The emergence of age-dependent social cognitive deficits after generalized insult to the developing brain: a longitudinal prospective analysis using susceptibility-weighted imaging

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.

A new model to guide identity-focused multidisciplinary rehabilitation for children and young people following acquired brain injury: I-FoRM

A complexity of biological, psychological, environmental and systemic factors influences a child's adaption after acquired brain injury (ABI), all of which transform as the child matures. Multidisciplinary rehabilitation teams are challenged by balancing family system needs and the child's needs, whilst promoting the child's functional skills in difficult or unappealing tasks. This paper presents the conceptual basis for a model for use in childhood ABI neurorehabilitation to address these challenges. A non-systematic narrative review of literature pertinent to integrated neurorehabilitation of pediatric ABI was conducted. Contemporary models of adult and pediatric psychosocial adaptation involving identity following ABI were reviewed. Key findings were then synthesized with models of pediatric resilience and self-concept development. The resulting model describes a cyclical adaptation process whereby the child learns experientially about their self and their world after ABI. Processes of identity development play a central role - particularly emotive processes of self-evaluation - by influencing the child's motivation for participation, tolerance for challenge, self-regulation and emerging self-awareness. The model directs clinicians to use the psychosocial processes of identity development to enhance the child's willingness and capacity to engage in the daily challenges of rehabilitation. Further systematic development and evaluation of the model is needed.

Glucocorticoid Receptor Overexpression in the Dorsal Hippocampus Attenuates Spatial Learning and Synaptic Plasticity Deficits Following Pediatric Traumatic Brain Injury

Traumatic brain injury (TBI) in children younger than 4 years old leads to long-term deficits in cognitive and learning abilities that can persist or even worsen as children age into adolescence. In this study, the role of glucocorticoid receptor (GR) function in the dorsal hippocampus (DH) in hippocampal-dependent cognitive function and synaptic plasticity were assessed following injury to the 11-day-old rat. Brain injury produced significant impairments in spatial learning and memory in the Morris water maze in male and female rats at 1-month post-injury (adolescence) which was accompanied by impairments in induction and maintenance of long-term potentiation (LTP) in the CA1 region of the DH. Brain injury resulted in a significant decrease in the expression of the glucocorticoid-inducible gene, serum- and glucocorticoid-kinase 1 (sgk1), suggestive of an impairment in GR transcriptional activity within the hippocampus. Lentiviral transfection of the human GR (hGR) in the DH improved spatial learning and memory in the Morris water maze and attenuated LTP deficits following TBI. GR overexpression in the DH was also associated with a significant increase in the mRNA expression levels of sgk1, and the glutamate receptor subunits GluA1 and GluA2 within the hippocampus. Overall, these findings support an important role of dorsal hippocampal GR function in learning and memory deficits following pediatric TBI and suggest that these effects may be related to the regulation of glutamate receptor subunit expression in the DH.

Football and Dementia: Understanding the Link

Football, also known as soccer or association football, is popular but has a potential link with dementia developing in retired players. The FA and soccer regulators in the USA have imposed guidelines limiting players exposure to heading, despite controversy whether this dementia is caused by heading the ball, a form of mild repetitive head injury (RHI), over many years. Substantial data exist showing that many ex-North American Football players develop a specific neurodegenerative disease: chronic traumatic encephalopathy (CTE), the neuropathological disorder of boxers. In the United Kingdom evidence for the neuropathological basis of footballers' dementia has been slow to emerge. A 2017 study revealed that in six ex-soccer players four had CTE with Alzheimer's disease (AD) and two had AD. A 2019 study showed that ex-footballers were 3.5 times more likely to die from dementia or other neuro-degenerative diseases than matched controls. We argue that in childhood and adolescence the brain is vulnerable to heading, predicated on its disproportionate size and developmental immaturity. RHI in young individuals is associated with early neuroinflammation, a potential trigger for promoting neurodegeneration in later life. Evidence is available to support the guidelines limiting heading for players of all ages, while professional and non-players should be included in prospective studies to investigate the link between soccer and dementia.

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.

Social Cognition in Paediatric Traumatic Brain Injury: A Systematic Review and Meta-analysis

Recent evidence suggests social cognitive deficits may be among the most profound and disabling consequences of childhood traumatic brain injury (TBI); however, it is only over the last decade that this area has received increasing research attention. This study aims to systematically review all studies reporting on the effects of childhood TBI on social cognition. Meta-analytic techniques were employed to determine the magnitude of social cognitive deficits in childhood TBI. Literature searches were conducted in electronic databases (Medline/PubMed, Scopus, Cochrane, EMBASE, PsycINFO and CINAHL) to retrieve relevant articles on social cognitive outcomes of paediatric TBI published from 2007-2019. The systematic review identified fourteen eligible studies, which examined the effect of paediatric TBI on five dimensions of social cognition, including emotion recognition or perception, theory of Mind (ToM), pragmatic language, moral reasoning, and social problem solving. Of these studies, eleven articles were included in subsequent meta-analyses, which included 482 children with TBI. Meta-analysis using a random-effects model revealed non-significant differences between TBI and typically developing (TD) control groups on measures of emotion perception or recognition. In contrast, children and adolescents with TBI performed significantly worse than control groups on ToM and pragmatic language tasks, with small and medium effect sizes, respectively (Hedge's g = -0.46; -0.73). Meta-regression indicated that post-injury social cognitive deficits were not moderated by child age. While the effect of time since injury was not statistically significant, poorer social cognitive outcomes are documented soon after injury. Despite relatively intact basic social cognitive skills (i.e. emotion perception or recognition) children and adolescents with TBI are vulnerable to deficits in higher-order aspects of social cognition, including ToM and pragmatic language. These findings underscore the importance of further research, using well-validated, standardised outcome instruments, in larger paediatric TBI samples. Furthermore, longitudinal prospective studies are needed to evaluate the respective contribution of injury and non-injury factors to individual variation in outcome and recovery of social cognition after paediatric TBI.

Social Cognitive Dysfunction Following Pediatric Arterial Ischemic Stroke: Evidence From a Prospective Cohort Study

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Challenges and opportunities for neuroimaging in young patients with traumatic brain injury: a coordinated effort towards advancing discovery from the ENIGMA pediatric moderate/severe TBI group

Traumatic brain injury (TBI) is a major cause of death and disability in children in both developed and developing nations. Children and adolescents suffer from TBI at a higher rate than the general population, and specific developmental issues require a unique context since findings from adult research do not necessarily directly translate to children. Findings in pediatric cohorts tend to lag behind those in adult samples. This may be due, in part, both to the smaller number of investigators engaged in research with this population and may also be related to changes in safety laws and clinical practice that have altered length of hospital stays, treatment, and access to this population. The ENIGMA (Enhancing NeuroImaging Genetics through Meta-Analysis) Pediatric Moderate/Severe TBI (msTBI) group aims to advance research in this area through global collaborative meta-analysis of neuroimaging data. In this paper, we discuss important challenges in pediatric TBI research and opportunities that we believe the ENIGMA Pediatric msTBI group can provide to address them. With the paucity of research studies examining neuroimaging biomarkers in pediatric patients with TBI and the challenges of recruiting large numbers of participants, collaborating to improve statistical power and to address technical challenges like lesions will significantly advance the field. We conclude with recommendations for future research in this field of study.

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.

Delineating the Nature and Correlates of Social Dysfunction after Childhood Traumatic Brain Injury Using Common Data Elements: Evidence from an International Multi-Cohort Study

Although childhood traumatic brain injury (TBI) has been linked to heightened risk of impaired social skills and behavior, current evidence is weakened by small studies of variable methodological quality. To address these weaknesses, this international multi-cohort study involved synthesis of data from two large observational cohort studies of complicated mild-severe child TBI in Australia and North America. Both studies adopted a unified approach to data collection and coding procedures, providing the opportunity to merge datasets from multiple, well-characterized cohorts for which gold standard measures of social outcomes were collected during the chronic recovery phase. The study involved 218 children, including 33 children with severe TBI, 83 children with complicated mild-moderate TBI, 59 children with orthopedic injury, and 43 age- and sex-matched typically developing control children. All injured children were recruited from academic children's hospitals and underwent direct cognitive assessments including measures of theory of mind (ToM) at least 1-year post- injury. Parents rated their child's social adjustment using standardized measures of social skills, communication and behavior. Results showed a brain-injury specific effect on ToM abilities, such that children with both complicated mild to moderate and severe TBI displayed significantly poorer ToM than children without TBI. In mediator models, poorer ToM predicted poorer parent-rated self-direction and social skills, as well as more frequent behavioral symptoms. The ToM mediated the effect of severe TBI on parent ratings of communication and social skills, as well as on overall behavior symptoms. The findings suggest that deficits in ToM are evident across the spectrum of TBI severity and represent one mechanism linking severe child TBI to long-term social adjustment difficulties. The findings underscore the value of large-scale data harmonization projects to increase the quality of evidence regarding the outcomes of TBI. Clinical and scientific implications are discussed.

Time-varying Hazards Model for Incorporating Irregularly Measured, High-Dimensional Biomarkers

Clinical studies with time-to-event outcomes often collect measurements of a large number of time-varying covariates over time (e.g., clinical assessments or neuroimaging biomarkers) to build time-sensitive prognostic model. An emerging challenge is that due to resource-intensive or invasive (e.g., lumbar puncture) data collection process, biomarkers may be measured infrequently and thus not available at every observed event time point. Lever-aging all available, infrequently measured time-varying biomarkers to improve prognostic model of event occurrence is an important and challenging problem. In this paper, we propose a kernel-smoothing based approach to borrow information across subjects to remedy infrequent and unbalanced biomarker measurements under a time-varying hazards model. A penalized pseudo-likelihood function is proposed for estimation, and an efficient augmented penalization minimization algorithm related to the alternating direction method of multipliers (ADMM) is adopted for computation. Under some regularity conditions to carefully control approximation bias and stochastic variability, we show that even in the presence of ultra-high dimensionality, the proposed method selects important biomarkers with high probability. Through extensive simulation studies, we demonstrate superior performance in terms of estimation and selection performance compared to alternative methods. Finally, we apply the proposed method to analyze a recently completed real world study to model time to disease conversion using longitudinal, whole brain structural magnetic resonance imaging (MRI) biomarkers, and show a substantial improvement in performance over current standards including using baseline measures only.

Progesterone treatment following traumatic brain injury in the 11-day-old rat attenuates cognitive deficits and neuronal hyperexcitability in adolescence

Traumatic brain injury (TBI) in children younger than 4 years old results in cognitive and psychosocial deficits in adolescence and adulthood. At 4 weeks following closed head injury on postnatal day 11, male and female rats exhibited impairment in novel object recognition memory (NOR) along with an increase in open arm time in the elevated plus maze (EPM), suggestive of risk-taking behaviors. This was accompanied by an increase in intrinsic excitability and frequency of spontaneous excitatory post-synaptic currents (EPSCs), and a decrease in the frequency of spontaneous inhibitory post-synaptic currents in layer 2/3 neurons within the medial prefrontal cortex (PFC), a region that is implicated in both object recognition and risk-taking behaviors. Treatment with progesterone for the first week after brain injury improved NOR memory at the 4-week time point in both sham and brain-injured rats and additionally attenuated the injury-induced increase in the excitability of neurons and the frequency of spontaneous EPSCs. The effect of progesterone on cellular excitability changes after injury may be related to its ability to decrease the mRNA expression of the β3 subunit of the voltage-gated sodium channel and increase the expression of the neuronal excitatory amino acid transporter 3 in the medial PFC in sham- and brain-injured animals and also increase glutamic acid decarboxylase mRNA expression in sham- but not brain-injured animals. Progesterone treatment did not affect injury-induced changes in the EPM test. These results demonstrate that administration of progesterone immediately after TBI in 11-day-old rats reduces cognitive deficits in adolescence, which may be mediated by progesterone-mediated regulation of excitatory signaling mechanisms within the medial PFC.

Adolescent traumatic brain injuries: Onset, mechanism and links with current academic performance and physical injuries

Background

Traumatic brain injuries (TBIs) in adolescence are associated with adverse outcomes, but whether the timing of the onset of TBIs leads to greater deficits has not been determined. We evaluate the relationship between the first and most recent TBI, and current academic performance and medically treated physical injuries.

Methods

Data were derived from the 2015 Ontario Student Drug Use and Health Survey (OSDUHS) administered to adolescents in grades 7 to 12 (ages 12 to 18). TBI was defined as a head injury that resulted in loss of conscious for at least five minutes or at least one overnight hospitalization.

Results

One in five students reported having had a history of TBI in their lifetime and were more prevalent in males. Odds ratios were 2 times higher for males to have had their first (or only) and most recent TBI in grades 5 to 8, compared to females. Sports-related TBIs accounted for 41.1% of all TBIs. Hockey related TBIs were more frequent compared to soccer related TBIs. Reports of history of TBI was associated with lower academic performance and more physical injuries. First or only TBI occurring in grades 9–12 (occurring on average between 14 to 19 years of age) had higher significant odds of poorer academic performance than TBIs occurring in earlier grades (younger ages than 14 years old). Students who reported more visits for medical treatment of physical injuries in the past year had higher odds to report a history of TBIs in higher school grades.

Conclusions

Adverse physical and academic outcomes among young TBI survivors are associated with the onset and frequency of history of lifetime TBI. Prevention efforts to minimize TBIs during youth is critical.

Sex and Gender Differences in Emotion Recognition and Theory of Mind After TBI: A Narrative Review and Directions for Future Research

A growing body of literature has examined sex differences in a variety of outcomes from moderate-severe traumatic brain injury (TBI), including outcomes for social functioning. Social functioning is an area in which adults with TBI have significant long-term challenges (1-4), and a better understanding of sex and gender differences in this domain may have a significant clinical impact. This paper presents a brief narrative review of current evidence regarding sex differences in one aspect of social functioning in adults with TBI: social cognition, specifically affect recognition and Theory of Mind (ToM). Data from typical adults and adults with TBI are considered in the broader context of common stereotypes about social skills and behaviors in men vs. women. We then discuss considerations for future research on sex- and gender-based differences in social cognition in TBI, and in adults more generally.

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.

Measuring Change Over Time: A Systematic Review of Evaluative Measures of Cognitive Functioning in Traumatic Brain Injury

Objectives: The purpose of evaluative instruments is to measure the magnitude of change in a construct of interest over time. The measurement properties of these instruments, as they relate to the instrument's ability to fulfill its purpose, determine the degree of certainty with which the results yielded can be viewed. This work systematically reviews all instruments that have been used to evaluate cognitive functioning in persons with traumatic brain injury (TBI), and critically assesses their evaluative measurement properties: construct validity, test-retest reliability, and responsiveness. Data Sources: MEDLINE, Central, EMBASE, Scopus, PsycINFO were searched from inception to December 2016 to identify longitudinal studies focused on cognitive evaluation of persons with TBI, from which instruments used for measuring cognitive functioning were abstracted. MEDLINE, instrument manuals, and citations of articles identified in the primary search were then screened for studies on measurement properties of instruments utilized at least twice within the longitudinal studies. Study Selection: All English-language, peer-reviewed studies of longitudinal design that measured cognition in adults with a TBI diagnosis over any period of time, identified in the primary search, were used to identify instruments. A secondary search was carried out to identify all studies that assessed the evaluative measurement properties of the instruments abstracted in the primary search. Data Extraction: Data on psychometric properties, cognitive domains covered and clinical utility were extracted for all instruments. Results: In total, 38 longitudinal studies from the primary search, utilizing 15 instruments, met inclusion and quality criteria. Following review of studies identified in the secondary search, it was determined that none of the instruments utilized had been assessed for all the relevant measurement properties in the TBI population. The most frequently assessed property was construct validity. Conclusions: There is insufficient evidence for the validity and reliability of instruments measuring cognitive functioning, longitudinally, in persons with TBI. Several instruments with well-defined construct validity in TBI samples warrant further assessment for test-retest reliability and responsiveness. Registration Number: www.crd.york.ac.uk/PROSPERO/, identifier CRD42017055309.

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.

A systematic review of cross-sectional differences and longitudinal changes to the morphometry of the brain following paediatric traumatic brain injury

Paediatric traumatic brain injury (pTBI) is a leading cause of disability for children and young adults. Children are a uniquely vulnerable group with the disease process that occurs following a pTBI interacting with the trajectory of normal brain development. Quantitative MRI post-injury has suggested a long-term, neurodegenerative effect of TBI on the morphometry of the brain, in both adult and childhood TBI. Changes to the brain beyond that of anticipated, age-dependant differences may allow us to estimate the state of the brain post-injury and produce clinically relevant predictions for long-term outcome. The current review synthesises the existing literature to assess whether, following pTBI, the morphology of the brain exhibits either i) longitudinal change and/or ii) differences compared to healthy controls and outcomes. The current literature suggests that morphometric differences from controls are apparent cross-sectionally at both acute and late-chronic timepoints post-injury, thus suggesting a non-transient effect of injury. Developmental trajectories of morphometry are altered in TBI groups compared to patients, and it is unlikely that typical maturation overcomes damage post-injury, or even 'catches up' with that of typically-developing peers. However, there is limited evidence for diverted developmental trajectories being associated with cognitive impairment post-injury. The current review also highlights the apparent challenges to the existing literature and potential methods by which these can be addressed.

Vocabulary skills of school-age children with acquired brain injury: an exploration of tiered word knowledge and naming errors

BACKGROUND

Vocabulary deficits are the most frequently documented communication difficulty following childhood acquired brain injury (ABI). Given the adverse consequences of limited vocabulary on academic success, it is critical to identify the presence and nature of vocabulary impairments to provide effective intervention for children with ABI.

METHOD

Eleven children (7;6-11;11) with moderate/severe ABI (>12 months post-injury) and individually matched typically developing (TD) controls completed an Australian adaptation of a vocabulary assessment based on a three-tiered framework: tier 1 (basic words), tier 2 (high-frequency, cross-curricular words), and tier 3 (curriculum-based words). Overall scores and tiered accuracy were compared at individual and group level. Type and frequency of expressive naming errors were also coded.

RESULTS

In this pilot study, children with ABI demonstrated poorer overall scores than TD children. Equivalent accuracy was noted for tier 1 words and tier 2 receptive words. However, significantly poorer accuracy was noted in the ABI group for tier 2 expressive words and all tier 3 words. The majority of naming errors were semantic across both groups although TD participants showed a wider distribution of error types.

CONCLUSIONS

Findings support the use of tier 2 and 3 vocabulary as intervention targets in this population within education contexts and speech pathology settings.

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.

Advanced biomarkers of pediatric mild traumatic brain injury: Progress and perils

There is growing public concern about neurodegenerative changes (e.g., Chronic Traumatic Encephalopathy) that may occur chronically following clinically apparent and clinically silent (i.e., sub-concussive blows) pediatric mild traumatic brain injury (pmTBI). However, there are currently no biomarkers that clinicians can use to objectively diagnose patients or predict those who may struggle to recover. Non-invasive neuroimaging, electrophysiological and neuromodulation biomarkers have promise for providing evidence of the so-called "invisible wounds" of pmTBI. Our systematic review, however, belies that notion, identifying a relative paucity of high-quality, clinically impactful, diagnostic or prognostic biomarker studies in the sub-acute injury phase (36 studies on unique samples in 28 years), with the majority focusing on adolescent pmTBI. Ultimately, well-powered longitudinal studies with appropriate control groups, as well as standardized and clearly-defined inclusion criteria (time post-injury, injury severity and past history) are needed to truly understand the complex pathophysiology that is hypothesized (i.e., still needs to be determined) to exist during the acute and sub-acute stages of pmTBI and may underlie post-concussive symptoms.

White matter microstructure predicts longitudinal social cognitive outcomes after paediatric traumatic brain injury: a diffusion tensor imaging study

BACKGROUND

Deficits in social cognition may be among the most profound and disabling sequelae of paediatric traumatic brain injury (TBI); however, the neuroanatomical correlates of longitudinal outcomes in this domain remain unexplored. This study aimed to characterize social cognitive outcomes longitudinally after paediatric TBI, and to evaluate the use of sub-acute diffusion tensor imaging (DTI) to predict these outcomes.

METHODS

The sample included 52 children with mild complex-severe TBI who were assessed on cognitive theory of mind (ToM), pragmatic language and affective ToM at 6- and 24-months post-injury. For comparison, 43 typically developing controls (TDCs) of similar age and sex were recruited. DTI data were acquired sub-acutely (mean = 5.5 weeks post-injury) in a subset of 65 children (TBI = 35; TDC = 30) to evaluate longitudinal prospective relationships between white matter microstructure assessed using Tract-Based Spatial Statistics and social cognitive outcomes.

RESULTS

Whole brain voxel-wise analysis revealed significantly higher mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD) in the sub-acute TBI group compared with TDC, with differences observed predominantly in the splenium of the corpus callosum (sCC), sagittal stratum (SS), dorsal cingulum (DC), uncinate fasciculus (UF) and middle and superior cerebellar peduncles (MCP & SCP, respectively). Relative to TDCs, children with TBI showed poorer cognitive ToM, affective ToM and pragmatic language at 6-months post-insult, and those deficits were related to abnormal diffusivity of the sCC, SS, DC, UF, MCP and SCP. Moreover, children with TBI showed poorer affective ToM and pragmatic language at 24-months post-injury, and those outcomes were predicted by sub-acute alterations in diffusivity of the DC and MCP.

CONCLUSIONS

Abnormal microstructure within frontal-temporal, limbic and cerebro-cerebellar white matter may be a risk factor for long-term social difficulties observed in children with TBI. DTI may have potential to unlock early prognostic markers of long-term social outcomes.

Recovery of Working Memory Following Pediatric Traumatic Brain Injury: A Longitudinal Analysis

In a prospective longitudinal study, the trajectory of verbal and visual-spatial working memory (WM) development was examined 2-, 6-, 12-, and 24-months following complicated-mild to severe pediatric traumatic brain injury (TBI; n = 55) relative to an orthopedic injury comparison group (n = 47). Individual growth curve modeling revealed an interaction of age, severity, and time for verbal, but not visual-spatial WM. The youngest children with severe TBI had the lowest scores and slowest verbal WM growth. WM outcome is best understood in light of age at injury and TBI severity. Findings support the early vulnerability hypothesis and highlight the need for long-term follow-up.

Recent progress in understanding skills and impairments in social cognition

PURPOSE OF REVIEW

Social interaction is affected in many different developmental disorders; indeed, the new Diagnostic and Statistical Manual of Mental Disorders has introduced social cognition as one of six core components of neurocognitive functioning. Social cognition is not one thing, but a wide range of putative processes, which may be differentially affected in different clinical groups. This review focuses on recent advances in one aspect of social cognition, 'theory of mind' (ToM, representing what people think), and one core clinical group, autism spectrum disorder (ASD).

RECENT FINDINGS

It is 30 years since impaired ToM was proposed as an explanation for ASD social difficulties, and recently there has been a widening of interest to other clinical groups. ToM has been found to be distinct from emotion recognition and empathy. Recent research on ASD has focused increasingly on atypical sensory responses and commonly comorbid conditions. Interventions for social deficits, including ToM training and oxytocin, have shown mixed results to date.

SUMMARY

Heterogeneity poses a major obstacle to current research. Theoretical and empirical refinements are needed to elucidate neurocognitive and aetiological underpinnings of sociocognitive processes and inform clinical advances.

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.

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.

What's New in Traumatic Brain Injury: Update on Tracking, Monitoring and Treatment

Traumatic brain injury (TBI), defined as an alteration in brain functions caused by an external force, is responsible for high morbidity and mortality around the world. It is important to identify and treat TBI victims as early as possible. Tracking and monitoring TBI with neuroimaging technologies, including functional magnetic resonance imaging (fMRI), diffusion tensor imaging (DTI), positron emission tomography (PET), and high definition fiber tracking (HDFT) show increasing sensitivity and specificity. Classical electrophysiological monitoring, together with newly established brain-on-chip, cerebral microdialysis techniques, both benefit TBI. First generation molecular biomarkers, based on genomic and proteomic changes following TBI, have proven effective and economical. It is conceivable that TBI-specific biomarkers will be developed with the combination of systems biology and bioinformation strategies. Advances in treatment of TBI include stem cell-based and nanotechnology-based therapy, physical and pharmaceutical interventions and also new use in TBI for approved drugs which all present favorable promise in preventing and reversing TBI.