Thinner Cortex in Collegiate Football Players With, but not Without, a Self-Reported History of Concussion

Self-reported concussion history is not related to cortical volume in college athletes

The long-term consequences of concussion are still being uncovered but have been linked to disruptions in cognition and psychological well-being. Previous studies focusing on the association between concussion history and structural changes in the brain have reported inconsistent results. We sought to examine the effect of concussion history on cortical volume with a focus on functional networks. These networks are associated with many of the functions that can be disrupted in those with an extensive concussion history. We collected baseline behavioral data including the Immediate Post-Concussion Assessment and Cognitive Testing, a self-report measure of the number of diagnosed concussions, and structural MRI in college athletes (n=296; 263 men and 33 women, age range 17-24). Behavioral measures were collected by members of the Department of Athletics concussion management team using a standardized protocol as part of their on-boarding process. Collegiate athletes in the present study who self-reported concussion history did not report different baseline symptoms and did not exhibit consistent differences in cognitive performance relative to those who reported no concussion history. We found that concussion history was not related to cortical volume at the network or region level, even when we compared participants with two or more concussions to those with no concussion history. We did identify relationships between cortical volume in the visual network and dorsal attention network with cognitive performance. In addition to comparing cortical volume between individuals with and without reported concussion history, we also examined whether cortical volume changes could be observed within individuals from baseline to acutely following concussion. We found that network level cortical volume did not change within subjects from baseline measurement to acutely post-concussion. Together, these results suggest that both self-reported concussion history and acute concussion effects are not associated with changes in cortical volume in young adult athletes.

Unique cortical morphology in young adults who are diagnosed with and medicated for attention-deficit/hyperactivity disorder

Children diagnosed with attention-deficit/hyperactivity disorder (ADHD) often display reduced cortical volume and thickness, as well as changes in cortical folding. However, the impact of ADHD on cortical morphology in young adults remains elusive. This study aimed to characterize cortical thickness, gyrification, and sulcal depth profiles in adults aged 18-26 years old with ADHD. In this cross-sectional study, we employed multiparameter analyses between two groups: an ADHD group of individuals diagnosed with and medicated daily for ADHD (n = 30) and a non-ADHD group with age- and sex-matched individuals free from lifetime ADHD diagnosis (n = 30). The ADHD group exhibited significant cortical thinning in fronto-parieto-temporal regions, including the left superior parietal lobule, bilateral inferior temporal gyrus, and right lateral orbitofrontal gyrus, relative to the non-ADHD group. Greater gyrification and deeper sulcal depth were evident in various fronto-occipital-temporal regions in the ADHD group, although two regions (right postcentral and inferior temporal gyri) displayed shallower sulcal depth compared to the non-ADHD group. These data suggest that ADHD-related disparities persist into young adulthood, with alterations in brain morphology potentially serving as biomarkers for ADHD diagnosis in young adults.

Long-term neurobehavioral and neuroimaging outcomes in athletes with prior concussion(s) and head impact exposure

Objective: The long-term health of former athletes with a history of multiple concussions and/or repetitive head impact (RHI) exposure has been of growing interest among the public. The true proportion of dementia cases attributable to neurotrauma and the neurobehavioral profile/sequelae of multiple concussion and RHI exposure among athletes has been difficult to determine. Methods: Across three exposure paradigms (i.e. group comparisons of athletes vs. controls, number of prior concussions, and level of RHI exposure), this review characterizes the prevalence of neurodegenerative/neurological disease, changes in cognitive and psychiatric function, and alterations on neuroimaging. We highlight sources of variability across studies and provide suggested directions for future investigations. Results: The most robust finding reported in the literature suggests a higher level of symptom endorsement (general, psychiatric, and cognitive) among those with a greater history of sport-related concussion from adolescence to older adulthood. Pathological processes (e.g. atrophy, tau deposition, and hypometabolism) may be more likely to occur within select regions (frontal and temporal cortices) and structures (thalamus and hippocampus). However, studies examining concussion(s) and RHI exposure with imaging outcomes have yet to identify consistent associations or evidence of a dose-response relationship or a threshold at which associations are observed. Discussion: Studies have not observed a simple dose-response relationship between multiple concussions and/or RHI exposure with cognitive, psychiatric, or in vivo neurobiological outcomes, particularly at lower levels of play. The relationship between prior concussion and RHI exposure with long-term outcomes in former athletes is complex and likely influenced by -several non-injury-related factors.

Brain morphometry in former American football players: findings from the DIAGNOSE CTE research project

Exposure to repetitive head impacts in contact sports is associated with neurodegenerative disorders including chronic traumatic encephalopathy (CTE), which currently can be diagnosed only at post-mortem. American football players are at higher risk of developing CTE given their exposure to repetitive head impacts. One promising approach for diagnosing CTE in vivo is to explore known neuropathological abnormalities at post-mortem in living individuals using structural MRI. MRI brain morphometry was evaluated in 170 male former American football players ages 45-74 years (n = 114 professional; n = 56 college) and 54 same-age unexposed asymptomatic male controls (n = 54, age range 45-74). Cortical thickness and volume of regions of interest were selected based on established CTE pathology findings and were assessed using FreeSurfer. Group differences and interactions with age and exposure factors were evaluated using a generalized least squares model. A separate logistic regression and independent multinomial model were performed to predict each traumatic encephalopathy syndrome (TES) diagnosis, core clinical features and provisional level of certainty for CTE pathology using brain regions of interest. Former college and professional American football players (combined) showed significant cortical thickness and/or volume reductions compared to unexposed asymptomatic controls in the hippocampus, amygdala, entorhinal cortex, parahippocampal gyrus, insula, temporal pole and superior frontal gyrus. Post hoc analyses identified group-level differences between former professional players and unexposed asymptomatic controls in the hippocampus, amygdala, entorhinal cortex, parahippocampal gyrus, insula and superior frontal gyrus. Former college players showed significant volume reductions in the hippocampus, amygdala and superior frontal gyrus compared to the unexposed asymptomatic controls. We did not observe Age × Group interactions for brain morphometric measures. Interactions between morphometry and exposure measures were limited to a single significant positive association between the age of first exposure to organized tackle football and right insular volume. We found no significant relationship between brain morphometric measures and the TES diagnosis core clinical features and provisional level of certainty for CTE pathology outcomes. These findings suggested that MRI morphometrics detect abnormalities in individuals with a history of repetitive head impact exposure that resemble the anatomic distribution of pathological findings from post-mortem CTE studies. The lack of findings associating MRI measures with exposure metrics (except for one significant relationship) or TES diagnosis and core clinical features suggested that brain morphometry must be complemented by other types of measures to characterize individuals with repetitive head impacts.

Multiparameter cortical surface morphology in former amateur contact sport athletes

The lifetime effects of repetitive head impacts have captured considerable public and scientific interest over the past decade, yet a knowledge gap persists in our understanding of midlife neurological well-being, particularly in amateur level athletes. This study aimed to identify the effects of lifetime exposure to sports-related head impacts on brain morphology in retired, amateur athletes. This cross-sectional study comprised of 37 former amateur contact sports athletes and 21 age- and sex-matched noncontact athletes. High-resolution anatomical, T1 scans were analyzed for the cortical morphology, including cortical thickness, sulcal depth, and sulcal curvature, and cognitive function was assessed using the Dementia Rating Scale-2. Despite no group differences in cognitive functions, the contact group exhibited significant cortical thinning particularly in the bilateral frontotemporal regions and medial brain regions, such as the cingulate cortex and precuneus, compared to the noncontact group. Deepened sulcal depth and increased sulcal curvature across all four lobes of the brain were also notable in the contact group. These data suggest that brain morphology of middle-aged former amateur contact athletes differs from that of noncontact athletes and that lifetime exposure to repetitive head impacts may be associated with neuroanatomical changes.

Associations of prior concussion severity with brain microstructure using mean apparent propagator magnetic resonance imaging

Magnetic resonance imaging (MRI) diffusion studies have shown chronic microstructural tissue abnormalities in athletes with history of concussion, but with inconsistent findings. Concussions with post-traumatic amnesia (PTA) and/or loss of consciousness (LOC) have been connected to greater physiological injury. The novel mean apparent propagator (MAP) MRI is expected to be more sensitive to such tissue injury than the conventional diffusion tensor imaging. This study examined effects of prior concussion severity on microstructure with MAP-MRI. Collegiate-aged athletes (N = 111, 38 females; ≥6 months since most recent concussion, if present) completed semistructured interviews to determine the presence of prior concussion and associated injury characteristics, including PTA and LOC. MAP-MRI metrics (mean non-Gaussian diffusion [NG Mean], return-to-origin probability [RTOP], and mean square displacement [MSD]) were calculated from multi-shell diffusion data, then evaluated for associations with concussion severity through group comparisons in a primary model (athletes with/without prior concussion) and two secondary models (athletes with/without prior concussion with PTA and/or LOC, and athletes with/without prior concussion with LOC only). Bayesian multilevel modeling estimated models in regions of interest (ROI) in white matter and subcortical gray matter, separately. In gray matter, the primary model showed decreased NG Mean and RTOP in the bilateral pallidum and decreased NG Mean in the left putamen with prior concussion. In white matter, lower NG Mean with prior concussion was present in all ROI across all models and was further decreased with LOC. However, only prior concussion with LOC was associated with decreased RTOP and increased MSD across ROI. Exploratory analyses conducted separately in male and female athletes indicate associations in the primary model may differ by sex. Results suggest microstructural measures in gray matter are associated with a general history of concussion, while a severity-dependent association of prior concussion may exist in white matter.

Increased brain age and relationships with blood-based biomarkers following concussion in younger populations

OBJECTIVE

Brain age is increasingly being applied to the spectrum of brain injury to define neuropathological changes in conjunction with blood-based biomarkers. However, data from the acute/sub-acute stages of concussion are lacking, especially among younger cohorts.

METHODS

Predicted brain age differences were independently calculated in large, prospectively recruited cohorts of pediatric concussion and matched healthy controls (total N = 446), as well as collegiate athletes with sport-related concussion and matched non-contact sport controls (total N = 184). Effects of repetitive head injury (i.e., exposure) were examined in a separate cohort of contact sport athletes (N = 82), as well as by quantifying concussion history through semi-structured interviews and years of contact sport participation.

RESULTS

Findings of increased brain age during acute and sub-acute concussion were independently replicated across both cohorts, with stronger evidence of recovery for pediatric (4 months) relative to concussed athletes (6 months). Mixed evidence existed for effects of repetitive head injury, as brain age was increased in contact sport athletes, but was not associated with concussion history or years of contact sport exposure. There was no difference in brain age between concussed and contact sport athletes. Total tau decreased immediately (~ 1.5 days) post-concussion relative to the non-contact group, whereas pro-inflammatory markers were increased in both concussed and contact sport athletes. Anti-inflammatory markers were inversely related to brain age, whereas markers of axonal injury (neurofilament light) exhibited a trend positive association.

CONCLUSION

Current and previous findings collectively suggest that the chronicity of brain age differences may be mediated by age at injury (adults > children), with preliminary findings suggesting that exposure to contact sports may also increase brain age.

The effects of cytomegalovirus on brain structure following sport-related concussion

The neurotrophic herpes virus cytomegalovirus is a known cause of neuropathology in utero and in immunocompromised populations. Cytomegalovirus is reactivated by stress and inflammation, possibly explaining the emerging evidence linking it to subtle brain changes in the context of more minor disturbances of immune function. Even mild forms of traumatic brain injury, including sport-related concussion, are major physiological stressors that produce neuroinflammation. In theory, concussion could predispose to the reactivation of cytomegalovirus and amplify the effects of physical injury on brain structure. However, to our knowledge this hypothesis remains untested. This study evaluated the effect of cytomegalovirus serostatus on white and grey matter structure in a prospective study of athletes with concussion and matched contact-sport controls. Athletes who sustained concussion (n = 88) completed MRI at 1, 8, 15 and 45 days post-injury; matched uninjured athletes (n = 73) completed similar visits. Cytomegalovirus serostatus was determined by measuring serum IgG antibodies (n = 30 concussed athletes and n = 21 controls were seropositive). Inverse probability of treatment weighting was used to adjust for confounding factors between athletes with and without cytomegalovirus. White matter microstructure was assessed using diffusion kurtosis imaging metrics in regions previously shown to be sensitive to concussion. T1-weighted images were used to quantify mean cortical thickness and total surface area. Concussion-related symptoms, psychological distress, and serum concentration of C-reactive protein at 1 day post-injury were included as exploratory outcomes. Planned contrasts compared the effects of cytomegalovirus seropositivity in athletes with concussion and controls, separately. There was a significant effect of cytomegalovirus on axial and radial kurtosis in athletes with concussion but not controls. Cytomegalovirus positive athletes with concussion showed greater axial (P = 0.007, d = 0.44) and radial (P = 0.010, d = 0.41) kurtosis than cytomegalovirus negative athletes with concussion. Similarly, there was a significant association of cytomegalovirus with cortical thickness in athletes with concussion but not controls. Cytomegalovirus positive athletes with concussion had reduced mean cortical thickness of the right hemisphere (P = 0.009, d = 0.42) compared with cytomegalovirus negative athletes with concussion and showed a similar trend for the left hemisphere (P = 0.036, d = 0.33). There was no significant effect of cytomegalovirus on kurtosis fractional anisotropy, surface area, symptoms and C-reactive protein. The results raise the possibility that cytomegalovirus infection contributes to structural brain abnormalities in the aftermath of concussion perhaps via an amplification of concussion-associated neuroinflammation. More work is needed to identify the biological pathways underlying this process and to clarify the clinical relevance of this putative viral effect.

Current and Emerging Techniques in Neuroimaging of Sport-Related Concussion

SUMMARY

Sport-related concussion (SRC) affects an estimated 1.6 to 3.8 million Americans each year. Sport-related concussion results from biomechanical forces to the head or neck that lead to a broad range of neurologic symptoms and impaired cognitive function. Although most individuals recover within weeks, some develop chronic symptoms. The heterogeneity of both the clinical presentation and the underlying brain injury profile make SRC a challenging condition. Adding to this challenge, there is also a lack of objective and reliable biomarkers to support diagnosis, to inform clinical decision making, and to monitor recovery after SRC. In this review, the authors provide an overview of advanced neuroimaging techniques that provide the sensitivity needed to capture subtle changes in brain structure, metabolism, function, and perfusion after SRC. This is followed by a discussion of emerging neuroimaging techniques, as well as current efforts of international research consortia committed to the study of SRC. Finally, the authors emphasize the need for advanced multimodal neuroimaging to develop objective biomarkers that will inform targeted treatment strategies after SRC.

Cortical thickness and neurocognitive performance in former high-level female soccer and non-contact sport athletes

BACKGROUND

Long-term effects of playing soccer (football) on the brain structure and function of the brain are vividly debated. While some studies showed differences in neurocognitive performance and structural brain changes in retired male players, data on female players are scarce. The present study compares cortical thickness and neurocognitive performance in former high-level female soccer (SOC) and non-contact sport athletes (CON).

METHODS

3 T T1-weighted 3D MPRAGE MRI was performed, and vertex-wise cortical thickness was analyzed using FreeSurfer (v. 6.0.0). Neurocognitive performance in seven domains of SOC and CON was assessed. A multivariate linear model was used to analyze interactions with respect to heading frequency and a history of concussion.

RESULTS

SOC (n = 15, mean age 38.3 ± 5.1 years) and CON (n = 16, mean age 36.6 ± 5.8 years) had a similar cortical thickness and performed similarly in the neurocognitive tests except for verbal memory and psychomotor speed, where SOC performed significantly worse than CON. Moderate headers had a significantly larger cortical thickness than rare headers in the right inferior parietal region. Visual memory and cortical thickness were positively correlated in the group of frequent headers and negatively correlated in CON, but not in the other header groups.

PERSPECTIVE

In contrast to previous reports in male soccer players, female players did not reveal cortical thinning in comparison with control athletes, whereas neurocognitive profiles of female soccer players might not significantly differ from male athletes. Small sample sizes, subjective header assessment, and the case-control study design require a cautious interpretation.

Concussions in young adult athletes: No effect on cerebral white matter

Introduction

The media's recent focus on possible negative health outcomes following sports- related concussion has increased awareness as well as anxiety among parents and athletes. However, the literature on concussion outcomes is equivocal and limited by a variety of diagnostic approaches.

Methods

The current study used a rigorous, open- access concussion identification method-the Ohio State University Traumatic Brain Injury Identification method (OSU TBI-ID) to identify concussion and periods of repeated, subclinical head trauma in 108 young adult athletes who also underwent a comprehensive protocol of cognitive tests, mood/anxiety questionnaires, and high-angular-resolution diffusion-weighted brain imaging to evaluate potential changes in white matter microstructure.

Results

Analyses showed that athletes with a history of repetitive, subclinical impacts to the head performed slightly worse on a measure of inhibitory impulse control and had more anxiety symptoms compared to those who never sustained any type of head injury but were otherwise the same as athletes with no history of concussion. Importantly, there were no group differences in cerebral white matter as measured by tract- based spatial statistics (TBSS), nor were there any associations between OSU TBI-ID measures and whole-brain principal scalars and free-water corrected scalars.

Discussion

Our results provide support for the hypothesis that it is not concussion per se, but repetitive head impacts that beget worse outcomes.

Effects of docosahexaenoic acid and eicosapentaoic acid supplementation on white matter integrity after repetitive sub-concussive head impacts during American football: Exploratory neuroimaging findings from a pilot RCT

Context

Repetitive sub-concussive head impacts (RSHIs) are common in American football and result in changes to the microstructural integrity of white matter. Both docosahexaenoic acid (DHA) and eicosapentaoic acid (EPA) supplementation exerted neuroprotective effects against RSHIs in animal models and in a prior study in football players supplemented with DHA alone.

Objective

Here, we present exploratory neuroimaging outcomes from a randomized controlled trial of DHA + EPA supplementation in American football players. We hypothesized that supplementation would result in less white matter integrity loss on diffusion weighted imaging over the season.

Design setting participants

We conducted a double-blind placebo-controlled trial in 38 American football players between June 2019 and January 2020.

Intervention

Participants were randomized to the treatment (2.442 g/day DHA and 1.020 g/day EPA) or placebo group for five times-per-week supplementation for 7 months. Of these, 27 participants were included in the neuroimaging data analysis (n = 16 placebo; n = 11 DHA + EPA).

Exploratory outcome measures

Changes in white matter integrity were quantified using both voxelwise diffusion kurtosis scalars and deterministic tractography at baseline and end of season. Additional neuroimaging outcomes included changes in regional gray matter volume as well as intra-regional, edge-wise, and network level functional connectivity. Serum neurofilament light (NfL) provided a peripheral biomarker of axonal damage.

Results

No voxel-wise between-group differences were identified on diffusion tensor metrics. Deterministic tractography using quantitative anisotropy (QA) revealed increased structural connectivity in ascending corticostriatal fibers and decreased connectivity in long association and commissural fibers in the DHA+EPA group compared to the placebo group. Serum NfL increases were correlated with increased mean (ρ = 0.47), axial (ρ = 0.44), and radial (ρ = 0.51) diffusivity and decreased QA (ρ = -0.52) in the corpus callosum and bilateral corona radiata irrespective of treatment group. DHA + EPA supplementation did preserve default mode/frontoparietal control network connectivity (g = 0.96, p = 0.024).

Conclusions

These exploratory findings did not provide strong evidence that DHA + EPA prevented or protected against axonal damage as quantified via neuroimaging. Neuroprotective effects on functional connectivity were observed despite white matter damage. Further studies with larger samples are needed to fully establish the relationship between omega-3 supplementation, RSHIs, and neuroimaging biomarkers.

Trial registration

ClinicalTrials.gov-NCT04796207.

Chronic cerebral blood flow alterations in traumatic brain injury and sports-related concussions

PRIMARY OBJECTIVE

Traumatic brain injury (TBI) and sports-related concussion (SRC) may result in chronic functional and neuroanatomical changes. We tested the hypothesis that neuroimaging findings (cerebral blood flow (CBF), cortical thickness, and ¹H-magnetic resonance (MR) spectroscopy (MRS)) were associated to cognitive function, TBI severity, and sex.

RESEARCH DESIGN

Eleven controls, 12 athletes symptomatic following ≥3SRCs and 6 patients with moderate-severe TBI underwent MR scanning for evaluation of cortical thickness, brain metabolites (MRS), and CBF using pseudo-continuous arterial spin labeling (ASL). Cognitive screening was performed using the RBANS cognitive test battery.

MAIN OUTCOMES AND RESULTS

RBANS-index was impaired in both injury groups and correlated with the injury severity, although not with any neuroimaging parameter. Cortical thickness correlated with injury severity (p = 0.02), while neuronal density, using the MRS marker ((NAA+NAAG)/Cr, did not. On multivariate analysis, injury severity (p = 0.0003) and sex (p = 0.002) were associated with CBF. Patients with TBI had decreased gray (p = 0.02) and white matter (p = 0.02) CBF compared to controls. CBF was significantly lower in total gray, white matter and in 16 of the 20 gray matter brain regions in female but not male athletes when compared to female and male controls, respectively.

CONCLUSIONS

Injury severity correlated with CBF, cognitive function, and cortical thickness. CBF also correlated with sex and was reduced in female, not male, athletes. Chronic CBF changes may contribute to the persistent injury mechanisms in TBI and rSRC.

Helmet Technology, Head Impact Exposure, and Cortical Thinning Following a Season of High School Football

The purpose of this study was to compare the effects of wearing older, lower-ranked football helmets (LRank) to wearing newer, higher-ranked football helmets (HRank) on pre- to post-season changes in cortical thickness in response to repetitive head impacts and assess whether changes in cortical thickness are associated with head impact exposure for either helmet type. 105 male high-school athletes (N_HRank = 52, N_LRank = 53) wore accelerometers affixed behind the left mastoid during all practices and games for one regular season of American football to monitor head impact exposure. Pre- and post-season magnetic resonance imaging (MRI) were completed to assess longitudinal changes in cortical thickness. Significant reductions in cortical thickness (i.e., cortical thinning) were observed pre- to post-season for each group, but these longitudinal alterations were not significantly different between the LRank and HRank groups. Further, significant group-by-head impact exposure interactions were observed when predicting changes in cortical thickness. Specifically, a greater frequency of high magnitude head impacts during the football season resulted in greater cortical thinning for the LRank group, but not for the HRank group. These data provide preliminary in vivo evidence that HRank helmets may provide a buffer between the specific effect of high magnitude head impacts on regional thinning by dissipating forces more evenly throughout the cortex. However, future research with larger sample sizes, increased longitudinal measures and additional helmet technologies is warranted to both expand upon and further validate the present study findings.

The Association Between Concussion History and Increased Symptom Severity Reporting Is Independent of Common Medical Comorbidities, Personality Factors, and Sleep Quality in Collegiate Athletes

OBJECTIVE

We investigated the degree to which the association between history of concussion with psychological distress and general symptom severity is independent of several factors commonly associated with elevated symptom severity. We also examined whether symptom severity endorsement was associated with concussion injury specifically or response to injury in general.

SETTING

Academic medical center.

PARTICIPANTS

Collegiate athletes ( N = 106; age: M = 21.37 ± 1.69 years; 33 female) were enrolled on the basis of strict medical/psychiatric exclusion criteria.

DESIGN

Cross-sectional single-visit study. Comprehensive assessment, including semistructured interviews to retrospectively diagnose the number of previous concussions, was completed. Single-predictor and stepwise regression models were fit to examine the predictive value of prior concussion and orthopedic injuries on symptom severity, both individually and controlling for confounding factors.

MAIN OUTCOME MEASURES

Psychological distress was operationalized as Brief Symptom Inventory-18 Global Severity Index (BSI-GSI) ratings; concussion-related symptom severity was measured using the Sport Concussion Assessment Tool.

RESULTS

Controlling for baseline factors associated with the symptom outcomes (agreeableness, neuroticism, negative emotionality, and sleep quality), concussion history was significantly associated with psychological distress ( B = 1.25 [0.55]; P = .025, Δ R2 = 0.034) and concussion-like symptom severity ( B = 0.22 [0.08]; P = .005, Δ R2 = 0.064) and accounted for a statistically significant amount of unique variance in symptom outcomes. Orthopedic injury history was not individually predictive of psychological distress ( B = -0.06 [0.53]; P = .905) or general symptom severity ( B = 0.06 [0.08]; P = .427) and did not explain the relationship between concussion history and symptom outcomes.

CONCLUSIONS

Concussion history is associated with subtle elevations in symptom severity in collegiate-aged athletes; this relationship is independent of medical, lifestyle (ie, sleep), and personality factors. Furthermore, this relationship is associated with brain injury (ie, concussion) and is not a general response to injury history.

Head impact exposure, grey matter volume, and moderating effects of estimated IQ and educational attainment in former athletes at midlife

Repetitive head impact (RHI) exposure has been associated with differences in brain structure among younger active athletes, most often within the hippocampus. Studies of former athletes at early-midlife are limited. We investigated the association between RHI exposure and grey matter structure, as well as moderating factors, among former athletes in early-midlife. Former collegiate football players (N=55; age=37.9+1.5 years) completed magnetic resonance imaging to quantify grey matter morphometry and extensive structured interviews of RHI history (Head Impact Exposure Estimate). Linear regression models tested the association between RHI exposure and GM structures of interest. Interactions were tested for moderators: two estimates of IQ (single word reading and picture vocabulary) and education history. Greater RHI exposure was associated with smaller hippocampal volume, β=-.36, p=.004. Conversely, RHI exposure was not significantly associated with other GM outcomes ps>.05. Education history significantly moderated the association between RHI exposure and hippocampal volume, β=.69, p=.047. Among those with a bachelor's degree, greater RHI exposure was significantly associated with smaller hippocampal volumes, β=-.58, p<.001. For those with graduate/professional degrees, the association between RHI and hippocampal volume was not significant, β=-.33, p=.134. Consistent with studies involving younger, active athletes, smaller hippocampal volumes were selectively associated with greater RHI exposure among former collegiate football players at midlife. This relationship was moderated by higher levels of education. Future longitudinal studies are needed to investigate the course of possible changes that can occur between early-midlife to older ages, as well as the continued protective effect of education and other potential influential factors.

Examining the association between traumatic brain injury and headache

Traumatic brain injury is a common and major cause of disability and death that might require emergency neurological and neurosurgical interventions. Traumatic brain injury can result in temporary or permanent physical, cognitive and psychological impairments. One of the most common complications associated with traumatic brain injury is post-traumatic headache, associated with significant disability and reduced quality of life. Post-traumatic headache is a public health concern that can affect the long-term outcome of traumatic brain injury patients. Clinical symptoms of post-traumatic headache significantly overlap with common primary headaches such as migraine and tension-type headaches. Beyond neurobiological factors, psychological factors can play crucial roles in the initiation and sustainment of post-traumatic headache. While neurological mechanisms underlying post-traumatic headache remains unknown, different studies suggest various mechanisms such as physical damages to the cranial nerves and neck structure, hyper-sensitization of the pain modulatory pathway, and inflammation as underlying causes for the neurobiology of headache. I explore the hypothesis that traumatic brain injury is associated with headaches. In particular, I provide an overview of the neurobiology of post-traumatic headache, its diagnosis, presenting recent findings on the etiology, explaining similarities and differences between with primary headaches such as migraine and tension-type headache, discuss pharmacological and non-pharmacological interventions for the treatments, as well as emphasising on the psychological importance of post-traumatic headache.

White matter abnormalities in active elite adult rugby players

The recognition, diagnosis and management of mild traumatic brain injuries are difficult and confusing. It is unclear how the severity and number of injuries sustained relate to brain injuries, such as diffuse axonal injury, diffuse vascular injury and progressive neurodegeneration. Advances in neuroimaging techniques enable the investigation of neuropathologies associated with acute and long-term effects of injury. Head injuries are the most commonly reported injury seen during professional rugby. There is increased vigilance for the immediate effects of these injuries in matches, but there has been surprisingly little research investigating the longer-term effects of rugby participation. Here, we present a longitudinal observational study investigating the relationship of exposure to rugby participation and sub-acute head injuries in professional adult male and female rugby union and league players using advanced MRI. Diffusion tensor imaging and susceptibility weighted imaging was used to assess white matter structure and evidence of axonal and diffuse vascular injury. We also studied changes in brain structure over time using Jacobian Determinant statistics extracted from serial volumetric imaging. We tested 41 male and 3 female adult elite rugby players, of whom 21 attended study visits after a head injury, alongside 32 non-sporting controls, 15 non-collision-sport athletic controls and 16 longitudinally assessed controls. Eighteen rugby players participated in the longitudinal arm of the study, with a second visit at least 6 months after their first scan. Neuroimaging evidence of either axonal injury or diffuse vascular injury was present in 23% (10/44) of players. In the non-acutely injured group of rugby players, abnormalities of fractional anisotropy and other diffusion measures were seen. In contrast, non-collision-sport athletic controls were not classified as showing abnormalities. A group level contrast also showed evidence of sub-acute injury using diffusion tensor imaging in rugby players. Examination of longitudinal imaging revealed unexpected reductions in white matter volume in the elite rugby players studied. These changes were not related to self-reported head injury history or neuropsychological test scores and might indicate excess neurodegeneration in white matter tracts affected by injury. Taken together, our findings suggest an association of participation in elite adult rugby with changes in brain structure. Further well-designed large-scale studies are needed to understand the impact of both repeated sports-related head impacts and head injuries on brain structure, and to clarify whether the abnormalities we have observed are related to an increased risk of neurodegenerative disease and impaired neurocognitive function following elite rugby participation.

White and Gray Matter Abnormalities in Australian Footballers With a History of Sports-Related Concussion: An MRI Study

Sports-related concussion (SRC) is a form of mild traumatic brain injury that has been linked to long-term neurological abnormalities. Australian rules football is a collision sport with wide national participation and is growing in popularity worldwide. However, the chronic neurological consequences of SRC in Australian footballers remain poorly understood. This study investigated the presence of brain abnormalities in Australian footballers with a history of sports-related concussion (HoC) using multimodal MRI. Male Australian footballers with HoC (n = 26), as well as noncollision sport athletes with no HoC (n = 27), were recruited to the study. None of the footballers had sustained a concussion in the preceding 6 months, and all players were asymptomatic. Data were acquired using a 3T MRI scanner. White matter integrity was assessed using diffusion tensor imaging. Cortical thickness, subcortical volumes, and cavum septum pellucidum (CSP) were analyzed using structural MRI. Australian footballers had evidence of widespread microstructural white matter damage and cortical thinning. No significant differences were found regarding subcortical volumes or CSP. These novel findings provide evidence of persisting white and gray matter abnormalities in Australian footballers with HoC, and raise concerns related to the long-term neurological health of these athletes.

Identifying degenerative effects of repetitive head trauma with neuroimaging: a clinically-oriented review

BACKGROUND AND SCOPE OF REVIEW

Varying severities and frequencies of head trauma may result in dynamic acute and chronic pathophysiologic responses in the brain. Heightened attention to long-term effects of head trauma, particularly repetitive head trauma, has sparked recent efforts to identify neuroimaging biomarkers of underlying disease processes. Imaging modalities like structural magnetic resonance imaging (MRI) and positron emission tomography (PET) are the most clinically applicable given their use in neurodegenerative disease diagnosis and differentiation. In recent years, researchers have targeted repetitive head trauma cohorts in hopes of identifying in vivo biomarkers for underlying biologic changes that might ultimately improve diagnosis of chronic traumatic encephalopathy (CTE) in living persons. These populations most often include collision sport athletes (e.g., American football, boxing) and military veterans with repetitive low-level blast exposure. We provide a clinically-oriented review of neuroimaging data from repetitive head trauma cohorts based on structural MRI, FDG-PET, Aβ-PET, and tau-PET. We supplement the review with two patient reports of neuropathology-confirmed, clinically impaired adults with prior repetitive head trauma who underwent structural MRI, FDG-PET, Aβ-PET, and tau-PET in addition to comprehensive clinical examinations before death.

REVIEW CONCLUSIONS

Group-level comparisons to controls without known head trauma have revealed inconsistent regional volume differences, with possible propensity for medial temporal, limbic, and subcortical (thalamus, corpus callosum) structures. Greater frequency and severity (i.e., length) of cavum septum pellucidum (CSP) is observed in repetitive head trauma cohorts compared to unexposed controls. It remains unclear whether CSP predicts a particular neurodegenerative process, but CSP presence should increase suspicion that clinical impairment is at least partly attributable to the individual's head trauma exposure (regardless of underlying disease). PET imaging similarly has not revealed a prototypical metabolic or molecular pattern associated with repetitive head trauma or predictive of CTE based on the most widely studied radiotracers. Given the range of clinical syndromes and neurodegenerative pathologies observed in a subset of adults with prior repetitive head trauma, structural MRI and PET imaging may still be useful for differential diagnosis (e.g., assessing suspected Alzheimer's disease).

Association of Previous Concussion with Hippocampal Volume and Symptoms in Collegiate-Aged Athletes

There is concern that previous concussion and contact-sport exposure may have negative effects on brain structure and function. Accurately quantifying previous concussion is complicated by the fact that multiple definitions exist, with recent definitions allowing for diagnosis based on the presence of symptoms alone (Concussion in Sport Group criteria; CISG) rather than the presence of acute injury characteristics such as alterations in mental status (American Congress of Rehabilitation Medicine criteria; ACRM). The goals of the current work were to determine the effects of previous concussion and contact-sport exposure on gray matter structure and clinical measures in healthy, young-adult athletes and determine the extent to which these associations are influenced by diagnostic criteria used to retrospectively quantify concussions. One-hundred eight collegiate-aged athletes were enrolled; 106 athletes were included in final analyses (age, 21.37 ± 1.69; 33 female). Participants completed a clinical battery of self-report and neurocognitive measures and magnetic resonance imaging to quantify subcortical volumes and cortical thickness. Semistructured interviews were conducted to measure exposure to contact sports and the number of previous concussions based on CISG and ACRM criteria. There was a significant association of concussion-related and psychological symptoms with previous concussions based on ACRM (ps < 0.05), but not CISG, criteria. Hippocampal volume was inversely associated with the number of previous concussions for both criteria (ps < 0.05). Findings provide evidence that previous concussions are associated with smaller hippocampal volumes and greater subjective clinical symptoms in otherwise healthy athletes and highlight the importance of diagnostic criteria used to quantify previous concussion.

The role of diffusion tensor imaging in characterizing injury patterns on athletes with concussion and subconcussive injury: a systematic review

Traumatic brain injury (TBI) is a major public health problem. The majority of TBIs are in the form of mild TBI (also known as concussion) with sports-related concussion (SRC) receiving public attention in recent years.Here we have performed a systematic review of the literature on the use of Diffusion Tensor Imaging (DTI) on sports-related concussion and subconcussive injuries. Our review found different patterns of change in DTI parameters between concussed and subconcussed groups. The Fractional Anisotropy (FA) was either unchanged or increased for the concussion group, while the subconcussed group generally experienced a decrease in FA. A reverse pattern was observed for Mean Diffusivity (MD) - where the concussed group experienced a decrease in MD while the subconcussed group showed an increase in MD. However, in general, discrepancies were observed in the results reported in the literature - likely due to the huge variations in DTI acquisition parameters, and image processing and analysis methods used in these studies. This calls for more comprehensive and well-controlled studies in this field, including those that combine the advanced brain imaging with biomechancial modeling and kinematic sensors - to shed light on the underlying mechanisms behind the structural changes observed from the imaging studies.

Systemic inflammation moderates the association of prior concussion with hippocampal volume and episodic memory in high school and collegiate athletes

BACKGROUND

There is a need to determine why prior concussion has been associated with adverse outcomes in some retired and active athletes. We examined whether serum inflammatory markers moderate the associations of prior concussion with hippocampal volumes and neurobehavioral functioning in active high school and collegiate athletes.

METHODS

Athletes (N = 201) completed pre-season clinical testing and serum collection (C-reactive protein [CRP]; Interleukin-6 [IL]-6; IL-1 receptor antagonist [RA]) and in-season neuroimaging. Linear mixed-effects models examined associations of prior concussion with inflammatory markers, self-reported symptoms, neurocognitive function, and hippocampal volumes. Models examined whether inflammatory markers moderated associations of concussion history and hippocampal volume and/or clinical measures.

RESULTS

Concussion history was significantly associated with higher symptom severity, p = 0.012, but not hippocampal volume or inflammatory markers (ps > 0.05). A significant interaction of prior concussion and CRP was observed for hippocampal volume, p = 0.006. Follow-up analyses showed that at high levels of CRP, athletes with two or more prior concussions had smaller hippocampal volume compared to athletes without prior concussion, p = 0.008. There was a significant interaction between prior concussion and levels of IL-1RA on memory scores, p = 0.044, i.e., at low levels of IL-1RA, athletes with two or more concussions had worse memory performance than those without prior concussion (p = 0.014).

CONCLUSION

Findings suggest that certain markers of systemic inflammation moderate the association between prior concussion and hippocampal volume and episodic memory performance. Current findings highlight potential markers for predicting at-risk individuals and identify therapeutic targets for mitigating the long-term adverse consequences of cumulative concussion.

Prospective study of the association between sport-related concussion and brain morphometry (3T-MRI) in collegiate athletes: study from the NCAA-DoD CARE Consortium

OBJECTIVES

To determine the acute and early long-term associations of sport-related concussion (SRC) and subcortical and cortical structures in collegiate contact sport athletes.

METHODS

Athletes with a recent SRC (n=99) and matched contact (n=91) and non-contact sport controls (n=95) completed up to four neuroimaging sessions from 24 to 48 hours to 6 months postinjury. Subcortical volumes (amygdala, hippocampus, thalamus and dorsal striatum) and vertex-wise measurements of cortical thickness/volume were computed using FreeSurfer. Linear mixed-effects models examined the acute and longitudinal associations between concussion and structural metrics, controlling for intracranial volume (or mean thickness) and demographic variables (including prior concussions and sport exposure).

RESULTS

There were significant group-dependent changes in amygdala volumes across visits (p=0.041); this effect was driven by a trend for increased amygdala volume at 6 months relative to subacute visits in contact controls, with no differences in athletes with SRC. No differences were observed in any cortical metric (ie, thickness or volume) for primary or secondary analyses.

CONCLUSION

A single SRC had minimal associations with grey matter structure across a 6-month time frame.

Cumulative Effects of Prior Concussion and Primary Sport Participation on Brain Morphometry in Collegiate Athletes: A Study From the NCAA-DoD CARE Consortium

Prior studies have reported long-term differences in brain structure (brain morphometry) as being associated with cumulative concussion and contact sport participation. There is emerging evidence to suggest that similar effects of prior concussion and contact sport participation on brain morphometry may be present in younger cohorts of active athletes. We investigated the relationship between prior concussion and primary sport participation with subcortical and cortical structures in active collegiate contact sport and non-contact sport athletes. Contact sport athletes (CS; N = 190) and matched non-contact sport athletes (NCS; N = 95) completed baseline clinical testing and participated in up to four serial neuroimaging sessions across a 6-months period. Subcortical and cortical structural metrics were derived using FreeSurfer. Linear mixed-effects (LME) models examined the effects of years of primary sport participation and prior concussion (0, 1+) on brain structure and baseline clinical variables. Athletes with prior concussion across both groups reported significantly more baseline concussion and psychological symptoms (all ps < 0.05). The relationship between years of primary sport participation and thalamic volume differed between CS and NCS (p = 0.015), driven by a significant inverse association between primary years of participation and thalamic volume in CS (p = 0.007). Additional analyses limited to CS alone showed that the relationship between years of primary sport participation and dorsal striatal volume was moderated by concussion history (p = 0.042). Finally, CS with prior concussion had larger hippocampal volumes than CS without prior concussion (p = 0.015). Years of contact sport exposure and prior concussion(s) are associated with differences in subcortical volumes in young-adult, active collegiate athletes, consistent with prior literature in retired, primarily symptomatic contact sport athletes. Longitudinal follow-up studies in these athletes are needed to determine clinical significance of current findings.

A Novel Gradient Echo Plural Contrast Imaging Method Detects Brain Tissue Abnormalities in Patients With TBI Without Evident Anatomical Changes on Clinical MRI: A Pilot Study

RESEARCH OBJECTIVES

It is widely accepted that mild traumatic brain injury (mTBI) causes injury to the white matter, but the extent of gray matter (GM) damage in mTBI is less clear.

METHODS

We tested 26 civilian healthy controls and 14 civilian adult subacute-chronic mTBI patients using quantitative features of MRI-based Gradient Echo Plural Contrast Imaging (GEPCI) technique. GEPCI data were reconstructed using previously developed algorithms allowing the separation of R2t*, a cellular-specific part of gradient echo MRI relaxation rate constant, from global R2* affected by BOLD effect and background gradients.

RESULTS

Single-subject voxel-wise analysis (comparing each mTBI patient to the sample of 26 control subjects) revealed GM abnormalities that were not visible on standard MRI images (T1w and T2w). Analysis of spatial overlap for voxels with low R2t* revealed tissue abnormalities in multiple GM regions, especially in the frontal and temporal regions, that are frequently damaged after mTBI. The left posterior insula was the region with abnormalities found in the highest proportion (50%) of mTBI patients.

CONCLUSIONS

Our data suggest that GEPCI quantitative R2t* metric has potential to detect abnormalities in GM cellular integrity in individual TBI patients, including abnormalities that are not detectable by a standard clinical MRI.

Cortical thinning in military blast compared to non-blast persistent mild traumatic brain injuries

In the military, explosive blasts are a significant cause of mild traumatic brain injuries (mTBIs). The symptoms associated with blast mTBIs causes significant economic burdens and a diminished quality of life for many service members. At present, the distinction of the injury mechanism (blast versus non-blast) may not influence TBI diagnosis. However, using noninvasive imaging, this study reveals significant distinctions between the blast and non-blast TBI mechanisms. A cortical whole-brain thickness analysis was performed using structural high-resolution T1-weighted MRI to identify the effects of blasts in persistent mTBI (pmTBI) subjects. A total of 41 blast pmTBI subjects were individually age- and gender-matched to 41 non-blast pmTBI subjects. Using FreeSurfer, cortical thickness was quantified for the blast group, relative to the non-blast group. Cortical thinning was identified within the blast mTBI group, in two clusters bilaterally. In the left hemisphere, the cluster overlapped with the lateral orbitofrontal, rostral middle frontal, medial orbitofrontal, superior frontal, rostral anterior cingulate and frontal pole cortices (p < 0.02, two-tailed, size = 1680 mm²). In the right hemisphere, the cluster overlapped with the lateral orbitofrontal, rostral middle frontal, medial orbitofrontal, pars orbitalis, pars triangularis and insula cortices (p < 0.002, two-tailed, cluster size = 2453 mm²). Self-report assessments suggest significant differences in the Post-Traumatic Stress Disorder Checklist-Civilian Version (p < 0.05, Bonferroni-corrected) and the Neurobehavioral Symptom Inventory (p < 0.01, uncorrected) between the blast and non-blast mTBI groups. These results suggest that blast may cause a unique injury pattern related to a reduction in cortical thickness within specific brain regions which could affect symptoms. No other study has found cortical thickness difference between blast and non-blast mTBI groups and further replication is needed to confirm these initial observations.

Unifying Pathophysiological Explanations for Sports-Related Concussion and Concussion Protocol Management: Literature Review

Objective

There is a plethora of theories about the pathophysiology behind a sport-related concussion. In this review of the literature, the authors evaluated studies on the pathophysiology of sport-related concussion and professional athlete return-to-play guidelines. The goal of this article is to summarize the most common hypotheses for sport-related concussion, evaluate if there are common underlying mechanisms, and determine if correlations are seen between published mechanisms and the most current return-to-play recommendations.

Methods

Two authors selected papers from the past 5 years for literature review involving discussion of sport-related concussion and pathophysiology, pathology, or physiology of concussion using mutually agreed-upon search criteria. After the articles were filtered based on search criteria, pathophysiological explanations for concussion were organized into tables. Following analysis of pathophysiology, concussion protocols and return-to-play guidelines were obtained via a Google search for the major professional sports leagues and synthesized into a summary table.

Results

Out of 1112 initially identified publications, 53 met our criteria for qualitative analysis. The 53 studies revealed 5 primary neuropathological explanations for sport-related concussion, regardless of the many theories talked about in the different papers. These 5 explanations, in order of predominance in the articles analyzed, were (1) tauopathy, (2) white matter changes, (3) neural connectivity alterations, (4) reduction in cerebral perfusion, and (5) gray matter atrophy. Pathology may be sport specific: white matter changes are seen in 47% of football reports, tauopathy is seen in 50% of hockey reports, and soccer reports 50% tauopathy as well as 50% neural connectivity alterations. Analysis of the return-to-play guidelines across professional sports indicated commonalities in concussion management despite individual policies.

Conclusions

Current evidence on pathophysiology for sport-related concussion does not yet support one unifying mechanism, but published hypotheses may potentially be simplified into 5 primary groups. The unification of the complex, likely multifactorial mechanisms for sport-related concussion to a few common explanations, combined with unique findings within individual sports presented in this report, may help filter and link concussion pathophysiology in sport. By doing so, the authors hope that this review will help guide future concussion research, treatment, and management.

A review of the effects of physical activity and sports concussion on brain function and anatomy

Physical activity has been associated with widespread anatomical and functional brain changes that occur following acute exercise or, in the case of athletes, throughout life. High levels of physical activity through the practice of sports also lead to better general health and increased cognitive function. Athletes are at risk, however, of suffering a concussion, the effects of which have been extensively described for brain function and anatomy. The level to which these effects are modulated by increased levels of fitness is not known. Here, we review literature describing the effects of physical activity and sports concussions on white matter, grey matter, neurochemistry and cortical excitability. We suggest that the effects of sports concussion can be coufounded by the effects of exercise. Indeed, available data show that the brain of athletes is different from that of healthy individuals with a non-active lifestyle. As a result, sports concussions take place in a context where structural/functional plasticity has occurred prior to the concussive event. The sports concussion literature does not permit, at present, to separate the effects of intense and repeated physical activity, and the abrupt removal from such activities, from those of concussion on brain structure and function.

Near-Term Decrease in Brain Volume following Mild Traumatic Injury Is Detectible in the Context of Preinjury Volumetric Stability: Neurobiologic Insights from Analysis of Historical Imaging Examinations

BACKGROUND AND PURPOSE

Neurodegeneration after mild traumatic brain injury may manifest as decreasing regional brain volume that evolves from months to years following mild traumatic brain injury and is associated with worse clinical outcomes. We hypothesized that quantitative brain volume derived from CT of the head, performed for clinical indications during routine care, would change with time and provide insights into the putative neuroinflammatory response to mild traumatic brain injury.

MATERIALS AND METHODS

We searched the electronic medical record of our institution for NCCTs of the head performed in patients with mild traumatic brain injury and included those who also underwent NCCTs of the head 1 month to 1 year before and after mild traumatic brain injury for an indication unrelated to trauma. Controls underwent 3 sequential NCCTs of the head with indications unrelated to trauma. The whole-brain and intracranial volume groups were computed using ITK-SNAP. Brain volumes normalized to intracranial volumes were compared across time points using the Wilcoxon signed-rank test.

RESULTS

We identified 48 patients from 2005 to 2015 who underwent NCCTs of the head in the emergency department for mild traumatic brain injury and had NCCTs of the head performed both before and after mild traumatic brain injury. Median normalized brain volumes significantly decreased on the follow-up study post-mild traumatic brain injury (0.86 versus 0.84, P < .001) and were similar compared with pre-mild traumatic brain injury studies (0.87 versus 0.86, P = .927). There was no significant difference between normalized brain volumes in the 48 controls.

CONCLUSIONS

A decrease in brain volume following mild traumatic brain injury is detectable on CT and is not seen in similar patients with non-mild traumatic brain injury during a similar timeframe. Given the stability of brain volume before mild traumatic brain injury, CT volume loss may represent the subtle effects of neurodegeneration.

Advanced biomarkers of pediatric mild traumatic brain injury: Progress and perils

There is growing public concern about neurodegenerative changes (e.g., Chronic Traumatic Encephalopathy) that may occur chronically following clinically apparent and clinically silent (i.e., sub-concussive blows) pediatric mild traumatic brain injury (pmTBI). However, there are currently no biomarkers that clinicians can use to objectively diagnose patients or predict those who may struggle to recover. Non-invasive neuroimaging, electrophysiological and neuromodulation biomarkers have promise for providing evidence of the so-called "invisible wounds" of pmTBI. Our systematic review, however, belies that notion, identifying a relative paucity of high-quality, clinically impactful, diagnostic or prognostic biomarker studies in the sub-acute injury phase (36 studies on unique samples in 28 years), with the majority focusing on adolescent pmTBI. Ultimately, well-powered longitudinal studies with appropriate control groups, as well as standardized and clearly-defined inclusion criteria (time post-injury, injury severity and past history) are needed to truly understand the complex pathophysiology that is hypothesized (i.e., still needs to be determined) to exist during the acute and sub-acute stages of pmTBI and may underlie post-concussive symptoms.

Postconcussive Symptoms After Single and Repeated Concussions in 10- to 20-Year-Olds: A Cross-Sectional Study

The objective was to characterize cognitive deficits and postconcussive symptoms in a pediatric population with no concussion, a single concussion, and ≥2 concussions, using a cross-sectional design. Cognitive function and postconcussive symptoms were assessed in participants (age 10-20) with no concussion (n = 1118), single concussion (n = 368), and repeated (≥2) concussions (n = 252). Analyses were adjusted for age and gender. Individuals with ≥2 concussions exhibited more total postconcussive symptoms; more loss of consciousness, amnesia and confusion; more headaches; and poorer cognitive function compared to no concussion and single concussion. Postconcussive symptoms may play a modulatory role in cognitive dysfunction after repeated concussions as those with loss of consciousness, amnesia, confusion, or headaches exhibited worse verbal memory, visual memory, visual-motor processing, and poorer impulse control compared to those without these symptoms. This analysis demonstrates that repeated concussions is associated with poorer cognitive function and postconcussive symptoms compared to a single concussion.

Cortical thickness and subcortical brain volumes in professional rugby league players

Purpose

The purpose of this study was to examine cortical thickness and subcortical volumes in professional rugby players with an extensive history of concussions compared to control subjects.

Method

Participants included 24 active and former professional rugby league players [Age M(SD) = 33.3(6.3); Range = 21–44] with an extensive history of concussion and 18 age- and education-matched controls with no history of neurotrauma or participation in contact sports. Participants underwent T1-weighted imaging and completed a neuropsychological battery, including two tests of memory. Whole brain cortical thickness analysis and structural volume analysis was performed using FreeSurfer version 6.0.

Results

Professional rugby league players reported greater alcohol consumption (p < .001) and had significantly worse delayed recall of a visually complex design (p = .04). They did not differ from controls on other clinical outcome measures. There were no differences in cortical thickness between the groups. Professional players had smaller whole brain (p = .003), bilateral hippocampi (ps = .03), and left amygdala volumes (p = .01) compared to healthy controls. Within the players group, there were significant associations between greater alcohol use and smaller bilateral hippocampi and left amygdala volumes. There were no associations between structural volumes and history of concussions or memory performance.

Conclusions

The literature examining cortical thickness in athletes with a history of multiple concussions is mixed. We did not observe differences in cortical thickness in professional rugby league players compared to controls. However, smaller subcortical volumes were found in players that were, in part, associated with greater alcohol consumption.

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No differences in cortical thickness were observed in rugby players compared to controls.

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Smaller hippocampal and amygdala volumes were observed in rugby players.

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Greater alcohol use was associated with smaller bilateral hippocampi and left amygdala volumes in rugby players.

Prefrontal Cortical Thickening after Mild Traumatic Brain Injury: A One-Year Magnetic Resonance Imaging Study

The objective of this study was to evaluate group-by-time interactions between gray matter morphology of healthy controls and that of patients with mild traumatic brain injury (mTBI) as they transitioned from acute to chronic stages, and to relate these findings to long-term cognitive alterations to identify distinct recovery trajectories between good outcome (GO) and poor outcome (PO). High-resolution T1-weighted magnetic resonance images were acquired in 49 mTBI patients within 7 days and 1 year post-injury and at equivalent times in 49 healthy controls. Using linear mixed-effects models, we performed mass-univariate analyses and associated the results of the interaction with changes in cognitive performance. Morphological alterations indexed by increased or decreased cortical thickness have been expected mainly in frontal, parietal, and temporal brain regions. A significant interaction was found in cortical thickness, spatially restricted to bilateral structures of the prefrontal cortex, showing thickening in mTBI and normal developmental thinning in controls. A discrete thickness increase that can interpreted as the absence of cortical thinning typically seen in the healthy population was associated with cognitive recovery in the GO subgroup, while the exaggerated cortical thickening in the PO patients was linked to worsening cognitive performance. Thickness of the prefrontal cortex is subject to structural alterations during the first year after mTBI. Beside beneficial neuroplasticity, a prolonged state of neuroinflammation for symptomatic patients (maladaptive neuroplasticity) cannot be excluded. If the underlying cellular processes responsible for cortical thickening following mTBI have been determined, brain stimulation or even pharmacological intervention targeting the prefrontal cortex might promote endogenous neural restoration.

Persistent post-traumatic headache vs. migraine: an MRI study demonstrating differences in brain structure

Background

The majority of individuals with post-traumatic headache have symptoms that are indistinguishable from migraine. The overlap in symptoms amongst these individuals raises the question as to whether post-traumatic headache has a unique pathophysiology or if head trauma triggers migraine. The objective of this study was to compare brain structure in individuals with persistent post-traumatic headache (i.e. headache lasting at least 3 months following a traumatic brain injury) attributed to mild traumatic brain injury to that of individuals with migraine.

Methods

Twenty-eight individuals with persistent post-traumatic headache attributed to mild traumatic brain injury and 28 individuals with migraine underwent brain magnetic resonance imaging on a 3 T scanner. Regional volumes, cortical thickness, surface area and curvature measurements were calculated from T1-weighted sequences and compared between subject groups using ANCOVA. MRI data from 28 healthy control subjects were used to interpret the differences in brain structure between migraine and persistent post-traumatic headache.

Results

Differences in regional volumes, cortical thickness, surface area and brain curvature were identified when comparing the group of individuals with persistent post-traumatic headache to the group with migraine. Structure was different between groups for regions within the right lateral orbitofrontal lobe, left caudal middle frontal lobe, left superior frontal lobe, left precuneus and right supramarginal gyrus (p < .05). Considering these regions only, there were differences between individuals with persistent post-traumatic headache and healthy controls within the right lateral orbitofrontal lobe, right supramarginal gyrus, and left superior frontal lobe and no differences when comparing the migraine cohort to healthy controls.

Conclusions

In conclusion, persistent post-traumatic headache and migraine are associated with differences in brain structure, perhaps suggesting differences in their underlying pathophysiology. Additional studies are needed to further delineate similarities and differences in brain structure and function that are associated with post-traumatic headache and migraine and to determine their specificity for each of the headache types.

The effect of repetitive subconcussive collisions on brain integrity in collegiate football players over a single football season: A multi-modal neuroimaging study

The cumulative effect of repetitive subconcussive collisions on the structural and functional integrity of the brain remains largely unknown. Athletes in collision sports, like football, experience a large number of impacts across a single season of play. The majority of these impacts, however, are generally overlooked, and their long-term consequences remain poorly understood. This study sought to examine the effects of repetitive collisions across a single competitive season in NCAA Football Bowl Subdivision athletes using advanced neuroimaging approaches. Players were evaluated before and after the season using multiple MRI sequences, including T₁-weighted imaging, diffusion tensor imaging (DTI), arterial spin labeling (ASL), resting-state functional MRI (rs-fMRI), and susceptibility weighted imaging (SWI). While no significant differences were found between pre- and post-season for DTI metrics or cortical volumes, seed-based analysis of rs-fMRI revealed significant (p < 0.05) changes in functional connections to right isthmus of the cingulate cortex (ICC), left ICC, and left hippocampus. ASL data revealed significant (p < 0.05) increases in global cerebral blood flow (CBF), with a specific regional increase in right postcentral gyrus. SWI data revealed that 44% of the players exhibited outlier rates (p < 0.05) of regional decreases in SWI signal. Of key interest, athletes in whom changes in rs-fMRI, CBF and SWI were observed were more likely to have experienced high G impacts on a daily basis. These findings are indicative of potential pathophysiological changes in brain integrity arising from only a single season of participation in the NCAA Football Bowl Subdivision, even in the absence of clinical symptoms or a diagnosis of concussion. Whether these changes reflect compensatory adaptation to cumulative head impacts or more lasting alteration of brain integrity remains to be further explored.

Repetitive Model of Mild Traumatic Brain Injury Produces Cortical Abnormalities Detectable by Magnetic Resonance Diffusion Imaging, Histopathology, and Behavior

Noninvasive detection of mild traumatic brain injury (mTBI) is important for evaluating acute through chronic effects of head injuries, particularly after repetitive impacts. To better detect abnormalities from mTBI, we performed longitudinal studies (baseline, 3, 6, and 42 days) using magnetic resonance diffusion tensor imaging (DTI) and diffusion kurtosis imaging (DKI) in adult mice after repetitive mTBI (r-mTBI; daily × 5) or sham procedure. This r-mTBI produced righting reflex delay and was first characterized in the corpus callosum to demonstrate low levels of axon damage, astrogliosis, and microglial activation, without microhemorrhages. High-resolution DTI-DKI was then combined with post-imaging pathological validation along with behavioral assessments targeted for the impact regions. In the corpus callosum, only DTI fractional anisotropy at 42 days showed significant change post-injury. Conversely, cortical regions under the impact site (M1–M2, anterior cingulate) had reduced axial diffusivity (AD) at all time points with a corresponding increase in axial kurtosis (K_a) at 6 days. Post-imaging neuropathology showed microglial activation in both the corpus callosum and cortex at 42 days after r-mTBI. Increased cortical microglial activation correlated with decreased cortical AD after r-mTBI (r = −0.853; n = 5). Using Thy1-YFP-16 mice to fluorescently label neuronal cell bodies and processes revealed low levels of axon damage in the cortex after r-mTBI. Finally, r-mTBI produced social deficits consistent with the function of this anterior cingulate region of cortex. Overall, vulnerability of cortical regions is demonstrated after mild repetitive injury, with underlying differences of DTI and DKI, microglial activation, and behavioral deficits.

Smaller Dentate Gyrus and CA2 and CA3 Volumes Are Associated with Kynurenine Metabolites in Collegiate Football Athletes

An imbalance in kynurenine pathway metabolism is hypothesized to be associated with dysregulated glutamatergic neurotransmission, which has been proposed as a mechanism underlying the hippocampal volume loss observed in a variety of neurological disorders. Pre-clinical models suggest that the CA2-3 and dentate gyrus hippocampal subfields are particularly susceptible to excitotoxicity after experimental traumatic brain injury. We tested the hypothesis that smaller hippocampal volumes in collegiate football athletes with (n = 25) and without (n = 24) a concussion history would be most evident in the dentate gyrus and CA2-3 subfields relative to nonfootball healthy controls (n = 27). Further, we investigated whether the concentration of peripheral levels of kynurenine metabolites are altered in football athletes. Football athletes with and without a self-reported concussion history had smaller dentate gyrus (p < 0.05, p < 0.10) and CA2-3 volumes (p's < 0.05) relative to healthy controls. Football athletes with and without a concussion history had a trend toward lower (p < 0.10) and significantly lower (p < 0.05) kynurenine levels compared with healthy controls, while athletes with a concussion history had greater levels of quinolinic acid compared with athletes without a concussion history (p < 0.05). Finally, plasma levels of 3-hydroxykynurenine inversely correlated with bilateral hippocampal volumes in football athletes with a concussion history (p < 0.01), and left hippocampal volume was correlated with the ratio of kynurenic acid to quinolinic acid in football athletes without a concussion history (p < 0.05). Our results raise the possibility that abnormalities of the kynurenine metabolic pathway constitute a mechanism for hippocampal volume differences in the context of sports-related brain injury.