What boxing tells us about repetitive head trauma and the brain

Brain trauma characteristics for lightweight and heavyweight fighters in professional mixed martial arts

Mixed martial arts (MMA) is a sport where the fighters are at high risk of brain trauma, with characteristics, such as the frequency, magnitude, and interval of head impacts influencing the risk of developing short- and long-term negative brain health outcomes. These characteristics may be influenced by weight class as they may have unique fighting styles. The purpose of this research was to compare frequency, magnitude, and interval of head impacts between lightweight and heavyweight fighters in professional MMA. Frequency, interval, event type, velocity, and location of head impacts were documented for 60 fighters from 15 Lightweight and 15 Heavyweight professional MMA fights. Head impact reconstructions of these events were performed using physical and finite element modelling methods to determine the strain in the brain tissues. The results found that LW and HW fighters sustained similar head impact frequencies and intervals. The LW fighters sustained a significantly higher frequency of very low and high magnitude impacts to the head from punches; HW a larger frequency of high category strains from elbow strikes. These brain trauma profiles reflect different fight strategies and may inform methods to manage and mitigate the long-term effects of repetitive impacts to the head.

Hospital Admissions Associated With Head and Neck Injuries From Olympic-style Sports and Activities Between 2010 and 2022

The objective of this study was to evaluate which Olympic-style sports and activities are most likely to result in hospitalizations relating to head and neck injuries. This was a cross-sectional study using the National Electronic Injury Surveillance System (NEISS) database. Subjects with head and neck injuries from selected Olympic-style sports and activities between 2010 and 2022 were included. Independent variables were demographics and injury characteristics (injury location and sport). The primary outcome variable was hospitalization (yes/no). Survey-weighted descriptive, bivariate, and logistic regression statistics were computed to measure the association between demographic/injury variables and hospitalization. There were 175,995 subjects (national estimate, 5,922,584) meeting inclusion criteria. After adjusting for demographic and injury characteristics, head injuries (odds ratio [OR] = 2.17; 95% CI, 1.83-2.56; P<0.001) demonstrated higher odds of hospitalization compared with facial injuries. Injuries from cycling (OR = 2.52; 95% CI, 2.16-2.95; P<0.001), mountain biking (OR = 2.56; 95% CI, 1.80-3.65; P<0.001), and horseback riding (OR = 4.01; 95% CI, 2.76-5.83; P<0.001) demonstrated higher odds of hospitalization relative to baseball injuries. In conclusion, head and neck injuries associated with high velocity Olympic-style sports and activities such as cycling, mountain biking, and horseback riding had the highest odds of hospitalization.

Articulation Rate, Pauses, and Disfluencies in Professional Fighters: Potential Speech Biomarkers for Repetitive Head Injury

OBJECTIVE

As part of a larger study dedicated to identifying speech and language biomarkers of neurological decline associated with repetitive head injury (RHI) in professional boxers and mixed martial artists (MMAs), we examined articulation rate, pausing, and disfluency in passages read aloud by participants in the Professional Athletes Brain Health Study.

SETTING

A large outpatient medical center specializing in neurological care.

PARTICIPANTS, DESIGN, AND MAIN MEASURES

Passages read aloud by 60 boxers, 40 MMAs, and 55 controls were acoustically analyzed to determine articulation rate (the number of syllables produced per second), number and duration of pauses, and number and duration of disfluencies in this observational study.

RESULTS

Both boxers and MMAs differed from controls in articulation rate, producing syllables at a slower rate than controls by nearly half a syllable per second on average. Boxers produced significantly more pauses and disfluencies in passages read aloud than MMAs and controls.

CONCLUSIONS

Slower articulation rate in both boxers and MMA fighters compared with individuals with no history of RHI and the increased occurrence of pauses and disfluencies in the speech of boxers suggest changes in speech motor behavior that may relate to RHI. These speech characteristics can be measured in everyday speaking conditions and by automatic recognition systems, so they have the potential to serve as effective, noninvasive clinical indicators for RHI-associated neurological decline.

Examining the occurrence and outcomes of concussion and mTBI in mixed martial arts athletes: a systematic review

INTRODUCTION

Mixed martial arts (MMA) is a sport growing in popularity around the world. However, many individuals participate in the sport with little understanding of the potential short- and long-term consequences of injuries sustained while participating. Specifically, individuals are placed at a high risk of minor traumatic brain injury (mTBI) and concussive episodes as a result of head injuries incurred during training and competition.

AIMS

The current review aimed to examine the literature surrounding the occurrence and outcomes of mTBI in MMA athletes to gain a better understanding of these consequences.

METHODS

Twenty-five studies were identified within the current review, of which 14 examined occurrence of mTBI within the sport setting, and elevenidentified outcomes of injury.

RESULTS

Overall, studies found that MMA athletes experienced mTBI and concussion to a greater extent than athletes in other sports. Deficits in memory, reaction time and processing speed were identified following occurrence of mTBI; however, several gaps in outcome measurement were identified within the current literature, including a lack of focus on speech and language outcomes.

CONCLUSION

Future research should examine a wider variety of outcomes to provide a clearer understanding of the consequences of participating in the sport.

Sparring and the Brain: The Associations between Sparring and Regional Brain Volumes in Professional Mixed Martial Arts Fighters

BACKGROUND

Mixed martial arts (MMA) fighters, due to exposure to repetitive head impacts, are at risk for brain atrophy and neurodegenerative sequelae. Simultaneously, motor skills training and cognition-rich activities have been linked with larger regional brain volumes. The majority of an MMA fighter's sporting activity occurs during practice (e.g., sparring) rather than formal competition. This study, therefore, aims to be the first to explore regional brain volumes associated with sparring in MMA fighters.

METHODS

Ninety-four active, professional MMA fighters from the Professional Fighters Brain Health Study met inclusion criteria for this cross-sectional analysis. Adjusted multivariable regression analyses were utilized to examine the relationship between the number of sparring practice rounds per week during typical training and a select number of regional brain volumes (i.e., caudate, thalamus, putamen, hippocampus, amygdala).

RESULTS

A higher number of weekly sparring rounds during training was significantly associated with larger left (beta = 13.5 µL/round, 95% CI 2.26-24.8) and right (beta = 14.9 µL/round, 95% CI 3.64-26.2) caudate volumes. Sparring was not significantly associated with left or right thalamus, putamen, hippocampus, or amygdala volumes.

CONCLUSIONS

More weekly rounds of sparring was not significantly associated with smaller volumes in any of the brain regions studied in active, professional MMA fighters. Sparring's significant association with larger caudate volume raises questions about whether fighters who spar more experience attenuated trauma-related decreases in caudate volume relative to fighters who spar less, whether fighters who spar more experience minimal or even positive changes to caudate volume, whether baseline differences in caudate size may have mediated results, or whether some other mechanism may be at play. Given limitations inherent to the cross-sectional study design, more research is needed to further explore the brain effects of sparring in MMA.

Neuroimaging Correlates of Post-Traumatic Stress Disorder in Traumatic Brain Injury: A Systematic Review of the Literature

Neuroimaging is widely utilized in studying traumatic brain injury (TBI) and post-traumatic stress disorder (PTSD). The risk for PTSD is greater after TBI than after non-TBI trauma, and PTSD is associated with worse outcomes after TBI. Studying the neuroimaging correlates of TBI-related PTSD may provide insights into the etiology of both conditions and help identify those TBI patients most at risk of developing persistent symptoms. The objectives of this systematic review were to examine the current literature on neuroimaging in TBI-related PTSD, summarize key findings, and highlight strengths and limitations to guide future research. A Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA) compliant literature search was conducted in PubMed (MEDLINE®), PsycINFO, Embase, and Scopus databases prior to January 2022. The database query yielded 4486 articles, which were narrowed based on specified inclusion criteria to a final cohort of 16 studies, composed of 854 participants with TBI. There was no consensus regarding neuroimaging correlates of TBI-related PTSD among the included articles. A small number of studies suggest that TBI-related PTSD is associated with white matter tract changes, particularly in frontotemporal regions, as well as changes in whole-brain networks of resting-state connectivity. Future studies hoping to identify reliable neuroimaging correlates of TBI-related PTSD would benefit from ensuring consistent case definition, preferably with clinician-diagnosed TBI and PTSD, selection of comparable control groups, and attention to imaging timing post-injury. Prospective studies are needed and should aim to further differentiate predisposing factors from sequelae of TBI-related PTSD.

Preliminary Development of a Brainwave Model for K1 Kickboxers Using Quantitative Electroencephalography (QEEG) with Open Eyes

K1 kickboxing fighting is characterised by high injury rates due to the low restrictions of fighting rules. In recent years, much attention has been paid to research on changes in brain function among athletes, including those in combat sports. One of the tools that are likely to help diagnose and assess brain function is quantitative electroencephalography (QEEG). Therefore, the aim of the present study was an attempt to develop a brainwave model using quantitative electroencephalography in competitive K1 kickboxers. A total of thirty-six male individuals were purposefully selected and then comparatively divided into two groups. The first group consisted of specialised K1 kickboxing athletes exhibiting a high level of sports performance (experimental group, n = 18, mean age: 29.83 ± 3.43), while the second group comprised healthy individuals not training competitively (control group, n = 18, mean age: 26.72 ± 1.77). Body composition assessment was performed in all participants before the main measurement process. Measurements were taken for kickboxers during the de-training period, after the sports competition phase. Quantitative electroencephalography of Delta, Theta, Alpha, sensimotor rhytm (SMR), Beta1 and Beta2 waves was performed using electrodes placed on nine measurement points (frontal: FzF3F4, central: CzC3C4, and parietal: PzP3P4) with open eyes. In the course of the analyses, it was found that the level of brain activity among the study population significantly differentiated the K1 formula competitors compared with the reference standards and the control group in selected measurement areas. For kickboxers, all results of the Delta amplitude activity in the area of the frontal lobe were significantly above the normative values for this wave. The highest value was recorded for the average value of the F3 electrode (left frontal lobe), exceeding the norm by 95.65%, for F4 by 74.45% and Fz by 50.6%, respectively. In addition, the Alpha wave standard value for the F4 electrode was exceeded by 14.6%. Normative values were found for the remaining wave amplitudes. Statistically significant differentiation of results, with a strong effect (d = 1.52-8.41), was shown for the activity of Delta waves of the frontal area and the central part of the parietal area (Fz,F3,F4,Cz-p < 0.001), Theta for the frontal area as well as the central and left parietal lobes (Fz,F3,F4-p < 0.001, Cz-p = 0.001, C3-p = 0.018; d = 1.05-3.18), Alpha for the frontal, parietal and occipital areas (for: Fz,F3-p < 0.001, F4-p = 0.036, Cz-p < 0.001, C3-p = 0.001, C4-p = 0.025, Pz-p = 0.010, P3-p < 0.001, P4-p = 0.038; d = 0.90-1.66), SMR for the central parietal and left occipital lobes (Cz-p = 0.043; d = 0.69, P3-p < 0.001; d = 1.62), Beta for the frontal area, occipital and central lobes and left parietal segment (Fz,F3-p < 0.001, F4-p = 0.008, Cz, C3, Pz, P3,P4-p < 0.001; d = 1.27-2.85) and Beta 2 for all measurement areas (Fz, F3, F4, Cz, C3, C4, Pz, P3, P4-p < 0.001; d = 1.90-3.35) among the study groups. Significantly higher results were shown in the kickboxer group compared to the control. In addition to problems with concentration or over-stimulation of neural structures, high Delta waves, with elevated Alpha, Theta and Beta 2 waves, can cause disorders in the limbic system and problems in the cerebral cortex.

Diagnostic Prospectives with Tau Protein and Imaging Techniques to Detect Development of Chronic Traumatic Encephalopathy

Brain damage sustained from repeated blows in boxing, wrestling, and other combat sports has serious physical and mental health consequences. The degenerative brain disease, chronic traumatic encephalopathy (CTE), presents clinically with memory loss, aggression, difficulty in rational thinking and other cognitive problems. This spectrum, which mimics Alzheimer's disease, is diagnosed post-mortem through a brain biopsy in many professional athletes. However, little is known about the process of development and how to identify vulnerable individuals who may be on course for developing CTE. Boxing is a sport that has a severe toll on athletes' health, primarily on their brain health and function. This review addresses the concerns of brain injury, describes the pathologies that manifest in multiple scales, e.g., molecular and cognitive, and also proposes possible diagnostic and prognostic markers to characterize the early onset of CTE along with the aim to identify a starting point for future precautions and interventions.

Comparison of Head Strike Incidence under K1 Rules of Kickboxing with and without Helmet Protection-A Pilot Study

BACKGROUND

Kickboxing is a combat sport that encompasses various forms of competition. K1 kickboxing is conducted without any restrictions on the force of strikes, and the bout can end prematurely through a knockout. Headgear has been introduced in amateur kickboxing to safeguard the head. However, scientific studies have shown that despite their use, serious head injuries can still occur. The aim of this study was to evaluate the temporal structure of the bout by calculating the number of head strikes in K1 kickboxing bouts with and without headgear.

METHODS

Thirty K1 kickboxing bouts were analyzed, with 30 participants included in the study. The fights were conducted according to the World Association Kickboxing Organization (WAKO) rules. The bouts consisted of three rounds of 2 min each, with a 1 min break between rounds. Sparring pairs were arranged according to weight categories. The first bouts were conducted without headgear, and two weeks later, the fights were repeated with WAKO-approved headgear. The number of head strikes was assessed retrospectively by analyzing video recordings of the bouts, categorizing strikes as hand or foot strikes, and differentiating between strikes that hit the head directly or indirectly.

RESULTS

The results showed statistically significant differences between bouts with and without headgear in terms of the number of strikes to the head (p = 0.002), strikes directly to the head (p < 0.001), all hand strikes to the head (p = 0.001), hand strikes directly to the head (p = 0.003), and foot strikes directly to the head (p = 0.03). Higher values were observed in bouts with headgear.

CONCLUSIONS

Headgear increases the probability of direct strikes to the head. Therefore, it is important to familiarize kickboxers with the use of headgear in their sport to minimize head injuries.

Deep Grey Matter Volume is Reduced in Amateur Boxers as Compared to Healthy Age-matched Controls

Purpose

Mild traumatic brain injuries (mTBI) sustained during contact sports like amateur boxing are found to have long-term sequelae, being linked to an increased risk of developing neurological conditions like Parkinson’s disease. The aim of this study was to assess differences in volume of anatomical brain structures between amateur boxers and control subjects with a special interest in the affection of deep grey matter structures.

Methods

A total of 19 amateur boxers and 19 healthy controls (HC), matched for age and intelligence quotient (IQ), underwent 3T magnetic resonance imaging (MRI) as well as neuropsychological testing. Body mass index (BMI) was evaluated for every subject and data about years of boxing training and number of fights were collected for each boxer. The acquired 3D high resolution T1 weighted MR images were analyzed to measure the volumes of cortical grey matter (GM), white matter (WM), cerebrospinal fluid (CSF) and deep grey matter structures. Multivariate analysis was applied to reveal differences between groups referencing deep grey matter structures to normalized brain volume (NBV) to adjust for differences in head size and brain volume as well as adding BMI as cofactor.

Results

Total intracranial volume (TIV), comprising GM, WM and CSF, was lower in boxers compared to controls (by 7.1%, P = 0.009). Accordingly, GM (by 5.5%, P = 0.038) and WM (by 8.4%, P = 0.009) were reduced in boxers. Deep grey matter showed statistically lower volumes of the thalamus (by 8.1%, P = 0.006), caudate nucleus (by 11.1%, P = 0.004), putamen (by 8.1%, P = 0.011), globus pallidus (by 9.6%, P = 0.017) and nucleus accumbens (by 13.9%, P = 0.007) but not the amygdala (by 5.5%, P = 0.221), in boxers compared to HC.

Conclusion

Several deep grey matter structures were reduced in volume in the amateur boxer group. Furthermore, longitudinal studies are needed to determine the damage pattern affecting deep grey matter structures and its neuropsychological relevance.

Functional performance of the upper limb and the most common boxing-related injuries in male boxers: a retrospective, observational, comparative study with non-boxing population

Background

To investigate the functional status and recording the most common injuries of the upper limb in male Greek boxing squad in comparison to the general population.

Methods

A retrospective injury surveillance study using an electronic questionnaire was performed in 2021. The questionnaire was sent to male members of the Greek Boxing Federation and consisted of three parts. Demographic data, functional status scales, training conditions, hours of training, the location and description of upper limb injuries and whether the injury occurred during competition or training and also whether it was a new or a recurrent one were gathered. The same questionnaire was sent to non-boxer males (military recruits), but without asking them to report any training parameters. Inclusion criteria were age < 35 years-old for all participants and no involvement in martial arts for the control group. Also, all participants (boxers and non-boxers) completed the Patient Rated Wrist Evaluation (PRWE) scale and the Quick Disabilities of Arm, Shoulder and Hand (quick-DASH) score.

Results

The final study cohort was consisted of 62 elite or amateur boxers and 75 non-boxer males, less than 35 years old. The quick-DASH score was found to be significantly lower (better) in boxers in comparison to the general population (15.65 ± 10.25 vs. 12.55 ± 8.62; p = 0.020) whereas the PRWE score was similar in both groups (9.25 ± 14.96 vs. 8.61 ± 13.05; p = 0.843). Physical therapy sessions, thumb injuries and boxer’s knuckle were also found to be significantly higher in the boxers group. On the other hand, upper limb surgeries were significantly less in the boxers group. Finally, the size of boxing gloves was associated to the number of finger fractures, thumb injuries and ulnar sided wrist pain in boxers.

Conclusions

Although a controversial sport, boxing appears to have no long-term consequences to the upper limb function, especially regarding hand performance. The size of gloves during heavy bag training was found to be an aggravating factor for hand injuries.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13102-022-00558-3.

Neuroimaging in professional combat sports: consensus statement from the association of ringside physicians

Professional boxing, kickboxing, and mixed martial arts (MMA) are popular sports with substantial risk for both acute and chronic traumatic brain injury (TBI). Although rare, combat sports athletes have died in the ring or soon after the completion of a bout. Deaths in these instances are usually the result of an acute catastrophic neurological event such as an acute subdural hematoma (SDH). Other causes may include acute epidural hematoma (EDH), subarachnoid hemorrhage (SAH), intraparenchymal hemorrhage (IPH), or a controversial, rare, and still disputed clinical entity called second-impact syndrome (SIS). Neuroimaging or brain imaging is currently included in the process of registering for a license to compete in combat sports in some jurisdictions of the United States of America and around the world. However, the required imaging specifics and frequency vary with no consensus guidelines. The Association of Ringside Physicians (an international, nonprofit organization dedicated to the health and safety of the combat sports athlete) sets forth this consensus statement to establish neuroimaging guidelines in combat sports. Commissions, ringside physicians, combat sports athletes, trainers, promoters, sanctioning bodies, and other healthcare professionals can use this statement for risk stratification of a professional combat sports athlete prior to licensure, identifying high-risk athletes and for prognostication of the brain health of these athletes over the course of their career. Guidelines are also put forth regarding neuroimaging requirements in the immediate aftermath of a bout.

Behavioral and Emotional Dyscontrol Following Traumatic Brain Injury: A Systematic Review of Neuroimaging and Electrophysiological Correlates

BACKGROUND

Behavioral and emotional dyscontrol commonly occur following traumatic brain injury (TBI). Neuroimaging and electrophysiological correlates of dyscontrol have not been systematically summarized in the literature to date.

OBJECTIVE

To complete a systematic review of the literature examining neuroimaging and electrophysiological findings related to behavioral and emotional dyscontrol due to TBI.

METHODS

A Preferred Reporting Items for Systematic Reviews and Meta-Analyses-compliant literature search was conducted in PubMed (MEDLINE), PsycINFO, EMBASE, and Scopus databases prior to May 2019. The database query yielded 4392 unique articles. These articles were narrowed based on specific inclusion criteria (e.g., clear TBI definition, statistical analysis of the relationship between neuroimaging and dyscontrol).

RESULTS

A final cohort of 24 articles resulted, comprising findings from 1552 patients with TBI. Studies included civilian (n = 12), military (n = 10), and sport (n = 2) samples with significant variation in the severity of TBI incorporated. Global and region-based structural imaging was more frequently used to study dyscontrol than functional imaging or diffusion tensor imaging. The prefrontal cortex was the most common neuroanatomical region associated with behavioral and emotional dyscontrol, followed by other frontal and temporal lobe findings.

CONCLUSIONS

Frontal and temporal lesions are most strongly implicated in the development of postinjury dyscontrol symptoms although they are also the most frequently investigated regions of the brain for these symptom categories. Future studies can make valuable contributions to the field by (1) emphasizing consistent definitions of behavioral and emotional dyscontrol, (2) assessing premorbid dyscontrol symptoms in subjects, (3) utilizing functional or structural connectivity-based imaging techniques, or (4) restricting analyses to more focused brain regions.

Serum BDNF and Selenium Levels in Elite Athletes Exposed to Blows

Background and Objectives: The study aimed to investigate the combined acute and long-term effects of exposure to blows and exercise on serum BDNF (brain-derived neurotrophic factor) and selenium levels. Materials and Methods: Serum BDNF and selenium levels were determined in 40 male elite athletes before and after vigorous exercise (training match) with a probability of exposure to blows and in 10 sedentary men subjected to exercise (Astrand running protocol). Results: Serum BDNF levels were found 11.50 ± 3.50 ng/mL before exercise and 14.02 ± 3.15 ng/mL after exercise in the athlete group (p = 0.02), and 12.18 ± 4.55 ng/ mL and 11.74 ± 2.48 ng/ mL before and after exercise in the sedentary group, respectively (p = 0.873). Serum BDNF (pre-exercise, baseline) levels were slightly lower in the athlete group than those in the sedentary group (11.50 ± 3.50 and 12.18 ± 4.55 ng/mL, respectively, p = 0.796). Pre-exercise serum selenium levels in athletes were significantly higher compared to those of sedentary participants (130.53 ± 36.79 and 95.51 ± 20.57 µg/L, respectively, p = 0.011). There was no difference in selenium levels after exercise (124.01 ± 29.96 µg/L) compared to pre-exercise (130.53 ± 36.79 µg/L) in the athlete group (p = 0.386). Similarly, there was no difference in selenium levels after exercise (113.28 ± 25.51 µg/L) compared to pre-exercise (95.51 ± 20.57 µg/L) in the sedentary group (p = 0.251). Conclusions: BDNF results show that even if athletes are exposed to blows, they may be protected from the long-term effects of blows thanks to the protective effect of their non-sedentary lifestyle. Regular exercise may have a protective effect on maintaining serum selenium levels in athletes even exposed to blows chronically.

Concussion and long-term cognitive function among rugby players-The BRAIN Study

Objective

The BRAIN Study was established to assess the associations between self‐reported concussions and cognitive function among retired rugby players.

Methods

Former elite‐level male rugby union players (50+ years) in England were recruited. Exposure to rugby‐related concussion was collected using the BRAIN‐Q tool. The primary outcome measure was the Preclinical Alzheimer Cognitive Composite (PACC). Linear regressions were conducted for the association between concussion and PACC score, adjusting for confounders.

Results

A total of 146 participants were recruited. The mean (standard deviation) length of playing career was 15.8 (5.4) years. A total of 79.5% reported rugby‐related concussion(s). No association was found between concussion and PACC (β –0.03 [95% confidence interval (CI): –1.31, 0.26]). However, participants aged 80+ years reporting 3+ concussions had worse cognitive function than those without concussion (β –1.04 [95% CI: –1.62, –0.47]).

Conclusions

Overall there was no association between concussion and cognitive function; however, a significant interaction with age revealed an association in older participants.

Neuroimaging Correlates of Syndromal Anxiety Following Traumatic Brain Injury: A Systematic Review of the Literature

BACKGROUND

Traumatic brain injury (TBI) can precipitate new-onset psychiatric symptoms or worsen existing psychiatric conditions. To elucidate specific mechanisms for this interaction, neuroimaging is often used to study both psychiatric conditions and TBI. This systematic review aims to synthesize the existing literature of neuroimaging findings among patients with anxiety after TBI.

METHODS

We conducted a Preferred Reporting Items for Systematic Review and Meta-Analyses-compliant literature search via PubMed (MEDLINE), PsychINFO, EMBASE, and Scopus databases before May, 2019. We included studies that clearly defined TBI, measured syndromic anxiety as a primary outcome, and statistically analyzed the relationship between neuroimaging findings and anxiety symptoms.

RESULTS

A total of 5982 articles were retrieved from the systematic search, of which 65 studied anxiety and 13 met eligibility criteria. These studies were published between 2004 and 2017, collectively analyzing 764 participants comprised of 470 patients with TBI and 294 non-TBI controls. Imaging modalities used included magnetic resonance imaging, functional magnetic resonance imaging, diffusion tensor imaging, electroencephalogram, magnetic resonance spectrometry, and magnetoencephalography. Eight of 13 studies presented at least one significant finding and together reflect a complex set of changes that lead to anxiety in the setting of TBI. The left cingulate gyrus in particular was found to be significant in 2 studies using different imaging modalities. Two studies also revealed perturbances in functional connectivity within the default mode network.

CONCLUSIONS

This is the first systemic review of neuroimaging changes associated with anxiety after TBI, which implicated multiple brain structures and circuits, such as the default mode network. Future research with consistent, rigorous measurements of TBI and syndromic anxiety, as well as attention to control groups, previous TBIs, and time interval between TBI and neuroimaging, are warranted. By understanding neuroimaging correlates of psychiatric symptoms, this work could inform future post-TBI screening and surveillance, preventative efforts, and early interventions to improve neuropsychiatric outcomes.

Assessing Clinical Change in Individuals Exposed to Repetitive Head Impacts: The Repetitive Head Impact Composite Index

Background: There is a current lack of any composite measure for the effective tracking and monitoring of clinical change in individuals exposed to repetitive head impacts (RHI). The aim of this study is to create a composite instrument for the purposes of detecting change over time in cognitive and behavioral function in individuals exposed to RHI. Methods: The data to derive the composite instrument came from the Professional Fighters Brain Health Study (PFBHS), a longitudinal study of active and retired professional fighters [boxers and mixed martial arts (MMA) fighters] and healthy controls. Participants in the PFBHS underwent assessment on an annual basis that included computerized cognitive testing and behavioral questionnaires. Multivariate logistic regression models were employed to compare active fighters (n = 117) with controls (n = 22), and retired fighters (n = 26) with controls to identify the predictors that could be used to differentiate the groups over time. In a second step, linear discriminant analysis was performed to derive the linear discriminant coefficients for the three groups by using the predictors from the two separate logistic regression models. Results: The composite scale is a weighted linear value of 12 standardized scores consisting of both current and yearly change scores in domains including: processing speed, choice reaction time, semantic fluency, letter fluency, and Barrett Impulsiveness Scale. Because the weighting of values differed between active and retired fighters, two versions emerged. The mean and standard deviation ratio (MSDR) showed that the new index had better sensitivity compared to the individual measures, with the ratio of MSDR of the new index to that of the existing measures of at least 1.84. Conclusion: With the increasing need for tools to follow individuals exposed to RHI and the potential of clinical trials on the horizon for CTE, the RHICI is poised to serve as an initial approach to a composite clinical measure.

Effect of Weight Class on Regional Brain Volume, Cognition, and Other Neuropsychiatric Outcomes among Professional Fighters

Traumatic brain injury (TBI) is a common source of functional impairment among athletes, military personnel, and the general population. Professional fighters in both boxing and mixed martial arts (MMA) are at particular risk for repetitive TBI and may provide valuable insight into both the pathophysiology of TBI and its consequences. Currently, effects of fighter weight class on brain volumetrics (regional and total) and functional outcomes are unknown. Fifty-three boxers and 103 MMA fighters participating in the Professional Fighters Brain Health Study (PRBHS) underwent volumetric magnetic resonance imaging (MRI) and neuropsychological testing. Fighters were divided into lightweight (≤139.9 lb), middleweight (140.0–178.5 lb), and heavyweight (>178.5 lb). Compared with lightweight fighters, heavyweights displayed greater yearly reductions in regional brain volume (boxers: bilateral thalami; MMA: left thalamus, right putamen) and functional performance (boxers: processing speed, simple and choice reaction; MMA: Trails A and B tests). Lightweights suffered greater reductions in regional brain volume on a per-fight basis (boxers: left thalamus; MMA: right putamen). Heavyweight fighters bore greater yearly burden of regional brain volume and functional decrements, possibly related to differing fight dynamics and force of strikes in this division. Lightweights demonstrated greater volumetric decrements on a per-fight basis. Although more research is needed, greater per-fight decrements in lightweights may be related to practices of weight-cutting, which may increase vulnerability to neurodegeneration post-TBI. Observed decrements associated with weight class may result in progressive impairments in fighter performance, suggesting interventions mitigating the burden of TBI in professional fighters may both improve brain health and increase professional longevity.

Sex Moderates the Relationship That Number of Professional Fights Has With Cognition and Brain Volumes

Objective: Incidence of concussions and report of symptoms are greater among women across sports. While structural brain changes and cognitive declines are associated with repetitive head impact (RHI), the role of sex is not well-understood. This study aimed to determine if there is a moderating effect of sex on the relationship the number of professional fights has with cognitive functioning and regional brain volumes in a cohort of boxers, mixed martial artists, and martial artists.

Methods: A total of 55 women were matched with 55 men based on age, years of education, ethnicity, and fighting style. Cognition was assessed via the CNS Vital Signs computerized cognitive battery and supplemental measures. Structural brain scans, demographic data, and number of professional fights (NoPF) were also considered. The matched pairs were compared via analysis of covariance, accounting for total brain volume. Within-subject moderation models were utilized to assess the moderating effect of sex on the relationship between NoPF and brain volumes and cognitive performance.

Results: Men were observed to have poorer performance on measures of psychomotor speed when compared to women. On a series of analyses assessing the role of sex as a moderator of the relationship between NoPF and regional brain volumes/cognitive performance, a significant moderation effect was observed across multiple measures of cognitive functioning, such that men had poorer performance. Differences in numerous regional brain volumes were also observed, such that the relationship between NoPF and brain volumes was steeper among men.

Conclusion: Sex was observed to be an important moderator in the relationship between NoPF, aspects of cognitive functioning, and volumes of numerous brain regions, suggesting that sex differences in neuroanatomic and cognitive response to RHI deserve further attention.

The Relations Among Depression, Cognition, and Brain Volume in Professional Boxers: A Preliminary Examination Using Brief Clinical Measures

OBJECTIVE

Depression, neuropathology, and cognitive decline are commonly observed with repetitive head injuries (RHIs). We examined whether in boxers (a) clinically significant depression is associated with structural brain changes and cognition; (b) minimal symptoms of depression moderate the relations among RHI and brain volumes and cognition; and (c) baseline depression is associated with longitudinal cognitive changes.

SETTING

Clinical Research Center.

PARTICIPANTS

A total of 205 male professional boxers.

DESIGN

Cross-sectional and longitudinal (subsample: n = 45; first visit to follow-up range = 1-6 years; mean = 2.61 years).

MAIN MEASURES

Patient Health Questionnaire-9 depression; CNS Vital Signs cognitive battery; brain imaging.

RESULTS

Clinically significant depression was associated with smaller regional volumes in insula, cingulate, orbitofrontal cortex, thalami, and middle corpus-callosum subregions; and with poorer verbal memory and psychomotor speed performance. Depression symptoms moderated the relations between RHI and bilateral thalami, left hippocampus, left medial orbitofrontal cortex, and bilateral insula volumes; but not cognition. Baseline depression was associated with poorer psychomotor speed and reaction time longitudinally and improved verbal memory performance longitudinally.

CONCLUSION

Clinical depression is associated with volumetric and cognitive changes occasioning RHI exposure, and even minimal depressive symptoms may moderate the relations between exposure and brain volumes in key regions. Longitudinally, there is preliminary evidence that depression precedes cognitive changes.

The Relationship Between Fighting Style, Cognition, and Regional Brain Volume in Professional Combatants: A Preliminary Examination Using Brief Neurocognitive Measures

OBJECTIVE

Repetitive head impacts (RHIs) in combat sports are associated with cognitive decline and brain volume reduction. While fighting style differences between boxers, mixed martial artists (MMAs), and martial artists (MAs) have resulted in a broader spectrum of injury, the effects of RHIs on MAs relative to other fighters have not yet been explored. This study aimed to determine a differential effect of fighting style on cognition and brain.

SETTING

A large outpatient medical center specializing in neurological care.

PARTICIPANTS, DESIGN, AND MAIN MEASURES

In total, 40 MAs, 188 boxers, and 279 MMAs were compared on baseline measures of subcortical regional brain volumes, after controlling for total brain volumes, and cognitive performance.

RESULTS

Significant differences between MAs, MMAs, and boxers were observed in subcortical brain structure volumes and cognitive measures. MMAs and MAs consistently had larger volumes and higher scores than boxers. Fighting style significantly moderated the relationship between the number of professional fights and the volumes of various subcortical brain structures and performance on a measure of processing speed at baseline.

CONCLUSIONS

Differences in RHIs across fighting styles may be of clinical significance. Exploring changes over time within the MA, boxer, and MMA cohorts may provide insight into longer-term discrepancies in subcortical regional brain volumes and cognitive functioning across fighting styles.

Understanding white matter structural connectivity differences between cognitively impaired and nonimpaired active professional fighters

Long-term traumatic brain injury due to repeated head impacts (RHI) has been shown to be a risk factor for neurodegenerative disorders, characterized by a loss in cognitive performance. Establishing the correlation between changes in the white matter (WM) structural connectivity measures and neuropsychological test scores might help to identify the neural correlates of the scores that are used in daily clinical setting to investigate deficits due to repeated head blows. Hence, in this study, we utilized high angular diffusion MRI (dMRI) of 69 cognitively impaired and 70 nonimpaired active professional fighters from the Professional Fighters Brain Health Study, and constructed structural connectomes to understand: (a) whether there is a difference in the topological WM organization between cognitively impaired and nonimpaired active professional fighters, and (b) whether graph-theoretical measures exhibit correlations with neuropsychological scores in these groups. A dMRI derived structural connectome was constructed for every participant using brain regions defined in AAL atlas as nodes, and the product of fiber number and average fractional anisotropy of the tracts connecting the nodes as edges. Our study identified a topological WM reorganization due to RHI in fighters prone to cognitive decline that was correlated with neuropsychological scores. Furthermore, graph-theoretical measures were correlated differentially with neuropsychological scores between groups. We also found differentiated WM connectivity involving regions of hippocampus, precuneus, and insula within our cohort of cognitively impaired fighters suggesting that there is a discernible WM topological reorganization in fighters prone to cognitive decline.

Low Prefrontal GABA Levels Are Associated With Poor Cognitive Functions in Professional Boxers

Cognitive dysfunction has long been recognized as a frequently observed symptom in individuals with repetitive mild traumatic brain injury (rmTBI) such as professional boxers. The exact neurobiological mechanisms underlying this cognitive deficit have not yet been identified, but it is agreed upon that the prefrontal cortex (PFC) is one of the most commonly affected brain regions in professional boxers. Noting the pivotal role of the two major brain metabolites in human cognitive functions, γ-aminobutyric acid (GABA) and glutamate/glutamine (Glx), we hypothesized that alterations in levels of GABA and Glx in the PFC would be prominent and may correlate with cognitive deficits in professional boxers. Twenty male professional boxers (Boxers) and 14 age-matched healthy males who had never experienced any TBI (CON) were recruited. Using a 3T magnetic resonance imaging (MRI) scanner, single-voxel proton magnetic resonance spectroscopy with Mescher-Garwood point-resolved spectroscopy (MEGA-PRESS) sequence was performed to evaluate the levels of GABA and Glx in the PFC. Cognitive function was assessed using the memory and attention domains from the Cambridge Neuropsychological Test Automated Battery. The Boxers showed lower GABA level in the PFC compared to the CON, while also showing lower performance in the attention and memory domains. There were no significant between-group differences in Glx levels. Furthermore, the GABA level correlated with memory performance in the Boxers, but not in attention performance. The current findings may suggest that alterations in GABA levels in the PFC may be a potential neurochemical correlate underlying memory dysfunction related to rmTBI.

Concussion management in combat sports: consensus statement from the Association of Ringside Physicians

Various organisations and experts have published numerous statements and recommendations regarding different aspects of sports-related concussion including definition, presentation, treatment, management and return to play guidelines. 1-7 To date, there have been no written consensus statements specific for combat sports regarding management of combatants who have suffered a concussion or for return to competition after a concussion. In combat sports, head contact is an objective of the sport itself. Accordingly, management and treatment of concussion in combat sports should, and must, be more stringent than for non-combat sports counterparts.The Association of Ringside Physicians (an international, non-profit organisation dedicated to the health and safety of the combat sports athlete) sets forth this consensus statement to establish management guidelines that ringside physicians, fighters, referees, trainers, promoters, sanctioning bodies and other healthcare professionals can use in the ringside setting. We also provide guidelines for the return of a combat sports athlete to competition after sustaining a concussion. This consensus statement does not address the management of moderate to severe forms of traumatic brain injury, such as intracranial bleeds, nor does it address the return to competition for combat sports athletes who have suffered such an injury. These more severe forms of brain injuries are beyond the scope of this statement. This consensus statement does not address neuroimaging guidelines in combat sports.

Investigating possible retinal biomarkers of head trauma in Olympic boxers using optical coherence tomography

Purpose

Changes to retina have been reported after a number of neurodegenerative conditions. The purpose of this study was to investigate retinal structures in Olympic boxers exposed to frequent head blows.

Methods

Retinal imaging offers potential as a non-invasive biomarker of neuropathology. Macula and retinal nerve fiber layer (RNFL) thickness was measured using optical coherence tomography (OCT) in UK Olympic boxers attending two mandatory eye screening programs, 18 months apart. Data from the two eye screenings provide longitudinal data of retinal change over time. Sedentary healthy subjects (controls) without past or present history of concussion were also screened at the time of the second boxer screening to provide comparison of cross-sectional data.

Results

Sixteen Olympic boxers aged 20–33 years and 20 sedentary healthy controls, aged 24–45 years, were recruited. Significant macula thickening was observed over time (18 months) in 75% of right and 50% of left eye sectors. For RNFL, left eye quadrants thickened. For right eye RNFL quadrants, thickening and thinning of this layer were observed. Cross-sectional results showed thinner macula sectors and RNFL quadrants in Olympic boxers compared to controls.

Conclusion

Significant change to macula and RNFL densities, occurring over an 18 month interval is an unexpected finding in otherwise heathy elite sportsmen. In addition, macula and RNFL were thinner than healthy sedentary controls. OCT may prove clinically useful as a candidate retinal biomarker of neuropathological change after mild traumatic brain injury and/or repeat head blows.

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.

Statistical advances in clinical trials and clinical research

Introduction

New treatments for neurodegenerative disease are urgently needed, and clinical trial methods are an essential component of new drug development. Although a parallel-group study design for neurological disorder clinical trials is commonly used to test the effectiveness of a new treatment as compared to placebo, it does not efficiently use information from the on-going study to increase the success rate of a trial or to stop a trial earlier when the new treatment is indeed ineffective.

Methods

We review some recent advances in designs for clinical trials, including futility designs and adaptive designs.

Results

Futility designs and noninferiority designs are used to test the nonsuperiority and the noninferiority of a new treatment, respectively. We provide some guidance on using these two designs and analyzing data from these studies properly. Adaptive designs are increasingly used in clinical trials to improve the flexibility and efficiency of trials with the potential to reduce resources, time, and costs. We review some typical adaptive designs and new statistical methods to handle the statistical challenges from adaptive designs.

Discussion

Statistical advances in clinical trial designs may be helpful to shorten study length and benefit more patients being treated with a better treatment during the discovery of new therapies for neurological disorders. Advancing statistical underpinnings of neuroscience research is a critical aspect of the core activities supported by the Center of Biomedical Research Excellence award supporting the Center for Neurodegeneration and Translational Neuroscience.

Sample size determination for a matched-pairs study with incomplete data using exact approach

This research was motivated by a clinical trial design for a cognitive study. The pilot study was a matched-pairs design where some data are missing, specifically the missing data coming at the end of the study. Existing approaches to determine sample size are all based on asymptotic approaches (e.g., the generalized estimating equation (GEE) approach). When the sample size in a clinical trial is small to medium, these asymptotic approaches may not be appropriate for use due to the unsatisfactory Type I and II error rates. For this reason, we consider the exact unconditional approach to compute the sample size for a matched-pairs study with incomplete data. Recommendations are made for each possible missingness pattern by comparing the exact sample sizes based on three commonly used test statistics, with the existing sample size calculation based on the GEE approach. An example from a real surgeon-reviewers study is used to illustrate the application of the exact sample size calculation in study designs.

Investigating structural and perfusion deficits due to repeated head trauma in active professional fighters

Repeated head trauma experienced by active professional fighters results in various structural, functional and perfusion damage. However, whether there are common regions of structural and perfusion damage due to fighting and whether these structural and perfusion differences are associated with neuropsychological measurements in active professional fighters is still unknown. To that end, T1-weighted and pseudocontinuous arterial spin labeling MRI on a group of healthy controls and active professional fighters were acquired. Voxelwise group comparisons, in a univariate and multivariate sense, were performed to investigate differences in gray and white matter density (GMD, WMD) and cerebral blood flow (CBF) between the two groups. A significantly positive association between global GMD and WMD was obtained with psychomotor speed and reaction time, respectively, in our cohort of active professional fighters. In addition, regional WMD deficit was observed in a cluster encompassing bilateral pons, hippocampus, and thalamus in fighters (0.49 ± 0.04 arbitrary units (a.u.)) as compared to controls (0.51 ± 0.05a.u.). WMD in the cluster of active fighters was also significantly associated with reaction time. Significantly lower CBF was observed in right inferior temporal lobe with both partial volume corrected (46.9 ± 14.93 ml/100 g/min) and non-partial volume corrected CBF maps (25.91 ± 7.99 ml/100 g/min) in professional fighters, as compared to controls (65.45 ± 22.24 ml/100 g/min and 35.22 ± 12.18 ml/100 g/min respectively). A paradoxical increase in CBF accompanying right cerebellum and fusiform gyrus in the active professional fighters (29.52 ± 13.03 ml/100 g/min) as compared to controls (19.43 ± 12.56 ml/100 g/min) was observed with non-partial volume corrected CBF maps. Multivariate analysis with both structural and perfusion measurements found the same clusters as univariate analysis in addition to a cluster in right precuneus. Both partial volume corrected and non-partial volume corrected CBF of the cluster in the thalamus had a significantly positive association with the number of fights. In addition, GMD of the cluster in right precuneus was significantly associated with psychomotor speed in our cohort of active professional fighters. Our results suggest a heterogeneous pattern of structural and CBF deficits due to repeated head trauma in active professional fighters. This finding indicates that investigating both structural and CBF changes in the same set of participants may help to understand the pathophysiology and progression of cognitive decline due to repeated head trauma.

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Repetitive head trauma revealed no global structural or global perfusion deficits.

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Cluster of significantly lower WMD was associated with reaction time in fighters.

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Fighters had lower CBF in right inferior temporal lobe.

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Multivariate analysis revealed a cluster associated with number of fights.

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Combined analysis of structural and perfusion measurements is recommended.

Cognitive Reserve as a Modifier of Clinical Expression in Chronic Traumatic Encephalopathy: A Preliminary Examination

This study conducted a preliminary examination on cognitive reserve (CR) as a modifier of symptom expression in subjects with autopsy-confirmed chronic traumatic encephalopathy (CTE). The sample included 25 former professional football players neuropathologically diagnosed with CTE stage III or IV. Next of kin interviews ascertained age at cognitive and behavioral/mood symptom onset and demographic/athletic characteristics. Years of education and occupational attainment defined CR. High occupational achievement predicted later age at cognitive (p=0.02) and behavioral/mood (p=0.02) onset. Education was not an individual predictor. These preliminary findings suggest that CR may forestall the clinical manifestation of CTE.

MR Imaging Applications in Mild Traumatic Brain Injury: An Imaging Update

Mild traumatic brain injury (mTBI), also commonly referred to as concussion, affects millions of Americans annually. Although computed tomography is the first-line imaging technique for all traumatic brain injury, it is incapable of providing long-term prognostic information in mTBI. In the past decade, the amount of research related to magnetic resonance (MR) imaging of mTBI has grown exponentially, partly due to development of novel analytical methods, which are applied to a variety of MR techniques. Here, evidence of subtle brain changes in mTBI as revealed by these techniques, which are not demonstrable by conventional imaging, will be reviewed. These changes can be considered in three main categories of brain structure, function, and metabolism. Macrostructural and microstructural changes have been revealed with three-dimensional MR imaging, susceptibility-weighted imaging, diffusion-weighted imaging, and higher order diffusion imaging. Functional abnormalities have been described with both task-mediated and resting-state blood oxygen level-dependent functional MR imaging. Metabolic changes suggesting neuronal injury have been demonstrated with MR spectroscopy. These findings improve understanding of the true impact of mTBI and its pathogenesis. Further investigation may eventually lead to improved diagnosis, prognosis, and management of this common and costly condition. (©) RSNA, 2016.

Cumulative Head Impact Exposure Predicts Later-Life Depression, Apathy, Executive Dysfunction, and Cognitive Impairment in Former High School and College Football Players

The term "repetitive head impacts" (RHI) refers to the cumulative exposure to concussive and subconcussive events. Although RHI are believed to increase risk for later-life neurological consequences (including chronic traumatic encephalopathy), quantitative analysis of this relationship has not yet been examined because of the lack of validated tools to quantify lifetime RHI exposure. The objectives of this study were: 1) to develop a metric to quantify cumulative RHI exposure from football, which we term the "cumulative head impact index" (CHII); 2) to use the CHII to examine the association between RHI exposure and long-term clinical outcomes; and 3) to evaluate its predictive properties relative to other exposure metrics (i.e., duration of play, age of first exposure, concussion history). Participants included 93 former high school and collegiate football players who completed objective cognitive and self-reported behavioral/mood tests as part of a larger ongoing longitudinal study. Using established cutoff scores, we transformed continuous outcomes into dichotomous variables (normal vs. impaired). The CHII was computed for each participant and derived from a combination of self-reported athletic history (i.e., number of seasons, position[s], levels played), and impact frequencies reported in helmet accelerometer studies. A bivariate probit, instrumental variable model revealed a threshold dose-response relationship between the CHII and risk for later-life cognitive impairment (p < 0.0001), self-reported executive dysfunction (p < 0.0001), depression (p < 0.0001), apathy (p = 0.0161), and behavioral dysregulation (p < 0.0001). Ultimately, the CHII demonstrated greater predictive validity than other individual exposure metrics.

Alzheimer's disease and chronic traumatic encephalopathy: Distinct but possibly overlapping disease entities

BACKGROUND

Alzheimer's disease (AD) and chronic traumatic encephalopathy (CTE) have long been recognized as sharing some similar neuropathological features, mainly the presence of neurofibrilary tangles and hyperphosphorylated tau, but have generally been described as distinct entities. Evidence indicates that neurotrauma increases the risk of developing dementia and accelerates the progression of disease. Findings are emerging that CTE and AD may be present in the same patients.

CLINICAL PRESENTATION

This study presents a series of previously unpublished cases, with one case demonstrating possible neurotrauma-related AD, one pure CTE, and an example of a case exhibiting features of both AD and CTE. The future significance of this work lies not only in the confirmation of AD-CTE co-existence, but, more importantly, ways of generating a hypothesis about the possibility that CTE may accelerate AD development. Understanding the relationship between neurotrauma and neurodegenerative disease will help elucidate how distinct disease entities can co-exist in the same patient. It will ultimately require the use of pre-clinical animal models and repeat injury paradigms to investigate clinically relevant injury mechanisms. These models should produce a CTE-like phenotype that must be both neuropathologically and behaviourally similar to human disease.

CONCLUSION

This case series and review of the literature presents a discussion of AD and CTE in the context of neurotrauma. It highlights recent work from repetitive neurotrauma models with an emphasis on those exhibiting a CTE-like phenotype. Potential mechanisms of interest shared amongst AD and CTE are briefly addressed and future experiments are advocated for to enhance understanding of CTE pathophysiology and the relationship between CTE and AD.

Clinical features of repetitive traumatic brain injury and chronic traumatic encephalopathy

Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease characterized by a distinct pattern of hyperphosphorylated tau (p-tau). Thought to be caused by repetitive concussive and subconcussive injuries, CTE is considered largely preventable. The majority of neuropathologically confirmed cases have occurred in professional contact sport athletes (eg, boxing, football). A recent post-mortem case series has magnified concerns for the public's health following its identification in six high school level athletes. CTE is diagnosed with certainty only following a post-mortem autopsy. Efforts to define the etiology and clinical progression during life are ongoing. The goal of this article is to characterize the clinical concepts associated with short- and long-term effects of repetitive traumatic brain injury, with a special emphasis on new clinical diagnostic criteria for CTE. Utilizing these new diagnostic criteria, two cases of neuropathologically confirmed CTE, one in a professional football player and one in a professional boxer, are reported. Differences in cerebellar pathology in CTE confirmed cases in boxing and football are discussed.

Expert consensus document: Mind the gaps—advancing research into short-term and long-term neuropsychological outcomes of youth sports-related concussions

Sports-related concussions and repetitive subconcussive exposure are increasingly recognized as potential dangers to paediatric populations, but much remains unknown about the short-term and long-term consequences of these events, including potential cognitive impairment and risk of later-life dementia. This Expert Consensus Document is the result of a 1-day meeting convened by Safe Kids Worldwide, the Alzheimer's Drug Discovery Foundation, and the Andrews Institute for Orthopaedics and Sports Medicine. The goal is to highlight knowledge gaps and areas of critically needed research in the areas of concussion science, dementia, genetics, diagnostic and prognostic biomarkers, neuroimaging, sports injury surveillance, and information sharing. For each of these areas, we propose clear and achievable paths to improve the understanding, treatment and prevention of youth sports-related concussions.

The Utilization of Biomechanics to Understand and Manage the Acute and Long-term Effects of Concussion

The acute and long-term effects of concussive and subconcussive head impacts on brain health have gained tremendous attention over the past five years. The treatment and management of concussion involves multiple providers from multiple disciplines and backgrounds. Varied backgrounds and approaches to assessing cognitive and motor function before and post-concussion are limiting factors in the efficient and effective management of concussion as discipline-specific rating scales and assessments serve as a barrier to effective patient hand-offs between providers. Combining principles of motor behavior with biomechanical approaches to data analysis has the potential to improve the continuity of care across the multiple providers managing athletes with concussion. Biomechanical measures have been developed and validated using mobile devices to provide objective and quantitative assessments of information processing, working memory, set switching, and postural stability. These biomechanical outcomes are integral to a clinical management algorithm, the Concussion Care Path, currently used across the Cleveland Clinic Health System. The objective outcomes provide a common data set that all providers in the spectrum of care can access which facilitates communication and the practice of medicine and in understanding the acute and long-term effects of concussion and subconcussive exposure on neurological function.

Chronic traumatic encephalopathy: historical origins and current perspective

Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease that is most often identified in postmortem autopsies of individuals exposed to repetitive head impacts, such as boxers and football players. The neuropathology of CTE is characterized by the accumulation of hyperphosphorylated tau protein in a pattern that is unique from that of other neurodegenerative diseases, including Alzheimer's disease. The clinical features of CTE are often progressive, leading to dramatic changes in mood, behavior, and cognition, frequently resulting in debilitating dementia. In some cases, motor features, including parkinsonism, can also be present. In this review, the historical origins of CTE are revealed and an overview of the current state of knowledge of CTE is provided, including the neuropathology, clinical features, proposed clinical and pathological diagnostic criteria, potential in vivo biomarkers, known risk factors, and treatment options.