21 days) (P < .001). Removal from play status was associated with the greatest risk of protracted recovery (adjusted odds ratio, 14.27; P = .001) compared with other predictors (eg, sex). The PLAYED group exhibited significantly worse neurocognitive and greater symptoms than the REMOVED group. CONCLUSIONS: SRC recovery time may be reduced if athletes are removed from participation. Immediate removal from play is the first step in mitigating prolonged SRC recovery, and these data support current consensus statements and management guidelines.

Diffuse white matter tract abnormalities in clinically normal ageing retired athletes with a history of sports-related concussions

Sports-related concussions have been shown to lead to persistent subclinical anomalies of the motor and cognitive systems in young asymptomatic athletes. In advancing age, these latent alterations correlate with detectable motor and cognitive function decline. Until now, the interacting effects of concussions and the normal ageing process on white matter tract integrity remain unknown. Here we used a tract-based spatial statistical method to uncover potential white matter tissue damage in 15 retired athletes with a history of concussions, free of comorbid medical conditions. We also investigated potential associations between white matter integrity and declines in cognitive and motor functions. Compared to an age- and education-matched control group of 15 retired athletes without concussions, former athletes with concussions exhibited widespread white matter anomalies along many major association, interhemispheric, and projection tracts. Group contrasts revealed decreases in fractional anisotropy, as well as increases in mean and radial diffusivity measures in the concussed group. These differences were primarily apparent in fronto-parietal networks as well as in the frontal aspect of the corpus callosum. The white matter anomalies uncovered in concussed athletes were significantly associated with a decline in episodic memory and lateral ventricle expansion. Finally, the expected association between frontal white matter integrity and motor learning found in former non-concussed athletes was absent in concussed participants. Together, these results show that advancing age in retired athletes presenting with a history of sports-related concussions is linked to diffuse white matter abnormalities that are consistent with the effects of traumatic axonal injury and exacerbated demyelination. These changes in white matter integrity might explain the cognitive and motor function declines documented in this population.

Neurometabolic and microstructural alterations following a sports-related concussion in female athletes

Abstract Background: Sports-related concussions are a major public health concern affecting millions of individuals annually. Neurometabolic and microstructural alterations have been reported in the chronic phase following a concussion in male athletes, while no study has investigated these alterations in female athletes. Methods: Neurometabolic and microstructural alterations following a concussion were investigated by comparing 10 female athletes with a concussion and 10 control female athletes, using magnetic resonance spectroscopy (MRS) and diffusion tensor imaging (DTI). Athletes with concussion were scanned at least 7 months post-concussion (mean = 18.9 months). Results: MRS revealed a significant lower level of myo-inositol in the hippocampus and the primary motor cortices (M1) bilaterally. DTI analysis using Tract-Based Spatial Statistics (TBSS) showed no difference in fractional anisotropy (FA) while higher level of mean diffusivity (MD) in athletes with concussion was detected in large white matter tracts including the forceps minors, inferior/superior longitudinal fasciculi, inferior fronto-occipital fasciculus, cingulum, uncinate fasciculus, anterior thalamic radiations and corticospinal tract. Moreover, a region of interest approach for the corpus callosum revealed a significant lower level of FA in the segment containing fibres projecting to M1. Conclusions: This study demonstrates persistent neurometabolic and microstructural alterations in female athletes suffering a sports-related concussion.

Motor system alterations in retired former athletes: the role of aging and concussion history

BackgroundRetired athletes with a history of sports concussions experience cognitive and motor declines with aging, and the risk of severe neurodegenerative conditions is magnified in this population. The present study investigated the effects of aging on motor system metabolism and function in former university-level athletes who sustained their last concussion several decades prior to testing.MethodsTo test the hypothesis that age and remote concussions induce functional as well as metabolic alterations of the motor system, we used proton magnetic resonance spectroscopy to detect metabolic abnormalities in the primary motor cortex and the serial reaction time task (SRTT) to evaluate motor learning.ResultsOur results indicate that motor learning is significantly reduced in former concussed athletes relative to controls. In addition, glutamate/H2O ratio in M1 was disproportionately reduced in concussed athletes with advancing age and was found to strongly correlate with motor learning impairments.ConclusionFindings from this study provide evidence that the acquisition of a repeated motor sequence is compromised in the aging concussed brain and that its physiological underpinnings could implicate disproportionate reductions of M1 glutamate concentrations with advancing age.