Update of neuropathology and neurological recovery after traumatic brain injury

Efficacy of biomarkers and imaging techniques for the diagnosis of traumatic brain injury: challenges and opportunities

Concussion is a pervasive health issue in the present day. Increased prevalence in recent years has indicated a need to improve the current understanding of minor traumatic brain injury (mTBI). Effort has been devoted to understanding the underlying pathophysiology of TBIs, but some mechanisms remain unknown. Potentially lethal secondary effects of concussion include second impact syndrome and chronic traumatic encephalopathy (CTE), introducing long-term considerations for the management of mTBI. Post-concussion syndrome is another long-term consequence of concussion and may be influenced by both neuroinflammation and hormonal imbalances resulting from head trauma. Genetically mutated apolipoprotein E may also contribute to the severity and persistence of concussion symptoms, perhaps even acting as a risk factor for CTE. As it stands, the diagnosis of concussion is nuanced, depending primarily on subjective diagnostic tools that incorporate patient-reported symptoms and neurocognitive tests. Diagnostic tools provide some assistance in concussion diagnosis, but still lack accuracy and inherently leave room for uncertainty. To mitigate some of this uncertainty, considerable research has been devoted to the development of methods to diagnose concussions objectively. Biomarkers such as S100 calcium binding protein B (S100B), glial fibrillary acidic protein (GFAP), neurofilament light protein (Nf-L), interleukin-6 (IL-6) and microRNAs (miRNAs) as well as imaging techniques including diffusion tensor imaging (DTI) and blood-oxygen level dependent functional magnetic resonance imaging (BOLD-fMRI) show great promise in this regard. This review aims to compile the relevant literature in these areas in the hopes of being used as a reference point for future research regarding concussions.

Traumatic Brain Injury and Chronic Traumatic Encephalopathy: Not Only Trigger for Neurodegeneration but Also for Cerebral Amyloid Angiopathy?

Traumatic brain injury (TBI) has been linked to the development of neurodegenerative diseases, particularly Alzheimer's disease (AD) and chronic traumatic encephalopathy (CTE). This review critically assesses the relationship between TBI and cerebral amyloid angiopathy (CAA), highlighting the complexities of diagnosing CAA in the context of prior head trauma. While TBI has been shown to facilitate the accumulation of amyloid plaques and tau pathology, the interplay between neurodegenerative processes and vascular contributions remains underexplored. Epidemiological studies indicate that TBI increases the risk of various dementias, not solely AD, emphasizing the need for a comprehensive understanding of TBI-related neurodegeneration as a polypathological condition. This review further delineates the mechanisms by which TBI can lead to CAA, particularly focusing on the vascular changes that occur post-injury. It discusses the challenges associated with diagnosing CAA after TBI, particularly due to the overlapping symptoms and pathologies that complicate clinical evaluations. Notably, this review includes a clinical case that exemplifies the diagnostic challenges posed by TBI in patients with subsequent cognitive decline and vascular pathology. By synthesizing current research on TBI, CAA, and associated neurodegenerative conditions, this review aims to foster a more nuanced understanding of how these conditions interact and contribute to long-term cognitive outcomes. The findings underscore the importance of developing standardized diagnostic criteria and imaging techniques to better elucidate the relationship between TBI and vascular pathology, which could enhance clinical interventions and inform therapeutic strategies for affected individuals.

Longitudinal multimodal neuroimaging after traumatic brain injury

Traumatic brain injury is a major cause of long-term cognitive impairment, yet the mechanisms underlying recovery remain poorly understood. Neuroimaging methods such as diffusion MRI, functional MRI, and positron emission tomography (PET) provide insight into micro- and macro-scale changes post-TBI, but the relationships between regional cellular and functional alterations remain unclear. In this study, we conducted a longitudinal, multimodal neuroimaging analysis quantifying TBI-related pathologies in four biomarkers, namely flumazenil PET derived binding potential, dMRI-derived structural connectivity, and resting-state fMRI-derived functional connectivity and fractional amplitude of low-frequency fluctuations in individuals with mild-to-severe brain injury at the subacute (4-6 months post-injury) and chronic (1-year postinjury) stages. Brain injury related regional pathologies, and their changes over time, were correlated across the four biomarkers. Our results reveal complex, dynamic changes over time. We found that flumazenil-PET binding potential was significantly reduced in frontal and thalamic regions in brain injured subjects, consistent with neuronal loss, with partial recovery over time. Functional hyperconnectivity was observed in brain injured subjects initially but declined while remaining elevated compared to non-injured controls, whereas cortical structural hypoconnectivity persisted. Importantly, we observed that brain injury related alterations across MRI modalities became more strongly correlated with flumazenil-PET at the chronic stage. Regions with chronic reductions in flumazenil-PET binding also showed weaker structural node strength and lower amplitude of low frequency fluctuations, a relationship that was not found at the subacute stage. This observation could suggest a progressive convergence of structural and functional disruptions with neuronal loss over time. Additionally, regions with declining structural node strength also exhibited decreases in functional node strength, while these same regions showed increased amplitude of low frequency fluctuations over time. This pattern suggests that heightened intrinsic regional activity may serve as a compensatory mechanism in regions increasingly disconnected due to progressive axonal degradation. Altogether, these findings advance our understanding of how multimodal neuroimaging captures the evolving interplay between neuronal integrity, structural connectivity, and functional dynamics after brain injury. Clarifying these interrelationships could inform prognostic models and enhance knowledge of degenerative, compensatory, and recovery mechanisms in traumatic brain injury.

Unexplained Coma and Sudden Death in Psychiatric Patients Due to Self-Induced Water Intoxication: Clinical Insights and Autopsy Findings From Two Fatal Cases

Self-induced water intoxication is a life-threatening condition caused by excessive water intake that surpasses renal excretion capacity, resulting in hypotonic hyponatremia. This acute imbalance leads to cerebral and pulmonary edema, neurological deterioration, and potentially fatal outcomes. Psychiatric disorders such as schizophrenia and postpartum psychosis are significant contributors, often driving these behaviors through unique psychopathological mechanisms exacerbated by inadequate patient supervision. This study presents two fatal cases. The first involves a 42-year-old woman with chronic schizophrenia and psychogenic polydipsia, whose condition progressed gradually, allowing partial therapeutic intervention. The second describes a 28-year-old woman with postpartum psychosis and compulsive water drinking linked to religious delusions, whose condition deteriorated rapidly, leading to cardiopulmonary arrest shortly after admission. Both cases highlight the connection between psychiatric disorders and severe hyponatremia (<120 mmol/L), resulting in irreversible brain damage and sudden death. Autopsy findings revealed diffuse cerebral edema, pulmonary congestion, and diffuse axonal injury with reactive astrogliosis, demonstrating the severe impact of electrolyte imbalances on neuronal damage. Neuropathological findings, such as ubiquitin-positive axonal swellings and astrocytic activation, underscore the critical role of ionic homeostasis disruption in bridging clinical and autopsy observations. These cases highlight the importance of early recognition of psychogenic polydipsia and compulsive water-drinking behaviors, particularly in high-risk psychiatric patients. Preventative strategies should include routine electrolyte monitoring, caregiver education, and proactive management of psychiatric disorders. Critically, water intoxication must always be considered among the possible causes of unexplained coma or sudden death in psychiatric patients, stressing the need for clinical vigilance and accurate postmortem assessment to improve prevention.

The Role of Nanotechnology in Understanding the Pathophysiology of Traumatic Brain Injury

Recently, traumatic brain injury (TBI) has been a growing disorder due to frequent brain dysfunction. The Glasgow Coma Scale expresses TBI as classified as having mild, moderate, or severe brain effects, according to the effects on the brain. Brain receptors undergo various modifications in their pathology through chemical synaptic pathways, leading to depression, Alzheimer's, and Parkinson's disease. These brain disorders can be controlled using central receptors such as dopamine, glutamate, and γ-aminobutyric acid, which are clearly explained in this review. Furthermore, there are many complications in TBI's clinical trials and diagnostics, leading to insignificant treatment, causing permanent neuro-damage, physical disability, and even death. Bio-screening and conventional molecular-based therapies are inappropriate due to poor preclinical testing and delayed recovery. Hence, modern nanotechnology utilizing nanopulsed laser therapy and advanced nanoparticle insertion will be suitable for TBI's diagnostics and treatment. In recent days, nanotechnology has an important role in TBI control and provides a higher success rate than conventional therapies. This review highlights the pathophysiology of TBI by comprising the drawbacks of conventional techniques and supports suitable modern alternates for treating TBI.

Traumatic brain injury and disorders of consciousness

Trauma is one of the most common causes of disorders of consciousness (DOC) worldwide. Traumatic brain injury (TBI) leads to heterogeneous, multifocal injury via focal brain damage and diffuse axonal injury, causing an acquired network disorder. Recovery occurs through reemergence of dynamic cortical and subcortical networks. Accurate diagnostic evaluation is essential toward promoting recovery and may be more challenging in traumatic than non-traumatic brain injuries. Standardized neurobehavioral assessment is the cornerstone for assessments in the acute, prolonged, and chronic phases of traumatic DOC, while structural and functional neuroimaging, tractography, nuclear medicine studies, and electrophysiologic techniques assist with differentiation of DOC states and prognostication. Prognosis for recovery is better for patients with TBI than those with non-traumatic brain injuries, and the timeline for recovery is longer. The majority of patients experience improvement in their DOC within the first year post-injury, but recovery can continue for five and even ten years after TBI. Pharmacologic therapy and device-related neuromodulation represent important areas for future research.

Traumatic Brain Injury as a Public Health Issue: Epidemiology, Prognostic Factors and Useful Data from Forensic Practice

Traumatic brain injury (TBI) represents a major public health problem, being a leading cause of disability and mortality among young people in developed countries. Head trauma occurs across all age groups, each experiencing consistently high rates of mortality and disability. This review aims to present an overview of TBI epidemiology and its socioeconomic impact, alongside data valuable for prevention, clinical management, and research efforts. Methods: A narrative review of TBI was performed with a particular focus on forensic pathology and public health. In fact, this review highlighted the economic and epidemiological aspects of TBI, as well as autopsy, histology, immunohistochemistry, and miRNA. Results: These data, together with immunohistochemical markers, are crucial for histopathological diagnosis and to determine the timing of injury onset, a fundamental aspect in forensic pathology practice. There is compelling evidence that brain injury biomarkers may enhance predictive models for clinical and prognostic outcomes. By clarifying the cause of death and providing details on survival time after trauma, forensic tools offer valuable information to improve the clinical management of TBI and guide preventive interventions. Conclusions: TBI is one of the most common causes of death today, with high costs for health care spending. Knowing the different mechanisms of TBI, reduces health care costs and helps improve prognosis.

Analysis of the correlation and influencing factors between delirium, sleep, self-efficacy, anxiety, and depression in patients with traumatic brain injury: a cohort study

Background

Patients with traumatic brain injury (TBI) often experience post-injury anxiety and depression, which can persist over time. However, the relationships between anxiety and depression in TBI patients and delirium, sleep quality, self-efficacy, and serum inflammatory markers require further investigation.

Objective

This study aims to explore the associations of delirium, sleep quality, self-efficacy, and serum inflammatory markers with anxiety and depression in TBI patients, and to examine potential influencing factors.

Methods

We conducted a cohort study involving 127 patients with TBI. Delirium was assessed using the Confusion Assessment Method (CAM) and CAM-ICU, while anxiety, depression, sleep quality, self-efficacy, and pain were evaluated using the appropriate tools, respectively. Serum inflammatory markers (CRP, TNF-α, IL-6) were collected within 1 day post-injury. Generalized estimating equations (GEE) were used to analyze the relationships between delirium, sleep, self-efficacy, and anxiety/depression.

Results

The study identified 56 patients with delirium. Patients with delirium differed significantly from those without delirium in age, TBI classification, sleep duration, CRP levels, TNF-α levels, pain, self-efficacy, and insomnia (P < 0.05). The GEE analysis revealed that delirium, CRP levels, self-efficacy, underlying diseases, insomnia, TBI classification, age, and sleep duration were associated with anxiety symptoms in TBI patients at 6 months post-discharge (P < 0.05). Depression in TBI patients at 6 months post-discharge was not associated with delirium or insomnia but correlated with CRP levels, TBI classification, and self-efficacy (P < 0.05).

Conclusion

TBI patients who experience delirium, insomnia, and low self-efficacy during the acute phase are likely to exhibit more anxiety at the 6-month follow-up. Depression in TBI patients is not associated with delirium or insomnia but is negatively correlated with self-efficacy. CRP levels post-TBI may serve as a biomarker to identify patients at risk of emotional symptoms and potentially accelerate patient recovery.

Traumatic brain injury: molecular biomarkers, genetics, secondary consequences, and medical management

Traumatic brain injury (TBI) has reached epidemic proportions worldwide. The consequences of TBI can be severe even with repetitive mild trauma. If death and coma are avoided, the consequences of TBI in the long term typically involve dizziness, sleep disturbances, headache, seizures, cognitive impairment, focal deficits, depression, and anxiety. The severity of brain injury is a significant predictor of outcome. However, the heterogenous nature of the injury makes prognosis difficult. The present review of the literature focuses on the genetics of TBI including genome wide (GWAS) data and candidate gene associations, among them brain-derived neurotrophic factor (BDNF) with TBI and development of post-traumatic epilepsy (PTE). Molecular biomarkers of TBI are also discussed with a focus on proteins and the inflammatory protein IL1-β. The secondary medical sequela to TBI of cognitive impairment, PTE, headache and risk for neurodegenerative disorders is also discussed. This overview of TBI concludes with a review and discussion of the medical management of TBI and the medicines used for and being developed at the preclinical and clinical stages for the treatment of TBI and its host of life-debilitating symptoms.

Actomyosin-II protects axons from degeneration induced by mild mechanical stress

Whether, to what extent, and how the axons in the central nervous system (CNS) can withstand sudden mechanical impacts remain unclear. By using a microfluidic device to apply controlled transverse mechanical stress to axons, we determined the stress levels that most axons can withstand and explored their instant responses at nanoscale resolution. We found mild stress triggers a highly reversible, rapid axon beading response, driven by actomyosin-II-dependent dynamic diameter modulations. This mechanism contributes to hindering the long-range spread of stress-induced Ca2+ elevations into non-stressed neuronal regions. Through pharmacological and molecular manipulations in vitro, we found that actomyosin-II inactivation diminishes the reversible beading process, fostering progressive Ca2+ spreading and thereby increasing acute axonal degeneration in stressed axons. Conversely, upregulating actomyosin-II activity prevents the progression of initial injury, protecting stressed axons from acute degeneration both in vitro and in vivo. Our study unveils the periodic actomyosin-II in axon shafts cortex as a novel protective mechanism, shielding neurons from detrimental effects caused by mechanical stress.

Accelerated Aging after Traumatic Brain Injury: An ENIGMA Multi-Cohort Mega-Analysis

OBJECTIVE

The long-term consequences of traumatic brain injury (TBI) on brain structure remain uncertain. Given evidence that a single significant brain injury event increases the risk of dementia, brain-age estimation could provide a novel and efficient indexing of the long-term consequences of TBI. Brain-age procedures use predictive modeling to calculate brain-age scores for an individual using structural magnetic resonance imaging (MRI) data. Complicated mild, moderate, and severe TBI (cmsTBI) is associated with a higher predicted age difference (PAD), but the progression of PAD over time remains unclear. We sought to examine whether PAD increases as a function of time since injury (TSI) and if injury severity and sex interacted to influence this progression.

METHODS

Through the ENIGMA Adult Moderate and Severe (AMS)-TBI working group, we examine the largest TBI sample to date (n = 343), along with controls, for a total sample size of n = 540, to replicate and extend prior findings in the study of TBI brain age. Cross-sectional T1w-MRI data were aggregated across 7 cohorts, and brain age was established using a similar brain age algorithm to prior work in TBI.

RESULTS

Findings show that PAD widens with longer TSI, and there was evidence for differences between sexes in PAD, with men showing more advanced brain age. We did not find strong evidence supporting a link between PAD and cognitive performance.

INTERPRETATION

This work provides evidence that changes in brain structure after cmsTBI are dynamic, with an initial period of change, followed by relative stability in brain morphometry, eventually leading to further changes in the decades after a single cmsTBI. ANN NEUROL 2024;96:365-377.

Outcomes of Decompressive Craniectomy in the Management of Traumatic Brain Injury: A Ten-Year Retrospective Analysis

OBJECTIVE

This study aimed to investigate factors associated with patient outcomes after decompressive craniectomy for severe traumatic brain injury (TBI) and to compare the authors' findings with the existing literature.

METHODS

The authors conducted a retrospective analysis of 50 patients who underwent decompressive craniectomy for severe TBI between 2013 and 2023. Patient characteristics, including age, sex, Glasgow Coma Scale (GCS) score, Injury Severity Score (ISS), electrolyte imbalances, nosocomial infections, and hospital stay duration, were collected. Outcomes were assessed at 12 months postsurgery, and statistical analyses were performed to determine factors associated with favorable and unfavorable outcomes.

RESULTS

Younger age, higher GCS scores, and lower ISS were significantly associated with favorable outcomes. Electrolyte imbalances, particularly hyponatremia, and hyperkalemia, were linked to unfavorable outcomes. Nosocomial infections were significantly more common in patients with unfavorable outcomes. Longer hospital stays were also associated with worse outcomes.

CONCLUSIONS

The authors' findings highlight the importance of individualized patient management based on age, admission GCS score, ISS, electrolyte imbalances, nosocomial infections, and hospital stay duration to maximize the potential for favorable outcomes. These results contribute to the growing literature on decompressive craniectomy for TBI and provide valuable insights for clinicians in optimizing patient management.

Cognitive-communication difficulties due to traumatic brain injury sustained in adults 55 years and older: A survey of speech-language pathology professional practice in Australia

PURPOSE

Limited research informs management of cognitive-communication difficulties following traumatic brain injury (TBI) in older adulthood. The purpose of this study was to understand the characteristics and practice of speech-language pathologists (SLPs) working with people who sustained TBI at ≥55 years and more specifically their management of cognitive-communication difficulties with this population. This included assessment and treatment practices, resource needs, barriers to practice, and impact to service delivery from COVID-19 restrictions.

METHOD

A cross-sectional survey-based design with non-probability sampling of SLPs working in Australia with adults with TBI was utilised. Descriptive statistics and content analysis were used for analysis of survey data.

RESULT

Fifty responses were eligible for inclusion. Participants predominantly worked in inpatient rehabilitation (48%), acute (40%), and community settings (36%). Service delivery to adults who sustained TBI at ≥55 years commonly included cognitive-communication management. Assessment and treatment trends are described. Most SLPs (74%) perceived barriers to cognitive-communication management, often relating to time and funding, that existed prior to the COVID-19 pandemic. Pandemic restrictions presented additional challenges.

CONCLUSION

Research relating to cognitive-communication difficulties following TBI in older adulthood is required to support evidence-based practice and inform services for older adults who sustain TBI.

Gross motor proficiency deficits among children and adolescents post posterior fossa brain tumor removal vs. traumatic brain injury in the chronic phase of recovery: a cross-sectional study

Introduction

Acquired brain injury (ABI) is a prevalent diagnosis in pediatric rehabilitation. Gross motor skills are often affected by ABI and limit the ability to participate in various physical activities. However, as ABI injury location is diverse, children and adolescents (youth) with localized ABI, such as ABI in the posterior fossa (ABI-PF) may present unique and different motor disabilities than youth with ABI on account of traumatic brain injury (TBI).

Aims

The aims of the study were: (1) to compare gross motor deficits in youth with TBI vs. ABI-PF; and (2) to compare two methods on scoring BOT2 to determine which is better for identifying motor deficits.

Methods

Participated in this study youth with TBI (N = 50) and ABI-PF (N = 30). Participants were tested on Bruininks-Oseretsky Test of Motor Proficiency-2nd Edition (BOT2) Upper-Limb Coordination, Balance, Strength, Running Speed and Agility, and Bilateral-Coordination subtests. Motor performance deficits were established using two-standard deviations (2SD) and age-equivalent methods. Between-group differences were assessed via independent t-tests and receiver operating characteristic curves (ROC).

Results

According to the 2SD method, motor deficits in the ABI-PF group ranged from 20% to 66.66%, whereas in the TBI group 8%-16%. According to the age-equivalent method, in the TBI and ABI-PF groups 40%-66.0% and 46.66%-76.66% of the youth presented motor deficits, respectively. Moreover, ROC analysis showed that motor performance deficits of both groups in all sub-scales except for Bilateral Coordination differed enough to result in medium area under the curve.

Conclusions

Motor deficits post-pediatric ABI are prevalent. In comparison to the TBI group, deficits are greater in the ABI-PF group. Moreover, compared to the 2SD method, the extent of motor deficiency is greater in the age-equivalent method. Therefore, using the later might provide a more valid classification of deficits in gross motor proficiency for youth post-ABI.

Functional Hearing Difficulties in Blast-Exposed Service Members With Normal to Near-Normal Hearing Thresholds

OBJECTIVES

Estimated prevalence of functional hearing and communication deficits (FHCDs), characterized by abnormally low speech recognition and binaural tone detection in noise or an abnormally high degree of self-perceived hearing difficulties, dramatically increases in active-duty service members (SMs) who have hearing thresholds slightly above the normal range and self-report to have been close to an explosive blast. Knowing the exact nature of the underlying auditory-processing deficits that contribute to FHCD would not only provide a better characterization of the effects of blast exposure on the human auditory system, but also allow clinicians to prescribe appropriate therapies to treat or manage patient complaints.

DESIGN

Two groups of SMs were initially recruited: (1) a control group (N = 78) with auditory thresholds ≤20 dB HL between 250 and 8000 Hz, no history of blast exposure, and who passed a short FHCD screener, and (2) a group of blast-exposed SMs (N = 26) with normal to near-normal auditory thresholds between 250 and 4000 Hz, and who failed the FHCD screener (cutoffs based on the study by Grant et al.). The two groups were then compared on a variety of audiometric, behavioral, cognitive, and electrophysiological measures. These tests were selected to characterize various aspects of auditory system processing from the cochlear to the cortex. A third, smaller group of blast-exposed SMs who performed within normal limits on the FHCD screener were also recruited (N = 11). This third subject group was unplanned at the onset of the study and was added to evaluate the effects of blast exposure on hearing and communication regardless of performance on the FHCD screener.

RESULTS

SMs in the blast-exposed group with FHCD performed significantly worse than control participants on several metrics that measured peripheral and mostly subcortical auditory processing. Cognitive processing was mostly unaffected by blast exposure with the exception of cognitive tests of language-processing speed and working memory. Blast-exposed SMs without FHCD performed similarly to the control group on tests of peripheral and brainstem processing, but performed similarly to blast-exposed SMs with FHCD on measures of cognitive processing. Measures derived from EEG recordings of the frequency-following response revealed that blast-exposed SMs who exhibited FHCD demonstrated increased spontaneous neural activity, reduced amplitude of the envelope-following response, poor internal signal to noise ratio, reduced response stability, and an absent or delayed onset response, compared with the other two participant groups.

CONCLUSIONS

Degradation in the neural encoding of acoustic stimuli is likely a major contributing factor leading to FHCD in blast-exposed SMs with normal to near-normal audiometric thresholds. Blast-exposed SMs, regardless of their performance on the FHCD screener, exhibited a deficit in language-processing speed and working memory, which could lead to difficulties in decoding rapid speech and in understanding speech in challenging speech communication settings. Further tests are needed to align these findings with clinical treatment protocols being used for patients with suspected auditory-processing disorders.

Prevention and treatment of traumatic brain injury-related delirium: a systematic review

BACKGROUND

Our systematic review examines the effectiveness and safety of non-pharmacologic and pharmacologic interventions in preventing or treating traumatic brain injury (TBI)-related delirium in acute care.

METHODS

We searched four electronic databases (MEDLINE, EMBASE, CENTRAL/CDSR, and PsycINFO) to identify randomized controlled trials (RCTs), quasi-experimental, and observational studies. Eligible studies included adults with TBI, at least one comparator group, delirium as an outcome and took place in acute care. Two reviewers independently completed all study screening, data abstraction, and risk of bias assessment using the Cochrane risk of bias 2 tool for RCTs or risk of bias in non-randomized studies-of interventions tool for observational studies. We implemented the PROGRESS-Plus framework to describe social determinants of health (SDoH) reporting.

RESULTS

We identified 20,022 citations, reviewed 301 in full text, and included eight studies in the descriptive synthesis. The mean age of study participants ranged from 32 to 62 years. 12.5% of included studies reported SDoH. Included studies had moderate-to-high risk of bias. Studies compared reorientation programs and an intervention bundle to usual care, but these interventions were not better than usual care in treating TBI-related delirium. Individual studies found that rosuvastatin and aripiprazole were more efficacious than placebo, and dexmedetomidine was more efficacious than propofol and haloperidol for preventing TBI-related delirium. No studies reported safety as the primary outcome.

CONCLUSIONS

We identified efficacious pharmacologic interventions for preventing TBI-related delirium, but these studies were at moderate-to-high risk of bias, which limits our confidence in these findings. Future studies should incorporate safety outcomes, and a diverse study population, including older adults.

The Relationship Between Cortical Morphological and Functional Topological Properties and Clinical Manifestations in Patients with Posttraumatic Diffuse Axonal Injury: An Individual Brain Network Study

To evaluate the altered network topological properties and their clinical relevance in patients with posttraumatic diffuse axonal injury (DAI). Forty-seven participants were recruited in this study, underwent 3D T1-weighted and resting-state functional MRI, and had single-subject morphological brain networks (MBNs) constructed by Kullback-Leibler divergence and functional brain networks (FBNs) constructed by Pearson correlation measurement interregional similarity. The global and regional properties were analyzed and compared using graph theory and network-based statistics (NBS), and the relationship with clinical manifestations was assessed. Compared with those of the healthy subjects, MBNs of patients with DAI showed a higher path length ([Formula: see text]: P = 0.021, [Formula: see text]: P = 0.011), lower clustering ([Formula: see text]: P = 0.002) and less small-worldness ([Formula: see text]: P = 0.002), but there was no significant difference in the global properties of FBNs (P: 0.161-0.216). For nodal properties of MBNs and FBNs, several regions showed significant differences between patients with DAI and healthy controls (HCs) (P < 0.05, FDR corrected). NBS analysis revealed that MBNs have more altered morphological connections in the frontal parietal control network and interhemispheric connections (P < 0.05). DAI-related global or nodal properties of MBNs were correlated with physical disability or dyscognition (P < 0.05/7, with Bonferroni correction), and the alteration of functional topology properties mediates this relationship. Our results suggested that disrupted morphological topology properties, which are mediated by FBNs and correlated with clinical manifestations of DAI, play a critical role in the short-term and medium-term phases after trauma.

Spatiotemporal profile of atrophy in the first year following moderate-severe traumatic brain injury

Traumatic brain injury (TBI) triggers progressive neurodegeneration resulting in brain atrophy that continues months-to-years following injury. However, a comprehensive characterization of the spatial and temporal evolution of TBI-related brain atrophy remains incomplete. Utilizing a sensitive and unbiased morphometry analysis pipeline optimized for detecting longitudinal changes, we analyzed a sample consisting of 37 individuals with moderate-severe TBI who had primarily high-velocity and high-impact injury mechanisms. They were scanned up to three times during the first year after injury (3 months, 6 months, and 12 months post-injury) and compared with 33 demographically matched controls who were scanned once. Individuals with TBI already showed cortical thinning in frontal and temporal regions and reduced volume in the bilateral thalami at 3 months post-injury. Longitudinally, only a subset of cortical regions in the parietal and occipital lobes showed continued atrophy from 3 to 12 months post-injury. Additionally, cortical white matter volume and nearly all deep gray matter structures exhibited progressive atrophy over this period. Finally, we found that disproportionate atrophy of cortex along sulci relative to gyri, an emerging morphometric marker of chronic TBI, was present as early as 3 month post-injury. In parallel, neurocognitive functioning largely recovered during this period despite this pervasive atrophy. Our findings demonstrate msTBI results in characteristic progressive neurodegeneration patterns that are divergent across regions and scale with the severity of injury. Future clinical research using atrophy during the first year of TBI as a biomarker of neurodegeneration should consider the spatiotemporal profile of atrophy described in this study.

Early Measures of TBI Severity Poorly Predict Later Individual Impairment in a Rat Fluid Percussion Model

BACKGROUND

Multiple measures of injury severity are suggested as common data elements in preclinical traumatic brain injury (TBI) research. The robustness of these measures in characterizing injury severity is unclear. In particular, it is not known how reliably they predict individual outcomes after experimental TBI.

METHODS

We assessed several commonly used measures of initial injury severity for their ability to predict chronic cognitive outcomes in a rat lateral fluid percussion (LFPI) model of TBI. At the time of injury, we assessed reflex righting time, neurologic severity scores, and 24 h weight loss. Sixty days after LFPI, we evaluated working memory using a spontaneous alternation T-maze task.

RESULTS

We found that righting time and weight loss had no correlation to chronic T-maze performance, while neurologic severity score correlated weakly.

DISCUSSION

Taken together, our results indicate that commonly used early measures of injury severity do not robustly predict longer-term outcomes. This finding parallels the uncertainty in predicting individual outcomes in TBI clinical populations.

Towards PPG-based anger detection for emotion regulation

BACKGROUND

Anger dyscontrol is a common issue after traumatic brain injury (TBI). With the growth of wearable physiological sensors, there is new potential to facilitate the rehabilitation of such anger in the context of daily life. This potential, however, depends on how well physiological markers can distinguish changing emotional states and for such markers to generalize to real-world settings. Our study explores how wearable photoplethysmography (PPG), one of the most widely available physiological sensors, could be used detect anger within a heterogeneous population.

METHODS

This study collected the TRIEP (Toronto Rehabilitation Institute Emotion-Physiology) dataset, which comprised of 32 individuals (10 TBI), exposed to a variety of elicitation material (film, pictures, self-statements, personal recall), over two day sessions. This complex dataset allowed for exploration into how the emotion-PPG relationship varied over changes in individuals, endogenous/exogenous drivers of emotion, and day-to-day differences. A multi-stage analysis was conducted looking at: (1) times-series visual clustering, (2) discriminative time-interval features of anger, and (3) out-of-sample anger classification.

RESULTS

Characteristics of PPG are largely dominated by inter-subject (between individuals) differences first, then intra-subject (day-to-day) changes, before differentiation into emotion. Both TBI and non-TBI individuals showed evidence of linear separable features that could differentiate anger from non-anger classes within time-interval analysis. However, what is more challenging is that these separable features for anger have various degrees of stability across individuals and days.

CONCLUSION

This work highlights how there are contextual, non-stationary challenges to the emotion-physiology relationship that must be accounted for before emotion regulation technology can perform in real-world scenarios. It also affirms the need for a larger breadth of emotional sampling when building classification models.

Machine learning classification of chronic traumatic brain injury using diffusion tensor imaging and NODDI: A replication and extension study

Individuals with acute and chronic traumatic brain injury (TBI) are associated with unique white matter (WM) structural abnormalities, including fractional anisotropy (FA) differences. Our research group previously used FA as a feature in a linear support vector machine (SVM) pattern classifier, observing high classification between individuals with and without acute TBI (i.e., an area under the curve [AUC] value of 75.50%). However, it is not known whether FA could similarly classify between individuals with and without history of chronic TBI. Here, we attempted to replicate our previous work with a new sample, investigating whether FA could similarly classify between incarcerated men with (n = 80) and without (n = 80) self-reported history of chronic TBI. Additionally, given limitations associated with FA, including underestimation of FA values in WM tracts containing crossing fibers, we extended upon our previous study by incorporating neurite orientation dispersion and density imaging (NODDI) metrics, including orientation dispersion (ODI) and isotropic volume (Viso). A linear SVM based classification approach, similar to our previous study, was incorporated here to classify between individuals with and without self-reported chronic TBI using FA and NODDI metrics as separate features. Overall classification rates were similar when incorporating FA and NODDI ODI metrics as features (AUC: 82.50%). Additionally, NODDI-based metrics provided the highest sensitivity (ODI: 85.00%) and specificity (Viso: 82.50%) rates. The current study serves as a replication and extension of our previous study, observing that multiple diffusion MRI metrics can reliably classify between individuals with and without self-reported history of chronic TBI.

Comprehensive evaluation of mitochondrial redox profile, calcium dynamics, membrane integrity and apoptosis markers in a preclinical model of severe penetrating traumatic brain injury

Traumatic Brain Injury (TBI) is caused by the external physical assaults damages the brain. It is a heterogeneous disorder that remains a leading cause of death and disability in the military and civilian population of the United States. Preclinical investigations of mitochondrial responses in TBI have ascertained that mitochondrial dysfunction is an acute indicator of cellular damage and plays a pivotal role in long-term injury progression through cellular excitotoxicity. The current study was designed to provide an in-depth evaluation of mitochondrial endpoints with respect to redox and calcium homeostasis, and cell death responses following penetrating TBI (PTBI). To evaluate these pathological cascades, anesthetized adult male rats (N = 6/group) were subjected to either 10% unilateral PTBI or Sham craniectomy. Animals were euthanized at 24 h post-PTBI, and purified mitochondrial fractions were isolated from the brain injury core and perilesional areas. Overall, increased reactive oxygen and nitrogen species (ROS/RNS) production, and elevated oxidative stress markers such as 4-hydroxynonenal (4-HNE), 3-nitrotyrosine (3-NT), and protein carbonyls (PC) were observed in the PTBI group compared to Sham. Mitochondrial antioxidants such as glutathione, peroxiredoxin (PRX-3), thioredoxin (TRX), nicotinamide adenine dinucleotide phosphate (NADPH), superoxide dismutase (SOD), and catalase (CAT) levels were significantly decreased after PTBI. Likewise, PTBI mitochondria displayed significant loss of Ca²⁺ homeostasis, early opening of mitochondrial permeability transition pore (mPTP), and increased mitochondrial swelling. Both, outer and inner mitochondrial membrane integrity markers, such as voltage-dependent anion channels (VDAC) and cytochrome c (Cyt C) expression were significantly decreased following PTBI. The apoptotic cell death was evidenced by significantly decreased B-cell lymphoma-2 (Bcl-2) and increased glyceraldehyde 3-phosphate dehydrogenase (GAPDH) expression after PTBI. Collectively, current results highlight the comprehensive picture of mitochondria-centric acute pathophysiological responses following PTBI, which may be utilized as novel prognostic indicators of disease progression and theragnostic indicators for evaluating neuroprotection therapeutics following TBI.

A model for estimating the brainstem volume in normal healthy individuals and its application to diffuse axonal injury patients

Diffuse axonal injury (DAI) is a subtype of traumatic brain injury that causes acute-phase consciousness disorders and widespread chronic-phase brain atrophy. Considering the importance of brainstem damage in DAI, a valid method for evaluating brainstem volume is required. We obtained volume measurements from 182 healthy adults by analyzing T1-weighted magnetic resonance images, and created an age-/sex-/intracranial volume-based quantitative model to estimate the normal healthy volume of the brainstem and cerebrum. We then applied this model to the volume measurements of 22 DAI patients, most of whom were in the long-term chronic phase and had no gross focal injury, to estimate the percentage difference in volume from the expected normal healthy volume in different brain regions, and investigated its association with the duration of posttraumatic amnesia (which is an early marker of injury severity). The average loss of the whole brainstem was 13.9%. Moreover, the percentage loss of the whole brainstem, and particularly of the pons and midbrain, was significantly negatively correlated with the duration of posttraumatic amnesia. Our findings suggest that injury severity, as denoted by the duration of posttraumatic amnesia, is among the factors affecting the chronic-phase brainstem volume in patients with DAI.

INCOG 2.0 Guidelines for Cognitive Rehabilitation Following Traumatic Brain Injury, Part III: Executive Functions

INTRODUCTION

Moderate-to-severe traumatic brain injury (MS-TBI) causes debilitating and enduring impairments of executive functioning and self-awareness, which clinicians often find challenging to address. Here, we provide an update to the INCOG 2014 guidelines for the clinical management of these impairments.

METHODS

An expert panel of clinicians/researchers (known as INCOG) reviewed evidence published from 2014 and developed updated recommendations for the management of executive functioning and self-awareness post-MS-TBI, as well as a decision-making algorithm, and an audit tool for review of clinical practice.

RESULTS

A total of 8 recommendations are provided regarding executive functioning and self-awareness. Since INCOG 2014, 4 new recommendations were made and 4 were modified and updated from previous recommendations. Six recommendations are based on level A evidence, and 2 are based on level C. Recommendations retained from the previous guidelines and updated, where new evidence was available, focus on enhancement of self-awareness (eg, feedback to increase self-monitoring; training with video-feedback), meta-cognitive strategy instruction (eg, goal management training), enhancement of reasoning skills, and group-based treatments. New recommendations addressing music therapy, virtual therapy, telerehabilitation-delivered metacognitive strategies, and caution regarding other group-based telerehabilitation (due to a lack of evidence) have been made.

CONCLUSIONS

Effective management of impairments in executive functioning can increase the success and well-being of individuals with MS-TBI in their day-to-day lives. These guidelines provide management recommendations based on the latest evidence, with support for their implementation, and encourage researchers to explore and validate additional factors such as predictors of treatment response.

INCOG 2.0 Guidelines for Cognitive Rehabilitation Following Traumatic Brain Injury, Part II: Attention and Information Processing Speed

INTRODUCTION

Moderate to severe traumatic brain injury (MS-TBI) commonly causes disruption in aspects of attention due to its diffuse nature and injury to frontotemporal and midbrain reticular activating systems. Attentional impairments are a common focus of cognitive rehabilitation, and increased awareness of evidence is needed to facilitate informed clinical practice.

METHODS

An expert panel of clinicians/researchers (known as INCOG) reviewed evidence published from 2014 and developed updated guidelines for the management of attention in adults, as well as a decision-making algorithm, and an audit tool for review of clinical practice.

RESULTS

This update incorporated 27 studies and made 11 recommendations. Two new recommendations regarding transcranial stimulation and an herbal supplement were made. Five were updated from INCOG 2014 and 4 were unchanged. The team recommends screening for and addressing factors contributing to attentional problems, including hearing, vision, fatigue, sleep-wake disturbance, anxiety, depression, pain, substance use, and medication. Metacognitive strategy training focused on everyday activities is recommended for individuals with mild-moderate attentional impairments. Practice on de-contextualized computer-based attentional tasks is not recommended because of lack of evidence of generalization, but direct training on everyday tasks, including dual tasks or dealing with background noise, may lead to gains for performance of those tasks. Potential usefulness of environmental modifications is also discussed. There is insufficient evidence to support mindfulness-based meditation, periodic alerting, or noninvasive brain stimulation for alleviating attentional impairments. Of pharmacological interventions, methylphenidate is recommended to improve information processing speed. Amantadine may facilitate arousal in comatose or vegetative patients but does not enhance performance on attentional measures over the longer term. The antioxidant Chinese herbal supplement MLC901 (NeuroAiD IITM) may enhance selective attention in individuals with mild-moderate TBI.

CONCLUSION

Evidence for interventions to improve attention after TBI is slowly growing. However, more controlled trials are needed, especially evaluating behavioral or nonpharmacological interventions for attention.

Age-Based Trends in Cognitive-Communication Management for Adults in Subacute Rehabilitation Following New Onset Traumatic Brain Injury

PURPOSE

Although traumatic brain injury (TBI) has a disproportionate impact on older adults, there has been limited inclusion of these individuals in post-TBI cognitive-communication research. This study was undertaken to compare demographic and injury characteristics, speech-language pathology input, and broad outcomes for younger and older adults admitted to inpatient rehabilitation following TBI.

METHOD

A retrospective audit of first occasion adult TBI admissions in 2019 to inpatient rehabilitation in an Australian metropolitan subacute hospital was conducted via medical record data. Admissions were located using International Statistical Classification of Diseases, Tenth Revision, Australian Modification (ICD-10-AM) coding that aligned with TBI. Comparisons were made for younger (18-54 years) and older (≥ 55 years) adults.

RESULTS

A total of 114 admissions (51.75% older adults) were included. Patient age ranged between 18 and 90 years. Falls caused TBI in the majority of older adults, whereas transport-related accidents were the most common cause for younger adults. Age-based trends for intracranial injury were observed. Cognitive-communication difficulties were the most common speech-language pathology diagnosis with no significant difference in prevalence between younger and older adults. Age group was not significantly associated with length of stay or discharge home.

CONCLUSIONS

The implications of injury-related trends for older adults on post-TBI cognitive-communication are poorly understood. This lack of information is problematic given the frequency of cognitive-communication difficulties in this population. Research into cognitive-communication following new onset TBI in older adults is crucial to support rehabilitation service provision and improve outcomes for older adults.

Relationships between predisposing, precipitating, and perpetuating factors and executive functioning following mild traumatic brain injury

INTRODUCTION

The aim of this study was to determine the sociodemographic and MTBI-related variables associated with executive functioning (EF).

METHODS

Based on the theoretical model of Hou and colleagues, data on predisposing (age, education, premorbid IQ), precipitating (post-traumatic amnesia, loss of consciousness, presence of frontal lesions, post-accident time to evaluation) and perpetuating (anxious and depressive affects and post-concussive symptoms) factors were retrospectively collected from the medical records of 172 patients with MTBI. EF data based on the 3 processes included in Miyake's prediction model (2000) (updating, cognitive flexibility and inhibition) were collected using respectively the Digit span task of the Weschler - 4^th edition, the Trails A and B as well as the initiation time on the Tower of London- Drexel University.

RESULTS

Updating was significantly associated with education, premorbid IQ, age, anxiety, and depressive affect. Inhibition was associated with education and age. No variable was associated with cognitive flexibility.

CONCLUSIONS

Following a MTBI, clinicians should consider that level of education and pre-morbid IQ may "predispose" patients to higher EF performances. They should also measure level of anxiety and depressive affect knowing that these may "perpetuate" some EF impairments (specifically the updating process).

Connectomic assessment of injury burden and longitudinal structural network alterations in moderate-to-severe traumatic brain injury

Traumatic brain injury (TBI) is a major public health problem. Caused by external mechanical forces, a major characteristic of TBI is the shearing of axons across the white matter, which causes structural connectivity disruptions between brain regions. This diffuse injury leads to cognitive deficits, frequently requiring rehabilitation. Heterogeneity is another characteristic of TBI as severity and cognitive sequelae of the disease have a wide variation across patients, posing a big challenge for treatment. Thus, measures assessing network-wide structural connectivity disruptions in TBI are necessary to quantify injury burden of individuals, which would help in achieving personalized treatment, patient monitoring, and rehabilitation planning. Despite TBI being a disconnectivity syndrome, connectomic assessment of structural disconnectivity has been relatively limited. In this study, we propose a novel connectomic measure that we call network normality score (NNS) to capture the integrity of structural connectivity in TBI patients by leveraging two major characteristics of the disease: diffuseness of axonal injury and heterogeneity of the disease. Over a longitudinal cohort of moderate-to-severe TBI patients, we demonstrate that structural network topology of patients is more heterogeneous and significantly different than that of healthy controls at 3 months postinjury, where dissimilarity further increases up to 12 months. We also show that NNS captures injury burden as quantified by posttraumatic amnesia and that alterations in the structural brain network is not related to cognitive recovery. Finally, we compare NNS to major graph theory measures used in TBI literature and demonstrate the superiority of NNS in characterizing the disease.

The Role of Neuroinflammation in Neuropsychiatric Disorders Following Traumatic Brain Injury: A Systematic Review

BACKGROUND

Neuropsychiatric symptoms are common following traumatic brain injury (TBI), but their etiological onset remains unclear. Mental health research implicates neuroinflammation in the development of psychiatric disorders. The presence of neuroinflammatory responses after TBI thus prompts an investigation of their involvement in the emergence of neuropsychiatric disorders postinjury.

OBJECTIVE

Review the literature surrounding the role of neuroinflammation and immune response post-TBI in the development of neuropsychiatric disorders.

METHODS

A search of scientific databases was conducted for original, empirical studies in human subjects. Key words such as "neuroinflammation," "TBI," and "depression" were used to identify psychopathology as an outcome TBI and the relation to neuroinflammatory response.

RESULTS

Study results provide evidence of neuroinflammation mediated post-TBI neuropsychiatric disorders including anxiety, trauma/stress, and depression. Inflammatory processes and stress response dysregulation can lead to secondary cell damage, which promote the development and maintenance of neuropsychiatric disorders postinjury.

CONCLUSION

This review identifies both theoretical and empirical support for neuroinflammatory response as feasible mechanisms underlying neuropsychiatric disorders after TBI. Further understanding of these processes in this context has significant clinical implications for guiding the development of novel treatments to reduce psychiatric symptoms postinjury. Future directions to address current limitations in the literature are discussed.

White matter abnormalities characterize the acute stage of sports-related mild traumatic brain injury

Sports-related concussion, a form of mild traumatic brain injury, is characterized by transient disturbances of brain function. There is increasing evidence that functional brain changes may be driven by subtle abnormalities in white matter microstructure, and diffusion MRI has been instrumental in demonstrating these white matter abnormalities in vivo. However, the reported location and direction of the observed white matter changes in mild traumatic brain injury are variable, likely attributable to the inherent limitations of the white matter models used. This cross-sectional study applies an advanced and robust technique known as fixel-based analysis to investigate fibre tract-specific abnormalities in professional Australian Football League players with a recent mild traumatic brain injury. We used the fixel-based analysis framework to identify common abnormalities found in specific fibre tracts in participants with an acute injury (≤12 days after injury; n = 14). We then assessed whether similar changes exist in subacute injury (&gt;12 days and &lt;3 months after injury; n = 15). The control group was 29 neurologically healthy control participants. We assessed microstructural differences in fibre density and fibre bundle morphology and performed whole-brain fixel-based analysis to compare groups. Subsequent tract-of-interest analyses were performed within five selected white matter tracts to investigate the relationship between the observed tract-specific abnormalities and days since injury and the relationship between these tract-specific changes with cognitive abnormalities. Our whole-brain analyses revealed significant increases in fibre density and bundle cross-section in the acute mild traumatic brain injury group when compared with controls. The acute mild traumatic brain injury group showed even more extensive differences when compared with the subacute injury group than with controls. The fibre structures affected in acute concussion included the corpus callosum, left prefrontal and left parahippocampal white matter. The fibre density and cross-sectional increases were independent of time since injury in the acute injury group, and were not associated with cognitive deficits. Overall, this study demonstrates that acute mild traumatic brain injury is characterized by specific white matter abnormalities, which are compatible with tract-specific cytotoxic oedema. These potential oedematous changes were absent in our subacute mild traumatic brain injury participants, suggesting that they may normalize within 12 days after injury, although subtle abnormalities may persist in the subacute stage. Future longitudinal studies are needed to elucidate individualized recovery after brain injury.

The Outcome of Neurorehabilitation Efficacy and Management of Traumatic Brain Injury

For public health professionals, traumatic brain injury (TBI) and its possible protracted repercussions are a significant source of worry. In opposed to patient neurorehabilitation with developed brain abnormalities of different etiologies, neurorehabilitation of affected persons has several distinct features. The clinical repercussions of the various types of TBI injuries will be discussed in detail in this paper. During severe TBI, the medical course frequently follows a familiar first sequence of coma, accompanied by disordered awareness, followed by agitation and forgetfulness, followed by return of function. Clinicians must be aware of common medical issues that might occur throughout the various stages of neurorehabilitation, for example, posttraumatic hydrocephalus, paroxysmal sympathetic hyperactivity and posttraumatic neuroendocrine disorders, at each step of the process. Furthermore, we address problems about the scheduling of various rehabilitation programs as well as the availability of current data for comprehensive rehabilitative neuropsychology techniques.

Brain-wide reconstruction of inhibitory circuits after traumatic brain injury

Despite the fundamental importance of understanding the brain's wiring diagram, our knowledge of how neuronal connectivity is rewired by traumatic brain injury remains remarkably incomplete. Here we use cellular resolution whole-brain imaging to generate brain-wide maps of the input to inhibitory neurons in a mouse model of traumatic brain injury. We find that somatostatin interneurons are converted into hyperconnected hubs in multiple brain regions, with rich local network connections but diminished long-range inputs, even at areas not directly damaged. The loss of long-range input does not correlate with cell loss in distant brain regions. Interneurons transplanted into the injury site receive orthotopic local and long-range input, suggesting the machinery for establishing distant connections remains intact even after a severe injury. Our results uncover a potential strategy to sustain and optimize inhibition after traumatic brain injury that involves spatial reorganization of the direct inputs to inhibitory neurons across the brain.

Detection of Chronic Blast-Related Mild Traumatic Brain Injury with Diffusion Tensor Imaging and Support Vector Machines

Blast-related mild traumatic brain injury (bmTBI) often leads to long-term sequalae, but diagnostic approaches are lacking due to insufficient knowledge about the predominant pathophysiology. This study aimed to build a diagnostic model for future verification by applying machine-learning based support vector machine (SVM) modeling to diffusion tensor imaging (DTI) datasets to elucidate white-matter features that distinguish bmTBI from healthy controls (HC). Twenty subacute/chronic bmTBI and 19 HC combat-deployed personnel underwent DTI. Clinically relevant features for modeling were selected using tract-based analyses that identified group differences throughout white-matter tracts in five DTI metrics to elucidate the pathogenesis of injury. These features were then analyzed using SVM modeling with cross validation. Tract-based analyses revealed abnormally decreased radial diffusivity (RD), increased fractional anisotropy (FA) and axial/radial diffusivity ratio (AD/RD) in the bmTBI group, mostly in anterior tracts (29 features). SVM models showed that FA of the anterior/superior corona radiata and AD/RD of the corpus callosum and anterior limbs of the internal capsule (5 features) best distinguished bmTBI from HCs with 89% accuracy. This is the first application of SVM to identify prominent features of bmTBI solely based on DTI metrics in well-defined tracts, which if successfully validated could promote targeted treatment interventions.

Traumatic Brain Injury and Risk of Neurodegenerative Disorder

Traumatic brain injury (TBI), particularly of greater severity (i.e., moderate to severe), has been identified as a risk factor for all-cause dementia and Parkinson's disease, with risk for specific dementia subtypes being more variable. Among the limited studies involving neuropathological (postmortem) confirmation, the association between TBI and risk for neurodegenerative disease increases in complexity, with polypathology often reported on examination. The heterogeneous clinical and neuropathological outcomes associated with TBI are likely reflective of the multifaceted postinjury acute and chronic processes that may contribute to neurodegeneration. Acutely in TBI, axonal injury and disrupted transport influences molecular mechanisms fundamental to the formation of pathological proteins, such as amyloid-β peptide and hyperphosphorylated tau. These protein deposits may develop into amyloid-β plaques, hyperphosphorylated tau-positive neurofibrillary tangles, and dystrophic neurites. These and other characteristic neurodegenerative disease pathologies may then spread across brain regions. The acute immune and neuroinflammatory response involves alteration of microglia, astrocytes, oligodendrocytes, and endothelial cells; release of downstream pro- and anti-inflammatory cytokines and chemokines; and recruitment of peripheral immune cells. Although thought to be neuroprotective and reparative initially, prolongation of these processes may promote neurodegeneration. We review the evidence for TBI as a risk factor for neurodegenerative disorders, including Alzheimer's dementia and Parkinson's disease, in clinical and neuropathological studies. Further, we describe the dynamic interactions between acute response to injury and chronic processes that may be involved in TBI-related pathogenesis and progression of neurodegeneration.

Temporal activity patterns of layer II and IV rat barrel cortex neurons in healthy and injured conditions

Neurons are known to encode information not just by how frequently they fire, but also at what times they fire. However, characterizations of temporal encoding in sensory cortices under conditions of health and injury are limited. Here we characterized and compared the stimulus-evoked activity of 1210 online-sorted units in layers II and IV of rat barrel cortex under healthy and diffuse traumatic brain injury (TBI) (caused by a weight-drop model) conditions across three timepoints post-injury: four days, two weeks, and eight weeks. Temporal activity patterns in the first 50 ms post-stimulus recording showed four categories of responses: no response or 1, 2, or 3 temporally-distinct response components, that is, periods of high unit activity separated by silence. The relative proportions of unit response categories were similar between layers II and IV in healthy conditions but not in early post-TBI conditions. For units with multiple response components, inter-component timings were reliable in healthy and late post-TBI conditions but disrupted by injury. Response component times typically shifted earlier with increasing stimulus intensity and this was more pronounced in layer IV than layer II. Surprisingly, injury caused a reversal of this trend and in the late post-TBI condition no stimulus intensity-dependence differences were observed between layers II and IV. We speculate this indicates a potential compensatory mechanism in response to injury. These results demonstrate how temporal encoding features maladapt or functionally recover differently in sensory cortex after TBI. Such maladaptation or functional recovery is layer-dependent, perhaps due to differences in thalamic input or local inhibitory neuronal makeup.

Treatment Patterns of Anxiety and Posttraumatic Stress Disorder Following Traumatic Brain Injury

OBJECTIVE

Symptoms of mental disorders are common, are underrecognized, and contribute to worse outcomes after traumatic brain injury (TBI). Post-TBI, prevalence of anxiety disorders and prevalence of posttraumatic stress disorder (PTSD) are comparable with that of depression, but evidence-based treatment guidelines are lacking. The investigators examined psychotropic medication use and psychotherapy patterns among individuals diagnosed with anxiety disorders and PTSD post-TBI.

METHODS

Administrative claims data were used to compare the prevalence and patterns of pharmacotherapy and psychotherapy utilization among individuals diagnosed with an anxiety disorder or PTSD post-TBI.

RESULTS

Among 207,354 adults with TBI, prevalence of anxiety disorders was 20.5%, and prevalence of PTSD was 0.6% post-TBI. Receipt of pharmacotherapy pre- and post-TBI (anxiety: pre-TBI=58.4%, post-TBI=76.2%; PTSD: pre-TBI=53.7%, post-TBI=75.2%) was considerably more common than receipt of psychotherapy (anxiety: pre-TBI=5.8%, post-TBI=19.1%; PTSD: pre-TBI=11.2%, post-TBI=36.0%). Individuals diagnosed with anxiety were 66% less likely to receive psychotherapy compared with individuals diagnosed with PTSD, although engagement in psychotherapy decreased faster over time among those with PTSD. Overall, psychotropic medication use and rates of antidepressant prescription use in the anxiety group were higher compared with those in the PTSD group. Benzodiazepines were the second most commonly prescribed medication class in the anxiety group, even though judicious use is warranted post-TBI.

CONCLUSIONS

Further exploration of differences and risks associated with pharmacotherapy for anxiety and PTSD post-TBI is warranted to refine treatment guidelines. The low level of psychotherapy engagement suggests that barriers and facilitators to psychotherapy utilization post-TBI should be examined in future studies.

Restoration of aberrant shape of caudate sub-regions associated with cognitive function improvement in mild traumatic brain injury

Mild traumatic brain injury (mTBI) is an important but less recognized public health concern. Research shows that altered subcortical structures mediate cognitive impairment in patients with mTBI. This has been performed mostly using voxel-based morphometry methods and traditional volume measurement methods, which have certain limitations. In this study, we conducted a vertex-wise shape analysis to understand the aberrant patterns of caudate sub-regions and recovery from mTBI. The study involved 36 mTBI patients and 34 matched healthy controls (HCs) observed at seven-days (acute phase) and followed-up for one-month (subacute phase) post-injury. Different aberrant shapes of the caudate sub-regions were observed at acute phase, which revealed atrophy in the bilateral dorsal medial caudate, and increase in the size of the right ventral anterior caudate in mTBI patients related to HCs. Moreover, specific and significant shape restoration of right dorsal medial caudate in mTBI was observed at subacute phase, which significantly associated with the cognitive function improvement of the patients. These findings suggest that the restoration of the aberrant shape atrophy of right dorsal medial caudate plays a vital role in the improvement of cognitive function of mTBI patients, providing an alternative clinical target for these patients.

Surface-based abnormalities of the executive frontostriatial circuit in pediatric TBI

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Cortical thickness of the dorsolateral prefrontal cortex is reduced in pediatric TBI.

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Shape abnormalities of the caudate and mediodorsal nucleus of the thalamus are a feature of pediatric TBI.

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Surface-based abnormalities of the dorsolateral prefrontal loop do not appear to relate to executive functioning.

Childhood traumatic brain injury (TBI) is one of the most common causes of acquired disability and has significant implications for executive functions (EF), such as impaired attention, planning, and initiation that are predictive of everyday functioning. Evidence has suggested attentional features of executive functioning require behavioral flexibility that is dependent on frontostriatial circuitry. The purpose of this study was to evaluate surface-based deformation of a specific frontostriatial circuit in pediatric TBI and its role in EF. Regions of interest included: the dorsolateral prefrontal cortex (DLPFC), caudate nucleus, globus pallidus, and the mediodorsal nucleus of the thalamus (MD). T1-weighted magnetic resonance images were obtained in a sample of children ages 8–13 with complicated mild, moderate, or severe TBI (n = 32) and a group of comparison children with orthopedic injury (OI; n = 30). Brain regions were characterized using high-dimensional surface-based brain mapping procedures. Aspects of EF were assessed using select subtests from the Test of Everyday Attention for Children (TEA-Ch). General linear models tested group and hemisphere differences in DLPFC cortical thickness and subcortical shape of deep-brain regions; Pearson correlations tested relationships with EF. Main effects for group were found in both cortical thickness of the DLPFC (F_1,60 = 4.30, p = 0.042) and MD mean deformation (F_1,60 = 6.50, p = 0.01) all with lower values in the TBI group. Statistical surface maps revealed significant inward deformation on ventral-medial aspects of the caudate in TBI relative to OI, but null results in the globus pallidus. No significant relationships between EF and any region of interest were observed. Overall, findings revealed abnormalities in multiple aspects of a frontostriatial circuit in pediatric TBI, which may reflect broader pathophysiological mechanisms. Increased consideration for the role of deep-brain structures in pediatric TBI can aid in the clinical characterization of anticipated long-term developmental effects of these individuals.

Acquired Brain Injury in Adults: A Review of Pathophysiology, Recovery, and Rehabilitation

Purpose

To summarize existing literature from a range of fields (i.e., neurology, neuropsychology, neuroscience, neuroimaging, rehabilitation, speech-language pathology) that is relevant to the development and/or revision of cognitive rehabilitation programs for individuals with acquired brain injury (ABI) and in particular, for young adults.

Method

This paper reviews a range of ABI-associated topics including: 1) mechanisms of injury; 2) biological, individual-specific, and behavioral drivers of recovery; and 3) current methods of cognitive rehabilitation. It then narrows focus to young adults, a frequently affected and growing population to sustain ABI. The paper concludes by providing: 1) suggestions for key components of cognitive rehabilitation for young adults with ABI; 2) an example from our own research providing intensive academically-focused cognitive rehabilitation for young adults with ABI pursuing college; and 3) recommendations for future behavioral and neuroimaging studies in this area.

Conclusions

ABI is on the rise in the United States. Young adults have been sustaining ABI at higher rates over the past several decades. These injuries occur when they would otherwise be advancing their academic and career goals, making the cognitive deficits that often accompany ABI especially devastating for this group. Review of existing literature suggests cognitive rehabilitation programs that combine aspects of restorative, comprehensive, and contextualized approaches could promote recovery for young adults with ABI. Future intervention studies may benefit from including both behavioral and neural outcomes to best understand how principles of neuroplasticity- naturally embedded within many cognitive rehabilitation approaches-could be manipulated to promote cognitive recovery and long-lasting brain reorganization in this group.

Estimated Prevalence of Functional Hearing Difficulties in Blast-Exposed Service Members With Normal to Near-Normal-Hearing Thresholds

OBJECTIVES

Over the past decade, U.S. Department of Defense and Veterans Affairs audiologists have reported large numbers of relatively young adult patients who have normal to near-normal audiometric thresholds but who report difficulty understanding speech in noisy environments. Many of these service members also reported having experienced exposure to explosive blasts as part of their military service. Recent studies suggest that some blast-exposed patients with normal to near-normal-hearing thresholds not only have an awareness of increased hearing difficulties, but also poor performance on various auditory tasks (sound source localization, speech recognition in noise, binaural integration, gap detection in noise, etc.). The purpose of this study was to determine the prevalence of functional hearing and communication deficits (FHCD) among healthy Active-Duty service men and women with normal to near-normal audiometric thresholds.

DESIGN

To estimate the prevalence of such FHCD in the overall military population, performance of roughly 3400 Active-Duty service members with hearing thresholds mostly within the normal range were measured on 4 hearing tests and a brief 6-question survey to assess FHCD. Subjects were subdivided into 6 groups depending on the severity of the blast exposure (3 levels: none, far away, or close enough to feel heat or pressure) and hearing thresholds (2 levels: audiometric thresholds of 20 dB HL or better, slight elevation in 1 or more thresholds between 500 and 4000 Hz in either ear).

RESULTS

While the probability of having hearing difficulty was low (≈4.2%) for the overall population tested, that probability increased by 2 to 3 times if the service member was blast-exposed from a close distance or had slightly elevated hearing thresholds (>20 dB HL). Service members having both blast exposure and mildly elevated hearing thresholds exhibited up to 4 times higher risk for performing abnormally on auditory tasks and more than 5 times higher risk for reporting abnormally low ratings on the subjective questionnaire, compared with service members with no history of blast exposure and audiometric thresholds ≤20 dB HL. Blast-exposed listeners were roughly 2.5 times more likely to experience subjective or objective hearing deficits than those with no-blast history.

CONCLUSIONS

These elevated rates of abnormal performance suggest that roughly 33.6% of Active-Duty service members (or approximately 423,000) with normal to near-normal-hearing thresholds (i.e., H1 profile) are at some risk for FHCD, and about 5.7% (approximately 72,000) are at high risk, but are currently untested and undetected within the current fitness-for-duty standards. Service members identified as "at risk" for FHCD according to the metrics used in the present study, in spite of their excellent hearing thresholds, require further testing to determine whether they have sustained damage to peripheral and early-stage auditory processing (bottom-up processing), damage to cognitive processes for speech (top-down processing), or both. Understanding the extent of damage due to noise and blast exposures and the balance between bottom-up processing deficits and top-down deficits will likely lead to better therapeutic strategies.

Morphometric evaluation of traumatic axonal injury and the correlation with post-traumatic cerebral atrophy and functional outcome

INTRODUCTION

Imaging plays a crucial role in the diagnosis, prognosis and follow-up of traumatic brain injury. Whereas computed tomography plays a pivotal role in the acute setting, magnetic resonance imaging is best suited to detect the true extent of traumatic brain injury, and more specifically diffuse axonal injury. Post-traumatic brain atrophy is a well-known complication of traumatic brain injury.

PURPOSE

This study investigated the correlation between diffuse axonal injury detected with fluid-attenuated inversion recovery and susceptibility-weighted imaging magnetic resonance imaging, post-traumatic brain atrophy and functional outcome (Glasgow outcome scale - extended).

MATERIALS AND METHODS

Twenty patients with a closed head injury and diffuse axonal injury detected with fluid-attenuated inversion recovery and susceptibility-weighted imaging were included. The total volumes of the diffuse axonal injury fluid-attenuated inversion recovery lesions were determined for each subject's initial (<14 days) and follow-up magnetic resonance scan (average: day 303 ± 83 standard deviation). The different brain volumes were automatically quantified using a validated and both US Food and Drug Administration-cleared and CE-marked machine learning algorithm (icobrain). The number of susceptibility-weighted imaging lesions and functional outcome scores (Glasgow outcome scale - extended) were retrieved from the Collaborative European NeuroTrauma Effectiveness Research Traumatic Brain Injury dataset.

RESULTS

The volumetric fluid-attenuated inversion recovery diffuse axonal injury lesion load showed a significant inverse correlation with functional outcome (Glasgow outcome scale - extended) (r = -0.57; P = 0.0094) and white matter volume change (r = -0.50; P = 0.027). In addition, white matter volume change correlated significantly with the Glasgow outcome scale - extended score (P = 0.0072; r = 0.58). Moreover, there was a strong inverse correlation between longitudinal fluid-attenuated inversion recovery lesion volume change and whole brain volume change (r = -0.63; P = 0.0028). No significant correlation existed between the number of diffuse axonal injury susceptibility-weighted imaging lesions, brain atrophy and functional outcome.

CONCLUSIONS

Volumetric analysis of diffuse axonal injury on fluid-attenuated inversion recovery imaging and automated brain atrophy calculation are potentially useful tools in the clinical management and follow-up of traumatic brain injury patients with diffuse axonal injury.

Evaluation of the Effectiveness of Newer Helmet Designs with Emergent Shell and Padding Technologies Versus Older Helmet Models for Preserving White Matter Following a Season of High School Football

We aimed to objectively compare the effects of wearing newer, higher-ranked football helmets (HRank) vs. wearing older, lower-ranked helmets (LRank) on pre- to post-season alterations to neuroimaging-derived metrics of athletes' white matter. Fifty-four high-school athletes wore an HRank helmet, and 62 athletes wore an LRank helmet during their competitive football season and completed pre- and post-season diffusion tensor imaging (DTI). Longitudinal within- and between-group DTI metrics [fractional anisotropy (FA) and mean/axial/radial diffusivity (MD, AD, RD)] were analyzed using tract-based spatial statistics. The LRank helmet group exhibited significant pre- to post-season reductions in MD, AD, and RD, the HRank helmet group displayed significant pre- to post-season increases in FA, and both groups showed significant pre- to post-season increases in AD (p's < .05 [corrected]). Between-group analyses revealed the pre- to post-season increase in AD was significantly less for athletes wearing HRank compared to LRank (p < .05 [corrected]). These data provide in vivo evidence that wearing an HRank helmet may be efficacious for preserving white matter from head impact exposure during high school football. Future prospective longitudinal investigations with complimentary imaging and behavioral outcomes are warranted to corroborate these initial in vivo findings.

Hypothermia for Patients Requiring Evacuation of Subdural Hematoma: A Multicenter Randomized Clinical Trial

Background

Hypothermia is neuroprotective in some ischemia–reperfusion injuries. Ischemia–reperfusion injury may occur with traumatic subdural hematoma (SDH). This study aimed to determine whether early induction and maintenance of hypothermia in patients with acute SDH would lead to decreased ischemia–reperfusion injury and improve global neurologic outcome.

Methods

This international, multicenter randomized controlled trial enrolled adult patients with SDH requiring evacuation of hematoma within 6 h of injury. The intervention was controlled temperature management of hypothermia to 35 °C prior to dura opening followed by 33 °C for 48 h compared with normothermia (37 °C). Investigators randomly assigned patients at a 1:1 ratio between hypothermia and normothermia. Blinded evaluators assessed outcome using a 6-month Glasgow Outcome Scale Extended score. Investigators measured circulating glial fibrillary acidic protein and ubiquitin C-terminal hydrolase L1 levels.

Results

Independent statisticians performed an interim analysis of 31 patients to assess the predictive probability of success and the Data and Safety Monitoring Board recommended the early termination of the study because of futility. Thirty-two patients, 16 per arm, were analyzed. Favorable 6-month Glasgow Outcome Scale Extended outcomes were not statistically significantly different between hypothermia vs. normothermia groups (6 of 16, 38% vs. 4 of 16, 25%; odds ratio 1.8 [95% confidence interval 0.39 to ∞], p = .35). Plasma levels of glial fibrillary acidic protein (p = .036), but not ubiquitin C-terminal hydrolase L1 (p = .26), were lower in the patients with favorable outcome compared with those with unfavorable outcome, but differences were not identified by temperature group. Adverse events were similar between groups.

Conclusions

This trial of hypothermia after acute SDH evacuation was terminated because of a low predictive probability of meeting the study objectives. There was no statistically significant difference in functional outcome identified between temperature groups.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12028-021-01334-w.

Severity of Traumatic Brain Injury in Older Adults and Risk of Ischemic Stroke and Depression

OBJECTIVE

Risk of ischemic stroke and depression is elevated among older adults following traumatic brain injury (TBI), yet little is known about how the severity of TBI influences risk. Thus, our objective was to assess the association between severity of the index TBI and risk of ischemic stroke and depression in a sample of older adults treated for TBI.

DESIGN

Retrospective cohort study.

SETTING

R Adams Cowley Shock Trauma Center.

PARTICIPANTS

Adults 65 years and older treated for TBI between 2006 and 2010 who survived to hospital discharge and could be linked to their Medicare administrative claims data with continuous enrollment for at least 6 months pre-TBI and 12 months post-TBI.

MAIN MEASURES

First dates of ischemic stroke and depression available in Medicare claims were used to exclude individuals with a history. Next, we separately assessed the association between TBI severity and time to first stroke and depression using Cox proportional hazards models.

RESULTS

Among 132 patients without preexisting history of stroke, high TBI severity was associated with increased risk of stroke compared with low TBI severity (adjusted hazard ratio 6.68, 95% confidence interval 2.49-17.94). Among 163 patients without preexisting history of depression, high TBI severity was not significantly associated with increased risk of depression compared with low TBI severity (adjusted hazard ratio 1.90, 95% confidence interval 0.94-3.84).

CONCLUSION

In this group of older adults with TBI, higher TBI severity was associated with increased risk of ischemic stroke, but not depression. These results suggest that increased monitoring of older adults with moderate-severe TBI for stroke may be warranted.

T1 and T2 quantification using magnetic resonance fingerprinting in mild traumatic brain injury

OBJECTIVES

To assess whether MR fingerprinting (MRF)-based relaxation properties exhibit cross-sectional and prospective correlations with patient outcome and compare the results with those from DTI.

METHODS

Clinical imaging, MRF, and DTI were acquired in patients (24 ± 10 days after injury (timepoint 1) and 90 ± 17 days after injury (timepoint 2)) and once in controls. Patient outcome was assessed with global functioning, symptom profile, and neuropsychological testing. ADC and fractional anisotropy (FA) from DTI and T₁ and T₂ from MRF were compared in 12 gray and white matter regions with Mann-Whitney tests. Bivariate associations between MR measures and outcome were assessed using the Spearman correlation and logistic regression.

RESULTS

Data from 22 patients (38 ± 12 years; 17 women) and 18 controls (32 ± 8 years; 12 women) were analyzed. Fourteen patients (37 ± 12 years; 11 women) returned for timepoint 2, while two patients provided only timepoint 2 clinical outcome data. At timepoint 1, there were no differences between patients and controls in T₁, T₂, and ADC, while FA was lower in mTBI frontal white matter. T₁ at timepoint 1 and the change in T₁ exhibited more (n = 18) moderate to strong correlations (|r|= 0.6-0.85) with clinical outcome at timepoint 2 than T₂ (n = 3), FA (n = 7), and ADC (n = 2). High T₁ at timepoint 1, and serially increasing T₁, accounted for five of the six MR measures with the highest utility for identification of non-recovered patients at timepoint 2 (AUC > 0.80).

CONCLUSION

T₁ derived from MRF was found to have higher utility than T₂, FA, and ADC for predicting 3-month outcome after mTBI.

KEY POINTS

• In a region-of-interest approach, FA, ADC, and T₁ and T₂ all showed limited utility in differentiating patients from controls at an average of 24 and 90 days post-mild traumatic brain injury. • T₁ at 24 days, and the serial change in T₁, revealed more and stronger predictive correlations with clinical outcome at 90 days than did T₂, ADC, or FA. • T₁ showed better prospective identification of non-recovered patients at 90 days than ADC, T₂, and FA.

Afferent Visual Manifestations of Traumatic Brain Injury

Traumatic brain injury (TBI) causes structural and functional damage to the central nervous system including the visual pathway. Defects in the afferent visual pathways affect visual function and in severe cases cause complete visual loss. Visual dysfunction is detectable by structural and functional ophthalmic examinations that are routine in the eye clinic, including examination of the pupillary light reflex and optical coherence tomography (OCT). Assessment of pupillary light reflex is a non-invasive assessment combining afferent and efferent visual function. While a assessment using a flashlight is relatively insensitive, automated pupillometry has 95% specificity and 78.1% sensitivity in detecting TBI-related visual and cerebral dysfunction with an area under the curve of 0.69-0.78. OCT may also serve as a noninvasive biomarker of TBI severity, demonstrating changes in the retinal ganglion cell layer and nerve fiber layer throughout the range of TBI severity even in the absence of visual symptoms. This review discusses the impact of TBI on visual structure and function.

Time-Course Evaluation of Brain Regional Mitochondrial Bioenergetics in a Pre-Clinical Model of Severe Penetrating Traumatic Brain Injury

Mitochondrial dysfunction is a pivotal target for neuroprotection strategies for traumatic brain injury (TBI). However, comprehensive time-course evaluations of mitochondrial dysfunction are lacking in the pre-clinical penetrating TBI (PTBI) model. The current study was designed to characterize temporal responses of mitochondrial dysfunction from 30 min to 2 weeks post-injury after PTBI. Anesthetized adult male rats were subjected to either PTBI or sham craniectomy (n = 6 animals per group × 7 time points). Animals were euthanized at 30 min, 3 h, 6 h, 24 h, 3 days, 7 days, and 14 days post-PTBI, and mitochondria were isolated from the ipsilateral hemisphere of brain regions near the injury core (i.e., frontal cortex [FC] and striatum [ST]) and a more distant region from the injury core (i.e., hippocampus [HIP]). Mitochondrial bioenergetics parameters were measured in real time using the high-throughput procedures of the Seahorse Flux Analyzer (Agilent Technologies, Santa Clara, CA). The post-injury time course of FC + ST showed a biphasic mitochondrial bioenergetics dysfunction response, indicative of reduced adenosine triphosphate synthesis rate and maximal respiratory capacity after PTBI. An initial phase of energy crisis was detected at 30 min (-42%; p < 0.05 vs. sham), which resolved to baseline levels between 3 and 6 h (non-significant vs. sham). This was followed by a second and more robust phase of bioenergetics dysregulation detected at 24 h that remained unresolved out to 14 days post-injury (-55% to -90%; p < 0.05 vs. sham). In contrast, HIP mitochondria showed a delayed onset of mitochondrial dysfunction at 7 days (-74%; p < 0.05 vs. sham) that remained evident out to 14 days (-51%; p < 0.05 vs. sham) post-PTBI. Collectively, PTBI-induced mitochondrial dysfunction responses were time and region specific, evident differentially at the injury core and distant region of PTBI. The current results provide the basis that mitochondrial dysfunction may be targeted differentially based on region specificity post-PTBI. Even more important, these results suggest that therapeutic interventions targeting mitochondrial dysfunction may require extended dosing regimens to achieve clinical efficacy after TBI.

White matter degeneration in diffuse axonal injury and mild traumatic brain injury observed with automatic tractography

A better understanding of white matter tract damage in patients with diffuse axonal injury (DAI) and mild traumatic brain injury (MTBI) is important to obtain an objective basis for sequelae. The purpose of this study was to clarify the characteristics of white matter tract degeneration in DAI and MTBI using automated tractography. T1-weighted and diffusion tensor imaging (DTI) was performed on seven DAI and seven MTBI patients as well as on nine healthy subjects. Automated probabilistic tractography analysis was performed using FreeSurfer and TRACULA (tracts constrained by underlying anatomy) for the reconstruction of major nerve fibers. We investigated the difference between DTI quantitative values in each white matter nerve fiber between groups and attempted to evaluate the classification accuracy of DAI and MTBI using receiver operator curve analysis. Both DAI and MTBI appeared to exhibit axonal degeneration along the nerve fiber tract in a scattered manner. The mean diffusivity of the ampulla of the corpus callosum was significantly higher in DAI than that in MTBI patients, suggesting axonal degeneration of the corpus callosum in DAI patients. Using mean diffusivity of the right cingulum-angular bundle, DAI and MTBI could be discriminated with an area under the curve of 94%. Both DAI and MTBI exhibited scattered axonal degeneration; however, DAI appeared to exhibit more pronounced axonal degeneration in the ampulla of the corpus callosum than MTBI. Our results suggest that DAI and MTBI can be accurately distinguished using DTI.