Neuroimaging biomarkers in mild traumatic brain injury (mTBI)

The Role of Neuroinflammation in Shaping Neuroplasticity and Recovery Outcomes Following Traumatic Brain Injury: A Systematic Review

Neuroplasticity and neuroinflammation are variables seen during recovery from traumatic brain injury (TBI), while biomarkers are useful in monitoring injury and guiding rehabilitation efforts. This systematic review examines how neuroinflammation affects neuroplasticity and recovery following TBI in animal models and humans. Studies were identified from an online search of the PubMed, Web of Science, and Embase databases without any search time range. This review has been registered on Open OSF (n) UDWQM. Recent studies highlight the critical role of biomarkers like serum amyloid A1 (SAA1) and Toll-like receptor 4 (TLR4) in predicting TBI patients' injury severity and recovery outcomes, offering the potential for personalized treatment and improved neurorehabilitation strategies. Additionally, insights from animal studies reveal how neuroinflammation affects recovery, emphasizing targets such as NOD-like receptor family pyrin domain-containing 3 (NLRP3) and microglia for enhancing therapeutic interventions. This review emphasizes the central role of neuroinflammation in TBI, and its adverse impact on neuroplasticity and recovery, and suggests that targeted anti-inflammatory treatments and biomarker-based personalized approaches hold the key to improvement. Such approaches will need further development in future research by integrating neuromodulation and pharmacological interventions, along with biomarker validation, to optimize management in TBI.

Assessment and theoretical interpretation of spoken discourse and cognitive skills in two adolescents with acquired brain injury

PURPOSE

Although discourse assessment is recommended, few tools exist for adolescent acquired brain injury (ABI) and few theories describe the contribution of cognition to discourse impairment. This study explored whether a novel discourse protocol can identify difficulties following ABI and whether a discourse processing model provides a useful account of impairment.

METHOD

Using a case-control design, two adolescent males with moderate ABI (12 and 14 years) were compared to a neurotypical sample on a range of language and cognitive assessments. Patterns in performance were interpreted using a theoretical model. Participants completed a standardised omnibus language assessment, discourse assessment, and battery of cognitive tasks.

RESULT

Analyses revealed significant differences in discourse and cognition between adolescents with and without ABI. No impairment was detected on a standardised language assessment. Patterns in discourse and cognition aligned with a contemporary model of discourse processing.

CONCLUSION

Participants with ABI demonstrated discourse deficits relative to the neurotypical reference sample. The findings demonstrate the value of discourse sampling across multiple genres and analysis of microlinguistic to superstructural features. A structure-building framework (SBF) model, originating in schizophrenia, provides a promising theory with which to interpret discourse impairment and has the potential to inform intervention for discourse in ABI.

NHE1 Protein in Repetitive Mild TBI-Mediated Neuroinflammation and Neurological Function Impairment

Mild traumatic brain injuries (mTBIs) are highly prevalent and can lead to chronic behavioral and cognitive deficits often associated with the development of neurodegenerative diseases. Oxidative stress and formation of reactive oxygen species (ROS) have been implicated in mTBI-mediated axonal injury and pathogenesis. However, the underlying mechanisms and contributing factors are not completely understood. In this study, we explore these pathogenic mechanisms utilizing a murine model of repetitive mTBI (r-mTBI) involving five closed-skull concussions in young adult C57BL/6J mice. We observed a significant elevation of Na+/H+ exchanger protein (NHE1) expression in GFAP+ reactive astrocytes, IBA1+ microglia, and OLIG2+ oligodendrocytes across various brain regions (including the cerebral cortex, corpus callosum, and hippocampus) after r-mTBI. This elevation was accompanied by astrogliosis, microgliosis, and the accumulation of amyloid precursor protein (APP). Mice subjected to r-mTBI displayed impaired motor learning and spatial memory. However, post-r-mTBI administration of a potent NHE1 inhibitor, HOE642, attenuated locomotor and cognitive functional deficits as well as pathological signatures of gliosis, oxidative stress, axonal damage, and white matter damage. These findings indicate NHE1 upregulation plays a role in r-mTBI-induced oxidative stress, axonal damage, and gliosis, suggesting NHE1 may be a promising therapeutic target to alleviate mTBI-induced injuries and restore neurological function.

Psychological distress and gender predict cognitive complaint after adult civilian mild traumatic brain injury in pre-morbidly healthy adults

Subjective cognitive symptoms are common after mild traumatic brain injury (mTBI), and are associated with important outcome factors including return to work. This study examined self-reported cognitive symptoms in mTBI and trauma controls (TCs), and explored psychological distress and gender as predictors of these symptoms. Pre-morbidly healthy adults with mTBI (n = 68) and general trauma (n = 40) were prospectively recruited from inpatient hospital wards and assessed 6-10 weeks post-injury. Primary measures included self-reported cognitive symptoms, post-concussion symptoms, and psychological distress. Groups were matched on all background variables, including objective cognitive performance. Within this context, subjective cognitive symptoms were significantly elevated after mTBI relative to TCs (t = 3.396, p = .001). In contrast, there was no difference in post-concussion symptoms between groups (t = 1.275, p = .206). Psychological distress (β = .536, p < .001) and gender (β = .253, p = .012) predicted subjective cognitive symptoms in mTBI, with females and those with higher distress reporting greater symptoms. Unlike general post-concussion symptoms, subjective cognitive symptoms were elevated after mTBI relative to TCs, suggesting that mTBI-specific factors underly this elevation. Females and individuals with high psychological distress are important subgroups to consider for potential intervention following mTBI.

White Matter Alterations in Military Service Members With Remote Mild Traumatic Brain Injury

Importance

Mild traumatic brain injury (mTBI) is the signature injury experienced by military service members and is associated with poor neuropsychiatric outcomes. Yet, there is a lack of reliable clinical tools for mTBI diagnosis and prognosis.

Objective

To examine the white matter microstructure and neuropsychiatric outcomes of service members with a remote history of mTBI (ie, mTBI that occurred over 2 years ago) using diffusion tensor imaging (DTI) and neurite orientation dispersion and density imaging (NODDI).

Design, Setting, and Participants

This case-control study examined 98 male service members enrolled in a study at the National Intrepid Center of Excellence. Eligible participants were active duty status or able to enroll in the Defense Enrollment Eligibility Reporting system, ages 18 to 60 years, and had a remote history of mTBI; controls were matched by age.

Exposures

Remote history of mTBI.

Main Outcomes and Measures

White matter microstructure was assessed using a region-of-interest approach of skeletonized diffusion images, including DTI (fractional anisotropy, mean diffusivity, radial diffusivity and axial diffusivity) and NODDI (orientation dispersion index [ODI], isotropic volume fraction, intra-cellular volume fraction). Neuropsychiatric outcomes associated with posttraumatic stress disorder (PTSD) and postconcussion syndrome were assessed.

Results

A total of 65 male patients with a remote history of mTBI (mean [SD] age, 40.5 [5.0] years) and 33 age-matched male controls (mean [SD] age, 38.9 [5.6] years) were included in analysis. Compared with the control cohort, the 65 service members with mTBI presented with significantly more severe PTSD-like symptoms (mean [SD] PTSD CheckList-Civilian [PCL-C] version scores: control, 19.0 [3.8] vs mTBI, 41.2 [11.6]; P < .001). DTI and NODDI metrics were altered in the mTBI group compared with the control, including intra-cellular volume fraction of the right cortico-spinal tract (β = -0.029, Cohen d = 0.66; P < .001), ODI of the left posterior thalamic radiation (β = -0.006, Cohen d = 0.55; P < .001), and ODI of the left uncinate fasciculus (β = 0.013, Cohen d = 0.61; P < .001). In service members with mTBI, fractional anisotropy of the left uncinate fasciculus was associated with postconcussion syndrome (β = 5.4 × 10-3; P = .003), isotropic volume fraction of the genu of the corpus callosum with PCL-C (β = 4.3 × 10-4; P = .01), and ODI of the left fornix and stria terminalis with PCL-C avoidance scores (β = 1.2 × 10-3; P = .02).

Conclusions and Relevance

In this case-control study of military-related mTBI, the results suggest that advanced magnetic resonance imaging techniques using NODDI can reveal white matter microstructural alterations associated with neuropsychiatric symptoms in the chronic phase of mTBI. Diffusion trends observed throughout widespread white matter regions-of-interest may reflect mechanisms of neurodegeneration as well as postinjury tissue scarring and reorganization.

The relationship between cognition and white matter tract damage after mild traumatic brain injury in a premorbidly healthy, hospitalised adult cohort during the post-acute period

Introduction

Recent developments in neuroimaging techniques enable increasingly sensitive consideration of the cognitive impact of damage to white matter tract (WMT) microstructural organisation after mild traumatic brain injury (mTBI).

Objective

This study investigated the relationship between WMT microstructural properties and cognitive performance.

Participants setting and design

Using an observational design, a group of 26 premorbidly healthy adults with mTBI and a group of 20 premorbidly healthy trauma control (TC) participants who were well-matched on age, sex, premorbid functioning and a range of physical, psychological and trauma-related variables, were recruited following hospital admission for traumatic injury.

Main measures

All participants underwent comprehensive unblinded neuropsychological examination and structural neuroimaging as outpatients 6-10 weeks after injury. Neuropsychological examination included measures of speed of processing, attention, memory, executive function, affective state, pain, fatigue and self-reported outcome. The WMT microstructural properties were estimated using both diffusion tensor imaging (DTI) and neurite orientation dispersion and density imaging (NODDI) modelling techniques. Tract properties were compared between the corpus callosum, inferior longitudinal fasciculus, uncinate fasciculus, anterior corona radiata and three segmented sections of the superior longitudinal fasciculus.

Results

For the TC group, in all investigated tracts, with the exception of the uncinate fasciculus, two DTI metrics (fractional anisotropy and apparent diffusion coefficient) and one NODDI metric (intra-cellular volume fraction) revealed expected predictive linear relationships between extent of WMT microstructural organisation and processing speed, memory and executive function. The mTBI group showed a strikingly different pattern relative to the TC group, with no relationships evident between WMT microstructural organisation and cognition on most tracts.

Conclusion

These findings indicate that the predictive relationship that normally exists in adults between WMT microstructural organisation and cognition, is significantly disrupted 6-10 weeks after mTBI and suggests that WMT microstructural organisation and cognitive function have disparate recovery trajectories.

Military-related mild traumatic brain injury: clinical characteristics, advanced neuroimaging, and molecular mechanisms

Mild traumatic brain injury (mTBI) is a significant health burden among military service members. Although mTBI was once considered relatively benign compared to more severe TBIs, a growing body of evidence has demonstrated the devastating neurological consequences of mTBI, including chronic post-concussion symptoms and deficits in cognition, memory, sleep, vision, and hearing. The discovery of reliable biomarkers for mTBI has been challenging due to under-reporting and heterogeneity of military-related mTBI, unpredictability of pathological changes, and delay of post-injury clinical evaluations. Moreover, compared to more severe TBI, mTBI is especially difficult to diagnose due to the lack of overt clinical neuroimaging findings. Yet, advanced neuroimaging techniques using magnetic resonance imaging (MRI) hold promise in detecting microstructural aberrations following mTBI. Using different pulse sequences, MRI enables the evaluation of different tissue characteristics without risks associated with ionizing radiation inherent to other imaging modalities, such as X-ray-based studies or computerized tomography (CT). Accordingly, considering the high morbidity of mTBI in military populations, debilitating post-injury symptoms, and lack of robust neuroimaging biomarkers, this review (1) summarizes the nature and mechanisms of mTBI in military settings, (2) describes clinical characteristics of military-related mTBI and associated comorbidities, such as post-traumatic stress disorder (PTSD), (3) highlights advanced neuroimaging techniques used to study mTBI and the molecular mechanisms that can be inferred, and (4) discusses emerging frontiers in advanced neuroimaging for mTBI. We encourage multi-modal approaches combining neuropsychiatric, blood-based, and genetic data as well as the discovery and employment of new imaging techniques with big data analytics that enable accurate detection of post-injury pathologic aberrations related to tissue microstructure, glymphatic function, and neurodegeneration. Ultimately, this review provides a foundational overview of military-related mTBI and advanced neuroimaging techniques that merit further study for mTBI diagnosis, prognosis, and treatment monitoring.

Biomarker-guided neuromodulation aids memory in traumatic brain injury

Traumatic brain injury (TBI) is a leading cause of cognitive disability in adults, often characterized by marked deficits in episodic memory and executive function. Prior studies have found that direct electrical stimulation of the temporal cortex yielded improved memory in epilepsy patients, but it is not clear if these results generalize to patients with a specific history of TBI. Here we asked whether applying closed-loop, direct electrical stimulation to lateral temporal cortex could reliably improve memory in a TBI cohort. Among a larger group of patients undergoing neurosurgical evaluation for refractory epilepsy, we recruited a subset of patients with a history of moderate-to-severe TBI. By analyzing neural data from indwelling electrodes as patients studied and recalled lists of words, we trained personalized machine-learning classifiers to predict momentary fluctuations in mnemonic function in each patient. We subsequently used these classifiers to trigger high-frequency stimulation of the lateral temporal cortex (LTC) at moments when memory was predicted to fail. This strategy yielded a 19% boost in recall performance on stimulated as compared with non-stimulated lists (P = 0.012). These results provide a proof-of-concept for using closed-loop stimulation of the brain in treatment of TBI-related memory impairment.

Altered longitudinal structural connectome in paediatric mild traumatic brain injury: an Advancing Concussion Assessment in Paediatrics study

Advanced diffusion-weighted imaging techniques have increased understanding of the neuropathology of paediatric mild traumatic brain injury (i.e. concussion). Most studies have examined discrete white-matter pathways, which may not capture the characteristically subtle, diffuse and heterogenous effects of paediatric concussion on brain microstructure. This study compared the structural connectome of children with concussion to those with mild orthopaedic injury to determine whether network metrics and their trajectories across time post-injury differentiate paediatric concussion from mild traumatic injury more generally. Data were drawn from of a large study of outcomes in paediatric concussion. Children aged 8-16.99 years were recruited from five paediatric emergency departments within 48 h of sustaining a concussion (n = 360; 56% male) or mild orthopaedic injury (n = 196; 62% male). A reliable change score was used to classify children with concussion into two groups: concussion with or without persistent symptoms. Children completed 3 T MRI at post-acute (2-33 days) and/or chronic (3 or 6 months, via random assignment) post-injury follow-ups. Diffusion-weighted images were used to calculate the diffusion tensor, conduct deterministic whole-brain fibre tractography and compute connectivity matrices in native (diffusion) space for 90 supratentorial regions. Weighted adjacency matrices were constructed using average fractional anisotropy and used to calculate global and local (regional) graph theory metrics. Linear mixed effects modelling was performed to compare groups, correcting for multiple comparisons. Groups did not differ in global network metrics. However, the clustering coefficient, betweenness centrality and efficiency of the insula, cingulate, parietal, occipital and subcortical regions differed among groups, with differences moderated by time (days) post-injury, biological sex and age at time of injury. Post-acute differences were minimal, whereas more robust alterations emerged at 3 and especially 6 months in children with concussion with persistent symptoms, albeit differently by sex and age. In the largest neuroimaging study to date, post-acute regional network metrics distinguished concussion from mild orthopaedic injury and predicted symptom recovery 1-month post-injury. Regional network parameters alterations were more robust and widespread at chronic timepoints than post-acutely after concussion. Results suggest that increased regional and local subnetwork segregation (modularity) and inefficiency occurs across time after concussion, emerging after post-concussive symptom resolve in most children. These differences persist up to 6 months after concussion, especially in children who showed persistent symptoms. While prognostic, the small to modest effect size of group differences and the moderating effects of sex likely would preclude effective clinical application in individual patients.

Long-Term Changes in Brain Connectivity Reflected in Quantitative Electrophysiology of Symptomatic Former National Football League Players

Exposure to repetitive head impacts (RHI) has been associated with long-term disturbances in cognition, mood, and neurobehavioral dysregulation, and reflected in neuroimaging. Distinct patterns of changes in quantitative features of the brain electrical activity (quantitative electroencephalogram [qEEG]) have been demonstrated to be sensitive to brain changes seen in neurodegenerative disorders and in traumatic brain injuries (TBI). While these qEEG biomarkers are highly sensitive at time of injury, the long-term effects of exposure to RHI on brain electrical activity are relatively unexplored. Ten minutes of eyes closed resting EEG data were collected from a frontal and frontotemporal electrode montage (BrainScope Food and Drug Administration-cleared EEG acquisition device), as well as assessments of neuropsychiatric function and age of first exposure (AFE) to American football. A machine learning methodology was used to derive a qEEG-based algorithm to discriminate former National Football League (NFL) players (n = 87, 55.40 ± 7.98 years old) from same-age men without history of RHI (n = 68, 54.94 ± 7.63 years old), and a second algorithm to discriminate former players with AFE <12 years (n = 33) from AFE ≥12 years (n = 54). The algorithm separating NFL retirees from controls had a specificity = 80%, a sensitivity = 60%, and an area under curve (AUC) = 0.75. Within the NFL population, the algorithm separating AFE <12 from AFE ≥12 resulted in a sensitivity = 76%, a specificity = 52%, and an AUC = 0.72. The presence of a profile of EEG abnormalities in the NFL retirees and in those with younger AFE includes features associated with neurodegeneration and the disruption of neuronal transmission between regions. These results support the long-term consequences of RHI and the potential of EEG as a biomarker of persistent changes in brain function.

Diffusion Tensor Imaging Reveals Elevated Diffusivity of White Matter Microstructure that Is Independently Associated with Long-Term Outcome after Mild Traumatic Brain Injury: A TRACK-TBI Study

Diffusion tensor imaging (DTI) literature on single-center studies contains conflicting results regarding acute effects of mild traumatic brain injury (mTBI) on white matter (WM) microstructure and the prognostic significance. This larger-scale multi-center DTI study aimed to determine how acute mTBI affects WM microstructure over time and how early WM changes affect long-term outcome. From Transforming Research and Clinical Knowledge in Traumatic Brain Injury (TRACK-TBI), a cohort study at 11 United States level 1 trauma centers, a total of 391 patients with acute mTBI ages 17 to 60 years were included and studied at two weeks and six months post-injury. Demographically matched friends or family of the participants were the control group (n = 148). Axial diffusivity (AD), fractional anisotropy (FA), mean diffusivity (MD), and radial diffusivity (RD) were the measures of WM microstructure. The primary outcome was the Glasgow Outcome Scale Extended (GOSE) score of injury-related functional limitations across broad life domains at six months post-injury. The AD, MD, and RD were higher and FA was lower in mTBI versus friend control (FC) at both two weeks and six months post-injury throughout most major WM tracts of the cerebral hemispheres. In the mTBI group, AD and, to a lesser extent, MD decreased in WM from two weeks to six months post-injury. At two weeks post-injury, global WM AD and MD were both independently associated with six-month incomplete recovery (GOSE <8 vs = 8) even after accounting for demographic, clinical, and other imaging factors. DTI provides reliable imaging biomarkers of dynamic WM microstructural changes after mTBI that have utility for patient selection and treatment response in clinical trials. Continued technological advances in the sensitivity, specificity, and precision of diffusion magnetic resonance imaging hold promise for routine clinical application in mTBI.

Memory retrieval brain-behavior disconnection in mild traumatic brain injury: A magnetoencephalography and diffusion tensor imaging study

Mild traumatic brain (mTBI) injury is often associated with long-term cognitive and behavioral complications, including an increased risk of memory impairment. Current research challenges include a lack of cross-modal convergence regarding the underlying neural-behavioral mechanisms of mTBI, which hinders therapeutics and outcome management for this frequently under-treated and vulnerable population. We used multi-modality imaging methods including magnetoencephalography (MEG) and diffusion tensor imaging (DTI) to investigate brain-behavior impairment in mTBI related to working memory. A total of 41 participants were recruited, including 23 patients with a first-time mTBI imaged within 3 months of injury (all male, age = 29.9, SD = 6.9), and 18 control participants (all male, age = 27.3, SD = 5.3). Whole-brain statistics revealed spatially concomitant functional-structural disruptions in brain-behavior interactions in working memory in the mTBI group compared with the control group. These disruptions are located in the hippocampal-prefrontal region and, additionally, in the amygdala (measured by MEG neural activation and DTI measures of fractional anisotropy in relation to working memory performance; p < .05, two-way ANCOVA, nonparametric permutations, corrected). Impaired brain-behavior connections found in the hippocampal-prefrontal and amygdala circuits indicate brain dysregulation of memory, which may leave mTBI patients vulnerable to increased environmental demands exerting memory resources, leading to related cognitive and emotional psychopathologies. The findings yield clinical implications and highlight a need for early rehabilitation after mTBI, including attention- and sensory-based behavioral exercises.

Neuroimaging Biomarkers of New-Onset Psychiatric Disorders Following Traumatic Brain Injury

Traumatic brain injury (TBI) has traditionally been associated with cognitive and behavioral changes during both the acute and chronic phases of injury. Because of its noninvasive nature, neuroimaging has the potential to provide unique information on underlying macroscopic and microscopic biological mechanisms that may serve as causative agents for these neuropsychiatric sequelae. This broad scoping review identifies at least 4 common macroscopic pathways that exist between TBI and new-onset psychiatric disorders, as well as several examples of how neuroimaging is currently being utilized in clinical research. The review then critically examines the strengths and limitations of neuroimaging for elucidating TBI-related microscopic pathology, such as microstructural changes, neuroinflammation, proteinopathies, blood-brain barrier damage, and disruptions in cellular signaling. A summary is then provided for how neuroimaging is currently being used to investigate TBI-related pathology in new-onset neurocognitive disorders, depression, and posttraumatic stress disorder. Identified gaps in the literature include a lack of prospective studies to definitively associate imaging findings with the development of new-onset psychiatric disorders, as well as antemortem imaging studies subsequently confirmed with postmortem correlates in the same study cohort. Although the spatial resolution and specificity of imaging biomarkers has greatly improved over the last 2 decades, we conclude that neuroimaging biomarkers do not yet exist for the definitive in vivo diagnosis of cellular pathology. This represents a necessary next step for further elucidating causal relationships between TBI and new-onset psychiatric disorders.

Methodology Matters: Comparing Approaches for Defining Persistent Symptoms after Mild Traumatic Brain Injury

Some people experience persistent post-concussion symptoms (PPCS) after mild traumatic brain injury (mTBI). A meaningful clinical classification and scientific progress are hampered by a lack of consensus regarding the phenomenology, assessment, and operationalization of PPCS. Here we demonstrate and evaluate how the methodology used to assess and define persistent symptoms after mTBI influences PPCS as a binary outcome. We present empirical data from 15 classification methods reflecting procedures found in the literature and clinical practice. In total, 221 patients with mTBI, 73 patients with orthopedic injuries, and 77 community controls were included in the study. The prevalence rate of PPCS in the mTBI group varied between 10% and 47%, depending on the method used to assess and define unfavorable outcome. There was generally low positive agreement between the different methods; even the two methods yielding the most similar prevalence rates (89.2% overall proportion agreement) agreed on less than half (45.5% positive agreement) of the PPCS cases. Using a liberal but not uncommon threshold for symptom severity, there was a considerable misclassification rate of PPCS in both comparison groups. Our results highlight the importance for researchers to be aware of the limitations of using binary approaches for classification of PPCS. The poor agreement between methods should be considered when (1) interpreting the heterogeneity in the existing PPCS literature and (2) developing new improved methods. An empirically informed consensus regarding classification of PPCS should be a priority for the research community.

Effective connectivity in the default mode network after paediatric traumatic brain injury

Children who experience a traumatic brain injury (TBI) are at elevated risk for a range of negative cognitive and neuropsychological outcomes. Identifying which children are at greatest risk for negative outcomes can be difficult due to the heterogeneity of TBI. To address this barrier, the current study applied a novel method of characterizing brain connectivity networks, Bayesian multi-subject vector autoregressive modelling (BVAR-connect), which used white matter integrity as priors to evaluate effective connectivity-the time-dependent relationship in functional magnetic resonance imaging (fMRI) activity between two brain regions-within the default mode network (DMN). In a prospective longitudinal study, children ages 8-15 years with mild to severe TBI underwent diffusion tensor imaging and resting state fMRI 7 weeks after injury; post-concussion and anxiety symptoms were assessed 7 months after injury. The goals of this study were to (1) characterize differences in positive effective connectivity of resting-state DMN circuitry between healthy controls and children with TBI, (2) determine if severity of TBI was associated with differences in DMN connectivity and (3) evaluate whether patterns of DMN effective connectivity predicted persistent post-concussion symptoms and anxiety. Healthy controls had unique positive connectivity that mostly emerged from the inferior temporal lobes. In contrast, children with TBI had unique effective connectivity among orbitofrontal and parietal regions. These positive orbitofrontal-parietal DMN effective connectivity patterns also differed by TBI severity and were associated with persisting behavioural outcomes. Effective connectivity may be a sensitive neuroimaging marker of TBI severity as well as a predictor of chronic post-concussion symptoms and anxiety.

Investigating White Matter Tract Microstructural Changes at Six-Twelve Weeks following Mild Traumatic Brain Injury: A Combined Diffusion Tensor Imaging and Neurite Orientation Dispersion and Density Imaging Study

Using diffusion-weighted imaging (DWI), research has demonstrated changes suggestive of damage to white matter tracts (WMT) following mild traumatic brain injury (mTBI). Yet due to the predominant use of the diffusion tensor imaging (DTI) model, which has numerous well-established limitations, it has not yet been possible to clearly examine the nature of changes to WMT microstructure following mTBI. This study used a second DWI-based technique, neurite orientation dispersion and density imaging (NODDI), in combination with DTI to measure microstructural changes within the corpus callosum, three long association and one projection WMTs at 6-12 weeks following mTBI, compared with matched trauma controls (TC). Between-groups differences were identified across all WMT for the DTI metric fractional anisotropy (FA), and the NODDI metrics orientation dispersion index (ODI) and isotropic volume fraction (ISO). No statistically significant between-groups differences were found for other DTI and NODDI metrics. Our study revealed that reduced FA was accompanied by increased ODI, suggesting that mTBI results in reduced coherence of axonal fiber bundles within the studied WMTs. These between-groups differences in WMT microstructure were found at 6-12 weeks post-injury, which suggests that structural recovery is not yet complete towards end of the typical 3-month recovery period.

Changes in brain metabolites and resting-state connectivity in collegiate basketball players as a function of play time

BACKGROUND AND PURPOSE

Magnetic resonance (MR) biomarkers are emerging for sports-related traumatic brain injury (TBI), but the effect of play time has not been characterized. Our goal was to characterize brain and inflammatory marker changes as a function of play time.

METHODS

Nine male players (21±2 years old) from a single collegiate basketball team were included. MR imaging (MRI), MR spectroscopy, and plasma were collected pre, mid, and postseason. Game time played was calculated for each subject. Changes in brain volume, diffusion tensor imaging (DTI), metabolites (normalized to total creatine, tCr), temperature, structural and functional connectivity, and inflammatory markers were quantified.

RESULTS

Myo-inositol/tCr in the left frontal white matter and brain temperature in the left frontal lobe varied significantly between time points. Glutamate (Glu/tCr) in the right frontal white matter and N-acetylaspartate in the posterior cingulate cortex (PCC) were negatively associated with minutes played. Midseason play time was associated with stronger blood-oxygen-level-dependent correlations between PCC and occipital areas, and weaker correlations between PCC and superior frontal connectivity. PCC Glu/tCr was positively associated with connectivity between the PCC and posterior supramarginal gyrus at preseason and with connectivity across time points among several right hemisphere regions. Volume, DTI, and inflammatory markers did not vary significantly.

CONCLUSION

Given that MR parameters vary with game play time in the absence of diagnosed injury, play time should be considered as a factor in sports-related TBI research.

White Matter Hyperintensities Are Not Related to Symptomatology or Cognitive Functioning in Service Members with a Remote History of Traumatic Brain Injury

This study aimed to determine whether magnetic resonance imaging (MRI) white matter hyperintensities (WMHs) are associated with symptom reporting and/or cognitive performance in 1202 active-duty service members with prior single or multiple mild traumatic brain injury (mTBI). Patients with mTBI evaluated at the National Intrepid Center of Excellence (NICoE) at Walter Reed National Military Medical Center (WRNMMC) were divided into those with (n = 632) and without (n = 570) WMHs. The groups were compared on several self-report scales including the Neurobehavioral Symptom Inventory (NSI), Post-Traumatic Stress Disorder (PTSD) Checklist-Civilian Version (PCL-C), Satisfaction with Life Scale (SWLS), and Short Form-36 Health Survey (SF-36). They were also compared on several neuropsychological measures, including tests of attention, working memory, learning and memory, executive functioning, and psychomotor functioning. After correction for multiple comparisons, there were no significant differences between the two groups on any self-reported symptom scale or cognitive test. When comparing a subgroup with the highest (20+) WMH burden (n = 60) with those with no WMHs (n = 60; matched on age, education, sex, race, rank, and TBI number), only SF-36 Health Change significantly differed between the subgroups; the multiple WMH subgroup reported worsening health over the past year (t[53] = 3.52, p = 0.001, d = 0.67) compared with the no WMH subgroup. These findings build on prior research suggesting total WMHs are not associated with significant changes in self-reported symptoms or cognitive performance in patients with a remote history of mTBI. As such, clinicians are encouraged to use caution when reporting such imaging findings.

White Matter Alteration Following SWAT Explosive Breaching Training and the Moderating Effect of a Neck Collar Device: A DTI and NODDI Study

INTRODUCTION

Special Weapons and Tactics (SWAT) personnel who practice breaching with blast exposure are at risk for blast-related head trauma. We aimed to investigate the impact of low-level blast exposure on underlying white matter (WM) microstructure based on diffusion tensor imaging (DTI) and neurite orientation and density imaging (NODDI) in SWAT personnel before and after breacher training. Diffusion tensor imaging is an advanced MRI technique sensitive to underlying WM alterations. NODDI is a novel MRI technique emerged recently that acquires diffusion weighted data from multiple shells modeling for different compartments in the microstructural environment in the brain. We also aimed to evaluate the effect of a jugular vein compression collar device in mitigating the alteration of the diffusion properties in the WM as well as its role as a moderator on the association between the diffusion property changes and the blast exposure.

MATERIALS AND METHODS

Twenty-one SWAT personnel (10 non-collar and 11 collar) completed the breacher training and underwent MRI at both baseline and after blast exposure. Diffusion weighted data were acquired with two shells (b = 1,000, 2,000 s/mm2) on 3T Phillips scanners. Diffusion tensor imaging metrices, including fractional anisotropy, mean, axial, and radial diffusivity, and NODDI metrics, including neurite density index (NDI), isotropic volume fraction (fiso), and orientation dispersion index, were calculated. Tract-based spatial statistics was used in the voxel-wise statistical analysis. Post hoc analyses were performed for the quantification of the pre- to post-blast exposure diffusion percentage change in the WM regions with significant group difference and for the assessment of the interaction of the relationship between blast exposure and diffusion alteration.

RESULTS

The non-collar group exhibited significant pre- to post-blast increase in NDI (corrected P < .05) in the WM involving the right internal capsule, the right posterior corona radiation, the right posterior thalamic radiation, and the right sagittal stratum. A subset of these regions showed significantly greater alteration in NDI and fiso in the non-collar group when compared with those in the collar group (corrected P < .05). In addition, collar wearing exhibited a significant moderating effect for the alteration of fiso for its association with average peak pulse pressure.

CONCLUSIONS

Our data provided initial evidence of the impact of blast exposure on WM diffusion alteration based on both DTI and NODDI. The mitigating effect of WM diffusivity changes and the moderating effect of collar wearing suggest that the device may serve as a promising solution to protect WM against blast exposure.

A Biomarker for Concussion: The Good, the Bad, and the Unknown

BACKGROUND

Traumatic brain injury (TBI) is a significant cause of morbidity, mortality, and disability in the US, with >2.8 million patients presenting to the emergency department (ED) annually. However, the diagnosis of TBI is challenging and presents a number of difficulties, particularly at the mildest end of the spectrum: concussion. A number of groups have researched biomarkers to aid in the evaluation of TBI, and most recently in 2018 the Food and Drug Administration approved a new blood-based immunoassay biomarker using ubiquitin carboxyl hydrolase L1 and glial fibrillary acidic protein to aid in head computed tomography (CT) triage.

CONTENT

This review clarifies the practical challenges in assessing and implementing a new blood biomarker. It then examines the clinical context and need, as well as the evidence used to validate this new immunoassay.

SUMMARY

Concussion is a multifaceted diagnosis with a need for biomarkers to assist in diagnostic and prognostic assessment. Recent articles in the lay press have revealed misunderstanding about the function of this new test, expressing hopes that this biomarker serves patients at the mildest end of the spectrum and is useful for athletes and children. None of these assumptions are correct, as this biomarker has been evaluated in patients only at the moderate end of the spectrum and has been validated only in adults presenting to the ED who have already been triaged to receive head CT, not in athletes or children. The next steps for this assay should consider clinical work flow and clarifying its intended use, including integration with existing triage methods, and validating the assay for a broader population.

The clinical utility of proton magnetic resonance spectroscopy in traumatic brain injury: recommendations from the ENIGMA MRS working group

Proton (1H) magnetic resonance spectroscopy provides a non-invasive and quantitative measure of brain metabolites. Traumatic brain injury impacts cerebral metabolism and a number of research groups have successfully used this technique as a biomarker of injury and/or outcome in both pediatric and adult TBI populations. However, this technique is underutilized, with studies being performed primarily at centers with access to MR research support. In this paper we present a technical introduction to the acquisition and analysis of in vivo 1H magnetic resonance spectroscopy and review 1H magnetic resonance spectroscopy findings in different injury populations. In addition, we propose a basic 1H magnetic resonance spectroscopy data acquisition scheme (Supplemental Information) that can be added to any imaging protocol, regardless of clinical magnetic resonance platform. We outline a number of considerations for study design as a way of encouraging the use of 1H magnetic resonance spectroscopy in the study of traumatic brain injury, as well as recommendations to improve data harmonization across groups already using this technique.

Use of Medical Cannabis to Treat Traumatic Brain Injury

There is not a single pharmacological agent with demonstrated therapeutic efficacy for traumatic brain injury (TBI). With recent legalization efforts and the growing popularity of medical cannabis, patients with TBI will inevitably consider medical cannabis as a treatment option. Pre-clinical TBI research suggests that cannabinoids have neuroprotective and psychotherapeutic properties. In contrast, recreational cannabis use has consistently shown to have detrimental effects. Our review identified a paucity of high-quality studies examining the beneficial and adverse effects of medical cannabis on TBI, with only a single phase III randomized control trial. However, observational studies demonstrate that TBI patients are using medical and recreational cannabis to treat their symptoms, highlighting inconsistencies between public policy, perception of potential efficacy, and the dearth of empirical evidence. We conclude that randomized controlled trials and prospective studies with appropriate control groups are necessary to fully understand the efficacy and potential adverse effects of medical cannabis for TBI.

Microstructure of the Corpus Callosum Long after Pediatric Concussion

OBJECTIVE

The long-term effects of pediatric concussion on white matter microstructure are poorly understood. This study investigated long-term changes in white matter diffusion properties of the corpus callosum in youth several years after concussion.

METHODS

Participants were 8-19 years old with a history of concussion (n = 36) or orthopedic injury (OI) (n = 21). Mean time since injury for the sample was 2.6 years (SD = 1.6). Participants underwent diffusion magnetic resonance imaging, completed cognitive testing, and rated their post-concussion symptoms. Measures of diffusivity (fractional anisotropy, mean, axial, and radial diffusivity) were extracted from white matter tracts in the genu, body, and splenium regions of the corpus callosum. The genu and splenium tracts were further subdivided into 21 equally spaced regions along the tract and diffusion values were extracted from each of these smaller regions.

RESULTS

White matter tracts in the genu, body, and splenium did not differ in diffusivity properties between youth with a history of concussion and those with a history of OI. No significant group differences were found in subdivisions of the genu and splenium after correcting for multiple comparisons. Diffusion metrics did not significantly correlate with symptom reports or cognitive performance.

CONCLUSIONS

These findings suggest that at approximately 2.5 years post-injury, youth with prior concussion do not have differences in their corpus callosum microstructure compared to youth with OI. Although these results are promising from the perspective of long-term recovery, further research utilizing longitudinal study designs is needed to confirm the long-term effects of pediatric concussion on white matter microstructure.

The evolution of white matter microstructural changes after mild traumatic brain injury: A longitudinal DTI and NODDI study

Neuroimaging biomarkers that can detect white matter (WM) pathology after mild traumatic brain injury (mTBI) and predict long-term outcome are needed to improve care and develop therapies. We used diffusion tensor imaging (DTI) and neurite orientation dispersion and density imaging (NODDI) to investigate WM microstructure cross-sectionally and longitudinally after mTBI and correlate these with neuropsychological performance. Cross-sectionally, early decreases of fractional anisotropy and increases of mean diffusivity corresponded to WM regions with elevated free water fraction on NODDI. This elevated free water was more extensive in the patient subgroup reporting more early postconcussive symptoms. The longer-term longitudinal WM changes consisted of declining neurite density on NODDI, suggesting axonal degeneration from diffuse axonal injury for which NODDI is more sensitive than DTI. Therefore, NODDI is a more sensitive and specific biomarker than DTI for WM microstructural changes due to mTBI that merits further study for mTBI diagnosis, prognosis, and treatment monitoring.

Cerebrovascular Reactivity After Sport Concussion: From Acute Injury to 1 Year After Medical Clearance

Neuroimaging has identified significant disturbances in cerebrovascular reactivity (CVR) in the early symptomatic phase of sport-related concussion. However, less is known about how whole-brain alterations in CVR evolve after concussion and whether they remain present beyond medical clearance to return to play (RTP). In the present study, CVR was evaluated using blood-oxygenation-level-dependent functional magnetic resonance imaging (BOLD fMRI) during a respiratory challenge. Imaging data were collected for 110 university-level athletes, including 39 concussed athletes and 71 athletic controls. The concussed athletes were imaged at the acute phase of injury (1–7 days post-injury), the subacute phase (8-14 days post-injury), medical clearance to RTP, 1 month post-RTP, and 1 year post-RTP. Enhanced negative BOLD response to controlled breathing was seen at acute injury, with attenuation of the effect mainly occurring by 1 year post-RTP. Secondary analyses showed that greater symptom severity and prolonged recovery were associated with enhanced BOLD response in the acute phase of injury, but a more attenuated BOLD response in the subacute phase. This study provides novel information characterizing the CVR response after concussion and shows CVR to be a sensitive technique for evaluating long-term brain recovery.

Functional magnetic resonance imaging study of working memory several years after pediatric concussion

PRIMARY OBJECTIVE

The neurophysiological effects of pediatric concussion several years after injury remain inadequately characterized. The objective of this study was to determine if a history of concussion was associated with BOLD response differences during an n-back working memory task in youth.

RESEARCH DESIGN

Observational, cross-sectional.

METHODS AND PROCEDURES

Participants include 52 children and adolescents (M = 15.1 years, 95%CI = 14.4-15.8, range = 9-19) with past concussion (n = 33) or orthopedic injury (OI; n = 19). Mean time since injury was 2.5 years (95%CI = 2.0-3.0). Measures included postconcussion symptom ratings, neuropsychological testing, and blood-oxygen-dependent-level (BOLD) functional magnetic resonance imaging (fMRI) during an n-back working memory task.

MAIN OUTCOMES AND RESULTS

Groups did not differ on accuracy or speed during the three n-back conditions. They also did not differ in BOLD signal change for the 1- vs. 0-back or 2- vs. 0-back contrasts (controlling for task performance).

CONCLUSIONS

This study does not support group differences in BOLD response during an n-back working memory task in youth who are on average 2.5 years post-concussion. The findings are encouraging from the perspective of understanding recovery after pediatric concussion.

Clinically Historical and Prospective Associations Between Learning Disorders and Concussion in Young Adult Athletes

Background. Athletes with specific learning disorder (LD) tend to score lower on neuropsychological tests and are at increased risk of personal injury than their counterparts without such disorders. Using a retrospective historical and prospective design, we examined whether adult athletes with LD, the most prevalent of neurodevelopmental disorders, experience greater chances of past and future concussions than their counterparts without LD. We expected to find that young athletes with LD would show greater risk of past (historical) and future (prospective) cerebral concussions. Methods. Participants (95 men and 53 women aged 18 to 25 years) were recruited from university sports teams and followed during an entire season. Of these, 38 participants had a history of LD and 101 had a history of at least 1 concussion (72 males, 29 females) at the preseason baseline. One-third experienced a new concussion. Data analytic procedures include inferential cross-tabulations. Results. Athletes with LD were twice more likely to have a concussion history at baseline and to have a history of multiple concussions than athletes without LD; 95% CI = [0.86, 4.92] and [0.77, 3.40], respectively. Athletes with LD were twice more likely to incur a new concussion than those without LD; 95% CI = [0.86, 4.92]. Conclusions. Adult athletes with LD experience greater chances of previous and future concussions compared with counterparts without LD. Preventive practices regarding individuals with neurodevelopmental disorders may not only prevent the biopsychosocial consequences of brain trauma for the individual, but also represent a cost-effective public health measure.

A Prospective Study of Childhood Predictors of Traumatic Brain Injuries Sustained in Adolescence and Adulthood

OBJECTIVE

Traumatic brain injuries (TBIs) are sustained by approximately 17% of males in the general population, many of whom subsequently present mental disorders, cognitive, and physical problems. Little is known about predictors of TBIs and how to prevent them. The present study aimed to determine whether inattention-hyperactivity and/or all externalizing problems presented by boys at age 10 predict subsequent TBIs to age 34 after taking account of previous TBIs and family social status (FSS).

METHOD

742 Canadian males were followed, prospectively, from age 6 to 34. Diagnoses of TBIs were extracted from health files, parents-reported sociodemographic and family characteristics at participants' age 6, and teachers-rated participants' behaviors at age 10. Separate logistic regression models predicted TBIs sustained from age 11 to 17 and from age 18 to 34. For each age period, two models were computed, one included previous TBIs, inattention-hyperactivity, FSS, and interaction terms, the second included previous TBIs, externalizing problems, FSS, and interaction terms.

RESULTS

In models that included inattention-hyperactivity, TBIs sustained from age 11 to 17 were predicted by age 10 inattention-hyperactivity (odds ratio [OR] = 1.46, 1.05 to 2.05) and by TBIs prior to age 11 (OR = 3.50, 1.48 to 8.24); TBIs sustained from age 18 to 34 were predicted by age 10 inattention-hyperactivity (OR = 1.31, 1.01 to 170). In models that included all externalizing problems, TBIs from age 11 to 17 were predicted by prior TBIs (OR = 3.66, 1.51 to 8.39); TBIs sustained from age 18 to 34 were predicted by age 10 externalizing problems (OR = 1.45, 1.12 to 1.86). Neither FSS nor interaction terms predicted TBIs in any of the models.

CONCLUSIONS

Among males, using evidence-based treatments to reduce inattention-hyperactivity and externalizing problems among boys could, potentially, decrease the risk of TBIs to age 34. Further, boys who sustain TBIs in childhood require monitoring to prevent recurrence in adolescence.

Post-acute white matter microstructure predicts post-acute and chronic post-concussive symptom severity following mild traumatic brain injury in children

INTRODUCTION

Mild traumatic brain injury (TBI) is a global public health concern that affects millions of children annually. Mild TBI tends to result in subtle and diffuse alterations in brain tissue, which challenges accurate clinical detection and prognostication. Diffusion tensor imaging (DTI) holds promise as a diagnostic and prognostic tool, but little research has examined DTI in post-acute mild TBI. The current study compared post-acute white matter microstructure in children with mild TBI versus those with mild orthopedic injury (OI), and examined whether post-acute DTI metrics can predict post-acute and chronic post-concussive symptoms (PCS).

MATERIALS AND METHODS

Children aged 8-16.99 years with mild TBI (n = 132) or OI (n = 69) were recruited at emergency department visits to two children's hospitals, during which parents rated children's pre-injury symptoms retrospectively. Children completed a post-acute (<2 weeks post-injury) assessment, which included a 3T MRI, and 3- and 6-month post-injury assessments. Parents and children rated PCS at each assessment. Mean diffusivity (MD) and fractional anisotropy (FA) were derived from diffusion-weighted MRI using Automatic Fiber Quantification software. Multiple multivariable linear and negative binomial regression models were used to test study aims, with False Discovery Rate (FDR) correction for multiple comparisons.

RESULTS

No significant group differences were found in any of the 20 white matter tracts after FDR correction. DTI metrics varied by age and sex, and site was a significant covariate. No interactions involving group, age, and sex were significant. DTI metrics in several tracts robustly predicted PCS ratings at 3- and 6-months post-injury, but only corpus callosum genu MD was significantly associated with post-acute PCS after FDR correction. Significant group by DTI metric interactions on chronic PCS ratings indicated that left cingulum hippocampus and thalamic radiation MD was positively associated with 3-month PCS in the OI group, but not in the mild TBI group.

CONCLUSIONS

Post-acute white matter microstructure did not differ for children with mild TBI versus OI after correcting for multiple comparisons, but was predictive of post-acute and chronic PCS in both injury groups. These findings support the potential prognostic utility of this advanced DTI technique.

Widespread White Matter Aberrations Are Associated with Phonemic Verbal Fluency Impairment in Chronic Traumatic Brain Injury

Microstructural white matter (WM) disruption and resulting abnormal structural connectivity form a potential underlying pathology in traumatic brain injury (TBI). Herein, to determine the potential mechanism of cognitive deterioration in TBI, we examined the association of damage to specific WM tracts with cognitive function in TBI patients. We recruited 18 individuals with mild-to-moderate/severe TBI in the chronic phase and 17 age-matched controls. We determined the pattern of WM aberrations in TBI using tract-based spatial statistics (TBSS) and then examined the relationship between cognitive impairment and WM damage using the threshold-free cluster enhancement correction in TBSS. TBSS analysis showed that TBI patients exhibited WM aberrations in a wide range of brain regions. In the majority of these regions, lower fractional anisotropy (FA) largely overlapped with increased radial diffusivity, but not with axial diffusivity. Further, voxel-wise correction in TBSS demonstrated that higher FA values were associated with better performance in the phonemic verbal fluency task (VFT) in widespread WM regions, but not with the semantic VFT. Despite variation in the magnitude and location of brain injury between individual cases, chronic TBI patients exhibited widespread WM aberrations. We confirmed the findings of previous studies that WM integrity is lower across the spectrum of TBI severity in chronic subjects compared to controls. Further, phonemic VFT may be a more sensitive cognitive measure of executive dysfunction associated with WM aberrations in TBI compared with semantic VFT.

Quantitative multivoxel proton MR spectroscopy for the identification of white matter abnormalities in mild traumatic brain injury: Comparison between regional and global analysis

BACKGROUND

3D brain proton MR spectroscopic imaging (1 H MRSI) facilitates simultaneous metabolic profiling of multiple loci, at higher, sub-1 cm3 , spatial resolution than single-voxel 1 H MRS with the ability to separate tissue-type partial volume contribution(s).

PURPOSE

To determine if: 1) white matter (WM) damage in mild traumatic brain injury (mTBI) is homogeneously diffuse, or if specific regions are more affected; 2) partial-volume-corrected, structure-specific 1 H MRSI voxel averaging is sensitive to regional WM metabolic abnormalities.

STUDY TYPE

Retrospective cross-sectional cohort study.

POPULATION

Twenty-seven subjects: 15 symptomatic mTBI patients, 12 matched controls.

FIELD STRENGTH/SEQUENCE

3T using 3D 1 H MRSI over a 360-cm3 volume of interest (VOI) centered over the corpus callosum, partitioned into 480 voxels, each 0.75 cm3 .

ASSESSMENT

N-acetyl-aspartate (NAA), creatine, choline, and myo-inositol concentrations estimated in predominantly WM regions: body, genu, and splenium of the corpus callosum, corona radiata, frontal, and occipital WM.

STATISTICAL TESTS

Analysis of covariance (ANCOVA) to compare patients with controls in terms of regional concentrations. The effect sizes (Cohen's d) of the mean differences were compared across regions and with previously published global data obtained with linear regression of the WM over the entire VOI in the same dataset.

RESULTS

Despite patients' global VOI WM NAA being significantly lower than the controls', no regional differences were observed for any metabolite. Regional NAA comparisons, however, were all unidirectional (patients' NAA concentrations < controls') within a narrow range: 0.3 ≤ Cohen's d ≤ 0.6.

DATA CONCLUSION

Since the patient group was symptomatic and exhibiting global WM NAA deficits, these findings suggest: 1) diffuse axonal mTBI damage; that is 2) below the 1 H MRSI detection threshold in small regions. Therefore, larger, ie, more sensitive, single-voxel 1 H MRS, placed anywhere in WM regions, may be well suited for mTBI 1 H MRS studies, given that these results are confirmed in other cohorts.

LEVEL OF EVIDENCE

2 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2019;50:1424-1432.

Juvenile mild traumatic brain injury elicits distinct spatiotemporal astrocyte responses

Mild-traumatic brain injury (mTBI) represents ~80% of all emergency room visits and increases the probability of developing long-term cognitive disorders in children. To date, molecular and cellular mechanisms underlying post-mTBI cognitive dysfunction are unknown. Astrogliosis has been shown to significantly alter astrocytes' properties following brain injury, potentially leading to significant brain dysfunction. However, such alterations have never been investigated in the context of juvenile mTBI (jmTBI). A closed-head injury model was used to study jmTBI on postnatal-day 17 mice. Astrogliosis was evaluated using glial fibrillary acidic protein (GFAP), vimentin, and nestin immunolabeling in somatosensory cortex (SSC), dentate gyrus (DG), amygdala (AMY), and infralimbic area (ILA) of prefrontal cortex in both hemispheres from 1 to 30 days postinjury (dpi). In vivo T2-weighted-imaging (T2WI) and diffusion tensor imaging (DTI) were performed at 7 and 30 dpi to examine tissue level structural alterations. Increased GFAP-labeling was observed up to 30 dpi in the ipsilateral SSC, the initial site of the impact. However, vimentin and nestin expression was not perturbed by jmTBI. The morphology of GFAP positive cells was significantly altered in the SSC, DG, AMY, and ILA up to 7 dpi that some correlated with magnetic resonance imaging changes. T2WI and DTI values were significantly altered at 30 dpi within these brain regions most prominently in regions distant from the impact site. Our data show that jmTBI triggers changes in astrocytic phenotype with a distinct spatiotemporal pattern. We speculate that the presence and time course of astrogliosis may contribute to pathophysiological processes and long-term structural alterations following jmTBI.

Repeated mild traumatic brain injuries induce persistent changes in plasma protein and magnetic resonance imaging biomarkers in the rat

A single mild traumatic brain injury (mTBI) typically causes only transient symptoms, but repeated mTBI (RmTBI) is associated with cumulative and chronic neurological abnormalities. Clinical management of mTBI is challenging due to the heterogeneous, subjective and transient nature of symptoms, and thus would be aided by objective biomarkers. Promising biomarkers including advanced magnetic resonance imaging (MRI) and plasma levels of select proteins were examined here in a rat model of RmTBI. Rats received either two mild fluid percussion or sham injuries administered five days apart. Rats underwent MRI and behavioral testing 1, 3, 5, 7, and 30 days after the second injury and blood samples were collected on days 1, 7, and 30. Structural and diffusion-weighted MRI revealed that RmTBI rats had abnormalities in the cortex and corpus callosum. Proteomic analysis of plasma found that RmTBI rats had abnormalities in markers indicating axonal and vascular injury, metabolic and mitochondrial dysfunction, and glial reactivity. These changes occurred in the presence of ongoing cognitive and sensorimotor deficits in the RmTBI rats. Our findings demonstrate that RmTBI can result in chronic neurological abnormalities, provide insight into potential contributing pathophysiological mechanisms, and supports the use of MRI and plasma protein measures as RmTBI biomarkers.

Metabolomics and Biomarker Discovery in Traumatic Brain Injury

Traumatic brain injury (TBI) is one of the leading causes of disability and mortality worldwide. The TBI pathogenesis can induce broad pathophysiological consequences and clinical outcomes attributed to the complexity of the brain. Thus, the diagnosis and prognosis are important issues for the management of mild, moderate, and severe forms of TBI. Metabolomics of readily accessible biofluids is a promising tool for establishing more useful and reliable biomarkers of TBI than using clinical findings alone. Metabolites are an integral part of all biochemical and pathophysiological pathways. Metabolomic processes respond to the internal and external stimuli resulting in an alteration of metabolite concentrations. Current high-throughput and highly sensitive analytical tools are capable of detecting and quantifying small concentrations of metabolites, allowing one to measure metabolite alterations after a pathological event when compared to a normal state or a different pathological process. Further, these metabolic biomarkers could be used for the assessment of injury severity, discovery of mechanisms of injury, and defining structural damage in the brain in TBI. Metabolic biomarkers can also be used for the prediction of outcome, monitoring treatment response, in the assessment of or prognosis of post-injury recovery, and potentially in the use of neuroplasticity procedures. Metabolomics can also enhance our understanding of the pathophysiological mechanisms of TBI, both in primary and secondary injury. Thus, this review presents the promising application of metabolomics for the assessment of TBI as a stand-alone platform or in association with proteomics in the clinical setting.

Randomised controlled clinical trial of a structured cognitive rehabilitation in patients with attention deficit following mild traumatic brain injury: study protocol

OBJECTIVES

To measure the clinical, structural and functional changes of an individualised structured cognitive rehabilitation in mild traumatic brain injury (mTBI) population.

SETTING

A single centre study, Malaysia.

PARTICIPANTS

Adults aged between 18 and 60 years with mTBI as a result of road traffic accident, with no previous history of head trauma, minimum of 9 years education and abnormal cognition at 3 months will be included. The exclusion criteria include pre-existing chronic illness or neurological/psychiatric condition, long-term medication that affects cognitive/psychological status, clinical evidence of substance intoxication at the time of injury and major polytrauma. Based on multiple estimated calculations, the minimum intended sample size is 50 participants (Cohen's d effect size=0.35; alpha level of 0.05; 85% power to detect statistical significance; 40% attrition rate).

INTERVENTIONS

Intervention group will receive individualised structured cognitive rehabilitation. Control group will receive the best patient-centred care for attention disorders. Therapy frequency for both groups will be 1 hour per week for 12 weeks.

OUTCOME MEASURES

Primary: Neuropsychological Assessment Battery-Screening Module (S-NAB) scores. Secondary: Diffusion Tensor Imaging (DTI) parameters and Goal Attainment Scaling score (GAS).

RESULTS

Results will include descriptive statistics of population demographics, CogniPlus cognitive program and metacognitive strategies. The effect of intervention will be the effect size of S-NAB scores and mean GAS T scores. DTI parameters will be compared between groups via repeated measure analysis. Correlation analysis of outcome measures will be calculated using Pearson's correlation coefficient.

CONCLUSION

This is a complex clinical intervention with multiple outcome measures to provide a comprehensive evidence-based treatment model.

ETHICS AND DISSEMINATION

The study protocol was approved by the Medical Research Ethics Committee UMMC (MREC ID NO: 2016928-4293). The findings of the trial will be disseminated through peer-reviewed journals and scientific conferences.

TRIAL REGISTRATION NUMBER

NCT03237676.

Psychological Intervention in Traumatic Brain Injury Patients

Objective

To provide a brief and comprehensive summary of recent research regarding psychological interventions for patients surviving a traumatic brain injury.

Methods

A bibliographical search was performed in PubMed, Cochrane Library, PsycNET, Scopus, ResearchGate, and Google Scholar online databases. Analysis included distribution by year of publication, age stage of participants (paediatric, adult), location of the research team, study design, type of intervention, and main outcome variables.

Results

The initial search eliciting 1541 citations was reduced to 62 relevant papers. Most publications had adult samples (88.7%). The United States outstands as the country with more research (58.1%); Latin America countries provided no results. Cognitive behavioural therapy (CBT) was the most widely used approach for treatment of (sub)clinical mental disturbances (41.9%). Neuropsychological interventions were scarce (4.8%). Outcome measures included psychiatric disorders (e.g., posttraumatic stress disorder (PTSD), depression, and anxiety) (37.1%), postconcussive symptoms (16.1%), cognitive and functional deficits (48.1%), and social and psychological dimensions (62.9%).

Conclusions

CBT outstands as the preferred therapeutic approach for treating behavioural and emotional disturbances. Also, other related therapies such as dialectical behaviour, mindfulness, and acceptance and commitment therapies have been proposed, and probably in the years to come, more literature regarding their effectiveness will be available. On the other hand, evidence showed that interventions from the field of neuropsychology are minimal if compared with its contribution to assessment. Future research should be aimed at performing studies on more diverse populations (e.g., nonmilitary communities and paediatric and Latin American populations) and at controlling designs to examine the therapeutic efficacy of psychotherapeutic and neurocognitive rehabilitation interventions and compare amelioration by injury severity, age of patients, and clinical profile, in the hopes of creating better guidelines for practitioners.

Trajectory of Postconcussive Symptoms 12 Months After Deployment in Soldiers With and Without Mild Traumatic Brain Injury: Warrior Strong Study

We analyzed data from a cohort of recently deployed soldiers from 2 US Army bases, Fort Carson and Fort Bragg (2009 to 2015). Soldiers with and without a recent history of mild traumatic brain injury (mTBI) on deployment were evaluated within days of return and at 3, 6, and 12 months. Those with mTBI were more likely than those without to endorse ≥1 postconcussive symptom as "severe" and/or "very severe" (47% vs. 21%, baseline; adjusted relative risk (RR) = 1.71, 95% confidence interval: 1.51, 1.93, all time points), which remained significant after adjusting for posttraumatic stress disorder (adjusted RR = 1.34, 95% confidence interval: 1.20, 1.50). Prevalence and relative risks for 3 of the most common baseline symptoms remained constant over time: sleep problems (RR = 2.19), forgetfulness (RR = 2.56), and irritability (RR = 2.73). The pattern was slightly different for headache (baseline, RR = 3.44; 12 months, RR = 3.26), due to increased prevalence of headache in those without mTBI. The prevalence of clinically relevant postconcussive symptoms remained relatively constant over 1 year of follow-up, whether or not symptoms were associated with concussion. Service members with recent mTBI reported more symptoms than those without at all time points.

Premorbid IQ Predicts Postconcussive Symptoms in OEF/OIF/OND Veterans with mTBI

Objective

Extant literature has demonstrated that symptoms of postconcussive syndrome (PCS) persist well beyond the expected 3-month post-injury recovery period in a minority of individuals with mild traumatic brain injury (mTBI). Suboptimal performance on validity measures and pre- and post-injury psychosocial stressors - rather than actual mTBI or current cognitive functioning - have been identified as predictors of chronic PCS. Whether premorbid IQ has any influence on chronic PCS has been understudied, in the context of established psychogenic etiologies.

Method

The sample included 31 veterans, who underwent mTBI neuropsychological evaluations six or more months post-injury in a VA outpatient neuropsychology clinic. A two-step multiple linear regression was conducted to examine the effects on the outcome variable, PCS (Neurobehavioral Symptom Inventory), of the following predictors: cognitive functioning (Repeatable Battery for the Assessment of Neuropsychological Status; Attention, Immediate Memory, and Delayed Memory Indices), performance validity, depression (Beck Depression Inventory-Second Edition), posttraumatic stress disorder (PTSD Checklist, Civilian Version), quality of sleep (Pittsburgh Sleep Quality Index), pain (Brief Pain Inventory), education, and Premorbid IQ (Wechsler Test of Adult Reading).

Results

The overall regression model containing all nine predictor variables was statistically significant. Depression (p < .05) and premorbid IQ (p < .05) were the most salient predictors of chronic PCS; in that lower premorbid IQ and greater endorsed symptoms of depression were associated with higher PCS scores. In Step 2 of the multiple linear regression, the WTAR explained an additional 6.7% of the variance in PCS after controlling for psychosocial stressors and current cognitive ability.

Conclusion

The findings support premorbid IQ as a unique and relevant predictor of chronic PCS, with significance variance accounted for beyond education, cognitive functioning, and psychosocial variables. Given the predictive relationship between premorbid IQ and PCS, adapting postconcussive interventions to meet the specific needs of individuals with varying levels of intellect may be important in minimizing ongoing symptomatology.

Stability of MRI metrics in the advanced research core of the NCAA-DoD concussion assessment, research and education (CARE) consortium

The NCAA-DoD Concussion Assessment, Research, and Education (CARE) consortium is performing a large-scale, comprehensive study of sport related concussions in college student-athletes and military service academy cadets. The CARE "Advanced Research Core" (ARC), is focused on executing a cutting-edge investigative protocol on a subset of the overall CARE athlete population. Here, we present the details of the CARE ARC MRI acquisition and processing protocol along with preliminary analyzes of within-subject, between-site, and between-subject stability across a variety of MRI biomarkers. Two experimental datasets were utilized for this analysis. First, two "human phantom" subjects were imaged multiple times at each of the four CARE ARC imaging sites, which utilize equipment from two imaging vendors. Additionally, a control cohort of healthy athletes participating in non-contact sports were enrolled in the study at each CARE ARC site and imaged at four time points. Multiple morphological image contrasts were acquired in each MRI exam; along with quantitative diffusion, functional, perfusion, and relaxometry imaging metrics. As expected, the imaging markers were found to have varying levels of stability throughout the brain. Importantly, between-subject variance was generally found to be greater than within-subject and between-site variance. These results lend support to the expectation that cross-site and cross-vendor advanced quantitative MRI metrics can be utilized to improve analytic power in assessing sensitive neurological variations; such as those effects hypothesized to occur in sports-related-concussion. This stability analysis provides a crucial foundation for further work utilizing this expansive dataset, which will ultimately be freely available through the Federal Interagency Traumatic Brain Injury Research Informatics System.

Physiological underarousal as a mechanism of aggressive behavior in university athletes with a history of concussion

INTRODUCTION

Research has indicated that athletes who engage in high-risk athletic activities, such as football and hockey, have riskier personalities than their low-risk and nonathlete counterparts (Ahmadi et al., 2011, Procedia Soc Behav Sci, 30 and 247-251; Zuckerman, 1983, Biological bases of sensation seeking, impulsivity, and anxiety, Lawrence Erlbaum Assoc Inc.). For instance, increased sensation-seeking and aggression are common in high-risk athletes, rendering these individuals more likely to sustain a subsequent injury, such as concussion. Elevated levels of certain personality traits, including impulsivity and aggression, have also been observed after concussion (Goswami et al., 2016, Brain Struct Funct, 221 and 1911-1925). The purpose of this study therefore was to determine whether aggressive behavior in university athletes may be accounted for, in part, by a history of concussion, rather than exclusively athletic status.

METHODS

Using a quasi-experimental design, 66 university students (n = 18 nonathletes, n = 24 low-risk athletes, n = 24 high-risk athletes) with (n = 27) and without a history of concussion (n = 39) completed the Buss & Perry Aggression Questionnaire (BPAQ; Buss & Perry, , J Pers Soc Psychol, 63 and 452) and provided electrodermal activation (EDA) as an index of physiological arousal.

RESULTS

It was found that decreased physiological arousal among students with a history of concussion was associated with greater endorsement of physical aggression. Moreover, athletic status did not account for this pattern of aggression, as athletes and nonathletes did not differ in terms of self-reported aggressive tendencies.

CONCLUSIONS

Physiological compromise after concussive injury may act as an independent mechanism of aggressive behavior in athletes beyond factors, such as athletic status.

Hybrid Diffusion Imaging in Mild Traumatic Brain Injury

Mild traumatic brain injury (mTBI) is an important public health problem. Although conventional medical imaging techniques can detect moderate-to-severe injuries, they are relatively insensitive to mTBI. In this study, we used hybrid diffusion imaging (HYDI) to detect white matter alterations in 19 patients with mTBI and 23 other trauma control patients. Within 15 days (standard deviation = 10) of brain injury, all subjects underwent magnetic resonance HYDI and were assessed with a battery of neuropsychological tests of sustained attention, memory, and executive function. Tract-based spatial statistics (TBSS) was used for voxel-wise statistical analyses within the white matter skeleton to study between-group differences in diffusion metrics, within-group correlations between diffusion metrics and clinical outcomes, and between-group interaction effects. The advanced diffusion imaging techniques, including neurite orientation dispersion and density imaging (NODDI) and q-space analyses, appeared to be more sensitive then classic diffusion tensor imaging. Only NODDI-derived intra-axonal volume fraction (V_ic) demonstrated significant group differences (i.e., 5–9% lower in the injured brain). Within the mTBI group, V_ic and a q-space measure, P₀, correlated with 6 of 10 neuropsychological tests, including measures of attention, memory, and executive function. In addition, the direction of correlations differed significantly between groups (R² > 0.71 and p_interation < 0.03). Specifically, in the control group, higher V_ic and P₀ were associated with better performances on clinical assessments, whereas in the mTBI group, higher V_ic and P₀ were associated with worse performances with correlation coefficients >0.83. In summary, the NODDI-derived axonal density index and q-space measure for tissue restriction demonstrated superior sensitivity to white matter changes shortly after mTBI. These techniques hold promise as a neuroimaging biomarker for mTBI.

Assessment of Oculomotor Function in Patients With Postconcussion Syndrome: A Systematic Review

BACKGROUND

Concussion and its associated sequel, postconcussion syndrome (PCS), have a debilitating impact on the lives of concussed patients. However, a diagnostic biomarker for this condition is lacking. Recently, there has been a surge of interest in using oculomotor function testing as an objective assessment of patients with PCS.

OBJECTIVES

To systematically synthesize, appraise, and summarize all published empirical studies that have assessed alteration of oculomotor functions in patients with PCS.

METHODS

Medline, Embase, PsychINFO, and CINAHL databases searched up to July 2016 for studies that used oculomotor function assessment in patients with postconcussion symptoms.

RESULTS

The search identified 1637 citations, and finally 8 case-control studies were included. Of these, 5 studies used a similar task with a target moving in a circular trajectory. Three other studies measured conventional oculomotor tasks such as saccade, vergence, and smooth pursuit eye movements.

CONCLUSIONS

Currently, there is limited support for the recommendation of oculomotor function assessments for diagnosis and identification of patients with PCS following head trauma. Therefore, more rigorous studies assessing oculomotor function changes in patients with PCS are warranted.