The spectrum of disease in chronic traumatic encephalopathy

Aberrant protein aggregation in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal disease. As its pathological mechanisms are not well understood, there are no efficient therapeutics for it at present. While it is highly heterogenous both etiologically and clinically, it has a common salient hallmark, i.e., aberrant protein aggregation (APA). The upstream pathogenesis and the downstream effects of APA in ALS are sophisticated and the investigation of this pathology would be of consequence for understanding ALS. In this paper, the pathomechanism of APA in ALS and the candidate treatment strategies for it are discussed.

REM sleep and neurodegeneration

Several brainstem, subcortical and cortical areas are involved in the generation of rapid eye movement (REM) sleep. The alteration of these structures as a result of a neurodegenerative process may therefore lead to REM sleep anomalies. REM sleep behaviour disorder is associated with nightmares, dream-enacting behaviours and increased electromyographic activity in REM sleep. Its isolated form is a harbinger of synucleinopathies such as Parkinson's disease or dementia with Lewy bodies, and neuroprotective interventions are advocated. This link might also be present in patients taking antidepressants, with post-traumatic stress disorder, or with a history of repeated traumatic head injury. REM sleep likely contributes to normal memory processes. Its alteration has also been proposed to be part of the neuropathological changes occurring in Alzheimer's disease.

Soccer (football) and brain health

Soccer is one of the most popular sports worldwide, played by over 270 million people and followed by many more. Several brain health benefits are promoted by practising soccer and physical exercise at large, which helps contrast the cognitive decline associated with ageing by enhancing neurogenesis processes. However, sport-related concussions have been increasingly recognised as a pressing public health concern, not only due to their acute impact but also, more importantly, due to mounting evidence indicating an elevated risk for the development of neurological sequelae following recurrent head traumas, especially chronic traumatic encephalopathy (CTE). While soccer players experience less frequent concussions compared with other contact or combat sports, such as American football or boxing, it stands alone in its purposeful use of the head to hit the ball (headings), setting its players apart as the only athletes exposed to intentional, sub-concussive head impacts. Additionally, an association between soccer and amyotrophic lateral sclerosis has been consistently observed, suggesting a potential "soccer-specific" risk factor. In this review, we discuss the neurological sequelae related to soccer playing, the emerging evidence of a detrimental effect related to recurrent headings, and the need for implementation of comprehensive strategies aimed at preventing and managing the burden of head impact in soccer.

Unusual combinations of neurodegenerative pathologies with chronic traumatic encephalopathy (CTE) complicates clinical prediction of CTE

BACKGROUND AND PURPOSE

Chronic traumatic encephalopathy (CTE) has gained widespread attention due to its association with multiple concussions and contact sports. However, CTE remains a postmortem diagnosis, and the link between clinical symptoms and CTE pathology is poorly understood. This study aimed to investigate the presence of copathologies and their impact on symptoms in former contact sports athletes.

METHODS

This was a retrospective case series design of 12 consecutive cases of former contact sports athletes referred for autopsy. Analyses are descriptive and include clinical history as well as the pathological findings of the autopsied brains.

RESULTS

All participants had a history of multiple concussions, and all but one had documented progressive cognitive, psychiatric, and/or motor symptoms. The results showed that 11 of the 12 participants had evidence of CTE in the brain, but also other copathologies, including different combinations of tauopathies, and other rare entities.

CONCLUSIONS

The heterogeneity of symptoms after repetitive head injuries and the diverse pathological combinations accompanying CTE complicate the prediction of CTE in clinical practice. It is prudent to consider the possibility of multiple copathologies when clinically assessing patients with repetitive head injuries, especially as they age, and attributing neurological or cognitive symptoms solely to presumptive CTE in elderly patients should be discouraged.

Pathology of neurodegenerative disease for the general neurologist

Neurodegeneration refers to progressive dysfunction or loss of selectively vulnerable neurones from brain and spinal cord regions. Despite important advances in fluid and imaging biomarkers, the definitive diagnosis of most neurodegenerative diseases still relies on neuropathological examination. Not only has careful clinicopathological correlation shaped current clinical diagnostic criteria and informed our understanding of the natural history of neurodegenerative diseases, but it has also identified conditions with important public health implications, including variant Creutzfeldt-Jakob disease, iatrogenic amyloid-β and chronic traumatic encephalopathy. Neuropathological examination may also point to previously unsuspected genetic diagnoses with potential implications for living relatives. Moreover, detailed neuropathological assessment is crucial for research studies that rely on curated postmortem tissue to investigate the molecular mechanisms responsible for neurodegeneration and for biomarker discovery and validation. This review aims to elucidate the hallmark pathological features of neurodegenerative diseases commonly seen in general neurology clinics, such as Alzheimer's disease and Parkinson's disease; rare but well-known diseases, including progressive supranuclear palsy, corticobasal degeneration and multiple system atrophy and more recently described entities such as chronic traumatic encephalopathy and age-related tau astrogliopathy.

Associations between repetitive head impact exposure and midlife mental health wellbeing in former amateur athletes

Introduction

Repetitive head impacts (RHI) have been suggested to increase the risk of developing a neurodegenerative disease, and many of these individuals develop a preceding mental health diagnosis. Given the lack of studies among amateur athletes, this study aimed to examine mental health outcomes in middle-aged amateur athletes who have been exposed to RHI through contact sport participation.

Methods

This is a single site, cohort study involving former amateur athletes aged between 30 and 60 with at least 10 years of organized contact or non-contact sport participation. All participants completed demographic and mental health questionnaires. Mental health outcomes included symptoms related to depression, anxiety, post-traumatic stress disorder (PTSD), attention deficit hyperactive disorder (ADHD), and aggression. Self-reported data on mental health diagnoses and associated prescription were elicited and used to estimate odds ratios (OR).

Results

Data from 41 contact athletes and 22 age/sex-matched non-contact athletes were available for analysis. The contact group exhibited a 2.25-fold higher likelihood of being diagnosed with mental health disorders and 1.29-fold higher likelihood of using associated medications compared to the non-contact group. The contact group reported significantly higher PTSD-related symptoms [4.61 (0.03,9.2), p=0.05] compared to the non-contact control group. While not statistically significant, the contact group showed increased depressive [2.37 (0.05, 4.79), p=0.07] and ADHD symptoms [4.53 (0.51, 9.57), p=0.08] compared to controls. In a secondary analysis, a distinct trend emerged within the contact group, revealing pronounced elevations in mental health symptoms among individuals with lower socioeconomic status (<$50,000/year) compared to higher income subgroups, and these symptoms decreased as income levels rose [depression: -3.08 (-4.47, -1.7), p<0.001; anxiety: -1.95 (-3.15, -0.76), p=0.002; ADHD: -4.99 (-8.28, -1.69), p=0.004; PTSD: -4.42 (-7.28, -1.57), p=0.003; aggression: -6.19 (-11.02, -1.36), p=0.01]. This trend was absent in the non-contact control group.

Discussion

Our data suggest that even individuals at the amateur level of contact sports have an increased likelihood of being diagnosed with mental health disorders or experiencing mental health symptoms compared to non-contact athletes. Our findings indicate that socioeconomic status may have an interactive effect on individuals' mental health, particularly among those with a long history of RHI exposure.

Strain concentration drives the anatomical distribution of injury in acute and chronic traumatic brain injury

Brain tissue injury caused by mild traumatic brain injury (mTBI) disproportionately concentrates in the midbrain, cerebellum, mesial temporal lobe, and the interface between cortex and white matter at sulcal depths 1-12. The bio-mechanical principles that explain why physical impacts to different parts of the skull translate to common foci of injury concentrated in specific brain structures are unknown. A general and longstanding idea, which has not to date been directly tested in humans, is that different brain regions are differentially susceptible to strain loading11,13-15. We use Magnetic Resonance Elastography (MRE) in healthy participants to develop whole-brain bio-mechanical vulnerability maps that independently define which regions of the brain exhibit disproportionate strain concentration. We then validate those vulnerability maps in a prospective cohort of mTBI patients, using diffusion MRI data collected at three cross-sectional timepoints after injury: acute, sub-acute, chronic. We show that regions that exhibit high strain, measured with MRE, are also the sites of greatest injury, as measured with diffusion MR in mTBI patients. This was the case in acute, subacute, and chronic subgroups of the mTBI cohort. Follow-on analyses decomposed the biomechanical cause of increased strain by showing it is caused jointly by disproportionately higher levels of energy arriving to 'high-strain' structures, as well as the inability of 'high strain' structures to effectively disperse that energy. These findings establish a causal mechanism that explains the anatomy of injury in mTBI based on in vivo rheological properties of the human brain.

Impact of repeated blast exposure on active-duty United States Special Operations Forces

United States (US) Special Operations Forces (SOF) are frequently exposed to explosive blasts in training and combat, but the effects of repeated blast exposure (RBE) on SOF brain health are incompletely understood. Furthermore, there is no diagnostic test to detect brain injury from RBE. As a result, SOF personnel may experience cognitive, physical, and psychological symptoms for which the cause is never identified, and they may return to training or combat during a period of brain vulnerability. In 30 active-duty US SOF, we assessed the relationship between cumulative blast exposure and cognitive performance, psychological health, physical symptoms, blood proteomics, and neuroimaging measures (Connectome structural and diffusion MRI, 7 Tesla functional MRI, [11C]PBR28 translocator protein [TSPO] positron emission tomography [PET]-MRI, and [18F]MK6240 tau PET-MRI), adjusting for age, combat exposure, and blunt head trauma. Higher blast exposure was associated with increased cortical thickness in the left rostral anterior cingulate cortex (rACC), a finding that remained significant after multiple comparison correction. In uncorrected analyses, higher blast exposure was associated with worse health-related quality of life, decreased functional connectivity in the executive control network, decreased TSPO signal in the right rACC, and increased cortical thickness in the right rACC, right insula, and right medial orbitofrontal cortex-nodes of the executive control, salience, and default mode networks. These observations suggest that the rACC may be susceptible to blast overpressure and that a multimodal, network-based diagnostic approach has the potential to detect brain injury associated with RBE in active-duty SOF.

Cortical circuit principles predict patterns of trauma induced tauopathy in humans

Connections in the cortex of diverse mammalian species are predicted reliably by the Structural Model for direction of pathways and signal processing (reviewed in 1,2). The model is rooted in the universal principle of cortical systematic variation in laminar structure and has been supported widely for connection patterns in animals but has not yet been tested for humans. Here, in postmortem brains of individuals neuropathologically diagnosed with chronic traumatic encephalopathy (CTE) we studied whether the hyperphosphorylated tau (p-tau) pathology parallels connection sequence in time by circuit mechanisms. CTE is a progressive p-tau pathology that begins focally in perivascular sites in sulcal depths of the neocortex (stages I-II) and later involves the medial temporal lobe (MTL) in stages III-IV. We provide novel quantitative evidence that the p-tau pathology in MTL A28 and nearby sites in CTE stage III closely follows the graded laminar patterns seen in homologous cortico-cortical connections in non-human primates. The Structural Model successfully predicted the laminar distribution of the p-tau neurofibrillary tangles and neurites and their density, based on the relative laminar (dis)similarity between the cortical origin (seed) and each connection site. The findings were validated for generalizability by a computational progression model. By contrast, the early focal perivascular pathology in the sulcal depths followed local columnar connectivity rules. These findings support the general applicability of a theoretical model to unravel the direction and progression of p-tau pathology in human neurodegeneration via a cortico-cortical mechanism. Cortical pathways converging on medial MTL help explain the progressive spread of p-tau pathology from focal cortical sites in early CTE to widespread lateral MTL areas and beyond in later disease stages.

Impact of prior axonal injury on subsequent injury during brain tissue stretching - A mesoscale computational approach

Epidemiology studies of traumatic brain injury (TBI) show individuals with a prior history of TBI experience an increased risk of future TBI with a significantly more detrimental outcome. But the mechanisms through which prior head injuries may affect risks of injury during future head insults have not been identified. In this work, we show that prior brain tissue injury in the form of mechanically induced axonal injury and glial scar formation can facilitate future mechanically induced tissue injury. To achieve this, we use finite element computational models of brain tissue and a history-dependent pathophysiology-based mechanically-induced axonal injury threshold to determine the evolution of axonal injury and scar tissue formation and their effects on future brain tissue stretching. We find that due to the reduced stiffness of injured tissue and glial scars, the existence of prior injury can increase the risk of future injury in the vicinity of prior injury during future brain tissue stretching. The softer brain scar tissue is shown to increase the strain and strain rate in its vicinity by as much as 40% in its vicinity during dynamic stretching that reduces the global strain required to induce injury by 20% when deformed at 15 s-1 strain rate. The results of this work highlight the need to account for patient history when determining the risk of brain injury.

Effect of Repetitive Head Impacts on Saccade Performance in Canadian University Football Players

OBJECTIVE

Investigate the effect of cumulative head impacts on saccade latency and errors, measured across two successive football seasons.

DESIGN

Participants were acquired from a sample of convenience-one Canadian university football team. Head impacts were collected during training camp, practices, eight regular season games, and four playoff games in each season. Saccade measurements were collected at five time points-before and after training camp, at midseason, after regular season, and after playoffs.

SETTING

Two seasons following players from a single USports football team during practices and games.

PARTICIPANTS

Players who completed a baseline saccade measurement and a minimum of one follow-up measurement were included in the study. A total of 127 players were monitored across two competitive seasons, including 61 players who participated in both seasons.

INDEPENDENT VARIABLES

Head impact measurements were collected using helmet-mounted sensors.

MAIN OUTCOME MEASURES

Saccade latency and number of errors were measured using high-speed video or electro-oculography.

RESULTS

On average, each head impact increased prosaccade latency by 5.16 × 10 -3 ms (95% confidence interval [CI], 2.26 × 10 -4 -1.00 × 10 -2 , P = 0.03) and antisaccade latency by 5.74 × 10 -3 ms (95% CI, 7.18 × 10 -4 -1.06 × 10 -2 , P = 0.02). These latency increases did not decrease between the two seasons; in fact, prosaccade latencies were 23.20 ms longer (95% CI, 19.40-27.14, P < 0.001) at the second season's baseline measurement than the first. The number of saccade errors was not affected by cumulative head impacts.

CONCLUSIONS

Repetitive head impacts in Canadian university football result in cumulative declines in brain function as measured by saccade performance.

CLINICAL RELEVANCE

Football organizations should consider implementing policies focused on reducing head impacts to improve player safety.

Prospective cohort study of long-term neurological outcomes in retired elite athletes: the Advanced BiomaRker, Advanced Imaging and Neurocognitive (BRAIN) Health Study protocol

INTRODUCTION

Although limited, recent research suggests that contact sport participation might have an adverse long-term effect on brain health. Further work is required to determine whether this includes an increased risk of neurodegenerative disease and/or subsequent changes in cognition and behaviour. The Advanced BiomaRker, Advanced Imaging and Neurocognitive Health Study will prospectively examine the neurological, psychiatric, psychological and general health of retired elite-level rugby union and association football/soccer players.

METHODS AND ANALYSIS

400 retired athletes will be recruited (200 rugby union and 200 association football players, male and female). Athletes will undergo a detailed clinical assessment, advanced neuroimaging, blood testing for a range of brain health outcomes and neuropsychological assessment longitudinally. Follow-up assessments will be completed at 2 and 4 years after baseline visit. 60 healthy volunteers will be recruited and undergo an aligned assessment protocol including advanced neuroimaging, blood testing and neuropsychological assessment. We will describe the previous exposure to head injuries across the cohort and investigate relationships between biomarkers of brain injury and clinical outcomes including cognitive performance, clinical diagnoses and psychiatric symptom burden.

ETHICS AND DISSEMINATION

Relevant ethical approvals have been granted by the Camberwell St Giles Research Ethics Committee (Ref: 17/LO/2066). The study findings will be disseminated through manuscripts in clinical/academic journals, presentations at professional conferences and through participant and stakeholder communications.

Chronic Traumatic Encephalopathy as the Course of Alzheimer's Disease

This editorial investigates chronic traumatic encephalopathy (CTE) as a course of Alzheimer's disease (AD). CTE is a debilitating neurodegenerative disease that is the result of repeated mild traumatic brain injury (TBI). Many epidemiological studies show that experiencing a TBI in early or middle life is associated with an increased risk of dementia later in life. Chronic traumatic encephalopathy (CTE) and Alzheimer's disease (AD) present a series of similar neuropathological features that were investigated in this work like recombinant tau into filaments or the accumulation and aggregation of Aβ protein. However, these two conditions differ from each other in brain-blood barrier damage. The purpose of this review was to evaluate information about CTE and AD from various articles, focusing especially on new therapeutic possibilities for the improvement in cognitive skills.

Lack of Association of Informant-Reported Traumatic Brain Injury and Chronic Traumatic Encephalopathy

Repetitive head impacts (RHIs) from football are associated with the neurodegenerative tauopathy chronic traumatic encephalopathy (CTE). It is unclear whether a history of traumatic brain injury (TBI) is sufficient to precipitate CTE neuropathology. We examined the association between TBI and CTE neuropathology in 580 deceased individuals exposed to RHIs from football. TBI history was assessed using a modified version of the Ohio State University TBI Identification Method Short Form administered to informants. There were 22 donors who had no TBI, 213 who had at least one TBI without loss of consciousness (LOC), 345 who had TBI with LOC, and, of those with a history of TBI with LOC, 36 who had at least one moderate-to-severe TBI (msTBI, LOC >30 min). CTE neuropathology was diagnosed in 405. There was no association between CTE neuropathology status or severity and TBI with LOC (odds ratio [OR] = 0.95, 95% confidence interval [CI] = 0.64-1.41; OR = 1.22, 95% CI = 0.71-2.09) or msTBI (OR = 0.70, 95% CI = 0.33-1.50; OR = 1.01, 95% CI = 0.30-3.41). There were no associations with other neurodegenerative or cerebrovascular pathologies examined. TBI with LOC and msTBI were not associated with CTE neuropathology in this sample of brain donors exposed to RHIs from American football.

Linking Type and Extent of Head Trauma to Cavum Septum Pellucidum in Older Adults With and Without Alzheimer Disease and Related Dementias

BACKGROUND AND OBJECTIVES

Cavum septum pellucidum (CSP) is a common but nonspecific MRI finding in individuals with prior head trauma. The type and extent of head trauma related to CSP, CSP features specific to head trauma, and the impact of brain atrophy on CSP are unknown. We evaluated CSP cross-sectionally and longitudinally in healthy and clinically impaired older adults who underwent detailed lifetime head trauma characterization.

METHODS

This is an observational cohort study of University of California, San Francisco Memory and Aging Center participants (healthy controls [HCs], those with Alzheimer disease or related dementias [ADRDs], subset with traumatic encephalopathy syndrome [TES]). We characterized traumatic brain injury (TBI) and repetitive head impacts (RHI) through contact/collision sports. Study groups were no RHI/TBI, prior TBI only, prior RHI only, and prior RHI + TBI. We additionally looked within TBI (1, 2, or 3+) and RHI (1-4, 5-10, and 11+ years). All underwent baseline MRI, and 67% completed a second MRI (median follow-up = 5.4 years). CSP measures included grade (0-4) and length (millimeters). Groups were compared on likelihood of CSP (logistic regression, odds ratios [ORs]) and whether CSP length discriminated groups (area under the curve [AUC]).

RESULTS

Our sample included 266 participants (N = 160 HCs, N = 106 with ADRD or TES; age 66.8 ± 8.2 years, 45.3% female). Overall, 123 (49.8%) participants had no RHI/TBI, 52 (21.1%) had TBI only, 41 (16.6%) had RHI only, 31 (12.6%) had RHI + TBI, and 20 were classified as those with TES (7.5%). Compared with no RHI/TBI, RHI + TBI (OR 3.11 [1.23-7.88]) and TES (OR 11.6 [2.46-54.8]) had greater odds of CSP. Approximately 5-10 years (OR 2.96 [1.13-7.77]) and 11+ years of RHI (OR 3.14 [1.06-9.31]) had higher odds of CSP. CSP length modestly discriminated participants with 5-10 years (AUC 0.63 [0.51-0.75]) and 11+ years of prior RHI (AUC 0.69 [0.55-0.84]) from no RHI/TBI (cut point = 6 mm). Strongest effects were noted in analyses of American football participation. Longitudinally, CSP grade was unchanged in 165 (91.7%), and length was unchanged in 171 (95.5%) participants.

DISCUSSION

Among older adults with and without neurodegenerative disease, risk of CSP is driven more by duration (years) of RHI, especially American football, than number of TBI. CSP length (≥6 mm) is relatively specific to individuals who have had substantial prior RHI. Neurodegenerative disease and progressive atrophy do not clearly influence development or worsening of CSP.

KCNJ2 inhibition mitigates mechanical injury in a human brain organoid model of traumatic brain injury

Traumatic brain injury (TBI) strongly correlates with neurodegenerative disease. However, it remains unclear which neurodegenerative mechanisms are intrinsic to the brain and which strategies most potently mitigate these processes. We developed a high-intensity ultrasound platform to inflict mechanical injury to induced pluripotent stem cell (iPSC)-derived cortical organoids. Mechanically injured organoids elicit classic hallmarks of TBI, including neuronal death, tau phosphorylation, and TDP-43 nuclear egress. We found that deep-layer neurons were particularly vulnerable to injury and that TDP-43 proteinopathy promotes cell death. Injured organoids derived from C9ORF72 amyotrophic lateral sclerosis/frontotemporal dementia (ALS/FTD) patients displayed exacerbated TDP-43 dysfunction. Using genome-wide CRISPR interference screening, we identified a mechanosensory channel, KCNJ2, whose inhibition potently mitigated neurodegenerative processes in vitro and in vivo, including in C9ORF72 ALS/FTD organoids. Thus, targeting KCNJ2 may reduce acute neuronal death after brain injury, and we present a scalable, genetically flexible cerebral organoid model that may enable the identification of additional modifiers of mechanical stress.

Applying the Consensus Criteria for Traumatic Encephalopathy Syndrome Retrospectively to Case Studies of Boxers from the 20th Century

There are no validated diagnostic criteria for traumatic encephalopathy syndrome (TES). During the early and middle 20th century, TES was described as a clinical condition that was experienced by some high-exposure boxers-and it was believed to reflect chronic traumatic brain injury. Consensus criteria for the diagnosis of TES were published in 2021. We applied the consensus criteria for TES retrospectively to cases of chronic brain damage in boxers described in articles published in the 20th century that were obtained from narrative and systematic reviews. The sample included 157 boxers identified in 21 articles published between 1929 and 1999. Two authors reviewed each case description and coded the criteria for TES. For the core clinical features, cognitive impairment was noted in 63.1%, and in 28.7% of cases the person's cognitive functioning appeared to be broadly normal. Neurobehavioral dysregulation was present in 25.5%. One third (34.4%) were identified as progressive, 30.6% were not progressive, and the course could not be clearly determined in 35.0%. In total, 29.9% met the TES consensus criteria, 28.0% did not, and 42.0% had insufficient information to make a diagnostic determination. TES, in the 20th century, was described as a neurological condition, not a psychiatric disorder-and this supports the decision of the 2021 consensus group to remove primary and secondary psychiatric diagnoses from being a core diagnostic feature. Future research is needed to determine whether, or the extent to which, cognitive impairment or neurobehavioral dysregulation described as characterizing TES are associated with chronic traumatic encephalopathy neuropathological change.

The role of the Pin1-cis P-tau axis in the development and treatment of vascular contribution to cognitive impairment and dementia and preeclampsia

Tauopathies are neurodegenerative diseases characterized by deposits of abnormal Tau protein in the brain. Conventional tauopathies are often defined by a limited number of Tau epitopes, notably neurofibrillary tangles, but emerging evidence suggests structural heterogeneity among tauopathies. The prolyl isomerase Pin1 isomerizes cis P-tau to inhibit the development of oligomers, tangles and neurodegeneration in multiple neurodegenerative diseases such as Alzheimer's disease, traumatic brain injury, vascular contribution to cognitive impairment and dementia (VCID) and preeclampsia (PE). Thus, cis P-tau has emerged as an early etiological driver, blood marker and therapeutic target for multiple neurodegenerative diseases, with clinical trials ongoing. The discovery of cis P-tau and other tau pathologies in VCID and PE calls attention for simplistic classification of tauopathy in neurodegenerative diseases. These recent advances have revealed the exciting novel role of the Pin1-cis P-tau axis in the development and treatment of vascular contribution to cognitive impairment and dementia and preeclampsia.

Correlation between gyral size, brain size, and head impact risk across mammalian species

A study on primates has established that gyral size is largely independent of overall brain size. Building on this-and other research suggesting that brain gyrification may mitigate the effects of head impacts-our study aims to explore potential correlations between gyral size and the risk of head impact across a diverse range of mammalian species. Our findings corroborate the idea that gyral sizes are largely independent of brain sizes, especially among species with larger brains, thus extending this observation beyond primates. Preliminary evidence also suggests a correlation between an animal's gyral size and its lifestyle, particularly in terms of head-impact risk. For instance, goats, known for their headbutting behaviors, exhibit smaller gyral sizes. In contrast, species such as manatees and dugongs, which typically face lower risks of head impact, have lissencephalic brains. Additionally, we explore mechanisms that may explain how narrower gyral sizes could offer protective advantages against head impact. Finally, we discuss a possible trade-off associated with gyrencephaly.

A meta-analysis of differentially expressed circulatory micro-RNAs in chronic traumatic encephalopathy and other tauopathies: A significant role of miR-181c-5p

BACKGROUND

Micro-RNA (miRs) targeting kinases and phosphatases regulate the hyper-phosphorylation of tau protein, which is a characteristic feature of Chronic Traumatic Encephalopathy (CTE).

PRIMARY OBJECTIVE

Identification of lead dysregulated miR expressed in CTE, and other similar tauopathies.

METHODS

A search strategy was devised using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines to mine into multiple indexing databases such as Web of Science, Google Scholar, and PubMed spanning from 2005 to June 2022. Seven articles were screened out of 34,221 publications based on inclusion criteria and were categorized into two groups i.e., (1) CTE and its risk factors and (2) Age-related neurodegenerative disorders.

RESULTS

Statistical analysis [RevMan 5.4.1] results showed that the overall risk ratio (RR) of the first group is significant (RR = 0.62, 95% CI = [0.38, 1.00], z = 1.95, p = 0.05) whereas, the second group favours the control population (RR = 1.64, 95% CI = [0.85, 3.16], z = 1.14, p = 0.14).

CONCLUSION

We observed that among all other dysregulated miRs, miR-181c-5p is significantly overexpressed in Alzhimers disease (AD) and CTE. Further, we found that miR-210-3p is also upregulated notably in all groups. In sum, we conclude that these miRs can be considered as potential target and biomarker in the diagnosis and treatment of various tauopathies.

Examining the New Consensus Criteria for Traumatic Encephalopathy Syndrome in Community-Dwelling Older Adults

In 2021, an expert panel of clinician-scientists published the first consensus research diagnostic criteria for traumatic encephalopathy syndrome (TES), a clinical condition thought to be associated with chronic traumatic encephalopathy neuropathological change. This study evaluated the TES criteria in older adults and assessed associations between TES criteria and a history of repetitive head impacts. This cross-sectional, survey-based study examined the symptoms of TES, previous repetitive head impacts, and a variety of current health difficulties. To meet symptom criteria for TES, participants had to report progressive changes with memory, executive functioning, and/or neurobehavioral dysregulation. To meet the criterion for substantial exposure to repetitive head impacts via contact sports, participants reported at least 5 years of contact sport exposure (with 2+ years in high school or beyond). A sample of 507 older adults (mean age = 70.0 years, 65% women) completed the survey and 26.2% endorsed having one or more of the progressive core clinical features of TES. Those who had a significant history of contact sport exposure were not significantly more likely to meet TES criteria compared with those who did not (31.3% vs. 25.3%, p = 0.46). In a binary logistic regression predicting TES status, current depression or anxiety (odds ratio [OR] = 12.55; 95% confidence interval [CI] = 4.43-35.51), history of psychiatric disorders (OR = 2.07, 95% CI = 1.22-3.49), male sex (OR = 1.87), and sleep problems (OR = 1.71, 95% CI = 1.01-2.91) were associated with meeting TES criteria. The sport exposure criterion, age, and current pain were not significantly associated with TES status (ps > 0.05). A significant minority of participants with no history of neurotrauma endorsed symptoms consistent with TES (22.0% of men and 19.8% of women). Nearly 80% of neurotrauma naïve participants with clinically significant anxiety/depression met criteria for TES. In summary, approximately one in four older adults met the symptom criteria for TES, many of whom had no history of repetitive neurotrauma. Mental health problems and sleep issues were associated with TES, whereas having a history of repetitive head impacts in contact sports was not. These data suggest that the new consensus diagnostic criteria for TES may have low specificity and may carry a higher risk of misdiagnosing those with other physical and mental health conditions as having TES.

Treatment with the vascular endothelial growth factor-A antibody, bevacizumab, has sex-specific effects in a rat model of mild traumatic brain injury

Mild traumatic brain injury (mTBI) involves damage to the cerebrovascular system. Vascular endothelial growth factor-A (VEGF-A) is an important modulator of vascular health and VEGF-A promotes the brain's ability to recover after more severe forms of brain injury; however, the role of VEGF-A in mTBI remains poorly understood. Bevacizumab (BEV) is a monoclonal antibody that binds to VEGF-A and neutralises its actions. To better understand the role of VEGF-A in mTBI recovery, this study examined how BEV treatment affected outcomes in rats given a mTBI. Adult Sprague-Dawley rats were assigned to sham-injury + vehicle treatment (VEH), sham-injury + BEV treatment, mTBI + VEH treatment, mTBI + BEV treatment groups. Treatment was administered intracerebroventricularly via a cannula beginning at the time of injury and continuing until the end of the study. Rats underwent behavioral testing after injury and were euthanized on day 11. In both females and males, BEV had a negative impact on cognitive function. mTBI and BEV treatment increased the expression of inflammatory markers in females. In males, BEV treatment altered markers related to hypoxia and vascular health. These novel findings of sex-specific responses to BEV and mTBI provide important insights into the role of VEGF-A in mTBI.

Chronic traumatic encephalopathy neuropathologic change in former Australian rugby players

AIMS

We applied the 2021 consensus criteria for both chronic traumatic encephalopathy neuropathological change and traumatic encephalopathy syndrome in a small case series of six former elite-level Australian rugby code players.

METHODS

Neuropathological assessment of these cases was carried out at the Sydney and Victorian Brain Banks. Clinical data were collected via clinical interviews and health questionnaires completed by the participants and/or their next of kin, and neuropsychological testing was conducted with participants who were capable of completing this testing.

RESULTS

All cases exhibited progressive cognitive impairment during life. Chronic traumatic encephalopathy neuropathological change was identified in four out of the six cases. However, coexisting neuropathologies were common, with limbic-predominant age-related TDP-43 encephalopathy and ageing-related tau astrogliopathy seen in all cases, intermediate or high Alzheimer's disease neuropathological change seen in four cases and hippocampal sclerosis seen in two of the six cases.

CONCLUSION

The presence of multiple neuropathologies in these cases complicates clinical diagnostic efforts for traumatic encephalopathy syndrome. It will be important for further clinicopathological studies on larger groups to report all neuropathological comorbidities found in cases diagnosed with either chronic traumatic encephalopathy neuropathological change and/or traumatic encephalopathy syndrome.

Overlaps and divergences between tauopathies and synucleinopathies: a duet of neurodegeneration

Proteinopathy, defined as the abnormal accumulation of proteins that eventually leads to cell death, is one of the most significant pathological features of neurodegenerative diseases. Tauopathies, represented by Alzheimer's disease (AD), and synucleinopathies, represented by Parkinson's disease (PD), show similarities in multiple aspects. AD manifests extrapyramidal symptoms while dementia is also a major sign of advanced PD. We and other researchers have sequentially shown the cross-seeding phenomenon of α-synuclein (α-syn) and tau, reinforcing pathologies between synucleinopathies and tauopathies. The highly overlapping clinical and pathological features imply shared pathogenic mechanisms between the two groups of disease. The diagnostic and therapeutic strategies seemingly appropriate for one distinct neurodegenerative disease may also apply to a broader spectrum. Therefore, a clear understanding of the overlaps and divergences between tauopathy and synucleinopathy is critical for unraveling the nature of the complicated associations among neurodegenerative diseases. In this review, we discuss the shared and diverse characteristics of tauopathies and synucleinopathies from aspects of genetic causes, clinical manifestations, pathological progression and potential common therapeutic approaches targeting the pathology, in the aim to provide a timely update for setting the scheme of disease classification and provide novel insights into the therapeutic development for neurodegenerative diseases.

Association between mammillary body atrophy and memory impairment in retired athletes with a history of repetitive mild traumatic brain injury

Cognitive dysfunction, especially memory impairment, is a typical clinical feature of long-term symptoms caused by repetitive mild traumatic brain injury (rmTBI). The current study aims to investigate the relationship between regional brain atrophy and cognitive impairments in retired athletes with a long history of rmTBI. Overall, 27 retired athletes with a history of rmTBI (18 boxers, 3 kickboxers, 2 wrestlers, and 4 others; rmTBI group) and 23 age/sex-matched healthy participants (control group) were enrolled. MPRAGE on 3 T MRI was acquired and segmented. The TBV and TBV-adjusted regional brain volumes were compared between groups, and the relationship between the neuropsychological test scores and the regional brain volumes were evaluated. Total brain volume (TBV) and regional brain volumes of the mammillary bodies (MBs), hippocampi, amygdalae, thalami, caudate nuclei, and corpus callosum (CC) were estimated using the SPM12 and ITK-SNAP tools. In the rmTBI group, the regional brain volume/TBV ratio (rmTBI vs. control group, Mann-Whitney U test, p < 0.05) underwent partial correlation analysis, adjusting for age and sex, to assess its connection with neuropsychological test results. Compared with the control group, the rmTBI group showed significantly lower the MBs volume/TBV ratio (0.13 ± 0.05 vs. 0.19 ± 0.03 × 10-3, p < 0.001). The MBs volume/TBV ratio correlated with visual memory, as assessed, respectively, by the Rey-Osterrieth Complex Figure test delayed recall (ρ = 0.62, p < 0.001). In conclusion, retired athletes with rmTBI have MB atrophy, potentially contributing to memory impairment linked to the Papez circuit disconnection.

Traumatic injury causes selective degeneration and TDP-43 mislocalization in human iPSC-derived C9orf72-associated ALS/FTD motor neurons

A hexanucleotide repeat expansion (HRE) in C9orf72 is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). However, patients with the HRE exhibit a wide disparity in clinical presentation and age of symptom onset suggesting an interplay between genetic background and environmental stressors. Neurotrauma as a result of traumatic brain or spinal cord injury has been shown to increase the risk of ALS/FTD in epidemiological studies. Here, we combine patient-specific induced pluripotent stem cells (iPSCs) with a custom-built device to deliver biofidelic stretch trauma to C9orf72 patient and isogenic control motor neurons (MNs) in vitro. We find that mutant but not control MNs exhibit selective degeneration after a single incident of severe trauma, which can be partially rescued by pretreatment with a C9orf72 antisense oligonucleotide. A single incident of mild trauma does not cause degeneration but leads to cytoplasmic accumulation of TDP-43 in C9orf72 MNs. This mislocalization, which only occurs briefly in isogenic controls, is eventually restored in C9orf72 MNs after 6 days. Lastly, repeated mild trauma ablates the ability of patient MNs to recover. These findings highlight alterations in TDP-43 dynamics in C9orf72 ALS/FTD patient MNs following traumatic injury and demonstrate that neurotrauma compounds neuropathology in C9orf72 ALS/FTD. More broadly, our work establishes an in vitro platform that can be used to interrogate the mechanistic interactions between ALS/FTD and neurotrauma.

Recent insights from non-mammalian models of brain injuries: an emerging literature

Traumatic brain injury (TBI) is a major global health concern and is increasingly recognized as a risk factor for neurodegenerative diseases including Alzheimer's disease (AD) and chronic traumatic encephalopathy (CTE). Repetitive TBIs (rTBIs), commonly observed in contact sports, military service, and intimate partner violence (IPV), pose a significant risk for long-term sequelae. To study the long-term consequences of TBI and rTBI, researchers have typically used mammalian models to recapitulate brain injury and neurodegenerative phenotypes. However, there are several limitations to these models, including: (1) lengthy observation periods, (2) high cost, (3) difficult genetic manipulations, and (4) ethical concerns regarding prolonged and repeated injury of a large number of mammals. Aquatic vertebrate model organisms, including Petromyzon marinus (sea lampreys), zebrafish (Danio rerio), and invertebrates, Caenorhabditis elegans (C. elegans), and Drosophila melanogaster (Drosophila), are emerging as valuable tools for investigating the mechanisms of rTBI and tauopathy. These non-mammalian models offer unique advantages, including genetic tractability, simpler nervous systems, cost-effectiveness, and quick discovery-based approaches and high-throughput screens for therapeutics, which facilitate the study of rTBI-induced neurodegeneration and tau-related pathology. Here, we explore the use of non-vertebrate and aquatic vertebrate models to study TBI and neurodegeneration. Drosophila, in particular, provides an opportunity to explore the longitudinal effects of mild rTBI and its impact on endogenous tau, thereby offering valuable insights into the complex interplay between rTBI, tauopathy, and neurodegeneration. These models provide a platform for mechanistic studies and therapeutic interventions, ultimately advancing our understanding of the long-term consequences associated with rTBI and potential avenues for intervention.

Flortaucipir tau PET findings from former professional and college American football players in the DIAGNOSE CTE research project

INTRODUCTION

Tau is a key pathology in chronic traumatic encephalopathy (CTE). Here, we report our findings in tau positron emission tomography (PET) measurements from the DIAGNOSE CTE Research Project.

METHOD

We compare flortaucipir PET measures from 104 former professional players (PRO), 58 former college football players (COL), and 56 same-age men without exposure to repetitive head impacts (RHI) or traumatic brain injury (unexposed [UE]); characterize their associations with RHI exposure; and compare players who did or did not meet diagnostic criteria for traumatic encephalopathy syndrome (TES).

RESULTS

Significantly elevated flortaucipir uptake was observed in former football players (PRO+COL) in prespecified regions (p < 0.05). Association between regional flortaucipir uptake and estimated cumulative head impact exposure was only observed in the superior frontal region in former players over 60 years old. Flortaucipir PET was not able to differentiate TES groups.

DISCUSSION

Additional studies are needed to further understand tau pathology in CTE and other individuals with a history of RHI.

Biomarkers associated with cognitive impairment in post-traumatic stress disorder: A systematic review of current evidence

OBJECTIVE

This systematic review aimed at synthesizing current evidence on biomarkers associated with cognitive impairment (CI) in Post-Traumatic Stress Disorder (PTSD).

METHODS

A systematic literature search was conducted for studies assessing biomarkers associated with CI in PTSD.

RESULTS

Of the 10,149 titles screened, 8 studies met our inclusion criteria. In a single longitudinal study, MRI volumes, Aβ and tau accumulation were not associated with CI in PTSD. Studies on structural imaging reported no significant association between morphological changes and CI. Two studies on diffusion neuroimaging showed abnormalities in white matter tracts which were cross-sectionally associated with CI in PTSD. Similarly, lower resting-state functional connectivity in neocortical networks, and elevated tau in the neocortex were also cross sectionally associated with CI. Two single studies on biochemical biomarkers showed that sixteen novel plasma proteins and lower BDNF, indicative of genetic vulnerabilities associated with neural and synaptic dysfunctions commonly observed in neurodegeneration, were cross-sectionally associated with CI in PTSD. Overall, evidence is of low quality.

CONCLUSIONS

Longitudinal research utilizing large representative samples of trauma exposed populations are needed to establish the utility of specific biomarkers in monitoring cognitive decline in PTSD.

Examination of parkinsonism in former elite American football players

BACKGROUND

Former American football players are at risk for chronic traumatic encephalopathy (CTE) which may have parkinsonism as a clinical feature.

OBJECTIVE

Former football players were prospectively assessed for parkinsonism.

METHODS

120 former professional football players, 58 former college football players, and 60 same-age asymptomatic men without repetitive head impacts, 45-74 years, were studied using the MDS-UPDRS to assess for parkinsonism, and the Timed Up and Go (TUG). Traumatic encephalopathy syndrome (TES), the clinical syndrome of CTE, was adjudicated and includes parkinsonism diagnosis. Fisher's Exact Test compared groups on parkinsonism due to small cell sizes; analysis of covariance or linear regressions controlling for age and body mass index were used otherwise.

RESULTS

Twenty-two (12.4%) football players (13.3% professional, 10.3% college) met parkinsonism criteria compared with two (3.3%) in the unexposed group. Parkinsonism was higher in professional (p = 0.037) but not college players (p = 0.16). There were no differences on the MDS-UPDRS Part III total scores. Scores on the individual MDS-UPDRS items were low. TUG times were longer in former professional but not college players compared with unexposed men (13.09 versus 11.35 s, p < 0.01). There were no associations between years of football, age of first exposure, position or level of play on motor outcomes. TES status was not associated with motor outcomes.

CONCLUSIONS

Parkinsonism rates in this sample of football players was low and highest in the professional football players. The association between football and parkinsonism is inconclusive and depends on factors related to sample selection, comparison groups, and exposure characteristics.

Associations of Prior Head Injury With Mild Behavioral Impairment Domains

OBJECTIVE

This study investigated associations of prior head injury and number of prior head injuries with mild behavioral impairment (MBI) domains.

SETTING

The Atherosclerosis Risk in Communities (ARIC) Study.

PARTICIPANTS

A total of 2534 community-dwelling older adults who took part in the ARIC Neurocognitive Study stage 2 examination were included.

DESIGN

This was a prospective cohort study. Head injury was defined using self-reported and International Classification of Diseases, Ninth Revision ( ICD -9) code data. MBI domains were defined using the Neuropsychiatric Inventory Questionnaire (NPI-Q) via an established algorithm mapping noncognitive neuropsychiatric symptoms to the 6 domains of decreased motivation, affective dysregulation, impulse dyscontrol, social inappropriateness, and abnormal perception/thought content.

MAIN MEASURES

The primary outcome was the presence of impairment in MBI domains.

RESULTS

Participants were a mean age of 76 years, with a median time from first head injury to NPI-Q administration of 32 years. The age-adjusted prevalence of symptoms in any 1+ MBI domains was significantly higher among individuals with versus without prior head injury (31.3% vs 26.0%, P = .027). In adjusted models, a history of 2+ head injuries, but not 1 prior head injury, was associated with increased odds of impairment in affective dysregulation and impulse dyscontrol domains, compared with no history of head injury (odds ratio [OR] = 1.83, 95% CI = 1.13-2.98, and OR = 1.74, 95% CI = 1.08-2.78, respectively). Prior head injury was not associated with symptoms in MBI domains of decreased motivation, social inappropriateness, and abnormal perception/thought content (all P > .05).

CONCLUSION

Prior head injury in older adults was associated with greater MBI domain symptoms, specifically affective dysregulation and impulse dyscontrol. Our results suggest that the construct of MBI can be used to systematically examine the noncognitive neuropsychiatric sequelae of head injury; further studies are needed to examine whether the systematic identification and rapid treatment of neuropsychiatric symptoms after head injury is associated with improved outcomes.

Acute Fluid Biomarkers for Diagnosis and Prognosis in Children with Mild Traumatic Brain Injury: A Systematic Review

BACKGROUND AND OBJECTIVE

Fluid biomarkers have the potential to improve the accuracy of diagnosis and prognosis in children with mild traumatic brain injury. Our primary objective was to assess the diagnostic and prognostic utility of acute blood and fluid biomarkers in children with mild traumatic brain injury.

METHODS

We performed a systematic review of the published literature in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) methodology. Fluid biomarker studies assessing pediatric mild traumatic brain injury diagnosis or prognosis were included if blood or fluids were sampled within 24 h of injury.

RESULTS

Thirty-two studies involving 4743 patients were included comprising 25 diagnostic studies and ten prognostic studies with three studies assessing both diagnosis and prognosis. Sixteen of the 25 diagnostic studies reported the area under the receiver operating characteristic curve (AUC) for predicting abnormal computed tomography scans of the head; S100 calcium binding protein B (S100B, N = 6 studies, AUC range 0.67-1.00), glial fibrillary acidic protein (N = 5, AUC range 0.41-0.85), ubiquitin C-terminal hydrolase (N = 3, AUC 0.59 and 0.83), neuron specific enolase (N = 1, AUC 0.99), total tau (N = 1, AUC 0.65), and interleukin-6 (N = 1, AUC 0.61). In four of the ten prognostic studies, increased acute serum S100B levels, tumor necrosis factor-α, or interleukin-8 were associated with post-concussive symptoms or fatigue from 3 to 12 months post-injury.

CONCLUSIONS

The largest amount of evidence supported the potential use of S100B, glial fibrillary acidic protein, and UCH-L1, but there was mixed accuracy for diagnosis and prognostication for all biomarkers in pediatric mTBI.

Cortical-sparing chronic traumatic encephalopathy (CSCTE): a distinct subtype of CTE

Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease caused by repetitive head impacts (RHI) and pathologically defined as neuronal phosphorylated tau aggregates around small blood vessels and concentrated at sulcal depths. Cross-sectional studies suggest that tau inclusions follow a stereotyped pattern that begins in the neocortex in low stage disease, followed by involvement of the medial temporal lobe and subcortical regions with significant neocortical burden in high stage CTE. Here, we define a subset of brain donors with high stage CTE and with a low overall cortical burden of tau inclusions (mean semiquantitative value ≤1) and classify them as cortical-sparing CTE (CSCTE). Of 620 brain donors with pathologically diagnosed CTE, 66 (11%) met criteria for CSCTE. Compared to typical high stage CTE, those with CSCTE had a similar age at death and years of contact sports participation and were less likely to carry apolipoprotein ε4 (p < 0.05). CSCTE had less overall tau pathology severity, but a proportional increase of disease burden in medial temporal lobe and brainstem regions compared to the neocortex (p's < 0.001). CSCTE also had lower prevalence of comorbid neurodegenerative disease. Clinically, CSCTE participants were less likely to have dementia (p =  0.023) and had less severe cognitive difficulties (as reported by informants using the Functional Activities Questionnaire (FAQ); p < 0.001, meta-cognitional index T score; p = 0.002 and Cognitive Difficulties Scale (CDS); p < 0.001,) but had an earlier onset age of behavioral (p = 0.006) and Parkinsonian motor (p = 0.013) symptoms when compared to typical high stage CTE. Other comorbid tauopathies likely contributed in part to these differences: when cases with concurrent Alzheimer dementia or frontal temporal lobar degeneration with tau pathology were excluded, differences were largely retained, but only remained significant for FAQ (p = 0.042), meta-cognition index T score (p = 0.014) and age of Parkinsonian motor symptom onset (p = 0.046). Overall, CSCTE appears to be a distinct subtype of high stage CTE with relatively greater involvement of subcortical and brainstem regions and less severe cognitive symptoms.

Chronic traumatic encephalopathy and aging-related tau astrogliopathy in community-dwelling older persons with and without moderate-to-severe traumatic brain injury

This study examined the frequency of chronic traumatic encephalopathy-neuropathologic change (CTE-NC) and aging-related tau astrogliopathy (ARTAG) in community-dwelling older adults and tested the hypothesis that these tau pathologies are associated with a history of moderate-to-severe traumatic brain injury (msTBI), defined as a TBI with loss of consciousness >30 minutes. We evaluated CTE-NC, ARTAG, and Alzheimer disease pathologies in 94 participants with msTBI and 94 participants without TBI matched by age, sex, education, and dementia status TBI from the Rush community-based cohorts. Six (3%) of brains showed the pathognomonic lesion of CTE-NC; only 3 of these had a history of msTBI. In contrast, ARTAG was common in older brains (gray matter ARTAG = 77%; white matter ARTAG = 54%; subpial ARTAG = 51%); there were no differences in severity, type, or distribution of ARTAG pathology with respect to history of msTBI. Furthermore, those with msTBI did not have higher levels of PHF-tau tangles density but had higher levels of amyloid-β load (Estimate = 0.339, SE = 0.164, p = 0.040). These findings suggest that CTE-NC is infrequent while ARTAG is common in the community and that both pathologies are unrelated to msTBI. The association of msTBI with amyloid-β, rather than with tauopathies suggests differential mechanisms of neurodegeneration in msTBI.

The Sport Concussion Assessment Tool: A multidimensional symptom model for detecting elevated post-concussion symptoms

Objective: Investigate whether a four-factor model of post-concussion symptoms (i.e. cognitive, physical, affective, and sleep-arousal) aids in identifying student-athletes with persistent concerns not reflected by a total symptom score. Method: Collegiate student-athletes (N = 32,066) from the Concussion Assessment Research and Education consortium completed the Sport Concussion Assessment Tool, 3rd edition Symptom Evaluation at baseline and two post-injury follow-ups (i.e. beginning RTP and 6-month). Confirmatory factor analysis was used to compare a one- and four-factor model of post-concussion symptoms. Normative reference data were compared across stratifications (e.g. sex, prior concussions, and number of pre-existing conditions) using Mann-Whitney U tests, and elevation rates (i.e. ≥ 84th percentile) for subscales and the total score were recorded. Results: The four-factor model fit well before and after injury (CFIs > .95). Greater symptom severity on the subscale and total scores was associated with female sex (ps<.001, r range: .07 to .14) and more pre-existing conditions (ps<.001, η 2 range: .01 to .04), while having more prior concussions was only related to total symptom scores (ps<.001, η 2<.01). After a concussion, a sizeable portion of student-athletes (i.e., RTP = 11.8%; 6-month = 8.3%) had subscale elevations despite no total score elevation. Physical subscale elevations at RTP were the most common (i.e., 11.9%), driven by head and neck pain. Conclusion: After a sport-related concussion, a four-factor symptom model can be used to assess persistent symptoms in collegiate student-athletes. Identifying athletes with domain-specific elevations may help clinicians identify areas for further assessment and, in some cases, personalized rehabilitation plans.

Kumanu Tāngata: the aftermatch study - protocol to examine the health outcomes of high-level male rugby union players using linked administrative data

There is increasing interest in the potential long-term outcomes of participation in contact and collision sports, driven by evidence of higher rates of neurodegenerative diseases among former athletes. Recent research has capitalised on large-scale administrative health data to examine health outcomes in contact sport athletes. However, there is limited research on outcomes associated with participation in rugby union, a contact sport with a relatively high incidence of head trauma and musculoskeletal injuries. Additionally, there is scope to investigate a greater range of health outcomes using large, population-based administrative data. The Kumanu Tāngata project is a retrospective cohort study that will use linked information from the New Zealand Rugby Register and health records within a comprehensive deidentified whole-population administrative research database known as the Integrated Data Infrastructure. First-class male rugby union players (N=13 227) will be compared with a general population comparison group (N=2 438 484; weighting will be applied due to demographic differences) on a range of mortality and morbidity outcomes (neurodegenerative diseases, musculoskeletal conditions, chronic physical conditions, mental health outcomes). A range of player-specific variables will also be investigated as risk factors. Analyses will consist primarily of Cox proportional hazards models. Ethics approval for the study has been granted by the Auckland Health Research Ethics Committee (Ref. AH23203). Primary research dissemination will be via peer-reviewed journal articles.

Assessment of brain response in operators subject to recoil force from firing long-range rifles

Mild traumatic brain injury (mTBI) may be caused by occupational hazards military personnel encounter, such as falls, shocks, exposure to blast overpressure events, and recoil from weapon firing. While it is important to protect against injurious head impacts, the repeated exposure of Canadian Armed Forces (CAF) service members to sub-concussive events during the course of their service may lead to a significant reduction in quality of life. Symptoms may include headaches, difficulty concentrating, and noise sensitivity, impacting how personnel complete their duties and causing chronic health issues. This study investigates how the exposure to the recoil force of long-range rifles results in head motion and brain deformation. Direct measurements of head kinematics of a controlled population of military personnel during firing events were obtained using instrumented mouthguards. The experimentally measured head kinematics were then used as inputs to a finite element (FE) head model to quantify the brain strains observed during each firing event. The efficacy of a concept recoil mitigation system (RMS), designed to mitigate loads applied to the operators was quantified, and the RMS resulted in lower loading to the operators. The outcomes of this study provide valuable insights into the magnitudes of head kinematics observed when firing long-range rifles, and a methodology to quantify effects, which in turn will help craft exposure guidelines, guide training to mitigate the risk of injury, and improve the quality of lives of current and future CAF service members and veterans.

A prospective investigation of the effects of soccer heading on cognitive and sensorimotor performances in semi-professional female players

Introduction

Repetitive head impacts (RHI) from routine soccer (football) heading have been suggested to contribute to the long-term development of neurodegenerative disorders. However, scientific evidence concerning the actual risk of these RHI on brain health remains inconclusive. Moreover, female athletes-despite a presumably increased vulnerability toward the effects of RHI-are largely underrepresented in previous approaches. Therefore, our aim was to prospectively investigate the effects of heading on cognitive and sensorimotor performances, health perception, and concussion symptoms in semi-professional female soccer players.

Methods

An extensive test battery was used to assess cognitive and sensorimotor performances as well as health status (SF-36) and concussion symptoms (SCAT3) of a total of 27 female soccer players (22.2 ± 4.2 years) and 15 control subjects (23.2 ± 3.0 years) before and after one-and-a-half years. Throughout this period, soccer players' heading exposure was determined using video analysis.

Results

Subgroup comparisons (control [n = 12], low exposure [n = 7], high exposure [n = 8]) showed no time-dependent differences in SF-36 or SCAT3 scores. Similarly, across most behavioral tests, soccer players' performances evolved equally or more favorably as compared to the control subjects. However, there were significant effects pointing toward slightly negative consequences of heading on aspects of fine motor control (p = 0.001), which were confirmed by correlation and multiple regression analyses. The latter, further, yielded indications for a relationship between heading exposure and negative alterations in postural control (p = 0.002).

Discussion

Our findings do not provide evidence for negative effects of soccer heading on female players' health perception, concussion symptoms, and cognitive performances over the course of one-and-a-half years. However, we found subtle negative alterations in fine motor and postural control that could be attributed to heading exposure. Other factors, like the number of previous head injuries, were not linked to the observed changes. Given the reduction of our initial sample size due to player fluctuation, the results need to be interpreted with caution and validated in larger-scale studies. These should not only focus on cognitive outcomes but also consider sensorimotor changes as a result of RHI from soccer heading.

Tau Imaging in Late Traumatic Brain Injury: A [18F]MK-6240 Positron Emission Tomography Study

Epidemiological studies have identified prior traumatic brain injury (TBI) as a risk factor for developing Alzheimer's disease (AD). Neurofibrillary tangles (NFTs) are common to AD and chronic traumatic encephalopathy following repetitive mild TBI. However, it is unclear if a single TBI is sufficient to cause accumulation of NFTs. We performed a [18F]MK-6240 positron emission tomography (PET) imaging study to assess NFTs in patients who had sustained a single TBI at least 2 years prior to study inclusion. Fourteen TBI patients (49 ± 20 years; 5 M/9 F; 8 moderate-severe, 1 mild-probable, 5 symptomatic-possible TBI) and 40 demographically similar controls (57 ± 19 years; 19 M/21 F) underwent simultaneous [18F]MK-6240 PET and magnetic resonance imaging (MRI) as well as neuropsychological assessment including the Cambridge Neuropsychological Test Automated Battery (CANTAB). A region-based voxelwise partial volume correction was applied, using parcels obtained by FreeSurfer v6.0, and standardized uptake value ratios (SUVR) were calculated relative to the cerebellar gray matter. Group differences were assessed on both a voxel- and a volume-of-interest-based level and correlations of [18F]MK-6240 SUVR with time since injury as well as with clinical outcomes were calculated. Visual assessment of TBI images did not show global or focal increases in tracer uptake in any subject. On a group level, [18F]MK-6240 SUVR was not significantly different in patients versus controls or between subgroups of moderate-severe TBI versus less severe TBI. Within the TBI group, One Touch Stockings problem solving and spatial working memory (executive function), reaction time (attention), and Mini-Mental State Examination (MMSE) (global cognition) were associated with [18F]MK-6240 SUVR. We found no group-based increase of [18F]MK-6240 brain uptake in patients scanned at least 2 years after a single TBI compared with healthy volunteers, which suggests that no NFTs are building up in the first years after a single TBI. Nonetheless, correlations with cognitive outcomes were found that warrant further investigation.

Diagnostic and therapeutic targeting of pathological tau proteins in neurodegenerative disorders

Tauopathies, characterized by fibrillar tau accumulation in neurons and glial cells, constitute a major neuropathological category of neurodegenerative diseases. Neurofibrillary tau lesions are strongly associated with cognitive deficits in these diseases, but the causal mechanisms underlying tau-induced neuronal dysfunction remain unresolved. Recent advances in cryo-electron microscopy examination have revealed various core structures of tau filaments from different tauopathy patients, which can be used to classify tauopathies. In vivo visualization of tau pathology is now available using several tau positron emission tomography tracers. Among these radioprobes, PM-PBB3 allows high-contrast imaging of tau deposits in the brains of patients with diverse disorders and tauopathy mouse models. Selective degradation of pathological tau species by the ubiquitin-proteasome system or autophagy machinery is a potential therapeutic strategy. Alternatively, the non-cell-autonomous clearance of pathological tau species through neuron-glia networks could be reinforced as a disease-modifying treatment. In addition, the development of neuroinflammatory biomarkers is required for understanding the contribution of immunocompetent cells in the brain to preventing neurodegeneration. This review provides an overview of the current research and development of diagnostic and therapeutic agents targeting divergent tau pathologies.

p17/C18-ceramide-mediated mitophagy is an endogenous neuroprotective response in preclinical and clinical brain injury

Repeat concussions (or repetitive mild traumatic brain injury [rmTBI]) are complex pathological processes consisting of a primary insult and long-term secondary complications and are also a prerequisite for chronic traumatic encephalopathy (CTE). Recent evidence implies a significant role of autophagy-mediated dysfunctional mitochondrial clearance, mitophagy, in the cascade of secondary deleterious events resulting from TBI. C18-ceramide, a bioactive sphingolipid produced in response to cell stress and damage, and its synthesizing enzyme (CerS1) are precursors to selective stress-mediated mitophagy. A transporter, p17, mediates the trafficking of CerS1, induces C18-ceramide synthesis in the mitochondrial membrane, and acts as an elimination signal in cell survival. Whether p17-mediated mitophagy occurs in the brain and plays a causal role in mitochondrial quality control in secondary disease development after rmTBI are unknown. Using a novel repetitive less-than-mild TBI (rlmTBI) injury paradigm, ablation of mitochondrial p17/C18-ceramide trafficking in p17 knockout (KO) mice results in a loss of C18-ceramide-induced mitophagy, which contributes to susceptibility and recovery from long-term secondary complications associated with rlmTBI. Using a ceramide analog with lipid-selenium conjugate drug, LCL768 restored mitophagy and reduced long-term secondary complications, improving cognitive deficits in rlmTBI-induced p17KO mice. We obtained a significant reduction of p17 expression and a considerable decrease of CerS1 and C18-ceramide levels in cortical mitochondria of CTE human brains compared with age-matched control brains. These data demonstrated that p17/C18-ceramide trafficking is an endogenous neuroprotective mitochondrial stress response following rlmTBI, thus suggesting a novel prospective strategy to interrupt the CTE consequences of concussive TBI.

Relative Contributions of Mixed Pathologies to Cognitive and Functional Symptoms in Brain Donors Exposed to Repetitive Head Impacts

OBJECTIVE

Exposure to repetitive head impacts (RHI) is associated with later-life cognitive symptoms and neuropathologies, including chronic traumatic encephalopathy (CTE). Cognitive decline in community cohorts is often due to multiple pathologies; however, the frequency and contributions of these pathologies to cognitive impairment in people exposed to RHI are unknown. Here, we examined the relative contributions of 13 neuropathologies to cognitive symptoms and dementia in RHI-exposed brain donors.

METHODS

Neuropathologists examined brain tissue from 571 RHI-exposed donors and assessed for the presence of 13 neuropathologies, including CTE, Alzheimer disease (AD), Lewy body disease (LBD), and transactive response DNA-binding protein 43 (TDP-43) inclusions. Cognitive status was assessed by presence of dementia, Functional Activities Questionnaire, and Cognitive Difficulties Scale. Spearman rho was calculated to assess intercorrelation of pathologies. Additionally, frequencies of pathological co-occurrence were compared to a simulated distribution assuming no intercorrelation. Logistic and linear regressions tested associations between neuropathologies and dementia status and cognitive scale scores.

RESULTS

The sample age range was 18-97 years (median = 65.0, interquartile range = 46.0-76.0). Of the donors, 77.2% had at least one moderate-severe neurodegenerative or cerebrovascular pathology. Stage III-IV CTE was the most common neurodegenerative disease (43.1%), followed by TDP-43 pathology, AD, and hippocampal sclerosis. Neuropathologies were intercorrelated, and there were fewer unique combinations than expected if pathologies were independent (p < 0.001). The greatest contributors to dementia were AD, neocortical LBD, hippocampal sclerosis, cerebral amyloid angiopathy, and CTE.

INTERPRETATION

In this sample of RHI-exposed brain donors with wide-ranging ages, multiple neuropathologies were common and correlated. Mixed neuropathologies, including CTE, underlie cognitive impairment in contact sport athletes. ANN NEUROL 2024;95:314-324.

Molecular mechanisms involved in the destabilization of two types of R3-R4 tau fibrils associated with chronic traumatic encephalopathy by Fisetin

Chronic traumatic encephalopathy is a neurodegenerative tauopathy pathologically characterized by fibrillary tau aggregates in the depth of sulci. Clearing fibrous tau aggregates is considered a promising strategy in the treatment of CTE. Fisetin (FS), a natural polyphenolic small molecule, was confirmed to disassociate the tau filaments in vitro. However, the molecular mechanisms of FS in destabilizing the CTE-related R3-R4 tau fibrils remain largely unknown. In this study, we compared the atomic-level structural differences of the two types of CTE-related R3-R4 tau fibrils and explored the influence and molecular mechanisms of FS on the two types of fibrils by conducting multiple molecular dynamics (MD) simulations. The results reveal that the type 1 fibril displays higher structural stability than the type 2 fibril, with a lower root-mean-square-fluctuation value and higher β-sheet structure probability. FS can destabilize both types of fibrils by decreasing the β-sheet structure content, interrupting the mainchain H-bond network, and increasing the solvent accessible surface area and β7-β8 angle of the fibrils. H-bonding, π-π stacking and cation-π are the common interactions driving FS molecules binding on the two types of fibrils, while the hydrophobic interaction occurs only in the type 2 fibril. Due to the relatively short simulation time, our study captures the early molecular mechanisms. However, it does provide beneficial information for the design of drugs to prevent or treat CTE.

Antiepileptic Drugs as Potential Dementia Prophylactics Following Traumatic Brain Injury

Seizures and other forms of neurovolatility are emerging as druggable prodromal mechanisms that link traumatic brain injury (TBI) to the progression of later dementias. TBI neurotrauma has both acute and long-term impacts on health, and TBI is a leading risk factor for dementias, including chronic traumatic encephalopathy and Alzheimer's disease. Treatment of TBI already considers acute management of posttraumatic seizures and epilepsy, and impressive efforts have optimized regimens of antiepileptic drugs (AEDs) toward that goal. Here we consider that expanding these management strategies could determine which AED regimens best prevent dementia progression in TBI patients. Challenges with this prophylactic strategy include the potential consequences of prolonged AED treatment and that a large subset of patients are refractory to available AEDs. Addressing these challenges is warranted because the management of seizure activity following TBI offers a rare opportunity to prevent the onset or progression of devastating dementias.

Determinants of health insurance coverage among women in Mauritania: a multilevel analysis

BACKGROUND

Health insurance has been documented as one of the primary methods of financing healthcare for Sustainable Development Goals (SDGs) by 2030. Yet, there is a dearth of evidence on the determinants of health insurance coverage among women in Mauritania. We examine the factors associated with health insurance coverage among women in Mauritania using a nationally representative survey dataset.

METHODS

We analyzed secondary data from the 2019-2021 Mauritania Demographic and Health Survey. A weighted sample of 15,714 women of reproductive age (15-49 years) was included in the study. Multilevel regression analysis was used to examined the factors associated with health insurance coverage. The results were presented using an adjusted odds ratio (aOR) with a 95% confidence interval (CI).

RESULTS

The coverage of health insurance among women was 8.7%. The majority of the women subscribed to social security health insurance (7.6%). Women aged 35 years and above [aOR = 1.54; 95% CI = 1.24, 1.92] were more likely to be covered by health insurance relative to those aged 15-24. The likelihood of being covered by health insurance increased with increasing level of education with the highest odds among women with higher education [aOR = 6.09; 95% CI = 3.93, 9.42]. Women in the richest wealth index households [aOR = 22.12; 95% CI = 9.52, 51.41] and those with grand parity [aOR = 2.16; 95% CI = 1.62, 2.87] had the highest odds of being covered by health insurance. Women who were working, those who watched television, and those who used the internet were more likely to be covered by health insurance relative to their counterparts who were not working, those who did not watch television, and those who did not use the internet. Women residing in Tiris zemour et Inchiri [aOR = 3.60; 95%CI = 1.60, 8.10], Tagant (aOR = 3.74; 95% CI = 1.61, 8.68], and Adrar [aOR = 2.76; 95% CI = 1.36, 5.61] regions were more likely to be covered by health insurance compared with those from Hodh Echargui.

CONCLUSION

Health insurance coverage among the women in our study was low. Achieving the SDG targets of ensuring universal health coverage and lowering maternal mortality to less than 70 deaths per 100,000 live births requires the implementation of interventions to increase health insurance coverage, taking into consideration the identified factors in the study. We recommend effective public education and awareness creation on the importance of being covered by health insurance by leveraging television and internet platforms. Also, interventions to increase health insurance coverage should consider younger women and those in rural areas.

Perivascular Space Burden and Cerebrospinal Fluid Biomarkers in US Veterans With Blast-Related Mild Traumatic Brain Injury

Blast-related mild traumatic brain injury (mTBI) is recognized as the "signature injury" of the Iraq and Afghanistan wars. Sleep disruption, mTBI, and neuroinflammation have been individually linked to cerebral perivascular space (PVS) dilatation. Dilated PVSs are putative markers of impaired cerebrospinal fluid (CSF) and interstitial fluid exchange, which plays an important role in removing cerebral waste. The aim of this cross-sectional, retrospective study was to define associations between biomarkers of inflammation and MRI-visible PVS (MV-PVS) burden in Veterans after blast-related mTBI (blast-mTBI) and controls. The CSF and plasma inflammatory biomarker concentrations were compared between blast-mTBI and control groups and correlated with MV-PVS volume and number per white matter cm3. Multiple regression analyses were performed with inflammatory biomarkers as predictors and MV-PVS burden as the outcome. Correction for multiple comparisons was performed using the Banjamini-Hochberg method with a false discovery rate of 0.05. There were no group-wise differences in MV-PVS burden between Veterans with blast-mTBI and controls. Greater MV-PVS burden was significantly associated with higher concentrations of several proinflammatory biomarkers from CSF (i.e., eotaxin, MCP-1, IL-6, IL-8) and plasma (i.e., MCP-4, IL-13) in the blast-mTBI group only. After controlling for sleep time and symptoms of post-traumatic stress disorder, temporal MV-PVS burden remained significantly associated with higher CSF markers of inflammation in the blast-mTBI group only. These data support an association between central, rather than peripheral, neuroinflammation and MV-PVS burden in Veterans with blast-mTBI independent of sleep. Future studies should continue to explore the role of blast-mTBI related central inflammation in MV-PVS development, as well as investigate the impact of subclinical exposures on MV-PVS burden.

Sub-region expression of brain-derived neurotrophic factor in the dorsal hippocampus and amygdala is Affected by mild traumatic brain injury and stress in male rats

The US population suffers 1.5 million head injuries annually, of which mild traumatic brain injuries (mTBI) comprise 75%. Many individuals subsequently experience long-lasting negative symptoms, including anxiety. Previous rat-based work in our laboratory has shown that mTBI changes neuronal counts in the hippocampus and amygdala, regions associated with anxiety. Specifically, mTBI increased neuronal death in the dorsal CA1 sub-region of the hippocampus, but attenuated it in the medial (MeA) and the basolateral nuclei of the amygdala nine days following injury, which was associated with greater anxiety. We have also shown that glucocorticoid receptor (GR) antagonism prior to concomitant stress and mTBI extinguishes anxiety-like behaviors. Using immunohistochemistry, this study examines the expression of brain-derived neurotrophic factor (BDNF) following social defeat and mTBI, and whether this is affected by prior glucocorticoid receptor antagonism as a potential mechanism behind these anxiety and neuronal differences. Here, stress and mTBI upregulate BDNF in the MeA, and both GR and mineralocorticoid receptor antagonism downregulate BDNF in the dorsal hippocampal CA1 and dentate gyrus, as well as the central nucleus of the amygdala. These findings suggest BDNF plays a role in the mechanism underlying neuronal changes following mTBI in amygdalar and hippocampal subregions, and may participate in stress elicited changes to neural plasticity in these regions. Taken together, these results suggest an essential role for BDNF in the development of anxiety behaviors following concurrent stress and mTBI.

Traumatic brain injury derived pathological tau polymorphs induce the distinct propagation pattern and neuroinflammatory response in wild type mice

The misfolding and aggregation of the tau protein into neurofibrillary tangles constitutes a central feature of tauopathies. Traumatic brain injury (TBI) has emerged as a potential risk factor, triggering the onset and progression of tauopathies. Our previous research revealed distinct polymorphisms in soluble tau oligomers originating from single versus repetitive mild TBIs. However, the mechanisms orchestrating the dissemination of TBI brain-derived tau polymorphs (TBI-BDTPs) remain elusive. In this study, we explored whether TBI-BDTPs could initiate pathological tau formation, leading to distinct pathogenic trajectories. Wild-type mice were exposed to TBI-BDTPs from sham, single-blast (SB), or repeated-blast (RB) conditions, and their memory function was assessed through behavioral assays at 2- and 8-month post-injection. Our findings revealed that RB-BDTPs induced cognitive and motor deficits, concurrently fostering the emergence of toxic tau aggregates within the injected hippocampus. Strikingly, this tau pathology propagated to cortical layers, intensifying over time. Importantly, RB-BDTP-exposed animals displayed heightened glial cell activation, NLRP3 inflammasome formation, and increased TBI biomarkers, particularly triggering the aggregation of S100B, which is indicative of a neuroinflammatory response. Collectively, our results shed light on the intricate mechanisms underlying TBI-BDTP-induced tau pathology and its association with neuroinflammatory processes. This investigation enhances our understanding of tauopathies and their interplay with neurodegenerative and inflammatory pathways following traumatic brain injury.

Chronic Traumatic Encephalopathy in Soccer Players: Review of 14 Cases

OBJECTIVE

Exposure to repetitive sports-related concussions or (sub)concussive head trauma may lead to chronic traumatic encephalopathy (CTE). Which impact (heading or concussion) poses the greatest risk of CTE development in soccer players?

DESIGN

Narrative review.

SETTING

Teaching hospital and University of Applied sciences.

PATIENTS

A literature search (PubMed) was conducted for neuropathologic studies in the period 2005-December 2022, investigating soccer players with dementia and a CTE diagnosis, limited to English language publications. 210 papers were selected for final inclusion, of which 7 papers described 14 soccer players.

ASSESSMENT

Magnetic resonance imaging studies in soccer players show that lifetime estimates of heading numbers are inversely correlated with cortical thickness, grey matter volume, and density of the anterior temporal cortex. Using diffusion tensor imaging-magnetic resonance imaging, higher frequency of headings-particularly with rotational accelerations-are associated with impaired white matter integrity. Serum neurofilament light protein is elevated after heading.

MAIN OUTCOME MEASURES

Chronic traumatic encephalopathy pathology, history of concussion, heading frequency.

RESULTS

In 10 of 14 soccer players, CTE was the primary diagnosis. In 4 cases, other dementia types formed the primary diagnosis and CTE pathology was a concomitant finding. Remarkably, 6 of the 14 cases had no history of concussion, suggesting that frequent heading may be a risk for CTE in patients without symptomatic concussion. Rule changes in heading duels, management of concussion during the game, and limiting the number of high force headers during training are discussed.

CONCLUSIONS

Data suggest that heading frequency and concussions are associated with higher risk of developing CTE in (retired) soccer players. However based on this review of only 14 players, questions persist as to whether or not heading is a risk factor for CTE or long-term cognitive decline.