Association between recurrent concussion and late-life cognitive impairment in retired professional football players

Progressive inflammation-mediated neurodegeneration after traumatic brain or spinal cord injury

Traumatic brain injury (TBI) has been linked to dementia and chronic neurodegeneration. Described initially in boxers and currently recognized across high contact sports, the association between repeated concussion (mild TBI) and progressive neuropsychiatric abnormalities has recently received widespread attention, and has been termed chronic traumatic encephalopathy. Less well appreciated are cognitive changes associated with neurodegeneration in the brain after isolated spinal cord injury. Also under-recognized is the role of sustained neuroinflammation after brain or spinal cord trauma, even though this relationship has been known since the 1950s and is supported by more recent preclinical and clinical studies. These pathological mechanisms, manifested by extensive microglial and astroglial activation and appropriately termed chronic traumatic brain inflammation or chronic traumatic inflammatory encephalopathy, may be among the most important causes of post-traumatic neurodegeneration in terms of prevalence. Importantly, emerging experimental work demonstrates that persistent neuroinflammation can cause progressive neurodegeneration that may be treatable even weeks after traumatic injury.

Policies, Procedures, and Practices Regarding Sport-Related Concussion in Community College Athletes

CONTEXT

College sport organizations and associations endorse concussion-management protocols and policies. To date, little information is available on concussion policies and practices at community college institutions.

OBJECTIVE

To assess and describe current practices and policies regarding the assessment, management, and return-to-play criteria for sport-related concussion (SRC) among member institutions of the California Community College Athletic Association (CCCAA).

DESIGN

Cross-sectional study.

SETTING

Web-based survey.

PATIENTS OR OTHER PARTICIPANTS

A total of 55 head athletic trainers (ATs) at CCCAA institutions.

MAIN OUTCOME MEASURE(S)

Data about policies, procedures, and practices regarding SRC were collected over a 3-week period in March 2012 and analyzed using descriptive statistics, the Fisher exact test, and the Spearman test.

RESULTS

Almost half (47%) of ATs stated they had a policy for SRC assessment, management, and return to play at their institution. They reported being in compliance with baseline testing guidelines (25%), management guidelines (34.5%), and return-to-play guidelines (30%). Nearly 31% of ATs described having an SRC policy in place for academic accommodations. Conference attendance was positively correlated with institutional use of academic accommodations after SRC (r = 0.44, P = .01). The number of meetings ATs attended and their use of baseline testing were also positively correlated (r = 0.38, P = .01).

CONCLUSIONS

At the time of this study, nearly half of CCCAA institutions had concussion policies and 31% had academic-accommodation policies. However, only 18% of ATs at CCCAA institutions were in compliance with all of their concussion policies. Our findings demonstrate improvements in the management of SRCs by ATs at California community colleges compared with previous research but a need for better compliance with SRC policies.

Motivations Associated With Nondisclosure of Self-Reported Concussions in Former Collegiate Athletes

BACKGROUND

Previous studies examining nondisclosure among athletes in various settings have found substantial proportions of athletes with undisclosed concussions. Substantial gaps exist in our understanding of the factors influencing athletes' disclosure of sports-related concussions.

PURPOSE

To examine the prevalence of, and factors associated with, nondisclosure of recalled concussions in former collegiate athletes.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Former collegiate athletes (N = 797) completed an online questionnaire. Respondents recalled self-identified sports-related concussions (SISRCs) that they sustained while playing sports in high school, college, or professionally, and whether they disclosed these SISRCs to others. Respondents also recalled motivations for nondisclosure. The prevalence of nondisclosure was calculated among those who recalled SISRCs. Multivariate binomial regression estimated adjusted prevalence ratios (PRs) with 95% CIs, controlling for sex, level of contact in sports, and year the athletes began playing collegiate sports.

RESULTS

A total of 214 respondents (26.9%) reported sustaining at least 1 SISRC. Of these, 71 (33.2%) reported not disclosing at least 1 SISRC. Former football athletes were most likely to report nondisclosure (68.3% of those recalling SISRCs); female athletes who participated in low/noncontact sports were the least likely to report nondisclosure (11.1% of those recalling SISRC). The prevalence of nondisclosure was higher among men than women in the univariate analysis (PR, 2.88; 95% CI, 1.62-5.14), multivariate analysis (PR, 2.11; 95% CI, 1.13-3.96), and multivariate analysis excluding former football athletes (PR, 2.11; 95% CI, 1.12-3.94). The most commonly reported motivations were as follows: did not want to leave the game/practice (78.9%), did not want to let the team down (71.8%), did not know it was a concussion (70.4%), and did not think it was serious enough (70.4%).

CONCLUSION

Consistent with previous studies, a substantial proportion of former athletes recalled SISRCs that were not disclosed. Male athletes were less likely to disclose all of their SISRCs than female athletes.

Progesterone treatment reduces neuroinflammation, oxidative stress and brain damage and improves long-term outcomes in a rat model of repeated mild traumatic brain injury

BACKGROUND

Repeated mild traumatic brain injuries, such as concussions, may result in cumulative brain damage, neurodegeneration and other chronic neurological impairments. There are currently no clinically available treatment options known to prevent these consequences. However, growing evidence implicates neuroinflammation and oxidative stress in the pathogenesis of repetitive mild brain injuries; thus, these may represent potential therapeutic targets. Progesterone has been demonstrated to have potent anti-inflammatory and anti-oxidant properties after brain insult; therefore, here, we examined progesterone treatment in rats given repetitive mild brain injuries via the repeated mild fluid percussion injury model.

METHODS

Male Long-Evans rats were assigned into four groups: sham injury + vehicle treatment, sham injury + progesterone treatment (8 mg/kg/day), repeated mild fluid percussion injuries + vehicle treatment, and repeated mild fluid percussion injuries + progesterone treatment. Rats were administered a total of three injuries, with each injury separated by 5 days. Treatment was initiated 1 h after the first injury, then administered daily for a total of 15 days. Rats underwent behavioural testing at 12-weeks post-treatment to assess cognition, motor function, anxiety and depression. Brains were then dissected for analysis of markers for neuroinflammation and oxidative stress. Ex vivo MRI was conducted in order to examine structural brain damage and white matter integrity.

RESULTS

Repeated mild fluid percussion injuries + progesterone treatment rats showed significantly reduced cognitive and sensorimotor deficits compared to their vehicle-treated counterparts at 12-weeks post-treatment. Progesterone treatment significantly attenuated markers of neuroinflammation and oxidative stress in rats given repeated mild fluid percussion injuries, with concomitant reductions in grey and white matter damage as indicated by MRI.

CONCLUSIONS

These findings implicate neuroinflammation and oxidative stress in the pathophysiological aftermath of mild brain injuries and suggest that progesterone may be a viable treatment option to mitigate these effects and their detrimental consequences.

The clinical presentation of chronic traumatic encephalopathy

Chronic traumatic encephalopathy (CTE) is a progressive neurodegenerative disorder attributed to repetitive mild traumatic brain injury. The diagnosis in a living individual can be challenging and can be made definitively only at autopsy. The symptoms are often nonspecific and overlap with neurodegenerative disorders such as Alzheimer's disease (AD) and frontotemporal dementia (FTD). Higher exposure to repetitive head trauma increases the risk of CTE. Genetic risk factors such as presence of an apolipoprotein E ε4 allele may be important. Individuals have varying degrees of cognitive, behavioral, and motor decline. Limitations in the manner in which data have been obtained over the years have led to different clinical descriptions of CTE. At present, there are no biomarkers to assist in the diagnosis. Standard neuroimaging may show nonspecific atrophic changes; however, newer imaging modalities such as positron emission tomography (PET) and diffusion tensor imaging (DTI) show promise. Neuropsychological testing may be helpful in determining the pattern of cognitive or behavioral decline.

Mild Traumatic Brain Injury and Attention-Deficit Hyperactivity Disorder in Young Student Athletes

A recent meta-analysis documented a significant statistical association between mild traumatic brain injury (mTBI) and attention deficit hyperactivity disorder (ADHD) (Adeyemo et al., 2014), but the direction of this effect was unclear. In this study, we hypothesized that ADHD would be an antecedent risk factor for mTBI. Participants were student athletes ages 12 to 25 who had sustained a mTBI and Controls of similar age and sex selected from studies of youth with and without ADHD. Subjects were assessed for symptoms of ADHD, concussion severity, and cognitive function. mTBI subjects had a significantly higher rate of ADHD than Controls, and in all cases the age of onset of ADHD was before mTBI onset. mTBI+ADHD subjects also had more severe concussion symptoms (fatigue and poor concentration) than mTBI-ADHD subjects. These results support ADHD as an antecedent risk factor for mTBI in student athletes and that its presence complicates the course of mTBI.

Found in translation: Understanding the biology and behavior of experimental traumatic brain injury

The aim of this review is to discuss in greater detail the topics covered in the recent symposium entitled "Traumatic brain injury: laboratory and clinical perspectives," presented at the 2014 International Behavioral Neuroscience Society annual meeting. Herein, we review contemporary laboratory models of traumatic brain injury (TBI) including common assays for sensorimotor and cognitive behavior. New modalities to evaluate social behavior after injury to the developing brain, as well as the attentional set-shifting test (AST) as a measure of executive function in TBI, will be highlighted. Environmental enrichment (EE) will be discussed as a preclinical model of neurorehabilitation, and finally, an evidence-based approach to sports-related concussion will be considered. The review consists predominantly of published data, but some discussion of ongoing or future directions is provided.

Modeling Chronic Traumatic Encephalopathy: The Way Forward for Future Discovery

Despite the extensive media coverage associated with the diagnosis of chronic traumatic encephalopathy (CTE), our fundamental understanding of the disease pathophysiology remains in its infancy. Only recently have scientific laboratories and personnel begun to explore CTE pathophysiology through the use of preclinical models of neurotrauma. Some studies have shown the ability to recapitulate some aspects of CTE in rodent models, through the use of various neuropathological, biochemical, and/or behavioral assays. Many questions related to CTE development, however, remain unanswered. These include the role of impact severity, the time interval between impacts, the age at which impacts occur, and the total number of impacts sustained. Other important variables such as the location of impacts, character of impacts, and effect of environment/lifestyle and genetics also warrant further study. In this work, we attempt to address some of these questions by exploring work previously completed using single- and repetitive-injury paradigms. Despite some models producing some deficits similar to CTE symptoms, it is clear that further studies are required to understand the development of neuropathological and neurobehavioral features consistent with CTE-like features in rodents. Specifically, acute and chronic studies are needed that characterize the development of tau-based pathology.

Cognitive-motor integration deficits in young adult athletes following concussion

BACKGROUND

The ability to perform visually-guided motor tasks requires the transformation of visual information into programmed motor outputs. When the guiding visual information does not align spatially with the motor output, the brain processes rules to integrate the information for an appropriate motor response. Here, we look at how performance on such tasks is affected in young adult athletes with concussion history.

METHODS

Participants displaced a cursor from a central to peripheral targets on a vertical display by sliding their finger along a touch sensitive screen in one of two spatial planes. The addition of a memory component, along with variations in cursor feedback increased task complexity across conditions.

RESULTS

Significant main effects between participants with concussion history and healthy controls without concussion history were observed in timing and accuracy measures. Importantly, the deficits were distinctly more pronounced for participants with concussion history compared to healthy controls, especially when the brain had to control movements having two levels of decoupling between vision and action. A discriminant analysis correctly classified athletes with a history of concussion based on task performance with an accuracy of 94 %, despite the majority of these athletes being rated asymptomatic by current standards.

CONCLUSIONS

These findings correspond to our previous work with adults at risk of developing dementia, and support the use of cognitive motor integration as an enhanced assessment tool for those who may have mild brain dysfunction. Such a task may provide a more sensitive metric of performance relevant to daily function than what is currently in use, to assist in return to play/work/learn decisions.

Age at First Exposure to Football Is Associated with Altered Corpus Callosum White Matter Microstructure in Former Professional Football Players

Youth football players may incur hundreds of repetitive head impacts (RHI) in one season. Our recent research suggests that exposure to RHI during a critical neurodevelopmental period prior to age 12 may lead to greater later-life mood, behavioral, and cognitive impairments. Here, we examine the relationship between age of first exposure (AFE) to RHI through tackle football and later-life corpus callosum (CC) microstructure using magnetic resonance diffusion tensor imaging (DTI). Forty retired National Football League (NFL) players, ages 40-65, were matched by age and divided into two groups based on their AFE to tackle football: before age 12 or at age 12 or older. Participants underwent DTI on a 3 Tesla Siemens (TIM-Verio) magnet. The whole CC and five subregions were defined and seeded using deterministic tractography. Dependent measures were fractional anisotropy (FA), trace, axial diffusivity, and radial diffusivity. Results showed that former NFL players in the AFE <12 group had significantly lower FA in anterior three CC regions and higher radial diffusivity in the most anterior CC region than those in the AFE ≥12 group. This is the first study to find a relationship between AFE to RHI and later-life CC microstructure. These results suggest that incurring RHI during critical periods of CC development may disrupt neurodevelopmental processes, including myelination, resulting in altered CC microstructure.

Functional connectivity changes detected with magnetoencephalography after mild traumatic brain injury

Mild traumatic brain injury (mTBI) may affect normal cognition and behavior by disrupting the functional connectivity networks that mediate efficient communication among brain regions. In this study, we analyzed brain connectivity profiles from resting state Magnetoencephalographic (MEG) recordings obtained from 31 mTBI patients and 55 normal controls. We used phase-locking value estimates to compute functional connectivity graphs to quantify frequency-specific couplings between sensors at various frequency bands. Overall, normal controls showed a dense network of strong local connections and a limited number of long-range connections that accounted for approximately 20% of all connections, whereas mTBI patients showed networks characterized by weak local connections and strong long-range connections that accounted for more than 60% of all connections. Comparison of the two distinct general patterns at different frequencies using a tensor representation for the connectivity graphs and tensor subspace analysis for optimal feature extraction showed that mTBI patients could be separated from normal controls with 100% classification accuracy in the alpha band. These encouraging findings support the hypothesis that MEG-based functional connectivity patterns may be used as biomarkers that can provide more accurate diagnoses, help guide treatment, and monitor effectiveness of intervention in mTBI.

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We analyzed resting state connectivity profiles in 31 mTBI patients and 55 controls.

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We quantified frequency-specific connectivity couplings using phase-locking values.

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Normal control networks showed dense local and sparse long-range connections.

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TBI patient networks showed sparse local and dense long-range connections.

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Tensor subspace analysis could classify subjects with 100% accuracy in the α band

Effect of luminance on the visually-evoked potential in visually-normal individuals and in mTBI/concussion

PURPOSE

To assess quantitatively the effect of luminance on VEP amplitude and latency in visually-normals (VN) and patients with mild traumatic brain injury (mTBI).

METHODS

VN individuals (n = 20) and those with mTBI (n = 19) participated. Those with mTBI were assessed 1-10 years post-injury (mean = 4.97 years), with the exception of one subject. Pattern VEP testing was employed using the DIOPSYS™ NOVA-TR system, with a 74 cd m-2 baseline luminance. Luminance levels were reduced with five different neutral density (ND) filters (0.5, 1.0, 1.5, 2.0 and 2.5) and compared to the baseline response. All testing was performed under binocular-viewing conditions with full refractive correction in place.

RESULTS

In both groups, mean VEP amplitude reduced with decrease in luminance (p < 0.05). At each luminance level, the mean VEP amplitude was significantly lower in mTBI than in the VN population (p < 0.05). In both groups, the mean VEP latency increased progressively with reduction in luminance (p < 0.05), with it being significantly higher in mTBI than in the VN population (p < 0.05).

CONCLUSIONS

High luminance levels produced an optimal VEP response in both populations. VEP amplitude was robust, whereas latency progressively increased in both groups as luminance decreased. The latency increase with decreased luminance was significantly larger in those with mTBI, thus suggesting that latency can be used to differentiate reliably between VN individuals and those with mTBI.

Association of traumatic brain injury with subsequent neurological and psychiatric disease: a meta-analysis

OBJECTIVE

Mild traumatic brain injury (TBI) has been proposed as a risk factor for the development of Alzheimer's disease, Parkinson's disease, depression, and other illnesses. This study's objective was to determine the association of prior mild TBI with the subsequent diagnosis (that is, at least 1 year postinjury) of neurological or psychiatric disease.

METHODS

All studies from January 1995 to February 2012 reporting TBI as a risk factor for diagnoses of interest were identified by searching PubMed, study references, and review articles. Reviewers abstracted the data and assessed study designs and characteristics.

RESULTS

Fifty-seven studies met the inclusion criteria. A random effects meta-analysis revealed a significant association of prior TBI with subsequent neurological and psychiatric diagnoses. The pooled odds ratio (OR) for the development of any illness subsequent to prior TBI was 1.67 (95% CI 1.44-1.93, p < 0.0001). Prior TBI was independently associated with both neurological (OR 1.55, 95% CI 1.31-1.83, p < 0.0001) and psychiatric (OR 2.00, 95% CI 1.50-2.66, p < 0.0001) outcomes. Analyses of individual diagnoses revealed higher odds of Alzheimer's disease, Parkinson's disease, mild cognitive impairment, depression, mixed affective disorders, and bipolar disorder in individuals with previous TBI as compared to those without TBI. This association was present when examining only studies of mild TBI and when considering the influence of study design and characteristics. Analysis of a subset of studies demonstrated no evidence that multiple TBIs were associated with higher odds of disease than a single TBI.

CONCLUSIONS

History of TBI, including mild TBI, is associated with the development of neurological and psychiatric illness. This finding indicates that either TBI is a risk factor for heterogeneous pathological processes or that TBI may contribute to a common pathological mechanism.

The toll of the gridiron: damage-associated molecular patterns and hypertension in American football

American football has unequivocally been linked to elevations in blood pressure and hypertension, especially in linemen. However, the mechanisms of this increase cannot be attributed solely to increased body weight and associated cardiometabolic risk factors (e.g.,dyslipidemia or hyperglycemia). Therefore, understanding the etiology of football-associated hypertension is essential for improving the quality of life in this mostly young population, as well as for lowering the potential for chronic disease in the future. We propose that inflammatogenic damage-associated molecular patterns (DAMPs) released into the circulation from football-induced musculoskeletal trauma activate pattern-recognition receptors of the innate immune system-specifically, high mobility group box 1 protein (HMGB1) and mitochondrial (mt)DNA which activate Toll-like receptor (TLR)4 and -9, respectively. Previously, we observed that circulating levels of these 2 DAMPs are increased in hypertension, and activation of TLR4 and -9 causes endothelial dysfunction and hypertension. Therefore, our novel hypothesis is that musculoskeletal injury from repeated hits in football players, particularly in linemen, leads to elevated circulating HMGB1 and mtDNA to activate TLRs on endothelial cells leading to impaired endothelium-dependent vasodilation, increased vascular tone, and hypertension.

Military blast exposure, ageing and white matter integrity

Mild traumatic brain injury, or concussion, is associated with a range of neural changes including altered white matter structure. There is emerging evidence that blast exposure-one of the most pervasive causes of casualties in the recent overseas conflicts in Iraq and Afghanistan-is accompanied by a range of neurobiological events that may result in pathological changes to brain structure and function that occur independently of overt concussion symptoms. The potential effects of brain injury due to blast exposure are of great concern as a history of mild traumatic brain injury has been identified as a risk factor for age-associated neurodegenerative disease. The present study used diffusion tensor imaging to investigate whether military-associated blast exposure influences the association between age and white matter tissue structure integrity in a large sample of veterans of the recent conflicts (n = 190 blast-exposed; 59 without exposure) between the ages of 19 and 62 years. Tract-based spatial statistics revealed a significant blast exposure × age interaction on diffusion parameters with blast-exposed individuals exhibiting a more rapid cross-sectional age trajectory towards reduced tissue integrity. Both distinct and overlapping voxel clusters demonstrating the interaction were observed among the examined diffusion contrast measures (e.g. fractional anisotropy and radial diffusivity). The regions showing the effect on fractional anisotropy included voxels both within and beyond the boundaries of the regions exhibiting a significant negative association between fractional anisotropy and age in the entire cohort. The regional effect was sensitive to the degree of blast exposure, suggesting a 'dose-response' relationship between the number of blast exposures and white matter integrity. Additionally, there was an age-independent negative association between fractional anisotropy and years since most severe blast exposure in a subset of the blast-exposed group, suggesting a specific influence of time since exposure on tissue structure, and this effect was also independent of post-traumatic stress symptoms. Overall, these data suggest that blast exposure may negatively affect brain-ageing trajectories at the microstructural tissue level. Additional work examining longitudinal changes in brain tissue integrity in individuals exposed to military blast forces will be an important future direction to the initial findings presented here.

Epidemiology of sports-related concussion in seven US high school and collegiate sports

BACKGROUND

The epidemiology of sports-related concussion is not well-described in the literature. This paper presents a descriptive epidemiology of concussion in seven high school and collegiate sports.

METHODS

We used the data from Concussion Prevention Initiative (CPI), which enrolled 8905 athletes at 210 high schools and 26 colleges in a prospective cohort study of 7 sports (football, men's and women's soccer, men's and women's lacrosse, and men's and women's ice hockey) between 1999 and 2001. Injury risks and injury rates were used to characterize the incidence of concussion, and changes in symptoms over time were described.

RESULTS

A total of 375 concussions were observed. The incidence of concussion was highest in football, followed by women's lacrosse, men's lacrosse, men's soccer, and women's soccer (only 10 ice hockey teams were included, too few to quantify incidence). The rate of incident concussion was strongly associated with history of concussion in the previous 24 months (rate ratio = 5.5; 95 %CI: 3.9, 7.8, for 2 or more concussions relative to no previous concussion). The most common symptoms at time of injury were headache (87 %), balance problems/dizziness (77 %), and feeling "in a fog" (62 %). Loss of consciousness and amnesia were present in relatively few cases (9 and 30 %). The most common mechanism of injury was collision with another player.

CONCLUSIONS

Sports-related concussions present with a diverse range of symptoms and are associated with previous concussion history.

Cognitive function and brain structure after recurrent mild traumatic brain injuries in young-to-middle-aged adults

Recurrent mild traumatic brain injuries (mTBIs) are regarded as an independent risk factor for developing dementia in later life. We here aimed to evaluate associations between recurrent mTBIs, cognition, and gray matter volume and microstructure as revealed by structural magnetic resonance imaging (MRI) in the chronic phase after mTBIs in young adulthood. We enrolled 20 young-to-middle-aged subjects, who reported two or more sports-related mTBIs, with the last mTBI > 6 months prior to study enrolment (mTBI group), and 21 age-, sex- and education matched controls with no history of mTBI (control group). All participants received comprehensive neuropsychological testing, and high resolution T1-weighted and diffusion tensor MRI in order to assess cortical thickness (CT) and microstructure, hippocampal volume, and ventricle size. Compared to the control group, subjects of the mTBI group presented with lower CT within the right temporal lobe and left insula using an a priori region of interest approach. Higher number of mTBIs was associated with lower CT in bilateral insula, right middle temporal gyrus and right entorhinal area. Our results suggest persistent detrimental effects of recurrent mTBIs on CT already in young-to-middle-aged adults. If additional structural deterioration occurs during aging, subtle neuropsychological decline may progress to clinically overt dementia earlier than in age-matched controls, a hypothesis to be assessed in future prospective trials.

Acyl-2-aminobenzimidazoles: a novel class of neuroprotective agents targeting mGluR5

Positive allosteric modulators (PAMs) of the metabotropic glutamate receptor 5 (mGluR5) are promising therapeutic agents for treating traumatic brain injury (TBI). Using computational and medicinal methods, the structure-activity relationship of a class of acyl-2-aminobenzimidazoles (1-26) is reported. The new compounds are designed based on the chemical structure of 3,3'-difluorobenzaldazine (DFB), a known mGluR5 PAM. Ligand design and prediction of binding affinities of the new compounds have been performed using the site identification by ligand competitive saturation (SILCS) method. Binding affinities of the compounds to the transmembrane domain of mGluR5 have been evaluated using nitric oxide (NO) production assay, while the safety of the compounds is tested. One new compound found in this study, compound 22, showed promising activity with an IC₅₀ value of 6.4 μM, which is ∼20 fold more potent than that of DFB. Compound 22 represents a new lead for possible development as a treatment for TBI and related neurodegenerative conditions.

Incidence and Severity of Foot and Ankle Injuries in Men's Collegiate American Football

Background:

American football is an extremely physical game with a much higher risk of injury than other sports. While many studies have reported the rate of injury for particular body regions or for individual injuries, very little information exists that compares the incidence or severity of particular injuries within a body region. Such information is critical for prioritizing preventative interventions.

Purpose:

To retrospectively analyze epidemiological data to identify the most common and most severe foot and ankle injuries in collegiate men’s football.

Study Design:

Descriptive epidemiology study.

Methods:

Injury data were obtained from the National Collegiate Athletic Association (NCAA) Injury Surveillance System (ISS) for all foot and ankle injuries during the 2004-2005 to 2008-2009 seasons. Injuries were analyzed in terms of incidence and using multiple measures of severity (time loss, surgeries, medical disqualifications). This frequency and severity information is summarized in tabular form as well as in a 4 × 4 quantitative injury risk assessment matrix (QIRAM).

Results:

The rate of foot and ankle injuries was 15 per 10,000 athletic exposures (AEs). Five injuries were found to be responsible for more than 80% of all foot and ankle injuries: lateral ankle ligament sprains, syndesmotic (high ankle) sprains, medial ankle ligament sprains, midfoot injuries, and first metatarsophalangeal joint injuries. Ankle dislocations were found to be the most severe in terms of median time loss (100 days), percentage of surgeries (83%), and percentage of medical disqualifications (94%), followed by metatarsal fractures (38 days, 36%, and 49%, respectively) and malleolus fractures (33 days, 41%, and 59%, respectively). Statistical analysis suggests that the 3 measures of severity are highly correlated (r > 0.94), thereby justifying the use of time loss as a suitable proxy for injury severity in the construction of the QIRAM.

Conclusion:

Based on the QIRAM analysis, the 5 highest risk injuries were identified based on both incidence and severity (ankle dislocations, syndesmotic sprains, lateral ankle ligament sprains, metatarsal fractures, and malleolus fractures). A better understanding of the relative incidence and severity of these injuries will allow coaches, trainers, and researchers to more effectively focus their preventative interventions.

Cyclopropyl-containing positive allosteric modulators of metabotropic glutamate receptor subtype 5

Positive allosteric modulators (PAMs) binding to the transmembrane (TM) domain of metabotropic glutamate receptor 5 (mGluR5) are promising therapeutic agents for psychiatric disorders and traumatic brain injury (TBI). Novel PAMs based on a trans-2-phenylcyclopropane amide scaffold have been designed and synthesized. Facilitating ligand design and allowing estimation of binding affinities to the mGluR5 TM domain was the novel computational strategy, site identification by ligand competitive saturation (SILCS). The potential protective activity of the new compounds was evaluated using nitric oxide (NO) production in BV2 microglial cell cultures treated with lipopolysaccharide (LPS), and the toxicity of the new compounds tested using a cell viability assay. One of the new compounds, 3a, indicated promising activity with potency of 30 μM, which is 4.5-fold more potent than its lead compound 3,3'-difluorobenzaldazine (DFB), and showed no detectable toxicity with concentrations as high as 1000 μM. Thus this compound represents a new lead for possible development as treatment for TBI and related neurodegenerative disorders.

Estimating Contact Exposure in Football Using the Head Impact Exposure Estimate

Over the past decade, there has been significant debate regarding the effect of cumulative subconcussive head impacts on short and long-term neurological impairment. This debate remains unresolved, because valid epidemiological estimates of athletes' total contact exposure are lacking. We present a measure to estimate the total hours of contact exposure in football over the majority of an athlete's lifespan. Through a structured oral interview, former football players provided information related to primary position played and participation in games and practice contacts during the pre-season, regular season, and post-season of each year of their high school, college, and professional football careers. Spring football for college was also included. We calculated contact exposure estimates for 64 former football players (n = 32 college football only, n = 32 professional and college football). The head impact exposure estimate (HIEE) discriminated between individuals who stopped after college football, and individuals who played professional football (p < 0.001). The HIEE measure was independent of concussion history (p = 0.82). Estimating total hours of contact exposure may allow for the detection of differences between individuals with variation in subconcussive impacts, regardless of concussion history. This measure is valuable for the surveillance of subconcussive impacts and their associated potential negative effects.

Age of first exposure to football and later-life cognitive impairment in former NFL players

OBJECTIVE

To determine the relationship between exposure to repeated head impacts through tackle football prior to age 12, during a key period of brain development, and later-life executive function, memory, and estimated verbal IQ.

METHODS

Forty-two former National Football League (NFL) players ages 40-69 from the Diagnosing and Evaluating Traumatic Encephalopathy using Clinical Tests (DETECT) study were matched by age and divided into 2 groups based on their age of first exposure (AFE) to tackle football: AFE <12 and AFE ≥12. Participants completed the Wisconsin Card Sort Test (WCST), Neuropsychological Assessment Battery List Learning test (NAB-LL), and Wide Range Achievement Test, 4th edition (WRAT-4) Reading subtest as part of a larger neuropsychological testing battery.

RESULTS

Former NFL players in the AFE <12 group performed significantly worse than the AFE ≥12 group on all measures of the WCST, NAB-LL, and WRAT-4 Reading tests after controlling for total number of years of football played and age at the time of evaluation, indicating executive dysfunction, memory impairment, and lower estimated verbal IQ.

CONCLUSIONS

There is an association between participation in tackle football prior to age 12 and greater later-life cognitive impairment measured using objective neuropsychological tests. These findings suggest that incurring repeated head impacts during a critical neurodevelopmental period may increase the risk of later-life cognitive impairment. If replicated with larger samples and longitudinal designs, these findings may have implications for safety recommendations for youth sports.

Alcohol exposure after mild focal traumatic brain injury impairs neurological recovery and exacerbates localized neuroinflammation

Traumatic brain injury (TBI) represents a leading cause of morbidity and mortality among young individuals. Alcohol abuse is a risk factor associated with increased TBI incidence. In addition, up to 26% of TBI patients engage in alcohol consumption after TBI. Limited preclinical studies have examined the impact of post-injury alcohol exposure on TBI recovery. The aim of this study was to determine the isolated and combined effects of TBI and alcohol on cognitive, behavioral, and physical recovery, as well as on associated neuroinflammatory changes. Male Sprague-Dawley rats (∼300g) were subjected to a mild focal TBI by lateral fluid percussion (∼30PSI, ∼25ms) under isoflurane anesthesia. On day 4 after TBI, animals were exposed to either sub-chronic intermittent alcohol vapor (95% ethanol 14h on/10h off; BAL∼200mg/dL) or room air for 10days. TBI induced neurological dysfunction reflected by an increased neurological severity score (NSS) showed progressive improvement in injured animals exposed to room air (TBI/air). In contrast, TBI animals exposed to alcohol vapor (TBI/alcohol) showed impaired NSS recovery throughout the 10-day period of alcohol exposure. Open-field exploration test revealed an increased anxiety-like behavior in TBI/alcohol group compared to TBI/air group. Additionally, alcohol-exposed animals showed decreased locomotion and impaired novel object recognition. Immunofluorescence showed enhanced reactive astrocytes, microglial activation, and HMGB1 expression localized to the injured cortex of TBI/alcohol as compared to TBI/air animals. The expression of neuroinflammatory markers showed significant positive correlation with NSS. These findings indicated a close relationship between accentuated neuroinflammation and impaired neurological recovery from post-TBI alcohol exposure. The clinical implications of long-term consequences in TBI patients exposed to alcohol during recovery warrant further investigation.

Frequency and impact of recurrent traumatic brain injury in a population-based sample

The aim of this study was to determine the frequency, mechanism(s), and impact of recurrent traumatic brain injury (TBI) over a 1-year period. Population-based TBI incidence and 1-year outcomes study with embedded case-control analysis. All participants (adults and children) who experienced a recurrent TBI (more than one) in the 12 months after an index injury and matched controls who sustained one TBI within the same period were enrolled in a population-based TBI incidence and outcomes study. Details of all recurrent TBIs sustained within 12 months of the initial index injury were recorded. Each recurrent TBI case was matched to a case sustaining one TBI based on age (±2 years), gender, and index TBI severity. Cognitive ability, disability, and postconcussion symptoms (PCS) were assessed 1 year after the index injury. Overall, 9.9% (n=72) of TBI cases experienced at least one recurrent TBI within the year after initial index injury. Males, people <35 years of age, and those who had experienced a TBI before their index injury were at highest risk of recurrent TBI. Recurrent TBI cases reported significantly increased PCS at 1 year, compared to the matched controls (n=72) sustaining one TBI. There was no difference in overall cognitive ability and disability between the two groups. People experiencing recurrent TBIs are more likely to experience increased frequency and severity of PCS. Greater public awareness of the potential effects of recurrent brain injury is needed.

Repetitive mild traumatic brain injury induces ventriculomegaly and cortical thinning in juvenile rats

Traumatic brain injury (TBI) most frequently occurs in pediatric patients and remains a leading cause of childhood death and disability. Mild TBI (mTBI) accounts for nearly 75% of all TBI cases, yet its neuropathophysiology is still poorly understood. While even a single mTBI injury can lead to persistent deficits, repeat injuries increase the severity and duration of both acute symptoms and long-term deficits. In this study, to model pediatric repetitive mTBI (rmTBI) we subjected unrestrained juvenile animals (postnatal day 20) to repeat weight-drop impacts. Animals were anesthetized and subjected to sham injury or rmTBI once per day for 5 days. Magnetic resonance imaging (MRI) performed 14 days after injury revealed marked cortical atrophy and ventriculomegaly in rmTBI animals. Specifically, beneath the impact zone the thickness of the cortex was reduced by up to 46% and the area of the ventricles increased by up to 970%. Immunostaining with the neuron-specific marker NeuN revealed an overall loss of neurons within the motor cortex but no change in neuronal density. Examination of intrinsic and synaptic properties of layer II/III pyramidal neurons revealed no significant difference between sham-injured and rmTBI animals at rest or under convulsant challenge with the potassium channel blocker 4-aminopyridine. Overall, our findings indicate that the neuropathological changes reported after pediatric rmTBI can be effectively modeled by repeat weight drop in juvenile animals. Developing a better understanding of how rmTBI alters the pediatric brain may help improve patient care and direct "return to game" decision making in adolescents.

Canadian pediatric emergency physician knowledge of concussion diagnosis and initial management

Introduction

The diagnosis of concussion is a critical step in the appropriate management of patients following minor head trauma. The authors hypothesized that wide practice variation exists among pediatric emergency medicine physicians in the application of physical and cognitive rest recommendations following an acute concussion.

Methods

The authors developed a 35-item questionnaire incorporating case vignettes to examine pediatric emergency physician knowledge of concussion diagnosis, understanding of initial management using return-to-play/school/work guidelines, use of existing concussion protocols, and perceived barriers to protocol use. Using a modified Dillman technique, the authors distributed an online survey to members of Pediatric Emergency Research Canada, a national association of pediatric emergency physicians.

Results

Of 176 potential participants, 115 (65%) responded to the questionnaire, 89% (95% confidence interval [CI]: 0.81, 0.93) of whom reported having diagnosed 20 or more concussions annually. Although 90% (95% CI: 0.83, 0.94) of respondents adequately diagnosed concussion, only 64% (95% CI: 0.54, 0.72) correctly applied graduated return-to-play guidelines. Cognitive rest recommendations were also frequently limited: 40% (95% CI: 0.31, 0.49) did not recommend school absence, 30% (95% CI: 0.22, 0.39) did not recommend schoolwork reduction, and 35% (95% CI: 0.27, 0.45) did not recommend limiting screen time. Eighty percent (95% CI: 0.72, 0.87) of respondents reported having used guidelines frequently or always to guide clinical decisions regarding concussion.

Conclusion

Despite a proficiency in the diagnosis of concussion, pediatric emergency physicians exhibit wide variation in recommending the graduated return to play and cognitive rest following concussion.

Chronic traumatic encephalopathy: a critical appraisal

Chronic traumatic encephalopathy (CTE) formerly known as dementia pugilistica is a long-term neurodegenerative disorder associated with repeated subconcussive head injuries in high-contact sports. We reviewed the existing literature on CTE and examined epidemiological trends, risk factors, and its temporal progression, and proposed the underlying pathophysiological mechanisms that may provide unique insights to clinicians with an in-depth understanding of the disease to aid in the diagnosis and prevention, and provide future perspectives for research via search of Medline and Cochrane databases as well as manual review of bibliographies from selected articles and monographs. The prevalence of CTE in recent years is on the rise and almost exclusively affects men, with pathologic signs characterized by progressive memory loss, behavioral changes, and violent tendencies with some patients demonstrating Parkinsonian-like symptoms and signs. Many patients with CTE die following suicide, accident, or complications of drug or alcohol use. Postmortem pathologic analysis is characterized by neurofibrillary tangles and Aβ plaques in 50 % of cases. Currently, there are no ante-mortem diagnostic criteria, but modern imaging techniques such as functional magnetic resonance (MR) imaging, MR spectroscopy, and diffusion tension imaging hold promise for delineating the future diagnostic criteria. Further long-term longitudinal studies are warranted to investigate risk factors that will enhance understanding of the disease progression and its pathogenesis.

Association between concussion and mental health in former collegiate athletes

BACKGROUND

The existing research on the association between concussion and mental health outcomes is largely limited to former professional athletes. This cross-sectional study estimated the association between recurrent concussion and depression, impulsivity, and aggression in former collegiate athletes.

METHODS

Former collegiate athletes who played between 1987-2012 at a Division I university completed an online questionnaire. The main exposure, total number of self-recalled concussions (sport-related and non-sport-related), were categorized as: zero (referent), one, two, or three or more concussions. The main outcomes were the depression module of The Patient Health Questionnaire (PHQ-9), the Short Form of the Barratt Impulsiveness scale (BIS15); and the 12-item Short Form of the Buss-Perry Aggression Questionnaire (BPAQ-SF). Depression was categorized into a binomial severity classification that differentiated between no or mild depression (PHQ-9 scores <10) and moderate to severe depression (PHQ-9 scores ≥10). Impulsivity and aggression were kept as continuous outcomes. Binomial regression estimated adjusted prevalence ratios (PR). Linear regression estimated adjusted mean differences (MD).

RESULTS

Of the 797 respondents with complete data (21.9% completion rate), 38.8% reported at least one concussion. Controlling for alcohol dependence and family history of depression, the prevalence of moderate to severe depression among former collegiate athletes reporting three or more concussions in total was 2.4 times that of those reporting zero concussions [95% Confidence Interval (CI): 1.0, 5.7]. Controlling for alcohol dependence, family history of anxiety, relationship status, obtaining a post-graduate degree, and playing primary college sport professionally, former collegiate athletes reporting two or more concussions in total had higher mean scores for impulsivity, compared to those reporting no concussions (2 concussions MD = 2.7; 95% CI: 1.2, 4.1; 3+ concussions MD = 1.9; 95% CI: 0.6, 3.2). Controlling for alcohol dependence, sex, and relationship status, former collegiate athletes reporting three or more concussions in total had a higher mean score for aggression, compared to those reporting no concussions (MD = 3.0; 95% CI: 1.4, 4.7).

CONCLUSIONS

Our study found an association between former concussion and greater risk of severe depression and higher levels of impulsivity and aggression among former collegiate athletes. Additional prospective studies better addressing causality and ascertaining valid lifetime concussion histories and medical histories are needed.

A case study of magnetic resonance imaging of cerebrovascular reactivity: a powerful imaging marker for mild traumatic brain injury

PRIMARY OBJECTIVE

To use breath-hold functional magnetic resonance imaging (fMRI) to localize the brain regions with impaired cerebrovascular reactivity (CVR) in a female patient diagnosed with mild traumatic brain injury (mTBI). The extent of impaired CVR was evaluated 2 months after concussion. Follow-up scan was performed 1 year post-mTBI using the same breath-hold fMRI technique.

RESEARCH DESIGN

Case report.

METHODS AND PROCEDURES

fMRI blood oxygenation dependent level (BOLD) signals were measured under breath-hold challenge in a female mTBI patient 2 months after concussion followed by a second fMRI with breath-hold challenge 1 year later. CVR was expressed as the percentage change of BOLD signals per unit time of breath-hold.

MAIN OUTCOMES

In comparison with CVR measurement of normal control subjects, statistical maps of CVR revealed substantial neurovascular deficits and hemispheric asymmetry within grey and white matter in the initial breath-hold fMRI scan. Follow-up breath-hold fMRI performed 1 year post-mTBI demonstrated normalization of CVR accompanied with symptomatic recovery.

CONCLUSIONS

CVR may serve as an imaging biomarker to detect subtle deficits in both grey and white matter for individual diagnosis of mTBI. The findings encourage further investigation of hypercapnic fMRI as a diagnostic tool for mTBI.

Neuroinflammation and brain atrophy in former NFL players: An in vivo multimodal imaging pilot study

There are growing concerns about potential delayed, neuropsychiatric consequences (e.g, cognitive decline, mood or anxiety disorders) of sports-related traumatic brain injury (TBI). Autopsy studies of brains from a limited number of former athletes have described characteristic, pathologic changes of chronic traumatic encephalopathy (CTE) leading to questions about the relationship between these pathologic and the neuropsychiatric disturbances seen in former athletes. Research in this area will depend on in vivo methods that characterize molecular changes in the brain, linking CTE and other sports-related pathologies with delayed emergence of neuropsychiatric symptoms. In this pilot project we studied former National Football League (NFL) players using new neuroimaging techniques and clinical measures of cognitive functioning. We hypothesized that former NFL players would show molecular and structural changes in medial temporal and parietal lobe structures as well as specific cognitive deficits, namely those of verbal learning and memory. We observed a significant increase in binding of [(11)C]DPA-713 to the translocator protein (TSPO), a marker of brain injury and repair, in several brain regions, such as the supramarginal gyrus and right amygdala, in 9 former NFL players compared to 9 age-matched, healthy controls. We also observed significant atrophy of the right hippocampus. Finally, we report that these same former players had varied performance on a test of verbal learning and memory, suggesting that these molecular and pathologic changes may play a role in cognitive decline. These results suggest that localized brain injury and repair, indicated by increased [(11)C]DPA-713 binding to TSPO, may be linked to history of NFL play. [(11)C]DPA-713 PET is a promising new tool that can be used in future study design to examine further the relationship between TSPO expression in brain injury and repair, selective regional brain atrophy, and the potential link to deficits in verbal learning and memory after NFL play.

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.

Head rotational acceleration characteristics influence behavioral and diffusion tensor imaging outcomes following concussion

A majority of traumatic brain injuries (TBI) in motor vehicle crashes and sporting environments are mild and caused by high-rate acceleration of the head. For injuries caused by rotational acceleration, both magnitude and duration of the acceleration pulse were shown to influence injury outcomes. This study incorporated a unique rodent model of rotational acceleration-induced mild TBI (mTBI) to quantify independent effects of magnitude and duration on behavioral and neuroimaging outcomes. Ninety-two Sprague-Dawley rats were exposed to head rotational acceleration at peak magnitudes of 214 or 350 krad/s(2) and acceleration pulse durations of 1.6 or 3.4 ms in a full factorial design. Rats underwent a series of behavioral tests including the Composite Neuroscore (CN), Elevated Plus Maze (EPM), and Morris Water Maze (MWM). Ex vivo diffusion tensor imaging (DTI) of the fixed brains was conducted to assess the effects of rotational injury on brain microstructure as revealed by the parameter fractional anisotropy (FA). While the injury did not cause significant locomotor or cognitive deficits measured with the CN and MWM, respectively, a main effect of duration was consistently observed for the EPM. Increased duration caused significantly greater activity and exploratory behaviors measured as open arm time and number of arm changes. DTI demonstrated significant effects of both magnitude and duration, with the FA of the amygdala related to both the magnitude and duration. Increased duration also caused FA changes at the interface of gray and white matter. Collectively, the findings demonstrate that the consequences of rotational acceleration mTBI were more closely associated with duration of the rotational acceleration impulse, which is often neglected as an independent factor, and highlight the need for animal models of TBI with strong biomechanical foundations to associate behavioral outcomes with brain microstructure.

Effects of subconcussive head trauma on the default mode network of the brain

Although they are less severe than a full blown concussive episodes, subconcussive impacts happen much more frequently and current research has suggested this form of head trauma may have an accumulative effect and lead to neurological impairment later in life. To investigate the acute effects that subconcussive head trauma may have on the default mode network of the brain resting-state, functional magnetic resonance was performed. Twenty-four current collegiate rugby players were recruited and all subjects underwent initial scanning 24 h prior to a scheduled full contact game to provide a baseline. Follow-up scanning of the rugby players occurred within 24 h following that game to assess acute effects from subconcussive head trauma. Differences between pre-game and post-game scans showed both increased connectivity from the left supramarginal gyrus to bilateral orbitofrontal cortex and decreased connectivity from the retrosplenial cortex and dorsal posterior cingulate cortex. To assess whether or not a history of previous concussion may lead to a differential response following subconcussive impacts, subjects were further divided into two subgroups based upon history of previous concussion. Individuals with a prior history of concussion exhibited only decreased functional connectivity following exposure to subconcussive head trauma, while those with no history showed increased connectivity. Even acute exposure to subconcussive head trauma demonstrates the ability to alter functional connectivity and there is possible evidence of a differential response in the brain for those with and without a history of concussion.

The impact of multiple concussions on emotional distress, post-concussive symptoms, and neurocognitive functioning in active duty United States marines independent of combat exposure or emotional distress

Controversy exists as to whether the lingering effects of concussion on emotional, physical, and cognitive symptoms is because of the effects of brain trauma or purely to emotional factors such as post-traumatic stress disorder or depression. This study examines the independent effects of concussion on persistent symptoms. The Defense Automated Neurobehavioral Assessment, a clinical decision support tool, was used to assess neurobehavioral functioning in 646 United States Marines, all of whom were fit for duty. Marines were assessed for concussion history, post-concussive symptoms, emotional distress, neurocognitive functioning, and deployment history. Results showed that a recent concussion or ever having experienced a concussion was associated with an increase in emotional distress, but not with persistent post-concussive symptoms (PPCS) or neurocognitive functioning. Having had multiple lifetime concussions, however, was associated with greater emotional distress, PPCS, and reduced neurocognitive functioning that needs attention and rapid discrimination, but not for memory-based tasks. These results are independent of deployment history, combat exposure, and symptoms of post-traumatic stress disorder and depression. Results supported earlier findings that a previous concussion is not generally associated with post-concussive symptoms independent of covariates. In contrast with other studies that failed to find a unique contribution for concussion to PPCS, however, evidence of recent and multiple concussion was seen across a range of emotional distress, post-concussive symptoms, and neurocognitive functioning in this study population. Results are discussed in terms of implications for assessing concussion on return from combat.

The Sport Concussion Education Project. A brief report on an educational initiative: from concept to curriculum

Current research on concussion is primarily focused on injury identification and treatment. Prevention initiatives are, however, important for reducing the incidence of brain injury. This report examines the development and implementation of an interactive electronic teaching program (an e-module) that is designed specifically for concussion education within an adolescent population. This learning tool and the accompanying consolidation rubric demonstrate that significant engagement occurs in addition to the knowledge gained among participants when it is used in a school curriculum setting.

Tauopathy PET and amyloid PET in the diagnosis of chronic traumatic encephalopathies: studies of a retired NFL player and of a man with FTD and a severe head injury

Single, severe traumatic brain injury (TBI) which elevates CNS amyloid, increases the risk of Alzheimer's disease (AD); while repetitive concussive and subconcussive events as observed in athletes and military personnel, may increase the risk of chronic traumatic encephalopathy (CTE). We describe two clinical cases, one with a history of multiple concussions during a career in the National Football League (NFL) and the second with frontotemporal dementia and a single, severe TBI. Both patients presented with cognitive decline and underwent [(18)F]-Florbetapir positron emission tomography (PET) imaging for amyloid plaques; the retired NFL player also underwent [(18)F]-T807 PET imaging, a new ligand binding to tau, the main constituent of neurofibrillary tangles (NFT). Case 1, the former NFL player, was 71 years old when he presented with memory impairment and a clinical profile highly similar to AD. [(18)F]-Florbetapir PET imaging was negative, essentially excluding AD as a diagnosis. CTE was suspected clinically, and [(18)F]-T807 PET imaging revealed striatal and nigral [(18)F]-T807 retention consistent with the presence of tauopathy. Case 2 was a 56-year-old man with personality changes and cognitive decline who had sustained a fall complicated by a subdural hematoma. At 1 year post injury, [(18)F]-Florbetapir PET imaging was negative for an AD pattern of amyloid accumulation in this subject. Focal [(18)F]-Florbetapir retention was noted at the site of impact. In case 1, amyloid imaging provided improved diagnostic accuracy where standard clinical and laboratory criteria were inadequate. In that same case, tau imaging with [(18)F]-T807 revealed a subcortical tauopathy that we interpret as a novel form of CTE with a distribution of tauopathy that mimics, to some extent, that of progressive supranuclear palsy (PSP), despite a clinical presentation of amnesia without any movement disorder complaints or signs. A key distinguishing feature is that our patient presented with hippocampal involvement, which is more frequently seen in CTE than in PSP. In case 2, focal [(18)F]-Florbetapir retention at the site of injury in an otherwise negative scan suggests focal amyloid aggregation. In each of these complex cases, a combination of [(18)F]-fluorodeoxyglucose, [(18)F]-Florbetapir and/or [(18)F]-T807 PET molecular imaging improved the accuracy of diagnosis and prevented inappropriate interventions.

Counseling athletes on the risk of chronic traumatic encephalopathy

Context:

Chronic traumatic encephalopathy (CTE) is a rare progressive neurologic disorder that can manifest as a combination of cognitive, mood and behavioral, and neurologic symptoms. Despite clinically apparent symptoms, there is no imaging or other diagnostic test that can confirm diagnosis in living subjects. Diagnosis can only be confirmed postmortem by specific histopathologic features within the brain tissue identified on autopsy. CTE represents a unique tauopathy that is distinct from other neurodegenerative diseases.

Evidence Acquisition:

PubMed was searched from 1990 to 2013 for sport concussion and chronic traumatic encephalopathy. Articles were also identified from bibliographies of recent reviews and consensus statements.

Study Design:

Clinical review.

Level of Evidence:

Level 5.

Results:

Although CTE is postulated to occur as a result of repetitive mild traumatic brain injury, the specific etiology and risk factors have not yet been elucidated, and postmortem diagnosis makes causality difficult to determine.

Conclusion:

When counseling athletes and families about the potential association of recurrent concussions and the development of CTE, discussion of proper management of concussion is cornerstone. Unfortunately, to date, there is no equipment that can prevent concussions; however, rule changes and legislation may decrease the risk. It is imperative that return to play is medically supervised by a provider trained in the management of concussion and begins only once symptoms have resolved. In addition, athletes with permanent symptoms should be retired from contact sport.

The utility of the balance error scoring system for mild brain injury assessments in children and adolescents

The Balance Error Scoring System (BESS) is widely recognized as an acceptable assessment of postural control for adult patients following a mild traumatic brain injury (mTBI) or concussion. However, the measurement properties of the BESS as a post-mTBI assessment test for younger patients are not well understood. The purpose of this study was to evaluate the utility of the BESS as a post-mTBI assessment test for children and adolescents aged 8 to 18 years through 2 investigations: (1) a retrospective medical records review of the relationship among age, BESS scores, and other common post-mTBI assessment tests; and (2) a prospective study comparing BESS scores for a cohort of children with a recent mTBI and BESS scores for a cohort of matched healthy peers. Age was found to be significantly correlated with several of the BESS measures and the total BESS score (P < 0.05). Significant differences were observed between the injured and healthy cohorts for 3 of the BESS measures and the total BESS score. However, the observed differences were not likely to be clinically meaningful. Cumulatively, evidence from the literature and the results of these studies indicate that the BESS may be limited for producing accurate assessments of younger athletes' post-mTBI postural control abilities. Future research recommendations include testing of modified versions of the BESS or other alternatives for post-mTBI postural control assessments with younger individuals.

Is There Chronic Brain Damage in Retired NFL Players? Neuroradiology, Neuropsychology, and Neurology Examinations of 45 Retired Players

BACKGROUND

Neuropathology and surveys of retired National Football League (NFL) players suggest that chronic brain damage is a frequent result of a career in football. There is limited information on the neurological statuses of living retired players. This study aimed to fill the gap in knowledge by conducting in-depth neurological examinations of 30- to 60-year-old retired NFL players.

HYPOTHESIS

In-depth neurological examinations of 30- to 60-year-old retired players are unlikely to detect objective clinical abnormalities in the majority of subjects.

STUDY DESIGN

A day-long medical examination was conducted on 45 retired NFL players, including state-of-the-art magnetic resonance imaging (MRI; susceptibility weighted imaging [SWI], diffusion tensor imaging [DTI]), comprehensive neuropsychological and neurological examinations, interviews, blood tests, and APOE (apolipoprotein E) genotyping.

LEVEL OF EVIDENCE

Level 3.

METHODS

Participants' histories focused on neurological and depression symptoms, exposure to football, and other factors that could affect brain function. The neurological examination included Mini-Mental State Examination (MMSE) evaluation of cognitive function and a comprehensive search for signs of dysarthria, pyramidal system dysfunction, extrapyramidal system dysfunction, and cerebellar dysfunction. The Beck Depression Inventory (BDI) and Patient Health Questionnaire (PHQ) measured depression. Neuropsychological tests included pen-and-paper and ImPACT evaluation of cognitive function. Anatomical examination SWI and DTI MRI searched for brain injuries. The results were statistically analyzed for associations with markers of exposure to football and related factors, such as body mass index (BMI), ethanol use, and APOE4 status.

RESULTS

The retired players' ages averaged 45.6 ± 8.9 years (range, 30-60 years), and they had 6.8 ± 3.2 years (maximum, 14 years) of NFL play. They reported 6.9 ± 6.2 concussions (maximum, 25) in the NFL. The majority of retired players had normal clinical mental status and central nervous system (CNS) neurological examinations. Four players (9%) had microbleeds in brain parenchyma identified in SWI, and 3 (7%) had a large cavum septum pellucidum with brain atrophy. The number of concussions/dings was associated with abnormal results in SWI and DTI. Neuropsychological testing revealed isolated impairments in 11 players (24%), but none had dementia. Nine players (20%) endorsed symptoms of moderate or severe depression on the BDI and/or met criteria for depression on PHQ; however, none had dementia, dysarthria, parkinsonism, or cerebellar dysfunction. The number of football-related concussions was associated with isolated abnormalities on the clinical neurological examination, suggesting CNS dysfunction. The APOE4 allele was present in 38% of the players, a larger number than would be expected in the general male population (23%-26%).

CONCLUSION

MRI lesions and neuropsychological impairments were found in some players; however, the majority of retired NFL players had no clinical signs of chronic brain damage.

CLINICAL RELEVANCE

These results need to be reconciled with the prevailing view that a career in football frequently results in chronic brain damage.

Current Physical and Mental Health of Former Collegiate Athletes

Background:

There is a dearth of research on the current health of former collegiate athletes.

Purpose:

To examine the current health and related correlates in a cohort of former collegiate athletes who played in a diverse range of men’s and women’s sports with various levels of contact.

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

Former collegiate athletes (N = 3657) were asked to complete an online questionnaire addressing sports history, medical history, and demographics. The questionnaire also included the Veterans RAND 12-Item Health Survey (VR-12), which yielded 2 composite scores for physical (PCS) and mental (MCS) health. The VR-12 PCS and MCS scores were compared with published US normative data using t tests and analyses of variance.

Results:

Mean PCS and MCS scores of the 797 respondents with complete data (21.9% of target sample; average, 14.5 years since last played collegiate sport) were 53.0 ± 6.1 and 51.7 ± 9.4, respectively. When stratified by age and sex, PCS and MCS scores were similar to normative scores in the United States. Lower PCS scores were associated with sustaining ≥3 concussions, playing in collision sports during college, and sustaining a career-ending injury (all, P < .001). No association was found between concussion and MCS scores (P = .06). Among former collegiate athletes, prevalent medical conditions included anxiety (16.2%), hypercholesterolemia/high cholesterol (10.6%), and depression (10.4%). Additionally, 5.8% screened positive for alcohol dependence, and 5.8% screened positive for disordered eating (eg, binge eating, purging). These findings were more prevalent than those reported by the World Health Organization as representative of the US population. Conversely, there was a lower prevalence of depression, bipolar disorders, and attention deficit disorder, with or without hyperactivity (ADD/ADHD), than in the World Health Organization US population data sample.

Conclusion:

Former collegiate athletes appear similar to the general US population on many aspects of mental and physical health. However, observed health deficits associated with previous sports injuries warrant ongoing monitoring of the health and well-being of former collegiate athletes.

Acute reduction of microglia does not alter axonal injury in a mouse model of repetitive concussive traumatic brain injury

The pathological processes that lead to long-term consequences of multiple concussions are unclear. Primary mechanical damage to axons during concussion is likely to contribute to dysfunction. Secondary damage has been hypothesized to be induced or exacerbated by inflammation. The main inflammatory cells in the brain are microglia, a type of macrophage. This research sought to determine the contribution of microglia to axon degeneration after repetitive closed-skull traumatic brain injury (rcTBI) using CD11b-TK (thymidine kinase) mice, a valganciclovir-inducible model of macrophage depletion. Low-dose (1 mg/mL) valganciclovir was found to reduce the microglial population in the corpus callosum and external capsule by 35% after rcTBI in CD11b-TK mice. At both acute (7 days) and subacute (21 days) time points after rcTBI, reduction of the microglial population did not alter the extent of axon injury as visualized by silver staining. Further reduction of the microglial population by 56%, using an intermediate dose (10 mg/mL), also did not alter the extent of silver staining, amyloid precursor protein accumulation, neurofilament labeling, or axon injury evident by electron microscopy at 7 days postinjury. Longer treatment of CD11b-TK mice with intermediate dose and treatment for 14 days with high-dose (50 mg/mL) valganciclovir were both found to be toxic in this injury model. Altogether, these data are most consistent with the idea that microglia do not contribute to acute axon degeneration after multiple concussive injuries. The possibility of longer-term effects on axon structure or function cannot be ruled out. Nonetheless, alternative strategies directly targeting injury to axons may be a more beneficial approach to concussion treatment than targeting secondary processes of microglial-driven inflammation.

The spectrum of neurobehavioral sequelae after repetitive mild traumatic brain injury: a novel mouse model of chronic traumatic encephalopathy

There has been an increased focus on the neurological sequelae of repetitive mild traumatic brain injury (TBI), particularly neurodegenerative syndromes, such as chronic traumatic encephalopathy (CTE); however, no animal model exists that captures the behavioral spectrum of this phenomenon. We sought to develop an animal model of CTE. Our novel model is a modification and fusion of two of the most popular models of TBI and allows for controlled closed-head impacts to unanesthetized mice. Two-hundred and eighty 12-week-old mice were divided into control, single mild TBI (mTBI), and repetitive mTBI groups. Repetitive mTBI mice received six concussive impacts daily for 7 days. Behavior was assessed at various time points. Neurological Severity Score (NSS) was computed and vestibulomotor function tested with the wire grip test (WGT). Cognitive function was assessed with the Morris water maze (MWM), anxiety/risk-taking behavior with the elevated plus maze, and depression-like behavior with the forced swim/tail suspension tests. Sleep electroencephalogram/electromyography studies were performed at 1 month. NSS was elevated, compared to controls, in both TBI groups and improved over time. Repetitive mTBI mice demonstrated transient vestibulomotor deficits on WGT. Repetitive mTBI mice also demonstrated deficits in MWM testing. Both mTBI groups demonstrated increased anxiety at 2 weeks, but repetitive mTBI mice developed increased risk-taking behaviors at 1 month that persist at 6 months. Repetitive mTBI mice exhibit depression-like behavior at 1 month. Both groups demonstrate sleep disturbances. We describe the neurological sequelae of repetitive mTBI in a novel mouse model, which resemble several of the neuropsychiatric behaviors observed clinically in patients sustaining repetitive mild head injury.

Multimodal assessment of primary motor cortex integrity following sport concussion in asymptomatic athletes

OBJECTIVE

Recent studies have shown, in asymptomatic concussed athletes, metabolic disruption in the primary motor cortex (M1) and abnormal intracortical inhibition lasting for more than six months. The present study aims to assess if these neurochemical and neurophysiological alterations are persistent and linked to M1 cortical thickness.

METHODS

Sixteen active football players who sustained their last concussion, on average, three years prior to testing and 14 active football players who never sustained a concussion were recruited for a single session of proton magnetic resonance spectroscopy ((1)H-MRS) and transcranial magnetic stimulation (TMS). Measures of M1 and whole brain cortical thickness were acquired, and (1)H-MRS data were acquired from left M1 using a MEGA-PRESS sequence. Cortical silent period (CSP) and long-interval intracortical inhibition (LICI) were measured with TMS applied over left M1.

RESULTS

No significant group differences were observed for metabolic concentrations, TMS measures, and cortical thickness. However, whereas GABA and glutamate levels were positively correlated in control athletes, this relationship was absent in concussed athletes.

CONCLUSION

These data suggest the general absence of neurophysiologic, neurometabolic and neuroanatomical disruptions in M1 three years following the last concussive event. However, correlational analyses suggest the presence of a slight metabolic imbalance between GABA and glutamate concentrations in the primary motor cortex of concussed athletes.

SIGNIFICANCE

The present study highlights the importance of multimodal assesments of the impacts of sport concussions.

Prevalence of pituitary hormone dysfunction, metabolic syndrome, and impaired quality of life in retired professional football players: a prospective study

Hypopituitarism is common after moderate and severe traumatic brain injury (TBI). Herein, we address the association between mild TBI (mTBI) and pituitary and metabolic function in retired football players. Retirees 30-65 years of age, with one or more years of National Football League (NFL) play and poor quality of life (QoL) based on Short Form 36 (SF-36) Mental Component Score (MCS) were prospectively enrolled. Pituitary hormonal and metabolic syndrome (MetS) testing was performed. Using a glucagon stimulation test, growth hormone deficiency (GHD) was defined with a standard cut point of 3 ng/mL and with a more stringent body mass index (BMI)-adjusted cut point. Subjects with and without hormonal deficiency (HD) were compared in terms of QoL, International Index of Erectile Function (IIEF) scores, metabolic parameters, and football career data. Of 74 subjects, 6 were excluded because of significant non-football-related TBIs. Of the remaining 68 subjects (mean age, 47.3±10.2 years; median NFL years, 5; median NFL concussions, 3; mean BMI, 33.8±6.0), 28 (41.2%) were GHD using a peak GH cutoff of <3 ng/mL. However, with a BMI-adjusted definition of GHD, 13 of 68 (19.1%) were GHD. Using this BMI-adjusted definition, overall HD was found in 16 (23.5%) subjects: 10 (14.7%) with isolated GHD; 3 (4.4%) with isolated hypogonadism; and 3 (4.4%) with both GHD and hypogonadism. Subjects with HD had lower mean scores on the IIEF survey (p=0.016) and trended toward lower scores on the SF-36 MCS (p=0.113). MetS was present in 50% of subjects, including 5 of 6 (83%) with hypogonadism, and 29 of 62 (46.8%) without hypogonadism (p=0.087). Age, BMI, median years in NFL, games played, number of concussions, and acknowledged use of performance-enhancing steroids were similar between HD and non-HD groups. In summary, in this cohort of retired NFL players with poor QoL, 23.5% had HD, including 19% with GHD (using a BMI-adjusted definition), 9% with hypogonadism, and 50% had MetS. Although the cause of HD is unclear, these results suggest that GHD and hypogonadism may contribute to poor QoL, erectile dysfunction, and MetS in this population. Further study of pituitary function is warranted in athletes sustaining repetitive mTBI.

Traumatic brain injury and risk of dementia in older veterans

OBJECTIVES

Traumatic brain injury (TBI) is common in military personnel, and there is growing concern about the long-term effects of TBI on the brain; however, few studies have examined the association between TBI and risk of dementia in veterans.

METHODS

We performed a retrospective cohort study of 188,764 US veterans aged 55 years or older who had at least one inpatient or outpatient visit during both the baseline (2000-2003) and follow-up (2003-2012) periods and did not have a dementia diagnosis at baseline. TBI and dementia diagnoses were determined using ICD-9 codes in electronic medical records. Fine-Gray proportional hazards models were used to determine whether TBI was associated with greater risk of incident dementia, accounting for the competing risk of death and adjusting for demographics, medical comorbidities, and psychiatric disorders.

RESULTS

Veterans were a mean age of 68 years at baseline. During the 9-year follow-up period, 16% of those with TBI developed dementia compared with 10% of those without TBI (adjusted hazard ratio, 1.57; 95% confidence interval: 1.35-1.83). There was evidence of an additive association between TBI and other conditions on risk of dementia.

CONCLUSIONS

TBI in older veterans was associated with a 60% increase in the risk of developing dementia over 9 years after accounting for competing risks and potential confounders. Our results suggest that TBI in older veterans may predispose toward development of symptomatic dementia and raise concern about the potential long-term consequences of TBI in younger veterans and civilians.

Chronic traumatic encephalopathy: where are we and where are we going?

Chronic traumatic encephalopathy (CTE, previously called punch drunk and dementia pugilistica) has a rich history in the medical literature in association with boxing, but has only recently been recognized with other contact sports, such as football and ice hockey, as well as with military blast injuries. CTE is thought to be a neurodegenerative disease associated with repeated concussive and subconcussive blows to the head. There is characteristic gross and microscopic pathology found in the brain, including frontal and temporal atrophy, axonal degeneration, and hyperphosphorylated tau and TAR DNA-binding protein 43 pathology. Clinically, there are characteristic progressive deficits in cognition (memory, executive dysfunction), behavior (explosivity, aggression), mood (depression, suicidality), and motor function (parkinsonism), which correlate with the anatomic distribution of brain pathology. While CTE shares clinical and neuropathological traits with other neurodegenerative diseases, the clinical syndrome and the neuropathology as a whole are distinct from other neurodegenerative diseases. Here we review the CTE literature to date. We also draw on the literature from mild traumatic brain injury and other neurodegenerative dementias, particularly when these studies provide guidance for future CTE research. We conclude by suggesting seven essential areas for future CTE research.