Neuropsychological results and neuropathological findings at autopsy in a case of mild traumatic brain injury

Changes in decision-making function in patients with subacute mild traumatic brain injury

Although awareness regarding patients with mild traumatic brain injury has increased, they have not received sufficient attention in clinics; hence, many patients still experience only partial recovery. Deficits in decision-making function are frequently experienced by these patients. Accurate identification of impairment in the early stages after brain injury is particularly crucial for timely intervention and the prevention of long-term cognitive consequences. Therefore, we investigated the changes in decision-making ability under tasks of ambiguity and risk in patients with mild traumatic brain injury with a rule-based neuropsychological paradigm. In this study, patients (n = 39) and matched healthy controls (n = 38) completed general neuropsychological background tests and decision-making tasks (Iowa Gambling Task and Game of Dice Task). We found that patients had extensive cognitive impairment in general attention, memory and information processing speed in the subacute phase, and confirmed that patients had different degrees of impairment in decision-making abilities under ambiguity and risk. Furthermore, the decline of memory and executive function may be related to decision-making dysfunction.

Maximizing the Clinical Value of Blood-Based Biomarkers for Mild Traumatic Brain Injury

Mild traumatic brain injury (TBI) and concussion can have serious consequences that develop over time with unpredictable levels of recovery. Millions of concussions occur yearly, and a substantial number result in lingering symptoms, loss of productivity, and lower quality of life. The diagnosis may not be made for multiple reasons, including due to patient hesitancy to undergo neuroimaging and inability of imaging to detect minimal damage. Biomarkers could fill this gap, but the time needed to send blood to a laboratory for analysis made this impractical until point-of-care measurement became available. A handheld blood test is now on the market for diagnosis of concussion based on the specific blood biomarkers glial fibrillary acidic protein (GFAP) and ubiquitin carboxyl terminal hydrolase L1 (UCH-L1). This paper discusses rapid blood biomarker assessment for mild TBI and its implications in improving prediction of TBI course, avoiding repeated head trauma, and its potential role in assessing new therapeutic options. Although we focus on the Abbott i-STAT TBI plasma test because it is the first to be FDA-cleared, our discussion applies to any comparable test systems that may become available in the future. The difficulties in changing emergency department protocols to include new technology are addressed.

Diffusion tensor imaging in the courtroom: Distinction between scientific specificity and legally admissible evidence

Interest and uptake of science and medicine peer-reviewed literature by readers outside of a paper’s topical subject, field or even discipline is ever-expanding. While the application of knowledge from one field or discipline to others can stimulate innovative solutions to problems facing modern society, it is also fraught with danger for misuse. In the practice of law in the United States, academic papers are submitted to the courts as evidence in personal injury litigation from both the plaintiff (complainant) and defendant. Such transcendence of an academic publication over disciplinary boundaries is immediately met with the challenge of application by a group that inherently lacks in-depth knowledge on the scientific method, the practice of evidence-based medicine, or the publication process as a structured and internationally synthesized process involving peer review and guided by ethical standards and norms. A modern-day example of this is the ongoing conflict between the sensitivity of diffusion tensor imaging (DTI) and the legal standards for admissibility of evidence in litigation cases of mild traumatic brain injury (mTBI). In this review, we amalgamate the peer-reviewed research on DTI in mTBI with the court’s rationale underlying decisions to admit or exclude evidence of DTI abnormalities to support claims of brain injury. We found that the papers which are critical of the use of DTI in the courtroom reflect a primary misunderstanding about how diagnostic biomarkers differ legally from relevant and admissible evidence. The clinical use of DTI to identify white matter abnormalities in the brain at the chronic stage is a valid methodology both clinically as well as forensically, contributes data that may or may not corroborate the existence of white matter damage, and should be admitted into evidence in personal injury trials if supported by a clinician. We also delve into an aspect of science publication and peer review that can be manipulated by scientists and clinicians to publish an opinion piece and misrepresent it as an unbiased, evidence-based, systematic research article in court cases, the decisions of which establish precedence for future cases and have implications on future legislation that will impact the lives of every citizen and erode the integrity of science and medicine practitioners.

Neuro-psychiatric symptoms in directly and indirectly blast exposed civilian survivors of urban missile attacks

BACKGROUND

Blast-explosion may cause traumatic brain injury (TBI), leading to post-concussion syndrome (PCS). In studies on military personnel, PCS symptoms are highly similar to those occurring in post-traumatic stress disorder (PTSD), questioning the overlap between these syndromes. In the current study we assessed PCS and PTSD in civilians following exposure to rocket attacks. We hypothesized that PCS symptomatology and brain connectivity will be associated with the objective physical exposure, while PTSD symptomatology will be associated with the subjective mental experience.

METHODS

Two hundred eighty nine residents of explosion sites have participated in the current study. Participants completed self-report of PCS and PTSD. The association between objective and subjective factors of blast and clinical outcomes was assessed using multivariate analysis. White-matter (WM) alterations and cognitive abilities were assessed in a sub-group of participants (n = 46) and non-exposed controls (n = 16). Non-parametric analysis was used to compare connectivity and cognition between the groups.

RESULTS

Blast-exposed individuals reported higher PTSD and PCS symptomatology. Among exposed individuals, those who were directly exposed to blast, reported higher levels of subjective feeling of danger and presented WM hypoconnectivity. Cognitive abilities did not differ between groups. Several risk factors for the development of PCS and PTSD were identified.

CONCLUSIONS

Civilians exposed to blast present higher PCS/PTSD symptomatology as well as WM hypoconnectivity. Although symptoms are sub-clinical, they might lead to the future development of a full-blown syndrome and should be considered carefully. The similarities between PCS and PTSD suggest that despite the different etiology, namely, the physical trauma in PCS and the emotional trauma in PTSD, these are not distinct syndromes, but rather represent a combined biopsychological disorder with a wide spectrum of behavioral, emotional, cognitive and neurological symptoms.

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.

Volumetric MRI Findings in Mild Traumatic Brain Injury (mTBI) and Neuropsychological Outcome

Region of interest (ROI) volumetric assessment has become a standard technique in quantitative neuroimaging. ROI volume is thought to represent a coarse proxy for making inferences about the structural integrity of a brain region when compared to normative values representative of a healthy sample, adjusted for age and various demographic factors. This review focuses on structural volumetric analyses that have been performed in the study of neuropathological effects from mild traumatic brain injury (mTBI) in relation to neuropsychological outcome. From a ROI perspective, the probable candidate structures that are most likely affected in mTBI represent the target regions covered in this review. These include the corpus callosum, cingulate, thalamus, pituitary-hypothalamic area, basal ganglia, amygdala, and hippocampus and associated structures including the fornix and mammillary bodies, as well as whole brain and cerebral cortex along with the cerebellum. Ventricular volumetrics are also reviewed as an indirect assessment of parenchymal change in response to injury. This review demonstrates the potential role and limitations of examining structural changes in the ROIs mentioned above in relation to neuropsychological outcome. There is also discussion and review of the role that post-traumatic stress disorder (PTSD) may play in structural outcome in mTBI. As emphasized in the conclusions, structural volumetric findings in mTBI are likely just a single facet of what should be a multimodality approach to image analysis in mTBI, with an emphasis on how the injury damages or disrupts neural network integrity. The review provides an historical context to quantitative neuroimaging in neuropsychology along with commentary about future directions for volumetric neuroimaging research in mTBI.

Human embryonic stem cell-derived cerebral organoids for treatment of mild traumatic brain injury in a mouse model

OBJECTIVE

There are no effective treatments for relieving neuronal dysfunction after mild traumatic brain injury (TBI). Here, we evaluated therapeutic efficacy of human embryonic stem cell-derived cerebral organoids (hCOs) in a mild TBI model, in terms of repair of damaged cortical regions, neurogenesis, and improved cognitive function.

METHODS

Male C57BL/6 J mice were randomly divided into sham-operated, mild TBI, and mild TBI with hCO groups. hCOs cultured at 8 weeks were used for transplantation. Mice were sacrificed at 7 and 14 days after transplantation followed by immunofluorescence staining, cytokine profile microarray, and novel object recognition test.

RESULTS

8W-hCOs transplantation significantly reduced neuronal cell death, recovered microvessel density, and promoted neurogenesis in the ipsilateral subventricular zone and dentate gyrus of hippocampus after mild TBI. In addition, increased angiogenesis into the engrafted hCOs was observed. Microarray results of hCOs revealed neuronal differentiation potential and higher expression of early brain development proteins associated with neurogenesis, angiogenesis and extracellular matrix remodeling. Ultimately, 8W-hCO transplantation resulted in reconstruction of damaged cortex and improvement in cognitive function after mild TBI.

CONCLUSION

hCO transplantation may be feasible for treating mild TBI-related neuronal dysfunction via reconstruction of damaged cortex and neurogenesis in the hippocampus.

Reframing postconcussional syndrome as an interface disorder of neurology, psychiatry and psychology

Persistent symptoms following a minor head injury can cause significant morbidity, yet the underlying mechanisms for this are poorly understood. The shortcomings of the current terminology that refer to non-specific symptom clusters is discussed. This update considers the need for a multi-dimensional approach for the heterogenous mechanisms driving persistent symptoms after mild traumatic brain injury. Relevant pathophysiology is discussed to make the case for mild traumatic brain injury to be conceptualized as an interface disorder spanning neurology, psychiatry and psychology. The relevance of pre-injury factors, psychological co-morbidities and their interaction with the injury to produce persistent symptoms are reviewed. The interplay with psychiatric diagnoses, functional and somatic symptom disorder presentations and the influence of the medicolegal process is considered. The judicious use and interpretation of investigations given the above complexity is discussed, with suggestions of how the explanation of the diagnostic formulation to the patient can be tailored, including insight into the above processes, to aid recovery. Moving beyond the one-dimensional concept of 'postconcussional syndrome' and reframing the cause of persistent symptoms following mild traumatic brain injury in a bio-psycho-socio-ecological model will hopefully improve understanding of the underlying contributory mechanistic interactions and facilitate treatment.

Hidden Truth in Cerebral Concussion—Traumatic Axonal Injury: A Narrative Mini-Review

This study reviewed traumatic axonal injury (TAI) in patients with concussion. Concussion refers to transient changes in the neurological function of the brain resulting from head trauma that should not involve any organic brain injury. On the other hand, TAI has been reported in autopsy studies of the human brain and histopathological studies of animal brains following concussion before the development of diffusion tensor imaging (DTI). The diagnosis of TAI in live patients with concussion is limited because of the low resolution of conventional brain magnetic resonance imaging. Since the first study by Arfanakis et al. in 2002, several hundred studies have reported TAI in patients with concussion using DTI. Furthermore, dozens of studies have demonstrated TAI using diffusion tensor tractography for various neural tracts in individual patients with concussion. Hence, DTI provides valuable data for the diagnosis of TAI in patients with concussion. Nevertheless, the confirmation of TAI in live patients with concussion can be limited because a histopathological study via a brain biopsy is required to confirm TAI. Accordingly, further studies for a diagnostic approach to TAI using DTI without a histopathological test in individual patients with concussion will be necessary in the clinical field.

Noninvasive magnetic resonance imaging techniques in mild traumatic brain injury research and diagnosis

Mild traumatic brain injury (mTBI), frequently referred to as concussion, is one of the most common neurological disorders. The underlying neural mechanisms of functional disturbances in the brains of concussed individuals remain elusive. Novel forms of brain imaging have been developed to assess patients postconcussion, including functional magnetic resonance imaging (fMRI), susceptibility-weighted imaging (SWI), diffusion MRI (dMRI), and perfusion MRI [arterial spin labeling (ASL)], but results have been mixed with a more common utilization in the research environment and a slower integration into the clinical setting. In this review, the benefits and drawbacks of the methods are described: fMRI is an effective method in the diagnosis of concussion but it is expensive and time-consuming making it difficult for regular use in everyday practice; SWI allows detection of microhemorrhages in acute and chronic phases of concussion; dMRI is primarily used for the detection of white matter abnormalities, especially axonal injury, specific for mTBI; and ASL is an alternative to the BOLD method with its ability to track cerebral blood flow alterations. Thus, the absence of a universal diagnostic neuroimaging method suggests a need for the adoption of a multimodal approach to the neuroimaging of mTBI. Taken together, these methods, with their underlying functional and structural features, can contribute from different angles to a deeper understanding of mTBI mechanisms such that a comprehensive diagnosis of mTBI becomes feasible for the clinician.

Traumatic brain injury-induced cerebral microbleeds in the elderly

Traumatic brain injury (TBI) was shown to lead to the development of cerebral microbleeds (CMBs), which are associated with long term cognitive decline and gait disturbances in patients. The elderly is one of the most vulnerable parts of the population to suffer TBI. Importantly, ageing is known to exacerbate microvascular fragility and to promote the formation of CMBs. In this overview, the effect of ageing is discussed on the development and characteristics of TBI-related CMBs, with special emphasis on CMBs associated with mild TBI. Four cases of TBI-related CMBs are described to illustrate the concept that ageing exacerbates the deleterious microvascular effects of TBI and that similar brain trauma may induce more CMBs in old patients than in young ones. Recommendations are made for future prospective studies to establish the mechanistic effects of ageing on the formation of CMBs after TBI, and to determine long-term consequences of CMBs on clinically relevant outcome measures including cognitive performance, gait and balance function.

Apolipoprotein ɛ4 Status and Brain Structure 12 Months after Mild Traumatic Injury: Brain Age Prediction Using Brain Morphometry and Diffusion Tensor Imaging

Background: Apolipoprotein E (APOE) ɛ4 is associated with poor outcome following moderate to severe traumatic brain injury (TBI). There is a lack of studies investigating the influence of APOE ɛ4 on intracranial pathology following mild traumatic brain injury (MTBI). This study explores the association between APOE ɛ4 and MRI measures of brain age prediction, brain morphometry, and diffusion tensor imaging (DTI). Methods: Patients aged 16 to 65 with acute MTBI admitted to the trauma center were included. Multimodal MRI was performed 12 months after injury and associated with APOE ɛ4 status. Corrections for multiple comparisons were done using false discovery rate (FDR). Results: Of included patients, 123 patients had available APOE, volumetric, and DTI data of sufficient quality. There were no differences between APOE ɛ4 carriers (39%) and non-carriers in demographic and clinical data. Age prediction revealed high accuracy both for the DTI-based and the brain morphometry based model. Group comparisons revealed no significant differences in brain-age gap between ɛ4 carriers and non-carriers, and no significant differences in conventional measures of brain morphometry and volumes. Compared to non-carriers, APOE ɛ4 carriers showed lower fractional anisotropy (FA) in the hippocampal part of the cingulum bundle, which did not remain significant after FDR adjustment. Conclusion: APOE ɛ4 carriers might be vulnerable to reduced neuronal integrity in the cingulum. Larger cohort studies are warranted to replicate this finding.

Sex-Related Differences in the Effects of Sports-Related Concussion: A Review

Sports-related concussion is a serious health challenge, and females are at higher risk of sustaining a sports-related concussion compared to males. Although there are many studies that investigate outcomes following concussion, females remain an understudied population, despite representing a large proportion of the organized sports community. In this review, we provide a summary of studies that investigate sex-related differences in outcome following sports-related concussion. Moreover, we provide an introduction to the methods used to study sex-related differences after sports-related concussion, including common clinical and cognitive measures, neuroimaging techniques, as well as biomarkers. A literature search inclusive of articles published to March 2020 was performed using PubMed. The studies were reviewed and discussed with regard to the methods used. Findings from these studies remain mixed with regard to the effect of sex on clinical symptoms, concussion-related alterations in brain structure and function, and recovery trajectories. Nonetheless, there is initial evidence to suggest that sex-related differences following concussion are important to consider in efforts to develop objective biomarkers for the diagnosis and prognosis of concussion. Additional studies on this topic are, however, clearly needed to improve our understanding of sex-related differences following concussion, as well as to understand their neurobiological underpinnings. Such studies will help pave the way toward more personalized clinical management and treatment of sports-related concussion.

White Matter Changes Caused by Mild Traumatic Brain Injury in Mice Evaluated Using Neurite Orientation Dispersion and Density Imaging

Mild traumatic brain injury (mTBI) is common and can lead to persistent cognitive and behavioral symptoms. Although diffusion tensor imaging (DTI) has demonstrated some sensitivity to changes in white matter following mTBI, recent studies have suggested that more complex geometric models of diffusion, including the neurite orientation dispersion and density imaging (NODDI) model, may be more sensitive and specific. Here, we evaluate microstructural changes in white matter following mTBI using DTI and NODDI in a mouse model, and compare the time course of these changes to behavioral impairment and recovery. We also assess volumetric changes for a comprehensive picture of the structural alterations in the brain and histological staining to identify cellular changes that may contribute to the differences detected in the imaging data. Increased orientation dispersion index (ODI) was observed in the optic tracts of mTBI mice compared with shams. Changes in fractional anisotropy (FA) were not statistically significant. Volume deficits were detected in the optic tract as well as in several gray matter regions: the lateral geniculate nuclei of the thalamus, the entorhinal cortex, and the superior colliculi. Glial fibrillary acidic protein (GFAP) and ionized calcium binding adaptor molecule 1 (Iba1) staining was increased in the optic tracts of mTBI brains, and this staining correlated with ODI values. A transient impairment in working memory was observed, which resolved by 6 weeks, whereas increased ODI, GFAP, and Iba1 persisted to 18 weeks post-injury. We conclude that the optic tracts are particularly vulnerable to damage from the closed-skull impact model used in this study, and that ODI may be a more sensitive metric to this damage than FA. Differences in ODI and in histological measures of astrogliosis, neuroinflammation, and axonal degeneration persist beyond behavioral impairment in this model.

Brain injury-induced dysfunction of the blood brain barrier as a risk for dementia

The blood-brain barrier (BBB) is a complex and dynamic physiological interface between brain parenchyma and cerebral vasculature. It is composed of closely interacting cells and signaling molecules that regulate movement of solutes, ions, nutrients, macromolecules, and immune cells into the brain and removal of products of normal and abnormal brain cell metabolism. Dysfunction of multiple components of the BBB occurs in aging, inflammatory diseases, traumatic brain injury (TBI, severe or mild repetitive), and in chronic degenerative dementing disorders for which aging, inflammation, and TBI are considered risk factors. BBB permeability changes after TBI result in leakage of serum proteins, influx of immune cells, perivascular inflammation, as well as impairment of efflux transporter systems and accumulation of aggregation-prone molecules involved in hallmark pathologies of neurodegenerative diseases with dementia. In addition, cerebral vascular dysfunction with persistent alterations in cerebral blood flow and neurovascular coupling contribute to brain ischemia, neuronal degeneration, and synaptic dysfunction. While the idea of TBI as a risk factor for dementia is supported by many shared pathological features, it remains a hypothesis that needs further testing in experimental models and in human studies. The current review focusses on pathological mechanisms shared between TBI and neurodegenerative disorders characterized by accumulation of pathological protein aggregates, such as Alzheimer's disease and chronic traumatic encephalopathy. We discuss critical knowledge gaps in the field that need to be explored to clarify the relationship between TBI and risk for dementia and emphasize the need for longitudinal in vivo studies using imaging and biomarkers of BBB dysfunction in people with single or multiple TBI.

Diagnostic Problems in Diffuse Axonal Injury

In this study, three problems associated with diagnosing diffuse axonal injury (DAI) in patients with traumatic brain injury are reviewed: the shortage of scientific evidence supporting the 6-hour loss of consciousness (LOC) diagnostic criterion to discriminate concussion and DAI, the low sensitivity of conventional brain MRI in the detection of DAI lesions, and the inappropriateness of the term diffuse in DAI. Pathological study by brain biopsy is required to confirm DAI; however, performing a brain biopsy for the diagnosis of DAI in a living patient is impossible. Therefore, the diagnosis of DAI in a living patient is clinically determined based on the duration of LOC, clinical manifestations, and the results of conventional brain MRI. There is a shortage of scientific evidence supporting the use of the 6-hour LOC criterion to distinguish DAI from concussion, and axonal injuries have been detected in many concussion cases with a less than 6-hour LOC. Moreover, due to the low sensitivity of conventional brain MRI, which can only detect DAI lesions in approximately half of DAI patients, diagnostic MRI criteria for DAI are not well established. In contrast, diffusion tensor imaging (DTI) has been shown to have high sensitivity for the detection of DAI lesions. As DTI is a relatively new method, further studies aimed at the establishment of diagnostic criteria for DAI detection using DTI are needed. On the other hand, because DAI distribution is not diffuse but multifocal, and because axonal injury lesions have been detected in concussion patients, steps to standardize the use of terms related to axonal injury in both concussion and DAI are necessary.

Fractal dimension brain morphometry: a novel approach to quantify white matter in traumatic brain injury

Traumatic brain injury (TBI) is the main cause of disability in people younger than 35 in the United States. The mechanisms of TBI are complex resulting in both focal and diffuse brain damage. Fractal dimension (FD) is a measure that can characterize morphometric complexity and variability of brain structure especially white matter (WM) structure and may provide novel insights into the injuries evident following TBI. FD-based brain morphometry may provide information on WM structural changes after TBI that is more sensitive to subtle structural changes post injury compared to conventional MRI measurements. Anatomical and diffusion tensor imaging (DTI) data were obtained using a 3 T MRI scanner in subjects with moderate to severe TBI and in healthy controls (HC). Whole brain WM volume, grey matter volume, cortical thickness, cortical area, FD and DTI metrics were evaluated globally and for the left and right hemispheres separately. A neuropsychological test battery sensitive to cognitive impairment associated with traumatic brain injury was performed. TBI group showed lower structural complexity (FD) bilaterally (p < 0.05). No significant difference in either grey matter volume, cortical thickness or cortical area was observed in any of the brain regions between TBI and healthy controls. No significant differences in whole brain WM volume or DTI metrics between TBI and HC groups were observed. Behavioral data analysis revealed that WM FD accounted for a significant amount of variance in executive functioning and processing speed beyond demographic and DTI variables. FD therefore, may serve as a sensitive marker of injury and may play a role in outcome prediction in TBI.

Diagnostic Approach to Traumatic Axonal Injury of the Spinothalamic Tract in Individual Patients with Mild Traumatic Brain Injury

Objectives: We investigated an approach for the diagnosis of traumatic axonal injury (TAI) of the spinothalamic tract (STT) that was based on diffusion tensor tractography (DTT) results and a statistical comparison of individual patients who showed central pain following mild traumatic brain injury (mTBI) with the control group. Methods: Five right-handed female patients in their forties and with central pain following mTBI and 12 age-, sex-, and handedness-matched healthy control subjects were recruited. After DTT reconstruction of the STT, we analyzed the STT in terms of three DTT parameters (fractional anisotropy (FA), mean diffusivity (MD), and fiber number (FN)) and its configuration (narrowing and tearing). To assess narrowing, we determined the area of the STT on an axial slice of the subcortical white matter. Results: the FN values were significantly lower in at least one hemisphere of each patient when compared to those of the control subjects (p < 0.05). Significant decrements from the STT area in the control group were observed in at least one hemisphere of each patient (p < 0.05). Regarding configurational analysis, the STT showed narrowing and/or partial tearing in at least one hemisphere of each of the five patients. Conclusions: Herein, we demonstrate a DTT-based approach for the diagnosis of TAI of the STT. The approach involves a statistical comparison between DTT parameters of individual patients who show central pain following mTBI and those of an age-, gender-, and handedness-matched control group. We think that the method described in this study can be useful in the diagnosis of TAI of the STT in individual mTBI patients.

A Review of the Role of Auditory Evoked Potentials in Mild Traumatic Brain Injury Assessment

Around 75% to 90% of people who experience a traumatic brain injury (TBI) are classified as having a mild TBI (mTBI). The term mTBI is synonymous with concussion or mild head injury (MHI) and is characterized by symptoms of headache, nausea, dizziness, and blurred vision. Problems in cognitive abilities such as deficits in memory, processing speed, executive functioning, and attention are also considered symptoms of mTBI. Since these symptoms are subtle in nature and may not appear immediately following the injury, mTBI is often undetected on conventional neuropsychological tests. Current neuroimaging techniques may not be sensitive enough in identifying the array of microscopic neuroanatomical and subtle neurophysiological changes following mTBI. To this end, electrophysiological tests, such as auditory evoked potentials (AEPs), can be used as sensitive tools in tracking physiological changes underlying physical and cognitive symptoms associated with mTBI. The purpose of this review article is to examine the body of literature describing the application of AEPs in the assessment of mTBI and to explore various parameters of AEPs which may hold diagnostic value in predicting positive rehabilitative outcomes for people with mTBI.

Repeated mild traumatic brain injuries is not associated with volumetric differences in former high school football players

We investigated potential brain volumetric differences in a sample of former high school football players many years after these injuries. Forty community-dwelling males ages 40-65 who played high school football, but not college or professional sports, were recruited. The experimental group (n = 20) endorsed experiencing two or more mTBIs on an empirically validated mTBI assessment tool (median = 3, range = 2-15). The control group (n = 20) denied ever experiencing an mTBI. Participants completed a self-report index of current mTBI symptomatology and underwent high-resolution T1-weighted MRI scanning, which were analyzed using the Freesurfer software package. A priori regions of interest (ROIs) included total intracranial volume (ICV), total gray matter, total white matter, bilateral anterior cingulate cortex, bilateral hippocampi, and lateral ventricles. ROIs were corrected for head size using a normalization method that took ICV into account. Despite an adequate sample size and being matched on age, education, estimated premorbid IQ, current concussive symptomatology, there were no statistically significant volumetric group differences across all of the ROIs. These data suggest that multiple mTBIs from high school football may not be associated with measurable brain atrophy later in life. Accounting for the severity of injury and chronicity of sport exposure may be especially important when measuring long-term neuroanatomical differences.

Relationship between white matter integrity and post-traumatic cognitive deficits: a systematic review and meta-analysis

OBJECTIVE

To investigate relationships between cognitive domains and white matter changes in different regions in patients with cognitive deficits after traumatic brain injury (TBI).

METHODS

Databases including PubMed, Embase, Web of Science and CENTRAL were searched for studies published before 5 August 2017. Correlation coefficients between cognition and white matter integrity, measured by diffusion metrics, including fractional anisotropy (FA), were pooled from 49 studies including 1405 patients. The influence of demographic factors was assessed by meta-regression analysis.

RESULTS

Significant pooled FA-executive correlations (p<0.001) were found across various regions, including the corpus callosum (CC) (r=0.42, 95% CI 0.30 to 0.54), superior longitudinal fasciculus (r=0.50, 95% CI 0.41 to 0.59) and internal capsule (IC) (r=0.49, 95% CI 0.37 to 0.61). The fornix (r=0.62, 95% CI 0.45 to 0.78) and cingulum (r=0.57, 95% CI 0.34 to 0.81) particularly correlated with memory (p<0.001). The CC and IC also showed significant relationships with attention and processing speed (p<0.001). Demographic factors had no influence overall, except that studies with a greater proportion of males had stronger correlations between memory and white matter (p<0.05).

CONCLUSIONS

FA is the most sensitive metric for detecting post-TBI cognitive decline across various domains. Representative white matter regions, such as the CC and IC, perform better than whole-brain white matter for reflecting a wide range of cognitive domains, including memory, attention and executive functions. Moreover, the fornix and cingulum particularly reflect memory function. They yield insights into particular imaging indicators that have neuropsychological value.

The Involvement of Iron in Traumatic Brain Injury and Neurodegenerative Disease

Traumatic brain injury (TBI) consists of acute and long-term pathophysiological sequelae that ultimately lead to cognitive and motor function deficits, with age being a critical risk factor for poorer prognosis. TBI has been recently linked to the development of neurodegenerative diseases later in life including Alzheimer’s disease, Parkinson’s disease, chronic traumatic encephalopathy, and multiple sclerosis. The accumulation of iron in the brain has been documented in a number of neurodegenerative diseases, and also in normal aging, and can contribute to neurotoxicity through a variety of mechanisms including the production of free radicals leading to oxidative stress, excitotoxicity and by promoting inflammatory reactions. A growing body of evidence similarly supports a deleterious role of iron in the pathogenesis of TBI. Iron deposition in the injured brain can occur via hemorrhage/microhemorrhages (heme-bound iron) or independently as labile iron (non-heme bound), which is considered to be more damaging to the brain. This review focusses on the role of iron in potentiating neurodegeneration in TBI, with insight into the intersection with neurodegenerative conditions. An important implication of this work is the potential for therapeutic approaches that target iron to attenuate the neuropathology/phenotype related to TBI and to also reduce the associated risk of developing neurodegenerative disease.

Mild traumatic brain injury: Is DTI ready for the courtroom?

Important advances in neuroscience and neuroimaging have revolutionized our understanding of the human brain. Many of these advances provide new evidence regarding compensable injuries that have been used to support changes in legal policy. For example, we now know that regions of the brain involved in decision making continue to develop into the mid-20s, and this information weighs heavily in determining that execution or automatic sentence of life without the possibility of parole for someone younger than 18 years old, at the time of the crime, violates the 8th Amendment prohibition against "cruel and unusual punishment." The probative value of other testimony regarding neuroimaging, however, is less clear, particularly for mild traumatic brain injury (mTBI), also known as concussion. There is nonetheless some evidence that new imaging technologies, most notably diffusion tensor imaging (DTI), may be useful in detecting mTBI. More specifically, DTI is sensitive to detecting diffuse axonal brain injuries in white matter, the most common brain injury in mTBI. DTI is, in fact, the most promising technique available today for such injuries and it is beginning to be used clinically, although it remains largely within the purview of research. Its probative value is also not clear as it may be both prejudicial and misleading given that standardization is not yet established for use in either the clinic or the courtroom, and thus it may be premature for use in either. There are also concerns with the methods and analyses that have been used to provide quantitative evidence in legal cases. It is within this context that we provide a commentary on the use of neuroimaging in the courtroom, most particularly DTI, and the admissibility of evidence, as well as the definition and role of expert testimony. While there is a great deal of evidence demonstrating cognitive impairments in attention, processing speed, memory, and concentration from neuropsychological testing following mTBI, we focus here on the more recent introduction of DTI imaging in the courtroom. We also review definitions of mTBI followed by admissibility standards for scientific evidence in the courtroom, including Daubert criteria and two subsequent cases that comprise the so-called Daubert trilogy rulings on the admissibility of expert testimony. This is followed by a brief review of neuroimaging techniques available today, the latter with an emphasis on DTI and its application to mTBI. We then review some of the court rulings on the use of DTI. We end by highlighting the importance of neuroimaging in providing a new window on the brain, while cautioning against the premature use of new advances in imaging in the courtroom before standards are established in the clinical arena, which are informed by research. We also discuss further what is needed to reach a tipping point where such advances will provide important and meaningful data with respect to their probative value.

Neuroimaging of deployment-associated traumatic brain injury (TBI) with a focus on mild TBI (mTBI) since 2009

OBJECTIVES

A substantial body of recent research has aimed to better understand the clinical sequelae of military trauma through the application of advanced brain imaging procedures in Veteran populations. The primary objective of this review was to highlight a portion of these recent studies to demonstrate how imaging tools can be used to understand military-associated brain injury.

METHODS

We focus here on the phenomenon of mild traumatic brain injury (mTBI) given its high prevalence in the Veteran population and current recognition of the need to better understand the clinical implications of this trauma. This is intended to provide readers with an initial exposure to the field of neuroimaging of mTBI with a brief introduction to the concept of traumatic brain injury, followed by a summary of the major imaging techniques that have been applied to the study of mTBI.

RESULTS

Taken together, the collection of studies reviewed demonstrates a clear role for neuroimaging towards understanding the various neural consequences of mTBI as well as the clinical complications of such brain changes.

CONCLUSIONS

This information must be considered in the larger context of research into mTBI, including the potentially unique nature of blast exposure and the long-term consequences of mTBI.

Cerebral microhemorrhages due to traumatic brain injury and their effects on the aging human brain

Although cerebral microbleeds (CMBs) are frequently associated with traumatic brain injury (TBI), their effects on clinical outcome after TBI remain controversial and poorly understood, particularly in older adults. Here we (1) highlight major challenges and opportunities associated with studying the effects of TBI-mediated CMBs; (2) review the evidence on their potential effects on cognitive and neural outcome as a function of age at injury; and (3) suggest priorities for future research on understanding the clinical implications of CMBs. Although TBI-mediated CMBs are likely distinct from those due to cerebral amyloid angiopathy or other neurodegenerative diseases, the effects of these 2 CMB types on brain function may share common features. Furthermore, in older TBI victims, the incidence of TBI-mediated CMBs may approximate that of cerebral amyloid angiopathy-related CMBs, and thus warrants detailed study. Because the alterations effected by CMBs on brain structure and function are both unique and age-dependent, it seems likely that novel, age-tailored therapeutic approaches are necessary for the adequate clinical interpretation and treatment of these ubiquitous and underappreciated TBI sequelae.

Profiling biomarkers of traumatic axonal injury: From mouse to man

Traumatic brain injury (TBI) poses a major public health problem on a global scale. Its burden results from high mortality and significant morbidity in survivors. This stems, in part, from an ongoing inadequacy in diagnostic and prognostic indicators despite significant technological advances. Traumatic axonal injury (TAI) is a key driver of the ongoing pathological process following TBI, causing chronic neurological deficits and disability. The science underpinning biomarkers of TAI has been a subject of many reviews in recent literature. However, in this review we provide a comprehensive account of biomarkers from animal models to clinical studies, bridging the gap between experimental science and clinical medicine. We have discussed pathogenesis, temporal kinetics, relationships to neuro-imaging, and, most importantly, clinical applicability in order to provide a holistic perspective of how this could improve TBI diagnosis and predict clinical outcome in a real-life setting. We conclude that early and reliable identification of axonal injury post-TBI with the help of body fluid biomarkers could enhance current care of TBI patients by (i) increasing speed and accuracy of diagnosis, (ii) providing invaluable prognostic information, (iii) allow efficient allocation of rehabilitation services, and (iv) provide potential therapeutic targets. The optimal model for assessing TAI is likely to involve multiple components, including several blood biomarkers and neuro-imaging modalities, at different time points.

BrainPhys® increases neurofilament levels in CNS cultures, and facilitates investigation of axonal damage after a mechanical stretch-injury in vitro

Neurobasal®/B27 is a gold standard culture media used to study primary neurons in vitro. An alternative media (BrainPhys®/SM1) was recently developed which robustly enhances neuronal activity vs. Neurobasal® or DMEM. To the best of our knowledge BrainPhys® has not been explored in the setting of neuronal injury. Here we characterized the utility of BrainPhys® in a model of in vitro mechanical-stretch injury.

METHODS/RESULTS

Primary rat cortical neurons were maintained in classic Neurobasal®, or sequentially maintained in Neurocult® followed by BrainPhys® (hereafter simply referred to as "BrainPhys® maintained neurons"). The levels of axonal markers and proteins involved in neurotransmission were compared on day in vitro 10 (DIV10). BrainPhys® maintained neurons had higher levels of GluN2B, GluR1, Neurofilament light/heavy chain (NF-L & NF-H), and protein phosphatase 2 A (PP2A) vs. neurons in Neurobasal®. Mechanical stretch-injury (50ms/54% biaxial stretch) to BrainPhys® maintained neurons modestly (albeit significantly) increased 24h lactate dehydrogenase (LDH) levels but markedly decreased axonal NF-L levels post-injury vs. uninjured controls or neurons given a milder 38% stretch-injury. Furthermore, two 54% stretch-injuries (in tandem) exacerbated 24h LDH release, increased α-spectrin breakdown products (SBDPs), and decreased Tau levels. Also, BrainPhys® maintained cultures had decreased markers of cell damage 24h after a single 54% stretch-injury vs. neurons in Neurobasal®. Finally, we tested the hypothesis that lentivirus mediated overexpression of the pro-death protein RBM5 exacerbates neuronal and/or axonal injury in primary CNS cultures. RBM5 overexpression vs. empty-vector controls increased 24h LDH release, and SBDP levels, after a single 54% stretch-injury but did not affect NF-L levels or Tau.

CONCLUSION

BrainPhys® is a promising new reagent which facilities the investigation of molecular targets involved in axonal and/or neuronal injury in vitro.

Bidirectional Changes in Anisotropy Are Associated with Outcomes in Mild Traumatic Brain Injury

BACKGROUND AND PURPOSE

Mild traumatic brain injury results in a heterogeneous constellation of deficits and symptoms that persist in a subset of patients. This prospective longitudinal study identifies early diffusion tensor imaging biomarkers of mild traumatic brain injury that significantly relate to outcomes at 1 year following injury.

MATERIALS AND METHODS

DTI was performed on 39 subjects with mild traumatic brain injury within 16 days of injury and 40 controls; 26 subjects with mild traumatic brain injury returned for follow-up at 1 year. We identified subject-specific regions of abnormally high and low fractional anisotropy and calculated mean fractional anisotropy, axial diffusivity, radial diffusivity, and mean diffusivity across all white matter voxels brain-wide and each of several white matter regions. Assessment of cognitive performance and symptom burden was performed at 1 year.

RESULTS

Significant associations of brain-wide DTI measures and outcomes included the following: mean radial diffusivity and mean diffusivity with memory; and mean fractional anisotropy, radial diffusivity, and mean diffusivity with health-related quality of life. Significant differences in outcomes were found between subjects with and without abnormally high fractional anisotropy for the following white matter regions and outcome measures: left frontal lobe and left temporal lobe with attention at 1 year, left and right cerebelli with somatic postconcussion symptoms at 1 year, and right thalamus with emotional postconcussion symptoms at 1 year.

CONCLUSIONS

Individualized assessment of DTI abnormalities significantly relates to long-term outcomes in mild traumatic brain injury. Abnormally high fractional anisotropy is significantly associated with better outcomes and might represent an imaging correlate of postinjury compensatory processes.

Mild Traumatic Brain Injury

Mild traumatic brain injury (MTBI) is a significant public health problem worldwide. Injured individuals have an increased relative risk of developing a variety of neuropsychiatric conditions associated with the profile of brain regions typically affected in TBI. Within a neurobiopsychosocial framework, this article reviews what is known about the neuropsychiatric sequelae of MTBI, with an emphasis on recent advances.

Traumatic brain injury and the post-concussion syndrome: A diffusion tensor tractography study

Aim:

The aim of the present study is to evaluate diffusion tensor tractography (DTT) as a tool for detecting diffuse axonal injury in patients of acute, mild, and moderate traumatic brain injury (TBI), using two diffusion variables: Fractional anisotropy (FA) and mean diffusivity (MD). The correlation of these indices with the severity of post-concussive symptoms was also assessed.

Materials and Methods:

Nineteen patients with acute, mild, or moderate TBI and twelve age- and sex-matched healthy controls were recruited. Following Magnetic Resonance Imaging (MRI) on a 3.0-T scanner, DTT was performed using the ‘fiber assignment by continuous tracking’ (FACT) algorithm for fiber reconstruction. Appropriate statistical tools were used to see the difference in FA and MD values between the control and patient groups. In the latter group, the severity of post-concussive symptoms was assessed six months following trauma, using the Rivermead Postconcussion Symptoms Questionnaire (RPSQ).

Results:

The patients displayed significant reduction in FA compared to the controls (P < 0.05) in several tracts, notably the corpus callosum, fornix, bilateral uncinate fasciculus, and bilateral superior thalamic radiations. Changes in MD were statistically significant in the left uncinate, inferior longitudinal fasciculus, and left posterior thalamic radiation. A strong correlation between these indices and the RPSQ scores was observed in several white matter tracts.

Conclusion:

Diffusion tensor imaging (DTI)-based quantitative analysis in acute, mild, and moderate TBI can identify axonal injury neuropathology, over and above that visualized on conventional MRI scans. Furthermore, the significant correlation observed between FA and MD indices and the severity of post-concussive symptoms could make it a useful predictor of the long-term outcome.

Iron Deposition Is Positively Related to Cognitive Impairment in Patients with Chronic Mild Traumatic Brain Injury: Assessment with Susceptibility Weighted Imaging

Background. This study aimed to evaluate the usability of SWI in assessment of brain iron to detect cognitive dysfunction in patients with chronic mild traumatic brain injury (mTBI). Methods. 39 patients with mTBI and 37 normal controls were given the Mini-Mental State Examination (MMSE) and underwent SWI scanning at least 6 months after injury. Angle radian values were calculated with phase images. The angle radian values were compared between groups using analysis of covariance, and their association with MMSE scores was analyzed using Spearman correlations. Results. Significantly higher angle radian values (p < 0.05) were found in the head of the caudate nucleus, the lenticular nucleus, the hippocampus, the thalamus, the right substantia nigra, the red nucleus, and the splenium of the corpus callosum (SCC) in the mTBI group, compared to the control group. MMSE scores were negatively correlated with angle radian values in the right substantia nigra (r = −0.685, p < 0.001). Conclusions. Patients with chronic mTBI might have abnormally high accumulations of iron, and their MMSE scores are negatively associated with angle radian values in the right substantia nigra, suggesting a role of SWI in the assessment of cognitive impairments of these patients.

Diffusion tensor imaging and magnetic resonance spectroscopy in traumatic brain injury: a review of recent literature

Concussion is the most common form of traumatic brain injury (TBI), but diagnosis remains controversial because the brain appears quite normal in conventional computed tomography and magnetic resonance imaging (MRI). These conventional tools are not sensitive enough to detect diffuse traumatic axonal injury, and cannot depict aberrations in mild TBIs. Advanced MRI modalities including diffusion tensor imaging (DTI), and magnetic resonance spectroscopy (MRS), make it possible to detect brain injuries in TBI. The purpose of this review is to provide the latest information regarding the visualization and quantification of important abnormalities in TBI and new insights into their clinical significance. Advanced imaging modalities allow the discovery of biomarkers of injury and the detection of changes in brain injury over time. Such tools will likely be used to evaluate treatment efficacy in research. Combining multiple imaging modalities would not only provide greater insight into the underlying physiological changes in TBI, but also improve diagnostic accuracy in predicting outcomes. In this review we present evidence of brain abnormalities in TBI based on investigations using MRI, including DTI and MRS. Our review provides a summary of some of the important studies published from 2002 to 2012 on the topic of MRI findings in head trauma. With the growing realization that even mild head injury can lead to neurocognitive deficits, medical imaging has assumed preeminence for detecting abnormalities associated with TBI. Advanced MRI modalities such as DTI and MRS have an important role in the diagnosis of lesions for TBI patients.

A review of neuroimaging findings in repetitive brain trauma

Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease confirmed at postmortem. Those at highest risk are professional athletes who participate in contact sports and military personnel who are exposed to repetitive blast events. All neuropathologically confirmed CTE cases, to date, have had a history of repetitive head impacts. This suggests that repetitive head impacts may be necessary for the initiation of the pathogenetic cascade that, in some cases, leads to CTE. Importantly, while all CTE appears to result from repetitive brain trauma, not all repetitive brain trauma results in CTE. Magnetic resonance imaging has great potential for understanding better the underlying mechanisms of repetitive brain trauma. In this review, we provide an overview of advanced imaging techniques currently used to investigate brain anomalies. We also provide an overview of neuroimaging findings in those exposed to repetitive head impacts in the acute/subacute and chronic phase of injury and in more neurodegenerative phases of injury, as well as in military personnel exposed to repetitive head impacts. Finally, we discuss future directions for research that will likely lead to a better understanding of the underlying mechanisms separating those who recover from repetitive brain trauma vs. those who go on to develop CTE.

Systemic, local, and imaging biomarkers of brain injury: more needed, and better use of those already established?

Much progress has been made over the past two decades in the treatment of severe acute brain injury, including traumatic brain injury and subarachnoid hemorrhage, resulting in a higher proportion of patients surviving with better outcomes. This has arisen from a combination of factors. These include improvements in procedures at the scene (pre-hospital) and in the hospital emergency department, advances in neuromonitoring in the intensive care unit, both continuously at the bedside and intermittently in scans, evolution and refinement of protocol-driven therapy for better management of patients, and advances in surgical procedures and rehabilitation. Nevertheless, many patients still experience varying degrees of long-term disabilities post-injury with consequent demands on carers and resources, and there is room for improvement. Biomarkers are a key aspect of neuromonitoring. A broad definition of a biomarker is any observable feature that can be used to inform on the state of the patient, e.g., a molecular species, a feature on a scan, or a monitoring characteristic, e.g., cerebrovascular pressure reactivity index. Biomarkers are usually quantitative measures, which can be utilized in diagnosis and monitoring of response to treatment. They are thus crucial to the development of therapies and may be utilized as surrogate endpoints in Phase II clinical trials. To date, there is no specific drug treatment for acute brain injury, and many seemingly promising agents emerging from pre-clinical animal models have failed in clinical trials. Large Phase III studies of clinical outcomes are costly, consuming time and resources. It is therefore important that adequate Phase II clinical studies with informative surrogate endpoints are performed employing appropriate biomarkers. In this article, we review some of the available systemic, local, and imaging biomarkers and technologies relevant in acute brain injury patients, and highlight gaps in the current state of knowledge.

Specificity of cognitive and behavioral complaints in post-traumatic stress disorder and mild traumatic brain injury

Characterization of cognitive and behavioral complaints is explored in Post-traumatic stress disorder (PTSD) and mild traumatic brain injury (MTBI) samples according to the severity of PTSD, depression and general anxiety conditions. Self-reported questionnaires on cognitive and behavioral changes are administered to PTSD, MTBI, MTBI/PTSD and control groups. Confounding variables are controlled. All groups report more complaints since the traumatic event. PTSD and MTBI/PTSD groups report more anxiety symptoms, depression and complaints compared to the MTBI group. Relatives of the PTSD group confirm most of the behavioral changes reported. Results suggest the utility of self-reported questionnaires to personalize cognitive and behavioral interventions in PTSD and MTBI to cope with the impacts of the traumatic event.

Mild traumatic brain injury

Mild traumatic brain injury (TBI) is common but accurate diagnosis and defining criteria for mild TBI and its clinical consequences have been problematic. Mild TBI causes transient neurophysiologic brain dysfunction, sometimes with structural axonal and neuronal damage. Biomarkers, such as newer imaging technologies and protein markers, are promising indicators of brain injury but are not ready for clinical use. Diagnosis relies on clinical criteria regarding depth and duration of impaired consciousness and amnesia. These criteria are particularly difficult to confirm at the least severe end of the mild TBI continuum, especially when relying on subjective, retrospective accounts. The postconcussive syndrome is a controversial concept because of varying criteria, inconsistent symptom clusters and the evidence that similar symptom profiles occur with other disorders, and even in a proportion of healthy individuals. The clinical consequences of mild TBI can be conceptualized as two multidimensional disorders: (1) a constellation of acute symptoms that might be termed early phase post-traumatic disorder (e.g., headache, dizziness, imbalance, fatigue, sleep disruption, impaired cognition), that typically resolve in days to weeks and are largely related to brain trauma and concomitant injuries; (2) a later set of symptoms, a late phase post-traumatic disorder, evolving out of the early phase in a minority of patients, with a more prolonged (months to years), sometimes worsening set of somatic, emotional, and cognitive symptoms. The later phase disorder is highly influenced by a variety of psychosocial factors and has little specificity for brain injury, although a history of multiple concussions seems to increase the risk of more severe and longer duration symptoms. Effective early phase management may prevent or limit the later phase disorder and should include education about symptoms and expectations for recovery, as well as recommendations for activity modifications. Later phase treatment should be informed by thoughtful differential diagnosis and the multiplicity of premorbid and comorbid conditions that may influence symptoms. Treatment should incorporate a hierarchical, sequential approach to symptom management, prioritizing problems with significant functional impact and effective, available interventions (e.g., headache, depression, anxiety, insomnia, vertigo).

Objective neuropsychological deficits in post-traumatic stress disorder and mild traumatic brain injury: what remains beyond symptom similarity?

This exploratory study intends to characterize the neuropsychological profile in persons with post-traumatic stress disorder (PTSD) and mild traumatic brain injury (mTBI) using objective measures of cognitive performance. A neuropsychological battery of tests for attention, memory and executive functions was administered to four groups: PTSD (n = 25), mTBI (n = 19), subjects with two formal diagnoses: Post-traumatic Stress Disorder and Mild Traumatic Brain Injury (mTBI/PTSD) (n = 6) and controls (n = 25). Confounding variables, such as medical, developmental or neurological antecedents, were controlled and measures of co-morbid conditions, such as depression and anxiety, were considered. The PTSD and mTBI/PTSD groups reported more anxiety and depressive symptoms. They also presented more cognitive deficits than the mTBI group. Since the two PTSD groups differ in severity of PTSD symptoms but not in severity of depression and anxiety symptoms, the PTSD condition could not be considered as the unique factor affecting the results. The findings underline the importance of controlling for confounding medical and psychological co-morbidities in the evaluation and treatment of PTSD populations, especially when a concomitant mTBI is also suspected.

Enhanced attention capture by emotional stimuli in mild traumatic brain injury

Mild traumatic brain injury (mTBI) may be associated with compromised executive functioning and altered emotional reactivity. Despite frequent affective and cognitive symptoms in mTBI, objective evidence for brain dysfunction is often lacking. Previously we have reported compromised performance in symptomatic mTBI patients in an executive reaction time (RT) test, a computer-based RT test engaging several executive functions simultaneously. Here, we investigated the cognitive control processes in mTBI in context of threat-related stimuli. We used behavioral measures and event-related potentials (ERP) to investigate attentional capture by task-relevant and task-irrelevant emotional stimuli during a Go-NoGo task requiring cognitive control. We also assessed subjective cognitive, somatic, and emotional symptoms with questionnaires. Twenty-seven subjects with previous mTBI and 17 controls with previous ankle injury participated in the study over 9 months post-injury. Electroencephalogram (EEG) was recorded while patients performed a modified executive RT-test. N2-P3 ERP component was used as a general measure of allocated attentional and executive processing resources. Although at the time of the testing, the mTBI and the control groups did not differ in symptom endorsement, mTBI patients reported having had more emotional symptoms overall since the injury than controls. The overall RT-test performance levels did not differ between groups. However, when threat-related emotional stimuli were used as Go-signals, the mTBI group was faster than the control group. In comparison to neutral stimuli, threat-related stimuli were associated with increased N2-P3 amplitude in all conditions. This threat-related enhancement of the N2-P3 complex was greater in mTBI patients than in controls in response to Go signals and NoGo signals, independent of relevance. We conclude that mTBI may be associated with enhanced attentional and executive resource allocation to threat-related stimuli. Along with behavioral evidence for enhanced attention allocation to threat stimuli, increased brain responses to threat were observed in mTBI. Enhanced attention capture by threat-related emotional stimuli may reflect inefficient top-down control of bottom-up influences of emotion, and might contribute to affective symptoms in mTBI.

Mortality and morbidity 15 years after hospital admission with mild head injury: a prospective case-controlled population study

OBJECTIVE

To investigate mortality rate in a population of adults admitted to hospital with mild head injury (MHI) 15 years later.

DESIGN

A prospective case control, record linkage study.

PARTICIPANTS

2428 adults with MHI and an equal number of community controls (CC) were case-matched for age, gender and social deprivation. A further control group admitted with a non-head injury was in addition matched for duration of hospital admission. Controls with a history of head injury prior to study entry were excluded.

MAIN OUTCOME MEASURES

Death or survival 15 years poststudy entry.

RESULTS

Mortality per 1000 per year after MHI (24.49; 95% CI 23.21 to 25.79) was higher than in CC (13.34; 95% CI 12.29 to 14.44; p<0.0001) or 'other injury' controls (OIC) (19.63; 95% CI 18.43 to 20.87; p<0.0001). Age at injury was important: younger adults (15-54 years) with MHI had a 4.2-fold greater risk of death than CC; in adults aged over 54, the risk was 1.4 times higher. Gender and social deprivation showed a similar association with death in the MHI and control groups. Repeated head injury was a risk factor for death in the MHI group. The frequency of hospital admission with systemic disease preinjury and postinjury was higher in both injury groups than in CC and higher in MHI than OIC. Prospective data in the MHI group suggest an association between preinjury lifestyle and mortality. Causes of death after MHI were similar to those of the control groups.

CONCLUSIONS

Adults hospitalised with MHI had greater risk of death in the following 15 years than matched controls. The extent to which lifestyle and potential chronic changes in neuropathology explain these findings is unclear. Lifestyle factors do contribute to risk of death after MHI and this finding has implications for lifestyle management interventions.

Primary paranode demyelination modulates slowly developing axonal depolarization in a model of axonal injury

Neurological sequelae of mild traumatic brain injury are associated with the damage to white matter myelinated axons. In vitro models of axonal injury suggest that the progression to pathological ruin is initiated by the mechanical damage to tetrodotoxin-sensitive voltage-gated sodium channels that breaches the ion balance through alteration in kinetic properties of these channels. In myelinated axons, sodium channels are concentrated at nodes of Ranvier, making these sites vulnerable to mechanical injury. Nodal damage can also be inflicted by injury-induced partial demyelination of paranode/juxtaparanode compartments that flank the nodes and contain high density of voltage-gated potassium channels. Demyelination-induced potassium deregulation can further aggravate axonal damage; however, the role of paranode/juxtaparanode demyelination in immediate impairment of axonal function, and its contribution to the development of axonal depolarization remain elusive. A biophysically realistic computational model of myelinated axon that incorporates ion exchange mechanisms and nodal/paranodal/juxtaparanodal organization was developed and used to study the impact of injury-induced demyelination on axonal signal transmission. Injured axons showed alterations in signal propagation that were consistent with the experimental findings and with the notion of reduced axonal excitability immediately post trauma. Injury-induced demyelination strongly modulated the rate of axonal depolarization, suggesting that trauma-induced damage to paranode myelin can affect axonal transition to degradation. Results of these studies clarify the contribution of paranode demyelination to immediate post trauma alterations in axonal function and suggest that partial paranode demyelination should be considered as another "injury parameter" that is likely to determine the stability of axonal function.

Toward objective markers of concussion in sport: a review of white matter and neurometabolic changes in the brain after sports-related concussion

Abstract Sports-related concussion is an issue that has piqued the public's attention of late as concerns surrounding potential long-term sequelae as well as new methods of characterizing the effects of this form of injury continue to develop. For the most part, diagnosis of concussion is based on subjective clinical measures and thus is prone to under-reporting. In the current environment, where conventional imaging modalities, such as computed tomography and magnetic resonance imaging, are unable to elucidate the degree of white matter damage and neurometabolic change, a discussion of two advanced imaging techniques-diffusion tensor imaging (DTI) and magnetic resonance spectroscopy (MRS)-is undertaken with a view to highlighting their potential utility. Our aim is to outline a variety of the approaches to concussion research that have been employed, with special attention given to the clinical considerations and acute complications attributed to concussive injury. DTI and MRS have been at the forefront of research as a result of their noninvasiveness and ease of acquisition, and hence it is thought that the use of these neuroimaging modalities has the potential to aid clinical decision making and management, including guiding return-to-play protocols.

The presence and role of iron in mild traumatic brain injury: an imaging perspective

Mild traumatic brain injury (mTBI), although often presenting without the gross structural abnormalities seen in more severe forms of brain trauma, can nonetheless result in lingering cognitive and behavioral problems along with subtle alterations in brain structure and function. Repeated injuries are associated with brain atrophy and dementia in the form of chronic traumatic encephalopathy (CTE). The mechanisms underlying these dysfunctions are poorly understood. There is a growing body of evidence that brain iron is abnormal after TBI, and brain iron has also been implicated in a host of neurodegenerative disorders. The purpose of this article is to review evidence about the function of iron in the pathophysiology of mTBI and the role that advanced imaging modalities can play in further elucidating said function. MRI techniques sensitive to field inhomogeneities provide supporting evidence for both deep gray matter non-heme iron accumulation as well as focal microhemorrhage resulting from mTBI. In addition, there is evidence that iron may contribute to pathology after mTBI through a number of mechanisms, including generation of reactive oxygen species (ROS), exacerbation of oxidative stress from other sources, and encouragement of tau phosphorylation and the formation of neurofibrillary tangles. Finally, recent animal studies suggest that iron may serve as a therapeutic target in mitigating the effects of mTBI. However, research on the presence and role of iron in mTBI and CTE is still relatively sparse, and further work is necessary to elucidate issues such as the sources of increased iron and the chain of secondary injury.

Neuroimaging biomarkers in mild traumatic brain injury (mTBI)

Reviewed herein are contemporary neuroimaging methods that detect abnormalities associated with mild traumatic brain injury (mTBI). Despite advances in demonstrating underlying neuropathology in a subset of individuals who sustain mTBI, considerable disagreement persists in neuropsychology about mTBI outcome and metrics for evaluation. This review outlines a thesis for the select use of sensitive neuroimaging methods as potential biomarkers of brain injury recognizing that the majority of individuals who sustain an mTBI recover without neuroimaging signs or neuropsychological sequelae detected with methods currently applied. Magnetic resonance imaging (MRI) provides several measures that could serve as mTBI biomarkers including the detection of hemosiderin and white matter abnormalities, assessment of white matter integrity derived from diffusion tensor imaging (DTI), and quantitative measures that directly assess neuroanatomy. Improved prediction of neuropsychological outcomes in mTBI may be achieved with the use of targeted neuroimaging markers.

PTSD modifies performance on a task of affective executive control among deployed OEF/OIF veterans with mild traumatic brain injury

Individuals with post-traumatic stress disorder (PTSD) show a cognitive bias for threatening information, reflecting dysregulated executive control for affective stimuli. This study examined whether comorbid mild Traumatic Brain Injury (mTBI) with PTSD exacerbates this bias. A computer-administered Affective Go/No-Go task measured reaction times (RTs) and errors of omission and commission to words with a non-combat-related positive or negative valence in 72 deployed United States service members from the wars in Iraq and Afghanistan. Incidents of military-related mTBI were measured with the Boston Assessment of Traumatic Brain Injury-Lifetime. PTSD symptoms were measured with the Clinician-Administered PTSD Scale. Participants were divided into those with (mTBI+, n = 34) and without a history of military-related mTBI (mTBI-, n = 38). Valence of the target stimuli differentially impacted errors of commission and decision bias (criterion) in the mTBI+ and mTBI- groups. Specifically, within the mTBI+ group, increasing severity of PTSD symptoms was associated with an increasingly liberal response pattern (defined as more commission errors to negative distractors and greater hit rate for positive stimuli) in the positive compared to the negative blocks. This association was not observed in the mTBI- group. This study underscores the importance of considering the impact of a military-related mTBI and PTSD severity upon affective executive control.