Relationships between acute imaging biomarkers and theory of mind impairment in post-acute pediatric traumatic brain injury: A prospective analysis using susceptibility weighted imaging (SWI)

What predicts persisting social impairment following pediatric traumatic brain injury: contribution of a biopsychosocial approach

BACKGROUND

Psychosocial deficits, such as emotional, behavioral and social problems, reflect the most common and disabling consequences of pediatric traumatic brain injury (TBI). Their causes and recovery likely differ from physical and cognitive skills, due to disruption to developing brain networks and the influence of the child's environment. Despite increasing recognition of post-injury behavioral and social problems, there exists a paucity of research regarding the incidence of social impairment, and factors predicting risk and resilience in the social domain over time since injury.

METHODS

Using a prospective, longitudinal design, and a bio-psychosocial framework, we studied children with TBI (n = 107) at baseline (pre-injury function), 6 months, 1 and 2-years post-injury. We assessed intellectual ability, attention/executive function, social cognition, social communication and socio-emotional function. Children underwent structural magnetic resonance imaging (MRI) at 2-8 weeks post-injury. Parents rated their child's socio-emotional function and their own mental health, family function and perceived burden.

RESULTS

We distinguished five social recovery profiles, characterized by a complex interplay between environment and pre- and post-TBI factors, with injury factors playing a lesser role. Resilience in social competence was linked to intact family and parent function, intact pre-injury adaptive abilities, post-TBI cognition and social participation. Vulnerability in the social domain was related to poor pre- and post-injury adaptive abilities, greater behavioral concerns, and poorer pre- and post-injury parent health and family function.

CONCLUSIONS

We identified five distinct social recovery trajectories post-child-TBI, each characterized by a unique biopsychosocial profile, highlighting the importance of comprehensive social assessment and understanding of factors contributing to social impairment, to target resources and interventions to children at highest risk.

Social Functioning and Autistic Behaviors in Youth Following Acquired Brain Injury

Children and adolescents who survive the pediatric intensive care unit (PICU) with an acquired brain injury (ABI) often demonstrate a variety of physical, cognitive, emotional/behavioral, and social sequelae termed post-intensive care syndrome (PICS). Social communication and interaction challenges have also been observed clinically, and there is growing literature documenting these occurrences in youth following ABI. The extent of these social changes varies among patients, and a subset of patients go on to exhibit social and behavioral profiles closely resembling those of autistic youth. We reviewed empirical research regarding social functioning in youth following ABI, as well as the overlap between individuals with ABI and autistic youth, published from January 2009 to August 2022 on PubMed and Scopus databases. Clinical case examples from a well-established post-PICU follow-up program are also provided to exemplify the complexity of this phenomenon.

Exploring the measurement of pediatric cognitive-communication disorders in traumatic brain injury research: A scoping review

OBJECTIVE

To synthesize information about the constructs measured, measurement instruments used, and the timing of assessment of cognitive-communication disorders (CCDs) in pediatric traumatic brain injury (TBI) research.

METHODS AND PROCEDURES

Scoping review conducted in alignment with Arksey and O'Malley's five-stage methodological framework and reported per the PRISMA extension for Scoping Reviews. Inclusion criteria: (a) cohort description, case-control, and treatment studies; (b) participants with TBI aged 5-18 years; (c) communication or psychosocial outcomes; and (d) English full-text journal articles. The first author reviewed all titles, abstracts, and full-text articles; 10% were independently reviewed.

OUTCOMES AND RESULTS

Following screening, a total of 687 articles were included and 919 measurement instruments, measuring 2134 unique constructs, were extracted. The Child Behavior Checklist was the most used measurement instrument and 'Global Outcomes/Recovery' was the construct most frequently measured. The length of longitudinal monitoring ranged between ≤3 months and 16 years.

CONCLUSIONS AND IMPLICATIONS

We found considerable heterogeneity in the constructs measured, the measurement instruments used, and the timing of CCD assessment in pediatric TBI research. A consistent approach to measurement may support clinical decision-making and the efficient use of data beyond individual studies in systematic reviews and meta-analyses.

Global and domain-specific self-esteem after pediatric traumatic brain injury: Contribution of injury characteristics and parent mental health

This prospective, longitudinal case-control study examined global and domain-specific aspects of self-esteem 6-months following pediatric traumatic brain injury (TBI) and evaluated the contribution of injury-related factors and parent mental health to child self-esteem. Participants included 103 children with mild-severe TBI representing consecutive admissions to the emergency department of the Royal Children's Hospital, Melbourne, Australia. Forty-three age-and-sex matched typically developing controls were recruited for comparison. Information regarding injury characteristics including age at injury and clinical indicators of TBI severity were collected for participants at recruitment, with research magnetic resonance imaging conducted 2-8 weeks later. At 6 months post-injury, children rated their global and domain-specific self-esteem (Harter Self-Perception Profile for Children), and ratings of parent mental health were collected (General Health Questionnaire). Self-esteem for behavioural and academic domains was significantly poorer for children with TBI relative to TD children. In the TBI group, higher child-rated scores of global and domain-specific aspects of self-esteem were associated with more severe TBI, presence of frontal neuropathology, younger age at injury, and lower parental symptoms of anxiety/insomnia. Given the psychological status of parents represents a potentially modifiable risk factor, it may form the target of clinical interventions designed to bolster child self-esteem following pediatric TBI.

Magnetic Resonance Imaging Findings Are Associated with Long-Term Global Neurological Function or Death after Traumatic Brain Injury in Critically Ill Children

The identification of children with traumatic brain injury (TBI) who are at risk of death or poor global neurological functional outcome remains a challenge. Magnetic resonance imaging (MRI) can detect several brain pathologies that are a result of TBI; however, the types and locations of pathology that are the most predictive remain to be determined. Forty-two critically ill children with TBI were recruited prospectively from pediatric intensive care units at five Canadian children's hospitals. Pathologies detected on subacute phase MRIs included cerebral hematoma, herniation, cerebral laceration, cerebral edema, midline shift, and the presence and location of cerebral contusion or diffuse axonal injury (DAI) in 28 regions of interest were assessed. Global functional outcome or death more than 12 months post-injury was assessed using the Pediatric Cerebral Performance Category score. Linear modeling was employed to evaluate the utility of an MRI composite score for predicting long-term global neurological function or death after injury, and nonlinear Random Forest modeling was used to identify which MRI features have the most predictive utility. A linear predictive model of favorable versus unfavorable long-term outcomes was significantly improved when an MRI composite score was added to clinical variables. Nonlinear Random Forest modeling identified five MRI variables as stable predictors of poor outcomes: presence of herniation, DAI in the parietal lobe, DAI in the subcortical white matter, DAI in the posterior corpus callosum, and cerebral contusion in the anterior temporal lobe. Clinical MRI has prognostic value to identify children with TBI at risk of long-term unfavorable outcomes.

The Impact of Traumatic Injury to the Immature Human Brain: A Scoping Review with Insights from Advanced Structural Neuroimaging

Traumatic brain injury (TBI) during critical periods of early-life brain development can affect the normal formation of brain networks responsible for a range of complex social behaviors. Because of the protracted nature of brain and behavioral development, deficits in cognitive and socioaffective behaviors may not become evident until late adolescence and early adulthood, when such skills are expected to reach maturity. In addition, multiple pre- and post-injury factors can interact with the effects of early brain insult to influence long-term outcomes. In recent years, with advancements in magnetic-resonance-based neuroimaging techniques and analysis, studies of the pediatric population have revealed a link between neurobehavioral deficits, such as social dysfunction, with white matter damage. In this review, in which we focus on contributions from Australian researchers to the field, we have highlighted pioneering longitudinal studies in pediatric TBI, in relation to social deficits specifically. We also discuss the use of advanced neuroimaging and novel behavioral assays in animal models of TBI in the immature brain. Together, this research aims to understand the relationship between injury consequences and ongoing brain development after pediatric TBI, which promises to improve prediction of the behavioral deficits that emerge in the years subsequent to early-life injury.

Traumatic brain injury biomarkers in pediatric patients: a systematic review

Traumatic brain injury (TBI) is the main cause of pediatric trauma death and disability worldwide. Recent studies have sought to identify biomarkers of TBI for the purpose of assessing functional outcomes. The aim of this systematic review was to evaluate the utility of TBI biomarkers in the pediatric population by summarizing recent findings in the medical literature. A total of 303 articles were retrieved from our search. An initial screening to remove duplicate studies yielded 162 articles. After excluding all articles that did not meet the inclusion criteria, 56 studies were gathered. Among the 56 studies, 36 analyzed serum biomarkers; 11, neuroimaging biomarkers; and 9, cerebrospinal fluid (CSF) biomarkers. Most studies assessed biomarkers in the serum, reflecting the feasibility of obtaining blood samples compared to obtaining CSF or performing neuroimaging. S100B was the most studied serum biomarker in TBI, followed by SNE and UCH-L1, whereas in CSF analysis, there was no unanimity. Among the different neuroimaging techniques employed, diffusion tensor imaging (DTI) was the most common, seemingly holding diagnostic power in the pediatric TBI clinical setting. The number of cross-sectional studies was similar to the number of longitudinal studies. Our data suggest that S100B measurement has high sensitivity and great promise in diagnosing pediatric TBI, ideally when associated with head CT examination and clinical decision protocols. Further large-scale longitudinal studies addressing TBI biomarkers in children are required to establish more accurate diagnostic protocols and prognostic tools.

Theory of Mind after Pediatric Traumatic Brain Injury: A Scoping Review

This scoping review aims to synthesize existing literature regarding theory of mind (ToM) outcomes, the neuropathology associated with ToM outcomes, and the relationship between ToM outcomes and social functioning in children and adolescents with traumatic brain injury (TBI). We searched MEDLINE^® and PsycINFO databases to identify all literature that examined ToM following pediatric TBI until July 2019. A total of 29 articles met inclusion and exclusion criteria and were included in the results. These articles examined a variety of aspects of ToM, which could be broadly grouped into those focused on cognitive, cognitive-affective, and pragmatic factors. The existing literature suggests that children and adolescents with TBI, compared with their typically developing peers and peers with orthopedic injuries, are more likely to have deficits in ToM. The evidence further shows that the age at which brain injury occurs contributes to ToM disruption. Neuroimaging techniques have offered crucial insights into how TBI may impact ToM performance in children and adolescents. Finally, this review provides evidence that disruption in ToM plays a role in the difficulties in social functioning demonstrated by children and adolescents with TBI. Limitations and gaps in the existing literature warrant future research in this field.

Altered resting-state functional connectivity within the developing social brain after pediatric traumatic brain injury

Traumatic brain injury (TBI) in childhood and adolescence can interrupt expected development, compromise the integrity of the social brain network (SBN) and impact social skills. Yet, no study has investigated functional alterations of the SBN following pediatric TBI. This study explored functional connectivity within the SBN following TBI in two independent adolescent samples. First, 14 adolescents with mild complex, moderate or severe TBI and 16 typically developing controls (TDC) underwent resting‐state functional magnetic resonance imaging 12–24 months post‐injury. Region of interest analyses were conducted to compare the groups' functional connectivity using selected SBN seeds. Then, replicative analysis was performed in an independent sample of adolescents with similar characteristics (9 TBI, 9 TDC). Results were adjusted for age, sex, socioeconomic status and total gray matter volume, and corrected for multiple comparisons. Significant between‐group differences were detected for functional connectivity in the dorsomedial prefrontal cortex and left fusiform gyrus, and between the left fusiform gyrus and left superior frontal gyrus, indicating positive functional connectivity for the TBI group (negative for TDC). The replication study revealed group differences in the same direction between the left superior frontal gyrus and right fusiform gyrus. This study indicates that pediatric TBI may alter functional connectivity of the social brain. Frontal‐fusiform connectivity has previously been shown to support affect recognition and changes in the function of this network could relate to more effortful processing and broad social impairments.

Is diffuse axonal injury on susceptibility weighted imaging a biomarker for executive functioning in adolescents with traumatic brain injury?

Traumatic brain injury (TBI) is a heterogeneous disorder in which diffuse axonal injury (DAI) is an important component contributing to executive dysfunction. During adolescence, developing brain networks are especially vulnerable to acceleration-deceleration forces. We aimed to examine the correlation between DAI (number and localization) and executive functioning in adolescents with TBI. We recruited 18 adolescents with a mean age of 15y8m (SD = 1y7m), averaging 2.5 years after sustaining a moderate-to-severe TBI with documented DAI. Susceptibility Weighted Imaging sequence was administered to localize the DAI lesions. The adolescents performed a neurocognitive test-battery, addressing different aspects of executive functioning (working memory, attention, processing speed, planning ability) and their parents completed the Behavior Rating Inventory of Executive Function (BRIEF) - questionnaire. Executive performance of the TBI-group was compared with an age and gender matched control group of typically developing peers. Based on these results we focused on the Stockings of Cambridge test and the BRIEF to correlate with the total number and location of DAI. Results revealed that the anatomical distribution of DAI, especially in the corpus callosum and the deep brain nuclei, may have more implications for executive functioning than the total amount of DAI in adolescents. Results of this study may help guide targeted rehabilitation to redirect the disturbed development of executive function in adolescents with TBI.

Participation seven years after severe childhood traumatic brain injury. Disabil Rehabil 2019;42:2402-2411. [PMID: 30950661 DOI: 10.1080/09638288.2019.1594398]

Purpose: Participation in home, school and community activities is considered as the ultimate aim of rehabilitation. The aims of this study were to examine participation seven years post-severe childhood traumatic brain injury and factors associated with participation.Materials and methods: Participants were enrolled in the Traumatisme Grave de l'Enfant (Severe Childhood Injury) cohort study following severe accidental childhood traumatic brain injury. Participation seven years post-injury, was examined using parent- and self-report forms of the Child and Adolescent Scale of Participation among 37 patients [62% males, mean age 15.4 years (SD = 4.4), mean length of coma 6.68 days (SD = 4.96)] and 33 matched controls.Results: Parent reports indicated significantly lower participation among patients compared to controls, but the self-reports did not. In the traumatic brain injury group, parent-reported participation was variable, with 22% of the patients clearly showing greater restrictions than controls. Participation restrictions were significantly associated with injury severity, poor functional outcome one-year post-injury, executive and behavioral difficulties and higher fatigue levels seven years post-injury, but not with pre-injury nor family factors.Conclusions: Several years after severe childhood traumatic brain injury, participation appears to depend more on injury-related factors than on environmental factors. In self-reports assessments of participation, it could be difficult for children and adolescents to distinguish capacity from performance.Implications for rehabilitationParticipation outcomes were highly variable in a sample of patients who sustained severe childhood traumatic brain injury.Participation should be assessed systematically following severe traumatic brain injury, both initially but also in the long-term, ideally using a combination of self- and proxy-report measures.Among patients with severe injuries, the influence of initial brain injury severity markers on participation seems much stronger than that of social/family environment factors.Children's and adolescents' self-reported participation assessed with the Child and Adolescent Scale of Participation may be difficult to interpret.

Determinants of social behavior deficits and recovery after pediatric traumatic brain injury

Traumatic brain injury (TBI) during early childhood is associated with a particularly high risk of developing social behavior impairments, including deficits in social cognition that manifest as reduced social interactions, with profound consequences for the individuals' quality of life. A number of pre-injury, post-injury, and injury-related factors have been identified or hypothesized to determine the extent of social behavior problems after childhood TBI. These include variables associated with the individual themselves (e.g. age, genetics, the injury severity, and extent of white matter damage), proximal environmental factors (e.g. family functioning, parental mental health), and more distal environmental factors (e.g. socioeconomic status, access to resources). In this review, we synthesize the available evidence demonstrating which of these determinants influence risk versus resilience to social behavior deficits after pediatric TBI, drawing upon the available clinical and preclinical literature. Injury-related pathology in neuroanatomical regions associated with social cognition and behaviors will also be described, with a focus on findings from magnetic resonance imaging and diffusion tensor imaging. Finally, study limitations and suggested future directions are highlighted. In summary, while no single variable can alone accurately predict the manifestation of social behavior problems after TBI during early childhood, an increased understanding of how both injury and environmental factors can influence social outcomes provides a useful framework for the development of more effective rehabilitation strategies aiming to optimize recovery for young brain-injured patients.

Age-dependent differences in the impact of paediatric traumatic brain injury on executive functions: A prospective study using susceptibility-weighted imaging

Childhood and adolescence represent sensitive developmental periods for brain networks implicated in a range of complex skills, including executive functions (EF; inhibitory control, working memory, and cognitive flexibility). As a consequence, these skills may be particularly vulnerable to injuries sustained during these sensitive developmental periods. The present study investigated 1) whether age at injury differentially affects EF 6 months and 2 years after TBI in children aged 5-15 years, and 2) whether the association between brain lesions and EF depend on age at injury. Children with TBI (n = 105) were categorized into four age-at-injury groups based on previous studies and proposed timing of cerebral maturational spurts: early childhood (5-6 years, n = 14), middle childhood (7-9 years, n = 24), late childhood (10-12 years, n = 52), and adolescence (13-15 years, n = 15). EF were assessed with performance-based tasks and a parent-report of everyday EF. TBI patients' EF scores 6 months and 2 years post-injury were compared to those of typically developing (TD) controls (n = 42). Brain lesions were identified using susceptibility weighted imaging (SWI). Results indicated that inhibitory control performance 2 years post-injury was differentially affected by the impact of TBI depending on age at injury. Follow-up analyses did not reveal significant differences within the age groups, preventing drawing strong conclusions regarding the contribution of age at injury to EF outcome after TBI. Tentatively, large effect sizes suggest that vulnerability is most apparent in early childhood and adolescence. Everyday inhibitory control behaviour was worse for children with TBI than TD children across childhood and adolescence at the 2-year assessment. There was no evidence for impairment in working memory or cognitive flexibility after TBI at the group level. Given small group sizes, findings from analyses into correlations between EF and SWI lesions should be interpreted with caution. Extent, number and volume of brain lesions correlated with adolescent everyday EF behaviour 6 months post-injury. Taken together, the results emphasize the need for long-term follow-up after paediatric TBI during sensitive developmental periods given negative outcomes 2-year post injury. Inhibitory control seems to be particular vulnerable to the impact of TBI. Findings of associations between EF and SWI lesions need to be replicated with larger samples.

Moral reasoning and decision-making in adolescents who sustain traumatic brain injury

Objective: Emerging evidence suggests that moral processes are disrupted by traumatic brain injury (TBI). The objective of this study was to explore moral reasoning (MR) and decision-making in adolescents with TBI, and to examine potential associations with global manifestations of social competence.Design: This retrospective, cross-sectional research design compared MR and decision-making in adolescents with mild TBI (n = 20), moderate-severe TBI (n = 23) and typically developing controls (n = 93).Methods: Participants completed a visual task of socio-moral reasoning (SoMoral) and the Index of Empathy for Children and Adolescents. Their parents completed questionnaires documenting their child's behavior (Child Behavior Checklist) and adaptive functioning (Adaptive Behavior Assessment System-Second Edition).Main results: Adolescents with both mild and moderate-severe TBI displayed more immature MR than typically developing peers. Participants with TBI also provided fewer socially adapted decisions. Closer inspection revealed that this difference was apparent only in the mild TBI group. No significant group differences were observed for empathy, behavior or adaptive skills.Conclusions: Sustaining TBI appears to affect adolescents' ability to provide mature moral justifications when faced with moral dilemmas representative of everyday social conflicts. These difficulties do not appear to be associated with behavior problems, reduced empathy, or adaptive functioning.

Uncovering the neuroanatomical correlates of cognitive, affective and conative theory of mind in paediatric traumatic brain injury: a neural systems perspective

Deficits in theory of mind (ToM) are common after neurological insult acquired in the first and second decade of life, however the contribution of large-scale neural networks to ToM deficits in children with brain injury is unclear. Using paediatric traumatic brain injury (TBI) as a model, this study investigated the sub-acute effect of paediatric traumatic brain injury on grey-matter volume of three large-scale, domain-general brain networks (the Default Mode Network, DMN; the Central Executive Network, CEN; and the Salience Network, SN), as well as two domain-specific neural networks implicated in social-affective processes (the Cerebro-Cerebellar Mentalizing Network, CCMN and the Mirror Neuron/Empathy Network, MNEN). We also evaluated prospective structure-function relationships between these large-scale neural networks and cognitive, affective and conative ToM. 3D T1- weighted magnetic resonance imaging sequences were acquired sub-acutely in 137 children [TBI: n = 103; typically developing (TD) children: n = 34]. All children were assessed on measures of ToM at 24-months post-injury. Children with severe TBI showed sub-acute volumetric reductions in the CCMN, SN, MNEN, CEN and DMN, as well as reduced grey-matter volumes of several hub regions of these neural networks. Volumetric reductions in the CCMN and several of its hub regions, including the cerebellum, predicted poorer cognitive ToM. In contrast, poorer affective and conative ToM were predicted by volumetric reductions in the SN and MNEN, respectively. Overall, results suggest that cognitive, affective and conative ToM may be prospectively predicted by individual differences in structure of different neural systems-the CCMN, SN and MNEN, respectively. The prospective relationship between cerebellar volume and cognitive ToM outcomes is a novel finding in our paediatric brain injury sample and suggests that the cerebellum may play a role in the neural networks important for ToM. These findings are discussed in relation to neurocognitive models of ToM. We conclude that detection of sub-acute volumetric abnormalities of large-scale neural networks and their hub regions may aid in the early identification of children at risk for chronic social-cognitive impairment.

Vascular impairment as a pathological mechanism underlying long-lasting cognitive dysfunction after pediatric traumatic brain injury

Traumatic brain injury (TBI) is the leading cause of death and disability in children. Indeed, the acute mechanical injury often evolves to a chronic brain disorder with long-term cognitive, emotional and social dysfunction even in the case of mild TBI. Contrary to the commonly held idea that children show better recovery from injuries than adults, pediatric TBI patients actually have worse outcome than adults for the same injury severity. Acute trauma to the young brain likely interferes with the fine-tuned developmental processes and may give rise to long-lasting consequences on brain's function. This review will focus on cerebrovascular dysfunction as an important early event that may lead to long-term phenotypic changes in the brain after pediatric TBI. These, in turn may be associated with accelerated brain aging and cognitive dysfunction. Finally, since no effective treatments are currently available, understanding the unique pathophysiological mechanisms of pediatric TBI is crucial for the development of new therapeutic options.

Examining the Prospective Relationship between Family Affective Responsiveness and Theory of Mind in Chronic Paediatric Traumatic Brain Injury

Childhood and adolescence coincide with rapid structural and functional maturation of brain networks implicated in Theory of Mind (ToM); however, the impact of paediatric traumatic brain injury (TBI) on the development of these higher order skills is not well understood. ToM can be partitioned intoconative ToM, defined as the ability to understand how indirect speech acts involving irony and empathy are used to influence the mental or affective state of the listener; andaffective ToM, concerned with understanding that facial expressions are often used for social purposes to convey emotions that we want people to think we feel. In a sample of 84 children with mild-severe TBI and 40 typically developing controls, this study examined the effect of paediatric TBI on affective and conative ToM; and evaluated the respective contributions of injury-related factors (injury severity/lesion location) and non-injury-related environmental variables (socio-economic status (SES)/family functioning) to long-term ToM outcomes. Results showed that the poorest ToM outcomes were documented in association with mild-complicated and moderate TBI, rather than severe TBI. Lesion location and SES did not significantly contribute to conative or affective ToM. Post-injury family affective responsiveness was the strongest and most significant predictor of conative ToM. Results suggest that clinicians should exercise caution when prognosticating based on early clinical indicators, and that group and individual-level outcome prediction should incorporate assessment of a range of injury- and non-injury-related factors. Moreover, the affective quality of post-injury family interactions represents a potentially modifiable risk factor, and might be a useful target for family-centred interventions designed to optimise social cognitive outcomes after paediatric TBI.

Cognitive impairment after traumatic brain injury: The role of MRI and possible pathological basis

Traumatic brain injury (TBI) is closely related to increased incidence of cognitive impairment from the acute phase to chronic phase. At present, the pathological mechanism leading to cognitive impairment after TBI is still not fully understood. We hypothesize that neuron loss, diffuse axonal injury, microbleed, and blood-brain barrier (BBB) disruption altogether contribute to the development of cognitive impairment. Furthermore, the disruption of structural and functional neural network related to the cognitive function might bring about the final step in the occurrence of cognitive impairment after TBI. In this review, we summarize the role of different MRI techniques in the assessment of the pathological changes related to cognitive impairment after TBI. These MRI techniques include T1-MPRAGE sequence reflecting neuron loss, diffusion tensor imaging reflecting diffuse axonal injury, diffusion kurtosis imaging reflecting diffuse axonal injury and reactive gliosis, susceptibility weighted imaging showing microbleed, arterial spin labeling showing blood flow and dynamic contrast enhanced MRI showing BBB disruption. In the future, correlational study of multi-MRI sequences scan, pathological examination, and cognitive tests will provide valuable information for understanding the mechanism of cognitive impairment after TBI and manage TBI patients.

Social dysfunction after pediatric traumatic brain injury: A translational perspective

Social dysfunction is common after traumatic brain injury (TBI), contributing to reduced quality of life for survivors. Factors which influence the development or persistence of social deficits after injury remain poorly understood, particularly in the context of ongoing brain maturation during childhood and adolescence. Aberrant social interactions have recently been modeled in adult and juvenile rodents after experimental TBI, providing an opportunity to gain new insights into the underlying neurobiology of these behaviors. Here, we review our current understanding of social dysfunction in both humans and rodent models of TBI, with a focus on brain injuries acquired during early development. Modulators of social outcomes are discussed, including injury-related and environmental risk and resilience factors. Disruption of social brain network connectivity and aberrant neuroendocrine function are identified as potential mechanisms of social impairments after pediatric TBI. Throughout, we highlight the overlap and disparities between outcome measures and findings from clinical and experimental approaches, and explore the translational potential of future research to prevent or ameliorate social dysfunction after childhood TBI.

Theory of mind mediates the prospective relationship between abnormal social brain network morphology and chronic behavior problems after pediatric traumatic brain injury

Childhood and adolescence coincide with rapid maturation and synaptic reorganization of distributed neural networks that underlie complex cognitive-affective behaviors. These regions, referred to collectively as the 'social brain network' (SBN) are commonly vulnerable to disruption from pediatric traumatic brain injury (TBI); however, the mechanisms that link morphological changes in the SBN to behavior problems in this population remain unclear. In 98 children and adolescents with mild to severe TBI, we acquired 3D T1-weighted MRIs at 2-8 weeks post-injury. For comparison, 33 typically developing controls of similar age, sex and education were scanned. All participants were assessed on measures of Theory of Mind (ToM) at 6 months post-injury and parents provided ratings of behavior problems at 24-months post-injury. Severe TBI was associated with volumetric reductions in the overall SBN package, as well as regional gray matter structural change in multiple component regions of the SBN. When compared with TD controls and children with milder injuries, the severe TBI group had significantly poorer ToM, which was associated with more frequent behavior problems and abnormal SBN morphology. Mediation analysis indicated that impaired theory of mind mediated the prospective relationship between abnormal SBN morphology and more frequent chronic behavior problems. Our findings suggest that sub-acute alterations in SBN morphology indirectly contribute to long-term behavior problems via their influence on ToM. Volumetric change in the SBN and its putative hub regions may represent useful imaging biomarkers for prediction of post-acute social cognitive impairment, which may in turn elevate risk for chronic behavior problems.

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.

Modeling Chronic Traumatic Encephalopathy: The Way Forward for Future Discovery

Despite the extensive media coverage associated with the diagnosis of chronic traumatic encephalopathy (CTE), our fundamental understanding of the disease pathophysiology remains in its infancy. Only recently have scientific laboratories and personnel begun to explore CTE pathophysiology through the use of preclinical models of neurotrauma. Some studies have shown the ability to recapitulate some aspects of CTE in rodent models, through the use of various neuropathological, biochemical, and/or behavioral assays. Many questions related to CTE development, however, remain unanswered. These include the role of impact severity, the time interval between impacts, the age at which impacts occur, and the total number of impacts sustained. Other important variables such as the location of impacts, character of impacts, and effect of environment/lifestyle and genetics also warrant further study. In this work, we attempt to address some of these questions by exploring work previously completed using single- and repetitive-injury paradigms. Despite some models producing some deficits similar to CTE symptoms, it is clear that further studies are required to understand the development of neuropathological and neurobehavioral features consistent with CTE-like features in rodents. Specifically, acute and chronic studies are needed that characterize the development of tau-based pathology.

Predictors of longitudinal outcome and recovery of pragmatic language and its relation to externalizing behaviour after pediatric traumatic brain injury

The purpose of the present investigation was to evaluate the contribution of age-at-insult and brain pathology on longitudinal outcome and recovery of pragmatic language in a sample of children and adolescents with traumatic brain injury (TBI). Children and adolescents with mild to severe TBI (n=112) were categorized according to timing of brain insult: (i) Middle Childhood (5-9 years; n=41); (ii) Late Childhood (10-11 years; n=39); and (iii) Adolescence (12-15 years; n=32) and group-matched for age, gender and socio-economic status (SES) to a typically developing (TD) control group (n=43). Participants underwent magnetic resonance imaging (MRI) including a susceptibility weighted imaging (SWI) sequence 2-8 weeks after injury and were assessed on measures of pragmatic language and behavioural functioning at 6- and 24-months after injury. Children and adolescents with TBI of all severity levels demonstrated impairments in these domains at 6-months injury before returning to age-expected levels at 2-years post-TBI. However, while adolescent TBI was associated with post-acute disruption to skills that preceded recovery to age-expected levels by 2-years post injury, the middle childhood TBI group demonstrated impairments at 6-months post-injury that were maintained at 2-year follow up. Reduced pragmatic communication was associated with frontal, temporal and corpus callosum lesions, as well as more frequent externalizing behaviour at 24-months post injury. Findings show that persisting pragmatic language impairment after pediatric TBI is related to younger age at brain insult, as well as microhemorrhagic pathology in brain regions that contribute to the anatomically distributed social brain network. Relationships between reduced pragmatic communication and more frequent externalizing behavior underscore the need for context-sensitive rehabilitation programs that aim to increase interpersonal effectiveness and reduce risk for maladaptive behavior trajectories into the long-term post injury.