White Matter and Cognition in Traumatic Brain Injury

Current Evidence for the Use of Jugular Vein Compression Collars in Sport: A Systematic Review

ABSTRACT

Sport-related concussions are a common type of brain injury, and the best treatment is prevention. Recently, external jugular vein compression collars have been worn by National Football League players, but the current evidence is limited. To the best of the authors' knowledge, this is the first comprehensive, up-to-date systematic review addressing the use of jugular vein compression collars for decreasing concussion incidence in high-impact sports and activities. Overall, when compared to control, the results indicated that jugular vein compression collars resulted in significantly reduced white matter alteration, improved short-term neurocognitive outcomes, increased internal jugular vein cross-sectional area, decreased internal carotid artery cross-sectional area, and moderating effects on peak pulse pressure. There was no significant difference in concussion incidence rate between groups. While promising, these findings warrant future research to assess jugular vein compression collar's role in concussion prevention, brain injury, and long-term neurocognitive outcomes. The authors are hopeful for the role jugular vein compression collars will play in the future.

Approachability and Sensory Changes Following Mild Traumatic Brain Injury in Pigs

BACKGROUND/OBJECTIVES

Traumatic brain injury (TBI) is a global healthcare concern affecting millions, with wide-ranging symptoms including sensory and behavioral changes that can persist long-term. Due to similarities with human brain cytoarchitecture and inflammation, minipig models are advantageous for translational TBI research. However, gaps in knowledge exist regarding their behavioral and sensory sequelae following injury.

METHODS

Therefore, in this study, we assessed changes in approachability using a forced human approach task (FHAT) and mechanical nociception using the von Frey test in adult male and female Yucatan minipigs for up to one week following a sham or central fluid percussion injury (cFPI). Specifically, the FHAT assessed each animal's response to a forced interaction with either a known or unknown experimenter. To evaluate changes in nociceptive sensory sensitivity, von Frey monofilaments ranging from 0.008 to 300 g of force were applied to the pinna of the ear or base of the tail.

RESULTS

We found that forced approachability was affected by experimenter familiarity as well as cFPI in a sex-specific manner at subacute timepoints. We also found reductions in sensitivity following cFPI on the ear in male minipigs and on the tail in female minipigs.

CONCLUSION

Overall, the current study demonstrates that cFPI produces both behavioral and sensory changes in minipigs up to one-week post-injury.

A history of traumatic brain injury is associated with poorer cognition and imaging evidence of altered white matter tract integrity in UK Biobank (n = 50 376)

Traumatic brain injury (TBI) is a risk factor for neurodegenerative disease. We currently have no means to identify patients most at risk of neurodegenerative disease following injury and, resultantly, no means to target risk mitigation interventions. To address this, we explored the association between history of traumatic brain injury with cognitive performance and imaging measures of white matter integrity. From the UK Biobank imaging sub-study (n = 50 376), participants were identified with either self-reported (n = 177) or health record coded broad- (injury codes; n = 1096) or narrow-band (TBI specific codes; n = 274) TBI, or as controls with no such documented history (n = 49 280). Cognitive scores and imaging measures of corpus callosum white matter integrity were compared between injury participants (versus no injury), corrected for age, sex, socioeconomic status and medications. TBI was associated with poorer cognitive and imaging phenotypes. The strongest deleterious associations were for narrow-band injury (β difference 0.2-0.3; P < 0.01). All cognitive and imaging phenotypes were strongly inter-correlated (P < 0.001). This study provides insight into possible early biomarkers predating neurodegenerative disease following brain injury. Measures of cognition and white matter following injury may provide means to identify individuals most at risk of neurodegenerative disease, to which mitigation strategies might be targeted.

White matter damage and degeneration in traumatic brain injury

Traumatic brain injury (TBI) is a complex condition that can resolve over time but all too often leads to persistent symptoms, and the risk of poor patient outcomes increases with aging. TBI damages neurons and long axons within white matter tracts that are critical for communication between brain regions; this causes slowed information processing and neuronal circuit dysfunction. This review focuses on white matter injury after TBI and the multifactorial processes that underlie white matter damage, potential for recovery, and progression of degeneration. A multiscale perspective across clinical and preclinical advances is presented to encourage interdisciplinary insights from whole-brain neuroimaging of white matter tracts down to cellular and molecular responses of axons, myelin, and glial cells within white matter tissue.

ISRIB improves white matter injury following TBI by inhibiting NCOA4-mediated ferritinophagy

Traumatic brain injury (TBI) often results in persistent neurological dysfunction, which is closely associated with white matter injury. The mechanisms underlying white matter injury after TBI remain unclear. Ferritinophagy is a selective autophagic process that degrades ferritin and releases free iron, which may cause ferroptosis. Although ferroptosis has been demonstrated to be involved in TBI, it is unclear whether ferritinophagy triggers ferroptosis in TBI. Integrated stress response inhibitor (ISRIB) has neuroprotective properties. However, the effect of ISRIB on white matter after TBI remains uncertain. We aimed to investigate whether ferritinophagy was involved in white matter injury following TBI and whether ISRIB can mitigate white matter injury after TBI by inhibiting ferritinophagy. In this study, controlled cortical impact (CCI) was performed on rats to establish the TBI model. Ferritinophagy was measured by assessing the levels of nuclear receptor coactivator 4 (NCOA4), which regulates ferritinophagy, ferritin heavy chain 1(FTH1), LC3, ATG5, and FTH1 colocalization with LC3 in the white matter. Increased NCOA4 and decreased FTH1 were detected in our study. FTH1 colocalization with LC3 enhanced in the white matter after TBI, indicating that ferritinophagy was activated. Immunofluorescence co-localization results also suggested that ferritinophagy occurred in neurons and oligodendrocytes after TBI. Furthermore, ferroptosis was assessed by determining free iron content, MDA content, GSH content, and Perl's staining. The results showed that ferroptosis was suppressed by NCOA4 knockdown via shNCOA4 lentivirus infection, indicating that ferroptosis in TBI is triggered by ferritinophagy. Besides, NCOA4 deletion notably improved white matter injury following TBI, implying that ferritinophagy contributed to white matter injury. ISRIB treatment reduced the occurrence of ferritinophagy in neurons and oligodendrocytes, attenuated ferritinophagy-induced ferroptosis, and alleviated white matter injury. These findings suggest that NCOA4-mediated ferritinophagy is a critical mechanism underlying white matter injury after TBI. ISRIB holds promise as a therapeutic agent for this condition.

A conceptual framework for a neurophysiological basis of art therapy for PTSD

Post-traumatic stress disorder (PTSD) is a heterogeneous condition that affects many civilians and military service members. Lack of engagement, high dropout rate, and variable response to psychotherapy necessitates more compelling and accessible treatment options that are based on sound neuroscientific evidence-informed decision-making. Art therapy incorporates elements proven to be effective in psychotherapy, such as exposure, making it a potentially valuable treatment option. This conceptual paper aims to inform the neurophysiological rationale for the use of art therapy as a therapeutic approach for individuals with PTSD. A narrative synthesis was conducted using literature review of empirical research on the neurophysiological effects of art therapy, with supporting literature on neuroaesthetics and psychotherapies to identify art therapy factors most pertinent for PTSD. Findings were synthesized through a proposed framework based on the triple network model considering the network-based dysfunctions due to PTSD. Art therapy's active components, such as concretization and metaphor, active art engagement, emotion processing and regulation, perspective taking and reframing, and therapeutic alliance, may improve symptoms of PTSD and prompt adaptive brain functioning. Given the scarcity of rigorous studies on art therapy's effectiveness and mechanisms of alleviating PTSD symptoms, the suggested framework offers a neurophysiological rationale and a future research agenda to investigate the impact of art therapy as a therapeutic approach for individuals with PTSD.

ASK1-K716R reduces neuroinflammation and white matter injury via preserving blood-brain barrier integrity after traumatic brain injury

BACKGROUND

Traumatic brain injury (TBI) is a significant worldwide public health concern that necessitates attention. Apoptosis signal-regulating kinase 1 (ASK1), a key player in various central nervous system (CNS) diseases, has garnered interest for its potential neuroprotective effects against ischemic stroke and epilepsy when deleted. Nonetheless, the specific impact of ASK1 on TBI and its underlying mechanisms remain elusive. Notably, mutation of ATP-binding sites, such as lysine residues, can lead to catalytic inactivation of ASK1. To address these knowledge gaps, we generated transgenic mice harboring a site-specific mutant ASK1 Map3k5-e (K716R), enabling us to assess its effects and elucidate potential underlying mechanisms following TBI.

METHODS

We employed the CRIPR/Cas9 system to generate a transgenic mouse model carrying the ASK1-K716R mutation, aming to investigate the functional implications of this specific mutant. The controlled cortical impact method was utilized to induce TBI. Expression and distribution of ASK1 were detected through Western blotting and immunofluorescence staining, respectively. The ASK1 kinase activity after TBI was detected by a specific ASK1 kinase activity kit. Cerebral microvessels were isolated by gradient centrifugation using dextran. Immunofluorescence staining was performed to evaluate blood-brain barrier (BBB) damage. BBB ultrastructure was visualized using transmission electron microscopy, while the expression levels of endothelial tight junction proteins and ASK1 signaling pathway proteins was detected by Western blotting. To investigate TBI-induced neuroinflammation, we conducted immunofluorescence staining, quantitative real-time polymerase chain reaction (qRT-PCR) and flow cytometry analyses. Additionally, immunofluorescence staining and electrophysiological compound action potentials were conducted to evaluate gray and white matter injury. Finally, sensorimotor function and cognitive function were assessed by a battery of behavioral tests.

RESULTS

The activity of ASK1-K716R was significantly decreased following TBI. Western blotting confirmed that ASK1-K716R effectively inhibited the phosphorylation of ASK1, JNKs, and p38 in response to TBI. Additionally, ASK1-K716R demonstrated a protective function in maintaining BBB integrity by suppressing ASK1/JNKs activity in endothelial cells, thereby reducing the degradation of tight junction proteins following TBI. Besides, ASK1-K716R effectively suppressed the infiltration of peripheral immune cells into the brain parenchyma, decreased the number of proinflammatory-like microglia/macrophages, increased the number of anti-inflammatory-like microglia/macrophages, and downregulated expression of several proinflammatory factors. Furthermore, ASK1-K716R attenuated white matter injury and improved the nerve conduction function of both myelinated and unmyelinated fibers after TBI. Finally, our findings demonstrated that ASK1-K716R exhibited favorable long-term functional and histological outcomes in the aftermath of TBI.

CONCLUSION

ASK1-K716R preserves BBB integrity by inhibiting ASK1/JNKs pathway in endothelial cells, consequently reducing the degradation of tight junction proteins. Additionally, it alleviates early neuroinflammation by inhibiting the infiltration of peripheral immune cells into the brain parenchyma and modulating the polarization of microglia/macrophages. These beneficial effects of ASK1-K716R subsequently result in a reduction in white matter injury and promote the long-term recovery of neurological function following TBI.

An Understated Comorbidity: The Impact of Homelessness on Traumatic Brain Injury

Traumatic brain injury (TBI), a neurovascular injury caused by external force, is a common diagnosis among veterans and those experiencing homelessness (HL). There is a significant overlap in the veteran and homeless population, possibly accounting for the two to seven times greater incidence of TBI among those experiencing HL than the general population. Despite these statistics, individuals experiencing HL are often underdiagnosed and ineffectively treated for TBI. We introduced a novel model of HL. Over 5 weeks, adult Sprague-Dawley rats were randomly assigned to one of the following conditions: TBI only, HL only, TBI + HL, or control (n = 9 per group). To emulate HL, animals (2 animals per cage) were exposed to soiled beddings for 5 weeks. Subsequently, animals were introduced to TBI by using the moderate controlled cortical impact model, then underwent 4 consecutive days of behavioral testing (beam walk (BW), elevated body swing test (EBST), forelimb akinesia (FA), paw grasp (PG), Rotorod, and elevated T-maze). Nissl staining was performed to determine the peri-impact cell survival and the integrity of corpus callosum area. Motor function was significantly impaired by TBI, regardless of housing (beam walk or BW 85.0%, forelimb akinesia or FA 104.7%, and paw grasp or PG 100% greater deficit compared to control). Deficits were worsened by HL in TBI rats (BW 93.3%, FA 40.5%, and PG 50% greater deficit). Two-way ANOVA revealed BW (F(4, 160) = 31.69, p < 0.0001), FA (F(4, 160) = 13.71, p < 0.0001), PG (F(4, 160) = 3.873, p = 0.005), Rotorod (F(4, 160), p = 1.116), and EBST (F(4, 160) = 6.929, p < 0.0001) showed significant differences between groups. The Rotorod and EBST tests showed TBI-induced functional deficits when analyzed by day, but these deficits were not exacerbated by HL. TBI only and TBI + HL rats exhibited typical cortical impact damage (F(3,95) = 51.75, p < 0.0001) and peri-impact cell loss compared to control group (F(3,238) = 47.34, p < 0.0001). Most notably, TBI + HL rats showed significant alterations in WM area measured via the corpus callosum (F(3, 95) = 3.764, p = 0.0133). Worsened behavioral outcomes displayed by TBI + HL rats compared to TBI alone suggest HL contributes to TBI functional deficits. While an intact white matter, such as the corpus callosum, may lessen the consequent functional deficits associated with TBI by enhancing hemispheric communications, there are likely alternative cellular and molecular pathways mitigating TBI-associated inflammatory or oxidative stress responses. Here, we showed that the environmental condition of the patient, i.e., HL, participates in white matter integrity and behavioral outcomes, suggesting its key role in the disease diagnosis to aptly treat TBI patients.

Recombinant Erythropoietin Induces Oligodendrocyte Progenitor Cell Proliferation After Traumatic Brain Injury and Delayed Hypoxemia

Traumatic brain injury (TBI) can result in axonal loss and demyelination, leading to persistent damage in the white matter. Demyelinated axons are vulnerable to pathologies related to an abnormal myelin structure that expose neurons to further damage. Oligodendrocyte progenitor cells (OPCs) mediate remyelination after recruitment to the injury site. Often this process is inefficient due to inadequate OPC proliferation. To date, no effective treatments are currently available to stimulate OPC proliferation in TBI. Recombinant human erythropoietin (rhEPO) is a pleiotropic neuroprotective cytokine, and its receptor is present in all stages of oligodendroglial lineage cell differentiation. Therefore, we hypothesized that rhEPO administration would enhance remyelination after TBI through the modulation of OPC response. Utilizing a murine model of controlled cortical impact and a primary OPC culture in vitro model, we characterized the impact of rhEPO on remyelination and proliferation of oligodendrocyte lineage cells. Myelin black gold II staining of the peri-contusional corpus callosum revealed an increase in myelinated area in association with an increase in BrdU-positive oligodendrocytes in injured mice treated with rhEPO. Furthermore, morphological analysis of OPCs showed a decrease in process length in rhEPO-treated animals. RhEPO treatment increased OPC proliferation after in vitro CSPG exposure. Erythropoietin receptor (EPOr) gene knockdown using siRNA prevented rhEPO-induced OPC proliferation, demonstrating that the rhEPO effect on OPC response is EPOr activation dependent. Together, our findings demonstrate that rhEPO administration may promote myelination by increasing oligodendrocyte lineage cell proliferation after TBI.

The cortical NG2-glia response to traumatic brain injury

Traumatic brain injury (TBI) is a significant worldwide cause of morbidity and mortality. A chronic neurologic disease bearing the moniker of "the silent epidemic," TBI currently has no targeted therapies to ameliorate cellular loss or enhance functional recovery. Compared with those of astrocytes, microglia, and peripheral immune cells, the functions and mechanisms of NG2-glia following TBI are far less understood, despite NG2-glia comprising the largest population of regenerative cells in the mature cortex. Here, we synthesize the results from multiple rodent models of TBI, with a focus on cortical NG2-glia proliferation and lineage potential, and propose future avenues for glia researchers to address this unique cell type in TBI. As the molecular mechanisms that regulate NG2-glia regenerative potential are uncovered, we posit that future therapeutic strategies may exploit cortical NG2-glia to augment local cellular recovery following TBI.

Associations of mTBI and post-traumatic stress to amygdala structure and functional connectivity in military Service Members

INTRODUCTION

Traumatic brain injury (TBI) is one of the highest public health priorities, especially among military personnel where comorbidity with post-traumatic stress symptoms and resulting consequences is high. Brain injury and post-traumatic stress symptoms are both characterized by dysfunctional brain networks, with the amygdala specifically implicated as a region with both structural and functional abnormalities.

METHODS

This study examined the structural volumetrics and resting state functional connectivity of 68 Active Duty Service Members with or without chronic mild TBI (mTBI) and comorbid symptoms of Post-Traumatic Stress (PTS).

RESULTS AND DISCUSSION

Structural analysis of the amygdala revealed no significant differences in volume between mTBI and healthy comparison participants with and without post-traumatic stress symptoms. Resting state functional connectivity with bilateral amygdala revealed decreased anterior network connectivity and increased posterior network connectivity in the mTBI group compared to the healthy comparison group. Within the mTBI group, there were significant regions of correlation with amygdala that were modulated by PTS severity, including networks implicated in emotional processing and executive functioning. An examination of a priori regions of amygdala connectivity in the default mode network, task positive network, and subcortical structures showed interacting influences of TBI and PTS, only between right amygdala and right putamen. These results suggest that mTBI and PTS are associated with hypo-frontal and hyper-posterior amygdala connectivity. Additionally, comorbidity of these conditions appears to compound these neural activity patterns. PTS in mTBI may change neural resource recruitment for information processing between the amygdala and other brain regions and networks, not only during emotional processing, but also at rest.

Stem Cell Factor and Granulocyte Colony-Stimulating Factor Promote Remyelination in the Chronic Phase of Severe Traumatic Brain Injury

Severe traumatic brain injury (TBI) causes long-term disability and death in young adults. White matter is vulnerable to TBI damage. Demyelination is a major pathological change of white matter injury after TBI. Demyelination, which is characterized by myelin sheath disruption and oligodendrocyte cell death, leads to long-term neurological function deficits. Stem cell factor (SCF) and granulocyte colony-stimulating factor (G-CSF) treatments have shown neuroprotective and neurorestorative effects in the subacute and chronic phases of experimental TBI. Our previous study has revealed that combined SCF and G-CSF treatment (SCF + G-CSF) enhances myelin repair in the chronic phase of TBI. However, the long-term effect and mechanism of SCF + G-CSF-enhanced myelin repair remain unclear. In this study, we uncovered persistent and progressive myelin loss in the chronic phase of severe TBI. SCF + G-CSF treatment in the chronic phase of severe TBI enhanced remyelination in the ipsilateral external capsule and striatum. The SCF + G-CSF-enhanced myelin repair is positively correlated with the proliferation of oligodendrocyte progenitor cells in the subventricular zone. These findings reveal the therapeutic potential of SCF + G-CSF in myelin repair in the chronic phase of severe TBI and shed light on the mechanism underlying SCF + G-CSF-enhanced remyelination in chronic TBI.

DCC/netrin-1 regulates cell death in oligodendrocytes after brain injury

Hallmark pathological features of brain trauma are axonal degeneration and demyelination because myelin-producing oligodendrocytes (OLs) are particularly vulnerable to injury-induced death signals. To reveal mechanisms responsible for this OL loss, we examined a novel class of "death receptors" called dependence receptors (DepRs). DepRs initiate pro-death signals in the absence of their respective ligand(s), yet little is known about their role after injury. Here, we investigated whether the deleted in colorectal cancer (DCC) DepR contributes to OL loss after brain injury. We found that administration of its netrin-1 ligand is sufficient to block OL cell death. We also show that upon acute injury, DCC is upregulated while netrin-1 is downregulated in perilesional tissues. Moreover, after genetically silencing pro-death activity using DCCD1290N mutant mice, we observed greater OL survival, greater myelin integrity, and improved motor function. Our findings uncover a novel role for the netrin-1/DCC pathway in regulating OL loss in the traumatically injured brain.

Stem cell factor and granulocyte colony-stimulating factor promote remyelination in the chronic phase of severe traumatic brain injury

Severe traumatic brain injury (TBI) causes long-term disability and death in young adults. White matter is vulnerable to TBI damage. Demyelination is a major pathological change of white matter injury after TBI. Demyelination which is characterized by myelin sheath disruption and oligodendrocyte cell death leads to long-term neurological function deficits. Stem cell factor (SCF) and granulocyte colonyâ€"stimulating factor (G-CSF) treatments have shown neuroprotective and neurorestorative effects in the subacute and chronic phases of experimental TBI. Our previous study has revealed that combined SCF and G-CSF treatment (SCF+G-CSF) enhances myelin repair in the chronic phase of TBI. However, the long-term effect and mechanism of SCF+G-CSF-enhanced myelin repair remain unclear. In this study, we uncovered persistent and progressive myelin loss in the chronic phase of severe TBI. SCF+G-CSF treatment in the chronic phase of severe TBI enhanced remyelination in the ipsilateral external capsule and striatum. The SCF+G-CSF-enhanced myelin repair is positively correlated with the proliferation of oligodendrocyte progenitor cells in the subventricular zone. These findings reveal the therapeutic potential of SCF+G-CSF in myelin repair in the chronic phase of severe TBI and shed light on the mechanism underlying SCF+G-CSF-enhanced remyelination in chronic TBI.

White matter dementia then… and now

White matter dementia (WMD) is a concept introduced in 1988 to highlight the importance of white matter pathology in producing cognitive dysfunction and dementia. Whereas gray matter, particularly the cerebral cortex, has been primarily investigated in the dementias, subcortical pathology has long been correlated with cognitive loss, and a corticocentric perspective cannot account for the full range of neurobehavioral disorders. Within the subcortical regions, white matter is prominent, accounting for about half the volume of the adult brain, and many white matter diseases, injuries, and intoxications can produce cognitive dysfunction so severe as to justify the term dementia. Recognition of this novel syndrome relied heavily on the introduction of magnetic resonance imaging (MRI) that permitted in vivo visualization of white matter lesions. Neuropsychological studies clarified the clinical presentation of WMD by identifying a profile dominated by cognitive slowing and executive dysfunction, and a precursor syndrome of mild cognitive dysfunction was proposed to identify early cognitive impairment that may later evolve to WMD. As knowledge advanced, the role of white matter in structural connectivity within distributed neural networks was elucidated. In addition, highlighting the frequent commingling of gray and white matter involvement, white matter pathology was associated with neurodegenerative diseases such as Alzheimer's disease and chronic traumatic encephalopathy, with potentially transformative clinical implications. In particular, preventive measures and treatments exploiting white matter restoration and plasticity are gaining much attention. Today, WMD has matured into a concept that not only integrates knowledge from across the spectrum of clinical neuroscience, but also informs new investigations into many perplexing disorders and enables a more complete understanding of brain-behavior relationships.

A Calixarene Assembly Strategy of Combined Anti-Neuroinflammation and Drug Delivery Functions for Traumatic Brain Injury Therapy

Excessive inflammatory reaction aggravates brain injury and hinders the recovery of neural function in nervous system diseases. Microglia, as the major players of neuroinflammation, control the progress of the disease. There is an urgent need for effective non-invasive therapy to treat neuroinflammation mediated by microglia. However, the lack of specificity of anti-inflammatory agents and insufficient drug dose penetrating into the brain lesion area are the main problems. Here, we evaluated a series of calixarenes and found that among them the self-assembling architecture of amphiphilic sulfonatocalix[8]arene (SC8A12C) had the most potent ability to suppress neuroinflammation in vitro and in vivo. Moreover, SC8A12C assemblies were internalized into microglia through macropinocytosis. In addition, after applying the SC8A12C assemblies to the exposed brain tissue, we observed that SC8A12C assemblies penetrated into the brain parenchyma and eliminated the inflammatory factor storm, thereby restoring neurobiological functions in a mouse model of traumatic brain injury.

Acute axon damage and demyelination are mitigated by 4-aminopyridine (4-AP) therapy after experimental traumatic brain injury

Damage to long axons in white matter tracts is a major pathology in closed head traumatic brain injury (TBI). Acute TBI treatments are needed that protect against axon damage and promote recovery of axon function to prevent long term symptoms and neurodegeneration. Our prior characterization of axon damage and demyelination after TBI led us to examine repurposing of 4-aminopyridine (4-AP), an FDA-approved inhibitor of voltage-gated potassium (Kv) channels. 4-AP is currently indicated to provide symptomatic relief for patients with chronic stage multiple sclerosis, which involves axon damage and demyelination. We tested clinically relevant dosage of 4-AP as an acute treatment for experimental TBI and found multiple benefits in corpus callosum axons. This randomized, controlled pre-clinical study focused on the first week after TBI, when axons are particularly vulnerable. 4-AP treatment initiated one day post-injury dramatically reduced axon damage detected by intra-axonal fluorescence accumulations in Thy1-YFP mice of both sexes. Detailed electron microscopy in C57BL/6 mice showed that 4-AP reduced pathological features of mitochondrial swelling, cytoskeletal disruption, and demyelination at 7 days post-injury. Furthermore, 4-AP improved the molecular organization of axon nodal regions by restoring disrupted paranode domains and reducing Kv1.2 channel dispersion. 4-AP treatment did not resolve deficits in action potential conduction across the corpus callosum, based on ex vivo electrophysiological recordings at 7 days post-TBI. Thus, this first study of 4-AP effects on axon damage in the acute period demonstrates a significant decrease in multiple pathological hallmarks of axon damage after experimental TBI.

Neurological Music Therapy Rebuilds Structural Connectome after Traumatic Brain Injury: Secondary Analysis from a Randomized Controlled Trial

Background: Traumatic brain injury (TBI) is a common and devastating neurological condition, associated often with poor functional outcome and deficits in executive function. Due to the neuropathology of TBI, neuroimaging plays a crucial role in its assessment, and while diffusion MRI has been proposed as a sensitive biomarker, longitudinal studies evaluating treatment-related diffusion MRI changes are scarce. Recent evidence suggests that neurological music therapy can improve executive functions in patients with TBI and that these effects are underpinned by neuroplasticity changes in the brain. However, studies evaluating music therapy induced structural connectome changes in patients with TBI are lacking. Design: Single-blind crossover (AB/BA) randomized controlled trial (NCT01956136). Objective: Here, we report secondary outcomes of the trial and set out to assess the effect of neurological music therapy on structural white matter connectome changes and their association with improved execute function in patients with TBI. Methods: Using an AB/BA design, 25 patients with moderate or severe TBI were randomized to receive a 3-month neurological music therapy intervention either during the first (AB, n = 16) or second (BA, n = 9) half of a 6-month follow-up period. Neuropsychological testing and diffusion MRI scans were performed at baseline and at the 3-month and 6-month stage. Findings: Compared to the control group, the music therapy group increased quantitative anisotropy (QA) in the right dorsal pathways (arcuate fasciculus, superior longitudinal fasciculus) and in the corpus callosum and the right frontal aslant tract, thalamic radiation and corticostriatal tracts. The mean increased QA in this network of results correlated with improved executive function. Conclusions: This study shows that music therapy can induce structural white matter neuroplasticity in the post-TBI brain that underpins improved executive function.

Neuroimaging correlates of depression after traumatic brain injury: A systematic review

Depression is the most frequent neuropsychiatric complication after traumatic brain injury (TBI) and is associated with poorer outcomes. Neuroimaging has the potential to improve our understanding of the neural correlates of depression after TBI and may improve our capacity to accurately predict and effectively treat this condition. We conducted a systematic review of structural and functional neuroimaging studies that examined the association between depression after TBI, and neuroimaging measures. Electronic searches were conducted in four databases and were complemented by manual searches. In total, 2,035 citations were identified and, ultimately, 38 articles were included totaling 1,793 individuals (median [25%-75%] sample size of 38.5 (21.8-54.3) individuals). The most frequently used modality was structural magnetic resonance imaging (MRI) (n=17, 45%), followed by diffusion tensor imaging (n=11, 29%), resting-state functional MRI (n=10, 26%), task-based functional MRI (n=4, 8%), and positron emission tomography (n=2, 4%). Most studies (n=27, 71%) were cross-sectional. Overall, depression after TBI was associated with lower grey matter measures (volume, thickness, and/or density) and greater white matter damage. However, identification of specific brain areas was somewhat inconsistent. Findings that were replicated in more than one study included reduced grey matter in the rostral anterior cingulate cortex, prefrontal cortex and hippocampus, and damage in five white matter tracts (cingulum, internal capsule, superior longitudinal fasciculi, anterior, and posterior corona radiata). This systematic review found that the available data did not converge on a clear neuroimaging biomarker for depression after TBI. However, there are promising targets that warrant further study.

Refined Analysis of Chronic White Matter Changes after Traumatic Brain Injury and Repeated Sports-Related Concussions: Of Use in Targeted Rehabilitative Approaches?

Traumatic brain injury (TBI) or repeated sport-related concussions (rSRC) may lead to long-term memory impairment. Diffusion tensor imaging (DTI) is helpful to reveal global white matter damage but may underestimate focal abnormalities. We investigated the distribution of post-injury regional white matter changes after TBI and rSRC. Six patients with moderate/severe TBI, and 12 athletes with rSRC were included ≥6 months post-injury, and 10 (age-matched) healthy controls (HC) were analyzed. The Repeatable Battery for the Assessment of Neuropsychological Status was performed at the time of DTI. Major white matter pathways were tracked using q-space diffeomorphic reconstruction and analyzed for global and regional changes with a controlled false discovery rate. TBI patients displayed multiple classic white matter injuries compared with HC (p < 0.01). At the regional white matter analysis, the left frontal aslant tract, anterior thalamic radiation, and the genu of the corpus callosum displayed focal changes in both groups compared with HC but with different trends. Both TBI and rSRC displayed worse memory performance compared with HC (p < 0.05). While global analysis of DTI-based parameters did not reveal common abnormalities in TBI and rSRC, abnormalities to the fronto-thalamic network were observed in both groups using regional analysis of the white matter pathways. These results may be valuable to tailor individualized rehabilitative approaches for post-injury cognitive impairment in both TBI and rSRC patients.

Personalized Connectome-Based Modeling in Patients with Semi-Acute Phase TBI: Relationship to Acute Neuroimaging and 6 Month Follow-Up

Following traumatic brain injury (TBI), cognitive impairments manifest through interactions between microscopic and macroscopic changes. On the microscale, a neurometabolic cascade alters neurotransmission, while on the macroscale diffuse axonal injury impacts the integrity of long-range connections. Large-scale brain network modeling allows us to make predictions across these spatial scales by integrating neuroimaging data with biophysically based models to investigate how microscale changes invisible to conventional neuroimaging influence large-scale brain dynamics. To this end, we analyzed structural and functional neuroimaging data from a well characterized sample of 44 adult TBI patients recruited from a regional trauma center, scanned at 1–2 weeks postinjury, and with follow-up behavioral outcome assessed 6 months later. Thirty-six age-matched healthy adults served as comparison participants. Using The Virtual Brain, we fit simulations of whole-brain resting-state functional MRI to the empirical static and dynamic functional connectivity of each participant. Multivariate partial least squares (PLS) analysis showed that patients with acute traumatic intracranial lesions had lower cortical regional inhibitory connection strengths than comparison participants, while patients without acute lesions did not differ from the comparison group. Further multivariate PLS analyses found correlations between lower semiacute regional inhibitory connection strengths and more symptoms and lower cognitive performance at a 6 month follow-up. Critically, patients without acute lesions drove this relationship, suggesting clinical relevance of regional inhibitory connection strengths even when traumatic intracranial lesions were not present. Our results suggest that large-scale connectome-based models may be sensitive to pathophysiological changes in semi-acute phase TBI patients and predictive of their chronic outcomes.

Neurocognitive correlates of probable posttraumatic stress disorder following traumatic brain injury

Introduction

Neurocognitive problems associated with posttraumatic stress disorder (PTSD) can interact with impairment resulting from traumatic brain injury (TBI).

Research question

We aimed to identify neurocognitive problems associated with probable PTSD following TBI in a civilian sample.

Material and methods

The study is part of the CENTER-TBI project (Collaborative European Neurotrauma Effectiveness Research) that aims to better characterize TBI. For this cross-sectional study, we included patients of all severities aged over 15, and a Glasgow Outcome Score Extended (GOSE) above 3. Participants were assessed at six months post-injury on the PTSD Checklist-5 (PCL-5), the Trail Making Test (TMT), the Rey Auditory Verbal Learning Test (RAVLT) and the Cambridge Neuropsychological Test Automated Battery (CANTAB). Primary analysis was a complete case analysis. Regression analyses were performed to investigate the association between the PCL-5 and cognition.

Results

Of the 1134 participants included in the complete case analysis, 13.5% screened positive for PTSD. Probable PTSD was significantly associated with higher TMT-(B-A) (OR ​= ​1.35, 95% CI: 1.14–1.60, p ​< ​.001) and lower RAVLT-delayed recall scores (OR ​= ​0.74, 95% CI: 0.61–0.91, p ​= ​.004) after controlling for age, sex, psychiatric history, baseline Glasgow Coma Scale and education.

Discussion and conclusion

Poorer performance on cognitive tests assessing task switching and, to a lesser extent, delayed verbal recall is associated with probable PTSD in civilians who have suffered TBI.

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Six months after traumatic brain injury 13.5% of people screen positive for PTSD.

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Task switching performance and verbal memory are related to probable PTSD.

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PTSD severity is related to processing speed and task switching performance.

Temporal patterns of microglial activation in white matter following experimental mild traumatic brain injury: a systematic literature review

Mild traumatic brain injuries (mTBIs) are a prevalent form of injury that can result in persistent neurological impairments. Microglial activation has become increasingly recognized as a key process regulating the pathology of white matter in a wide range of brain injury and disease contexts. As white matter damage is known to be a major contributor to the impairments that follow mTBI, microglia have rightfully become a common target of investigation for the development of mTBI therapies and biomarkers. Recent work has demonstrated that the efficacy of microglial manipulation as a therapeutic intervention following injury or disease is highly time-sensitive, emphasizing the importance of advancing our understanding of the dynamics of post-mTBI microglial activation from onset to resolution. Current reporting of microglial activation in experimental studies of mTBI is non-standardized, which has limited our ability to identify concrete patterns of post-mTBI microglial activation over time. In this review, we examine preclinical studies of mTBI that report on microglial activation in white matter regions to summarize our current understanding of these patterns. Specifically, we summarize timecourses of post-mTBI microglial activation in white matter regions of the brain, identify factors that influence this activation, examine the temporal relationship between microglial activation and other post-mTBI assessments, and compare the relative sensitivities of various methods for detecting microglial activation. While the lack of replicated experimental conditions has limited the extent of conclusions that can confidently be drawn, we find that microglia are activated over a wide range of timecourses following mTBI and that microglial activation is a long-lasting outcome of mTBI that may resolve after most typical post-mTBI assessments, with the exception of those measuring oligodendrocyte lineage cell integrity. We identify several understudied parameters of post-mTBI microglial activation in white matter, such as the inclusion of female subjects. This review summarizes our current understanding of the progression of microglial activation in white matter structures following experimental mTBI and offers suggestions for important future research directions.

L-Serine, an Endogenous Amino Acid, Is a Potential Neuroprotective Agent for Neurological Disease and Injury

Central nervous system (CNS) lesions are major causes of human death and disability worldwide, and they cause different extents of motor and sensory dysfunction in patients. Thus, it is crucial to develop new effective neuroprotective drugs and approaches targeted to the heterogeneous nature of CNS injury and disease. L-serine is an indispensable neurotrophic factor and a precursor for neurotransmitters. Although L-serine is a native amino acid supplement, its metabolic products have been shown to be essential not only for cell proliferation but also for neuronal development and specific functions in the brain. Growing evidence has suggested that L-serine regulates the release of several cytokines in the brain under some neuropathological conditions to recover cognitive function, improve cerebral blood flow, inhibit inflammation, promote remyelination and exert other neuroprotective effects on neurological injury. L-serine has also been used to treat epilepsy, schizophrenia, psychosis, and Alzheimer’s Disease as well as other neurological diseases. Furthermore, the dosing of animals with L-serine and human clinical trials investigating the therapeutic effects of L-serine generally support the safety of L-serine. The high significance of this review lies in its emphasis on the therapeutic potential of using L-serine as a general treatment for numerous CNS diseases and injuries. Because L-serine performs a broad spectrum of functions, it may be clinically used as an effective neuroprotective agent.

Cordycepin confers long-term neuroprotection via inhibiting neutrophil infiltration and neuroinflammation after traumatic brain injury

Background

The secondary injury caused by traumatic brain injury (TBI), especially white matter injury (WMI), is highly sensitive to neuroinflammation, which further leads to unfavored long-term outcomes. Although the cross-talk between the three active events, immune cell infiltration, BBB breakdown, and proinflammatory microglial/macrophage polarization, plays a role in the vicious cycle, its mechanisms are not fully understood. It has been reported that cordycepin, an extract from Cordyceps militaris, can inhibit TBI-induced neuroinflammation although the long-term effects of cordycepin remain unknown. Here, we report our investigation of cordycepin’s long-term neuroprotective function and its underlying immunological mechanism.

Methods

TBI mice model was established with a controlled cortical impact (CCI) method. Cordycepin was intraperitoneally administered twice daily for a week. Neurological outcomes were assessed by behavioral tests, including grid walking test, cylinder test, wire hang test, and rotarod test. Immunofluorescence staining, transmission electron microscopy, and electrophysiology recording were employed to assess histological and functional lesions. Quantitative-PCR and flow cytometry were used to detect neuroinflammation. The tracers of Sulfo-NHS-biotin and Evans blue were assessed for the blood-brain barrier (BBB) leakage. Western blot and gelatin zymography were used to analyze protein activity or expression. Neutrophil depletion in vivo was performed via using Ly6G antibody intraperitoneal injection.

Results

Cordycepin administration ameliorated long-term neurological deficits and reduced neuronal tissue loss in TBI mice. Meanwhile, the long-term integrity of white matter was also preserved, which was revealed in multiple dimensions, such as morphology, histology, ultrastructure, and electrical conductivity. Cordycepin administration inhibited microglia/macrophage pro-inflammatory polarization and promoted anti-inflammatory polarization after TBI. BBB breach was attenuated by cordycepin administration at 3 days after TBI. Cordycepin suppressed the activities of MMP-2 and MMP-9 and the neutrophil infiltration at 3 days after TBI. Moreover, neutrophil depletion provided a cordycepin-like effect, and cordycepin administration united with neutrophil depletion did not show a benefit of superposition.

Conclusions

The long-term neuroprotective function of cordycepin via suppressing neutrophil infiltration after TBI, thereby preserving BBB integrity and changing microglia/macrophage polarization. These findings provide significant clinical potentials to improve the quality of life for TBI patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02188-x.

From Provider to Advocate: The Complexities of Traumatic Brain Injury Prompt the Evolution of Provider Engagement

Treating a patient with traumatic brain injury requires an interdisciplinary approach because of the pervasive, profound and protean manifestations of this condition. In this review, key aspects of the medical history and review of systems will be described in order to highlight how the role of any provider must evolve to become a better patient advocate. Although this review is written from the vantage point of a vision care provider, it is hoped that patients, caregivers and providers will recognize the need for a team approach.

National Institute of Neurological Disorders and Stroke Consensus Diagnostic Criteria for Traumatic Encephalopathy Syndrome

OBJECTIVE

To develop evidence-informed, expert consensus research diagnostic criteria for traumatic encephalopathy syndrome (TES), the clinical disorder associated with neuropathologically diagnosed chronic traumatic encephalopathy (CTE).

METHODS

A panel of 20 expert clinician-scientists in neurology, neuropsychology, psychiatry, neurosurgery, and physical medicine and rehabilitation, from 11 academic institutions, participated in a modified Delphi procedure to achieve consensus, initiated at the First National Institute of Neurological Disorders and Stroke Consensus Workshop to Define the Diagnostic Criteria for TES, April, 2019. Before consensus, panelists reviewed evidence from all published cases of CTE with neuropathologic confirmation, and they examined the predictive validity data on clinical features in relation to CTE pathology from a large clinicopathologic study (n = 298).

RESULTS

Consensus was achieved in 4 rounds of the Delphi procedure. Diagnosis of TES requires (1) substantial exposure to repetitive head impacts (RHIs) from contact sports, military service, or other causes; (2) core clinical features of cognitive impairment (in episodic memory and/or executive functioning) and/or neurobehavioral dysregulation; (3) a progressive course; and (4) that the clinical features are not fully accounted for by any other neurologic, psychiatric, or medical conditions. For those meeting criteria for TES, functional dependence is graded on 5 levels, ranging from independent to severe dementia. A provisional level of certainty for CTE pathology is determined based on specific RHI exposure thresholds, core clinical features, functional status, and additional supportive features, including delayed onset, motor signs, and psychiatric features.

CONCLUSIONS

New consensus diagnostic criteria for TES were developed with a primary goal of facilitating future CTE research. These criteria will be revised as updated clinical and pathologic information and in vivo biomarkers become available.

Ischemic Preconditioning Induces Oligodendrogenesis in Mouse Brain: Effects of Nrf2 Deficiency

Ischemic preconditioning (IPC) is an approach of protection against cerebral ischemia by inducing endogenous cytoprotective machinery. However, few studies in neurogenesis and oligodendrogenesis after IPC have been reported, especially the latter. The purpose of this study is to test our hypothesis that IPC may also induce cell proliferation and oligodendrogenesis in the subventricular zone and striatum, as well as to investigate the effect of nuclear factor erythroid 2-related factor 2 (Nrf2) on oligodendrogenesis. IPC was induced in mice by 12-min ischemia through the occlusion of the middle cerebral artery. Newly generated cells were labeled with 5-bromo-2'-deoxyuridine. Our findings demonstrated that IPC stimulated the proliferation of neural stem cells in the subventricular zone, promoted the generation of oligodendrocyte precursor cells in the striatum and corpus callosum/external capsule (CC/EC), and stimulated oligodendrocyte precursor cells differentiation into oligodendrocytes in the striatum and the CC/EC. Furthermore, we describe a crucial role for Nrf2 in IPC-induced oligodendrogenesis in the subventricular zone, striatum, and CC/EC and show for the first time that Nrf2 promoted the migration and differentiation of oligodendrocyte precursor cells into oligodendrocytes in the striatum and CC/EC. Our data imply that IPC stimulates the oligodendrogenesis in the brain and that Nrf2 signaling may contribute to the oligodendrogenesis.

Promoting Successful Cognitive Aging: A Ten-Year Update

A decade has passed since we published a comprehensive review in this journal addressing the topic of promoting successful cognitive aging, making this a good time to take stock of the field. Because there have been limited large-scale, randomized controlled trials, especially following individuals from middle age to late life, some experts have questioned whether recommendations can be legitimately offered about reducing the risk of cognitive decline and dementia. Despite uncertainties, clinicians often need to at least make provisional recommendations to patients based on the highest quality data available. Converging lines of evidence from epidemiological/cohort studies, animal/basic science studies, human proof-of-concept studies, and human intervention studies can provide guidance, highlighting strategies for enhancing cognitive reserve and preventing loss of cognitive capacity. Many of the suggestions made in 2010 have been supported by additional research. Importantly, there is a growing consensus among major health organizations about recommendations to mitigate cognitive decline and promote healthy cognitive aging. Regular physical activity and treatment of cardiovascular risk factors have been supported by all of these organizations. Most organizations have also embraced cognitively stimulating activities, a heart-healthy diet, smoking cessation, and countering metabolic syndrome. Other behaviors like regular social engagement, limiting alcohol use, stress management, getting adequate sleep, avoiding anticholinergic medications, addressing sensory deficits, and protecting the brain against physical and toxic damage also have been endorsed, although less consistently. In this update, we review the evidence for each of these recommendations and offer practical advice about behavior-change techniques to help patients adopt brain-healthy behaviors.

Long-Term Effects of Traumatic Brain Injury in a Mouse Model of Alzheimer's Disease

Alzheimer’s disease (AD) is the leading cause of dementia worldwide, affecting over 10% of the elderly population. Epidemiological evidence indicates that traumatic brain injury (TBI) is an important risk factor for developing AD later in life. However, which injury-induced processes that contribute to the disease onset remains unclear. The aim with the present study was to identify cellular processes that could link TBI to AD development, by investigating the chronic impact of two different injury models, controlled cortical impact (CCI) and midline fluid percussion injury (mFPI). The trauma was induced in 3-month-old tg-ArcSwe mice, carrying the Arctic mutation along with the Swedish mutation, and the influence of TBI on AD progression was analyzed at 12- and 24-weeks post-injury. The long-term effect of the TBI on memory deficiency, amyloid-β (Aβ) pathology, neurodegeneration and inflammation was investigated by Morris water maze, PET imaging, immunohistochemistry, and biochemical analyses. Morris water maze analysis demonstrated that mice subjected to CCI or mFPI performed significantly worse than uninjured tg-ArcSwe mice, especially at the later time point. Moreover, the injured mice showed a late upregulation of reactive gliosis, which concurred with a more pronounced Aβ pathology, compared to uninjured AD mice. Our results suggest that the delayed glial activation following TBI may be an important link between the two diseases. However, further studies in both experimental models and human TBI patients will be required to fully elucidate the reasons why TBI increases the risk of neurodegeneration.

TMT-based proteomics analysis to screen potential biomarkers of acute-phase TBI in rats

AIMS

Traumatic brain injury (TBI) is a common nervous system injury. However, the detailed mechanisms about functional dysregulation and dignostic biomarkers post-TBI are still unclear. So we aimed to identify potential differentially expressed proteins and genes in TBI for clinical diagnosis and therapeutic purposes.

MAIN METHODS

Rat TBI model was established by the weight-drop method. First, through TMT-proteomics, we screened for the change in the proteins expression profile acute phase post-TBI. The DAVID and Reactome databases were used to analyze and visualize the dysregulation proteins. Then, using publicly available microarray datasets GSE45997, differentially expressed genes (DGEs) were identified for the 24 h post-TBI stage. Also, the proteomic data were compared with microarray data to analyze the similarity.

KEY FINDINGS

We found significant proteomics and transcriptomic changes in post-TBI samples. 989, 881, 832, 1057 proteins were quantitated at 1 h, 6 h, 24 h, and 3 d post-injury correspondingly. Concerning proteomics findings, oxygen transport, acute-phase response, and negative regulation of endopeptidase activity were influenced throughout the acute phrase of TBI. Also, pathways related to scavenging of heme from plasma, binding, and uptake of ligands by scavenger receptors were highly enriched in all time-points of TBI samples.

SIGNIFICANCE

We noticed that the interaction-networks trend to get complicated with more node connections following the progression of TBI. We inferred that Hk-1, PRKAR2A, and MBP could be novel candidate biomarkers related to time-injury in acute-phase TBI. Also, Ceruloplasmin and Complement C3 were found to be important proteins and genes are involved in the TBI.

Functional connectivity of the anterior cingulate cortex in Veterans with mild traumatic brain injury

BACKGROUND

Traumatic brain injury (TBI) is one of the most prevalent injuries in the military with mild traumatic brain injury (mTBI) accounting for approximately 70-80 % of all TBI. TBI has been associated with diffuse and focal brain changes to structures and networks underlying cognitive-emotional processing. Although the anterior cingulate cortex (ACC) plays a critical role in emotion regulation and executive function and is susceptible to mTBI, studies focusing on ACC resting state functional connectivity (rs-fc) in Veterans are limited.

METHODS

Veterans with mTBI (n = 49) and with no history of TBI (n = 25), ages 20-54 completed clinical assessments and an 8-minute resting state functional magnetic resonance imaging (rs-fMRI) on a 3 T Siemens scanner. Imaging results were analyzed with left and right ACC as seed regions using SPM8. Regression analyses were performed with time since injury.

RESULTS

Seed-based analysis showed increased connectivity of the left and right ACC with brain regions including middle and posterior cingulate regions, preceneus, and occipital regions in the mTBI compared to the non-TBI group.

CONCLUSIONS

The rs-fMRI results indicate hyperconnectivity in Veterans with mTBI. These results are consistent with previous studies of recently concussed athletes showing ACC hyperconnectivity. Enhanced top-down control of attention networks necessary to compensate for the microstructural damage following mTBI may explain ACC hyperconnectivity post-mTBI.

Radiographic and neurobehavioral profile of sports-related concussion associated with scholastic wrestling: a case report

Sports-related concussions (SRCs) are typically characterized by transient neurologic deficits due to physiologic and metabolic brain injury. However, following an SRC, subsequent insults may lead to severe and permanent injury in the affected brain cells. We present the case of a 15-year-old female scholastic wrestler who developed acute encephalopathy, macroscopic white matter injury on imaging, and chronic behavioral changes from inadequate neuro-recovery after a documented SRC. We also compare her case with established SRC data, demonstrating that wrestling-related concussions and repetitive head impacts can produce similar degrees of diffuse neuroinflammation, myelinated axonopathy, blood-brain barrier disruption, and post-concussive symptoms.

Association of White Matter Rarefaction, Arteriolosclerosis, and Tau With Dementia in Chronic Traumatic Encephalopathy

IMPORTANCE

Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease associated with repetitive head impacts, including those from US football, that presents with cognitive and neuropsychiatric disturbances that can progress to dementia. Pathways to dementia in CTE are unclear and likely involve tau and nontau pathologic conditions.

OBJECTIVE

To investigate the association of white matter rarefaction and cerebrovascular disease with dementia in deceased men older than 40 years who played football and had CTE.

DESIGN, SETTING, AND PARTICIPANTS

This cross-sectional study involves analyses of data from the ongoing Understanding Neurologic Injury and Traumatic Encephalopathy (UNITE) Study, which is conducted via and included brain donors from the Veterans Affairs-Boston University-Concussion Legacy Foundation brain bank between 2008 and 2017. An original sample of 224 men who had played football and were neuropathologically diagnosed with CTE was reduced after exclusion of those younger than 40 years and those missing data.

EXPOSURES

The number of years of football play as a proxy for repetitive head impacts.

MAIN OUTCOMES AND MEASURES

Neuropathological assessment of white matter rarefaction and arteriolosclerosis severity (on a scale of 0-3, where 3 is severe); number of infarcts, microinfarcts, and microbleeds; and phosphorylated tau accumulation determined by CTE stage and semiquantitative rating of dorsolateral frontal cortex (DLFC) neurofibrillary tangles (NFTs) (none or mild vs moderate or severe). Informant-based retrospective clinical interviews determined dementia diagnoses via diagnostic consensus conferences.

RESULTS

A total of 180 men were included. The mean (SD) age of the sample at death was 67.9 (12.7) years. Of 180, 120 [66.7%]) were found to have had dementia prior to death. Moderate to severe white matter rarefaction (84 of 180 [46.6%]) and arteriolosclerosis (85 of 180 [47.2%]) were common; infarcts, microinfarcts, and microbleeds were not. A simultaneous equations regression model controlling for age and race showed that more years of play was associated with more severe white matter rarefaction (β, 0.16 [95% CI, 0.02-0.29]; P = .03) and greater phosphorylated tau accumulation (DLFC NFTs: β, 0.15 [95% CI, 0.004-0.30]; P = .04; CTE stage: β, 0.27 [95% CI, 0.14-0.41]; P < .001). White matter rarefaction (β, 0.16 [95% CI, 0.02-0.29]; P = .03) and DLFC NFTs (β, 0.16 [95% CI, 0.03-0.28]; P = .01) were associated with dementia. Arteriolosclerosis and years of play were not associated, but arteriolosclerosis was independently associated with dementia (β, 0.21 [95% CI, 0.07-0.35]; P = .003).

CONCLUSIONS AND RELEVANCE

Among older men who had played football and had CTE, more years of football play were associated with more severe white matter rarefaction and greater DLFC NFT burden. White matter rarefaction, arteriolosclerosis, and DLFC NFTs were independently associated with dementia. Dementia in CTE is likely a result of neuropathologic changes, including white matter rarefaction and phosphorylated tau, associated with repetitive head impact and pathologic changes not associated with head trauma, such as arteriolosclerosis.

Differences in pathological changes between two rat models of severe traumatic brain injury

The rat high-impact free weight drop model mimics the diffuse axonal injury caused by severe traumatic brain injury in humans, while severe controlled cortical impact can produce a severe traumatic brain injury model using precise strike parameters. In this study, we compare the pathological mechanisms and pathological changes between two rat severe brain injury models to identify the similarities and differences. The severe controlled cortical impact model was produced by an electronic controlled cortical impact device, while the severe free weight drop model was produced by dropping a 500 g free weight from a height of 1.8 m through a plastic tube. Body temperature and mortality were recorded, and neurological deficits were assessed with the modified neurological severity score. Brain edema and blood-brain barrier damage were evaluated by assessing brain water content and Evans blue extravasation. In addition, a cytokine array kit was used to detect inflammatory cytokines. Neuronal apoptosis in the brain and brainstem was quantified by immunofluorescence staining. Both the severe controlled cortical impact and severe free weight drop models exhibited significant neurological impairments and body temperature fluctuations. More severe motor dysfunction was observed in the severe controlled cortical impact model, while more severe cognitive dysfunction was observed in the severe free weight drop model. Brain edema, inflammatory cytokine changes and cortical neuronal apoptosis were more substantial and blood-brain barrier damage was more focal in the severe controlled cortical impact group compared with the severe free weight drop group. The severe free weight drop model presented with more significant apoptosis in the brainstem and diffused blood-brain barrier damage, with higher mortality and lower repeatability compared with the severe controlled cortical impact group. Severe brainstem damage was not found in the severe controlled cortical impact model. These results indicate that the severe controlled cortical impact model is relatively more stable, more reproducible, and shows obvious cerebral pathological changes at an earlier stage. Therefore, the severe controlled cortical impact model is likely more suitable for studies on severe focal traumatic brain injury, while the severe free weight drop model may be more apt for studies on diffuse axonal injury. All experimental procedures were approved by the Ethics Committee of Animal Experiments of Tianjin Medical University, China (approval No. IRB2012-028-02) in February 2012.