Diverging volumetric trajectories following pediatric traumatic brain injury

Structural and functional alterations in the contralateral hemisphere following pediatric intracranial surgery: a pilot longitudinal neuroimaging study

Background

Intracranial space-occupying lesions (ISOLs) are common pediatric conditions. Recent therapeutic advances have significantly improved survival rates, necessitating increased attention to post-operative cognitive outcomes, which are crucial determinants of patients' quality of life.

Objective

While previous studies have predominantly focused on short-term post-operative changes, this study aimed to investigate longitudinal changes in cognition, brain structure, and function of the contralateral hemisphere following pediatric neurosurgery.

Methods

Nineteen pediatric patients with ISOLs were enrolled in a paired design study. Cognitive assessments, structural imaging, and functional imaging data were collected at three time points: pre-operation, first post-operative follow-up (mean 75 days pre-operation), and second post-operative follow-up (mean 316 days pre-operation). Relevant metrics were computed and compared across time points.

Results

The majority of cognitive domains exhibited a gradual longitudinal improvement trajectory, with three domains showing significant enhancement at the second follow-up compared to preoperative baseline: cognitive flexibility (t = 4.201, p = 0.001), executive function (t = 3.478, p = 0.003), and social accuracy (t = 3.248, p = 0.004). The contralesional hemisphere demonstrated alterations primarily characterized by gray matter density reduction, progressing from subcortical structures (first follow-up: thalamus, peak intensity = -7.54, cluster p < 0.016) to cortical regions (second follow-up compared to previous follow-up: superior frontal gyrus, peak intensity = -7.80, cluster p < 0.016), followed by a subsequent increase in brain activity power of smaller magnitude (second follow-up: medial superior frontal gyrus, amplitude of low frequency fluctuation, peak intensity = 5.96, cluster p < 0.016). Correlation analysis suggests that there is an association between changes in brain structure and alterations in cognitive function (r = -0.53, p = 0.019).

Conclusion

Our findings suggest that post-craniotomy structural and functional brain changes in children follow a subcortical-to-cortical trajectory, with structural alterations (decreased gray matter density) preceding functional activation. This process demonstrates progressive and cumulative characteristics. These modifications appear to correlate with cognitive function recovery and may represent potential mechanisms underlying spontaneous cognitive rehabilitation in pediatric patients post-surgery. Cautiously interpreted, the deeper neuroplastic mechanisms underlying these changes might involve synaptic pruning-like processes induced by external perturbation.

Evidence Suggesting Prolonged Neuroinflammation in a Subset of Children after Moderate/Severe TBI: A UCLA RAPBI Study

Traumatic brain injury (TBI) presents a public health concern as a leading cause of death and disability in children. Pediatric populations are particularly vulnerable to adverse outcomes following TBI due to periods of rapid growth, synaptic pruning, and myelination. Pediatric patients with moderate-severe TBI (msTBI) and healthy controls were evaluated from the post-acute (2-5 months) to chronic phase (13-19 months) of recovery using diffusion magnetic resonance imaging (dMRI) and interhemispheric transfer time (IHTT), which is an event-related potential measure the speed of information transfer across the corpus callosum. We previously identified two subgroups of patients based on IHTT, with one group showing a significantly slower IHTT (TBI-slow), poorer cognitive performance, and progressive structural damage. In contrast, the other group (TBI-normal) did not differ from controls on IHTT or cognitive performance and showed relative structural recovery over time. Here, we examined group differences in restricted diffusion imaging (RDI), which is a dMRI metric sensitive to inflammation. Comparing TBI-slow, TBI-normal, and controls on RDI cross-sectionally, dMRI connectometry analysis revealed higher RDI across the white matter in the TBI-slow group compared to both the control and TBI-normal groups. Longitudinal analyses indicated that while both TBI groups exhibited a decrease in RDI over time, suggesting resolution of neuroinflammation and recovery, the decreases in the TBI-slow group were smaller. The differences in RDI between TBI-slow and TBI-normal suggest that inflammation may play a key role in the prolonged recovery, including brain structure, cognitive performance, and symptom reports, of pediatric patients with msTBI.

Differences in Brain Volume in Military Service Members and Veterans After Blast-Related Mild TBI: A LIMBIC-CENC Study

Importance

Blast-related mild traumatic brain injuries (TBIs), the "signature injury" of post-9/11 conflicts, are associated with clinically relevant, long-term cognitive, psychological, and behavioral dysfunction and disability; however, the underlying neural mechanisms remain unclear.

Objective

To investigate associations between a history of remote blast-related mild TBI and regional brain volume in a sample of US veterans and active duty service members.

Design, Setting, and Participants

Prospective cohort study of US veterans and active duty service members from the Long-Term Impact of Military-Relevant Brain Injury Consortium-Chronic Effects of Neurotrauma Consortium (LIMBIC-CENC), which enrolled more than 1500 participants at 5 sites used in this analysis between 2014 and 2023. Participants were recruited from Veterans Affairs medical centers across the US; 774 veterans and active duty service members of the US military met eligibility criteria for this secondary analysis. Assessment dates were from January 6, 2015, to March 31, 2023; processing and analysis dates were from August 1, 2023, to January 15, 2024.

Exposure

All participants had combat exposure, and 82% had 1 or more lifetime mild TBIs with variable injury mechanisms.

Main Outcomes and Measures

Regional brain volume was calculated using tensor-based morphometry on 3-dimensional, T1-weighted magnetic resonance imaging scans; history of TBI, including history of blast-related mild TBI, was assessed by structured clinical interview. Cognitive performance and psychiatric symptoms were assessed with a battery of validated instruments. We hypothesized that regional volume would be smaller in the blast-related mild TBI group and that this would be associated with cognitive performance.

Results

A total of 774 veterans (670 [87%] male; mean [SD] age, 40.1 [9.8] years; 260 [34%] with blast-related TBI) were included in the sample. Individuals with a history of blast-related mild TBI had smaller brain volumes than individuals without a history of blast-related mild TBI (which includes uninjured individuals and those with non-blast-related mild TBI) in several clusters, with the largest centered bilaterally in the superior corona radiata and subcortical gray and white matter (cluster peak Cohen d range, -0.23 to -0.38; mean [SD] Cohen d, 0.28 [0.03]). Additionally, causal mediation analysis revealed that these volume differences significantly mediated the association between blast-related mild TBI and performance on measures of working memory and processing speed.

Conclusions and Relevance

In this cohort study of 774 veterans and active duty service members, robust volume differences associated with blast-related TBI were identified. Furthermore, these volume differences significantly mediated the association between blast-related mild TBI and cognitive function, indicating that this pattern of brain differences may have implications for daily functioning.

Network analysis of structural MRI predicts executive function in paediatric traumatic brain injury

INTRO

Paediatric traumatic brain injury (pTBI) is likely to result in cognitive impairment, specifically executive dysfunction. Evidence of the neuroanatomical correlates of this executive function (EF) impairment is derived from studies that treat morphometry of brain regions as distinct, independent features, rather than as a complex network of interrelationships. Morphometric similarity captures the meso-scale organisation of the cortex as the interrelatedness of multiple macro-architectural features and presents a novel tool with which to investigate the brain post pTBI.

METHODS

In a retrospective sample (83 pTBI patients, 33 controls), we estimate morphometric similarity from structural MRI by correlating morphometric features between cortical regions. We compared the meso-scale organisation of the cortex between groups then, using partial least squares regression, assessed the predictive validity of morphometric similarity in understanding later executive functioning, two years post-injury.

RESULTS

We found that patients and controls did not differ in terms of the overall magnitude of morphometric similarity. However, a pattern of ROI-level morphometric similarity was predictive of day-to-day EF difficulties reported by parents two years post-injury. This prediction was validated using a leave-one-out, and 20-fold cross-validation approach. Prediction was driven by regions of the prefrontal cortex, typically important for healthy maturation of EF skills in childhood. The meso-scale organisation of the cortex also produced more accurate predictions than any one morphometric feature (i.e. cortical thickness or folding index) alone.

CONCLUSION

We conclude that these methodologies show utility in predicting later executive functioning in this population.

Structural and functional changes following brain surgery in pediatric patients with intracranial space-occupying lesions

We explored the structural and functional changes of the healthy hemisphere of the brain after surgery in children with intracranial space-occupying lesions. We enrolled 32 patients with unilateral intracranial space-occupying lesions for brain imaging and cognitive assessment. Voxel-based morphometry and surface-based morphometry analyses were used to investigate the structural images of the healthy hemisphere. Functional images were analyzed using regional homogeneity, amplitude of low-frequency fluctuations, and fractional-amplitude of low-frequency fluctuations. Voxel-based morphometry and surface-based morphometry analysis used the statistical model built into the CAT 12 toolbox. Paired t-tests were used for functional image and cognitive test scores. For structural image analysis, we used family-wise error correction of peak level (p < 0.05), and for functional image analysis, we use Gaussian random-field theory correction (voxel p < 0.001, cluster p < 0.05). We found an increase in gray matter volume in the healthy hemisphere within six months postoperatively, mainly in the frontal lobe. Regional homogeneity and fractional-amplitude of low-frequency fluctuations also showed greater functional activity in the frontal lobe. The results of cognitive tests showed that psychomotor speed and motor speed decreased significantly after surgery, and reasoning increased significantly after surgery. We concluded that in children with intracranial space-occupying lesions, the healthy hemisphere exhibits compensatory structural and functional effects within six months after surgery. This effect occurs mainly in the frontal lobe and is responsible for some higher cognitive compensation. This may provide some guidance for the rehabilitation of children after brain surgery.

Sex and Age-at-Injury as Determinants of Social Behavior Outcomes After TBI

While our understanding of long-term disability after traumatic brain injury (TBI) has habitually focused on cognitive and sensorimotor functioning, it is increasingly appreciated that changes in social function for survivors of a brain injury are common and have a profound impact on one's quality of life. In this chapter, we highlight the consequences of TBI on social behavior, taking into account evidence from studies of patient populations as well as from preclinical animal models. After first considering the protracted nature of the development of social behavior across the lifespan, including the neurobiological networks that underlie social functioning, we discuss how TBI results in social behavior impairments and how these manifest. We focus particularly on how age-at-injury influences TBI-induced social impairments, with most of the evidence suggesting age-dependent vulnerability after injury at a younger age. In addition, we explore how biological sex is a key determinant of social behavior impairments after TBI, while gender in humans may also influence the nature and extent of social outcomes. Finally, we identify key knowledge gaps and emphasize the need for further research in the field.

Neuroimaging Correlates of Functional Outcome Following Pediatric TBI

Neuroimaging plays an important role in assessing the consequences of TBI across the postinjury period. While identifying alterations to the brain is important, associating those changes to functional, cognitive, and behavioral outcomes is an essential step to establishing the value of advanced neuroimaging for pediatric TBI. Here we highlight research that has revealed links between advanced neuroimaging and outcome after TBI and point to opportunities where neuroimaging could expand our ability to prognosticate and potentially uncover opportunities to intervene.

Stress and traumatic brain injury: An inherent bi-directional relationship with temporal and synergistic complexities

Traumatic brain injury (TBI) and stress are prevalent worldwide and can both result in life-altering health problems. While stress often occurs in the absence of TBI, TBI inherently involves some element of stress. Furthermore, because there is pathophysiological overlap between stress and TBI, it is likely that stress influences TBI outcomes. However, there are temporal complexities in this relationship (e.g., when the stress occurs) that have been understudied despite their potential importance. This paper begins by introducing TBI and stress and highlighting some of their possible synergistic mechanisms including inflammation, excitotoxicity, oxidative stress, hypothalamic-pituitary-adrenal axis dysregulation, and autonomic nervous system dysfunction. We next describe different temporal scenarios involving TBI and stress and review the available literature on this topic. In doing so we find initial evidence that in some contexts stress is a highly influential factor in TBI pathophysiology and recovery, and vice versa. We also identify important knowledge gaps and suggest future research avenues that will increase our understanding of this inherent bidirectional relationship and could one day result in improved patient care.

Social problems and brain structure development following childhood mild traumatic brain injury

Childhood mild traumatic brain injury (mTBI) is associated with elevated risk of developing social problems, which may be underpinned by changes in the structural developmental trajectory of the social brain, a network of cortical regions supporting social cognition and behavior. However, limited sample sizes and cross-sectional designs generally used in neuroimaging studies of pediatric TBI have prevented explorations of this hypothesis. This longitudinal retrospective study examined the development of parent-reported social problems and cortical thickness in social brain regions following childhood mTBI using data from the large population-based Adolescent Brain Cognitive Development (ABCD) Study. Two-group latent change score models revealed different developmental trajectories from ages 10-12 years in the level of social problems between children with (n = 345) and without (n = 7,089) mTBI. Children with mTBI showed higher, but non-clinical, levels of social problems than controls at age 10. Then, social problems decreased over 2 years, but still remained higher, but non-clinical, than in controls in which they stayed stable. Both groups showed similar decreases in social brain cortical thickness between ages 10 and 12 years. Further studies providing detailed information on the injury mechanism and acute symptoms are needed to better understand individual differences in social functioning and brain development in pediatric TBI.

Brain volume abnormalities and clinical outcomes following paediatric traumatic brain injury

Long-term outcomes are difficult to predict after paediatric traumatic brain injury. The presence or absence of focal brain injuries often do not explain cognitive, emotional and behavioural disabilities that are common and disabling. In adults, traumatic brain injury produces progressive brain atrophy that can be accurately measured and is associated with cognitive decline. However, the effect of paediatric traumatic brain injury on brain volumes is more challenging to measure because of its interaction with normal brain development. Here we report a robust approach to the individualized estimation of brain volume following paediatric traumatic brain injury and investigate its relationship to clinical outcomes. We first used a large healthy control dataset (n > 1200, age 8-22) to describe the healthy development of white and grey matter regions through adolescence. Individual estimates of grey and white matter regional volume were then generated for a group of moderate/severe traumatic brain injury patients injured in childhood (n = 39, mean age 13.53 ± 1.76, median time since injury = 14 months, range 4-168 months) by comparing brain volumes in patients to age-matched controls. Patients were individually classified as having low or normal brain volume. Neuropsychological and neuropsychiatric outcomes were assessed using standardized testing and parent/carer assessments. Relative to head size, grey matter regions decreased in volume during normal adolescence development whereas white matter tracts increased in volume. Traumatic brain injury disrupted healthy brain development, producing reductions in both grey and white matter brain volumes after correcting for age. Of the 39 patients investigated, 11 (28%) had at least one white matter tract with reduced volume and seven (18%) at least one area of grey matter with reduced volume. Those classified as having low brain volume had slower processing speed compared to healthy controls, emotional impairments, higher levels of apathy, increased anger and learning difficulties. In contrast, the presence of focal brain injury and microbleeds were not associated with an increased risk of these clinical impairments. In summary, we show how brain volume abnormalities after paediatric traumatic brain injury can be robustly calculated from individual T1 MRI using a large normative dataset that allows the effects of healthy brain development to be controlled for. Using this approach, we show that volumetric abnormalities are common after moderate/severe traumatic brain injury in both grey and white matter regions, and are associated with higher levels of cognitive, emotional and behavioural abnormalities that are common after paediatric traumatic brain injury.

Fine Particulate Air Pollution, Early Life Stress, and Their Interactive Effects on Adolescent Structural Brain Development: A Longitudinal Tensor-Based Morphometry Study

Air pollution is a major environmental threat to public health; we know little, however, about its effects on adolescent brain development. Exposure to air pollution co-occurs, and may interact, with social factors that also affect brain development, such as early life stress (ELS). Here, we show that severity of ELS and fine particulate air pollution (PM2.5) are associated with volumetric changes in distinct brain regions, but also uncover regions in which ELS moderates the effects of PM2.5. We interviewed adolescents about ELS events, used satellite-derived estimates of ambient PM2.5 concentrations, and conducted longitudinal tensor-based morphometry to assess regional changes in brain volume over an approximately 2-year period (N = 115, ages 9-13 years at Time 1). For adolescents who had experienced less severe ELS, PM2.5 was associated with volumetric changes across several gray and white matter regions. Fewer effects of PM2.5 were observed for adolescents who had experienced more severe ELS, although occasionally they were in the opposite direction. This pattern of results suggests that for many brain regions, moderate to severe ELS largely constrains the effects of PM2.5 on structural development. Further theory and research is needed on the joint effects of ELS and air pollution on the brain.

Association of Attention-Deficit/Hyperactivity Disorder Diagnoses With Pediatric Traumatic Brain Injury: A Meta-analysis

IMPORTANCE

There are conflicting accounts about the risk for attention-deficit/hyperactivity disorder (ADHD) following traumatic brain injury (TBI), possibly owing to variations between studies in acute TBI severity or when ADHD was assessed postinjury. Analysis of these variations may aid in identifying the risk.

OBJECTIVE

To conduct a meta-analysis of studies assessing ADHD diagnoses in children between ages 4 and 18 years following concussions and mild, moderate, or severe TBI.

DATA SOURCES

PubMed, PsycInfo, and Cochrane Central Register of Controlled Trials (1981-December 19, 2019) were searched including the terms traumatic brain injury, brain injuries, closed head injury, blunt head trauma, concussion, attention deficit disorders, ADHD, and ADD in combination with childhood, adolescence, pediatric, infant, child, young adult, or teen.

STUDY SELECTION

Limited to English-language publications in peer-reviewed journals and patient age (4-18 years). Differences about inclusion were resolved through consensus of 3 authors.

DATA EXTRACTION AND SYNTHESIS

MOOSE guidelines for abstracting and assessing data quality and validity were used. Odds ratios with 95% credible intervals (CrIs) are reported.

MAIN OUTCOMES AND MEASURES

The planned study outcome was rate of ADHD diagnoses.

RESULTS

A total of 12 374 unique patients with TBI of all severity levels and 43 491 unique controls were included in the 24 studies in this review (predominantly male: TBI, 61.8%; noninjury control, 60.9%; other injury control, 66.1%). The rate of pre-TBI ADHD diagnoses was 16.0% (95% CrI, 11.3%-21.7%), which was significantly greater than the 10.8% (95% CrI, 10.2%-11.4%) incidence of ADHD in the general pediatric population. Compared with children without injuries, the odds for ADHD were not significantly increased following concussion (≤1 year: OR, 0.32; 95% CrI, 0.05-1.13), mild TBI (≤1 year: OR, 0.56; 0.16-1.43; >1 year: OR, 1.07; 95% CrI, 0.35-2.48), and moderate TBI (≤1 year: OR, 1.28; 95% CrI, 0.35-3.34; >1 year: OR, 3.67; 95% CrI, 0.83-10.56). The odds for ADHD also were not significantly increased compared with children with other injuries following mild TBI (≤1 year: OR, 1.07; 95% CrI, 0.33-2.47; >1 year: OR, 1.18; 95% CrI, 0.32-3.12) and moderate TBI (≤1 year: OR, 2.34; 95% CrI, 0.78-5.47; >1 year: OR, 3.78; 95% CrI, 0.93-10.33). In contrast, the odds for ADHD following severe TBI were increased at both time points following TBI compared with children with other injuries (≤1 year: OR, 4.81; 95% CrI, 1.66-11.03; >1 year: OR, 6.70; 95% CrI, 2.02-16.82) and noninjured controls (≤1 year: OR, 2.62; 95% CrI, 0.76-6.64; >1 year: OR, 6.25; 95% CrI, 2.06-15.06), as well as those with mild TBI (≤1 year OR, 5.69; 1.46-15.67: >1 year OR, 6.65; 2.14-16.44). Of 5920 children with severe TBI, 35.5% (95% CrI, 20.6%-53.2%) had ADHD more than 1 year postinjury.

CONCLUSIONS AND RELEVANCE

This study noted a significant association between TBI severity and ADHD diagnosis. In children with severe but not mild and moderate TBI, there was an association with an increase in risk for ADHD. The high rate of preinjury ADHD in children with TBI suggests that clinicians should carefully review functioning before a TBI before initiating treatment.

Pediatric Moderate-Severe Traumatic Brain Injury and Gray Matter Structural Covariance Networks: A Preliminary Longitudinal Investigation

Pediatric traumatic brain injury (TBI) is prevalent and can disrupt ongoing brain maturation. However, the long-term consequences of pediatric TBI on the brain's network architecture are poorly understood. Structural covariance networks (SCN), based on anatomical correlations between brain regions, may provide important insights into brain topology following TBI. Changes in global SCN (default-mode network [DMN], central executive network [CEN], and salience network [SN]) were compared sub-acutely (<90 days) and in the long-term (approximately 12-24 months) after pediatric moderate-severe TBI (n = 16), and compared to typically developing children assessed concurrently (n = 15). Gray matter (GM) volumes from selected seeds (DMN: right angular gyrus [rAG], CEN: right dorsolateral prefrontal cortex [rDLPFC], SN: right anterior insula) were extracted from T1-weighted images at both timepoints. No group differences were found sub-acutely; at the second timepoint, the TBI group showed significantly reduced structural covariance within the DMN seeded from the rAG and the (1) right middle frontal gyrus, (2) left superior frontal gyrus, and (3) left fusiform gyrus. Reduced structural covariance was also found within the CEN, that is, between the rDLPFC and the (1) calcarine sulcus, and (2) right occipital gyrus. In addition, injury severity was positively associated with GM volumes in the identified CEN regions. Over time, there were no significant changes in SCN in either group. The findings, albeit preliminary, suggest for the first time a long-term effect of pediatric TBI on SCN. SCN may be a complementary approach to characterize the global effect of TBI on the developing brain. Future work needs to further examine how disruptions of these networks relate to behavioral and cognitive difficulties.

Brain Magnetic Resonance Imaging Volumetric Measures of Functional Outcome after Severe Traumatic Brain Injury in Adolescents

Adolescent traumatic brain injury (TBI) is a major public health concern, resulting in >35,000 hospitalizations in the United States each year. Although neuroimaging is a primary diagnostic tool in the clinical assessment of TBI, our understanding of how specific neuroimaging findings relate to outcome remains limited. Our study aims to identify imaging biomarkers of long-term neurocognitive outcome after severe adolescent TBI. Twenty-four adolescents with severe TBI (Glasgow Coma Scale ≤8) enrolled in the ADAPT (Approaches and Decisions after Pediatric TBI) study were recruited for magnetic resonance imaging (MRI) scanning 1-2 years post-injury at 13 participating sites. Subjects underwent outcome assessments ∼1-year post-injury, including the Wechsler Abbreviated Scale of Intelligence (IQ) and the Pediatric Glasgow Outcome Scale-Extended (GOSE-Peds). A typically developing control cohort of 38 age-matched adolescents also underwent scanning and neurocognitive assessment. Brain-image segmentation was performed on T1-weighted images using Freesurfer. Brain and ventricular cerebrospinal fluid volumes were used to compute a ventricle-to-brain ratio (VBR) for each subject, and the corpus callosum cross-sectional area was determined in the midline for each subject. The TBI group demonstrated higher VBR and lower corpus callosum area compared to the control cohort. After adjusting for age and sex, VBR was significantly related with GOSE-Peds score in the TBI group (n = 24, p = 0.01, cumulative odds ratio = 2.18). After adjusting for age, sex, intracranial volume, and brain volume, corpus callosum cross-sectional area correlated significantly with IQ score in the TBI group (partial cor = 0.68, n = 18, p = 0.007) and with PSI (partial cor = 0.33, p = 0.02). No association was found between VBR and IQ or between corpus callosum and GOSE-Peds. After severe adolescent TBI, quantitative MRI measures of VBR and corpus callosum cross-sectional area are associated with global functional outcome and neurocognitive outcomes, respectively.

Reduced Brainstem Volume After Mild Traumatic Brain Injury

Supplemental digital content is available in the text.

Objective

The aims of this study were to investigate changes in regional brain volume after concussion (mild traumatic brain injury) and to examine the relationship between change in brain volume and cognitive deficits.

Design

Twenty-eight patients with mild traumatic brain injury and 27 age-matched controls were included in this study. Magnetic resonance imaging (3 T) data were obtained from the participants. Structural brain volume changes were examined using tensor-based morphometry, which identifies regional structural differences in the whole brain, including cerebrospinal fluid, gray matter, and white matter. Volume contraction and expansion were compared between groups using a two-sample t test. The association between time post-injury or neurocognitive function and volumetric changes was examined using regression analysis.

Results

Individuals with mild traumatic brain injury exhibited volume reduction in the brainstem, including the pontine reticular formation. Regional cerebral volume changes were not associated with time post-injury but were significantly associated with neurocognitive function, especially with executive card sorting test, forward digit span test, and performance on verbal learning test. The greater regional cerebral volume was associated with better cognitive performance after mild traumatic brain injury.

Conclusion

Decreased brainstem volume may indicate its vulnerability to traumatic injury, and cerebral volume in specific regions was positively associated with patients’ cognitive function after injury.

Lesion Induced Error on Automated Measures of Brain Volume: Data From a Pediatric Traumatic Brain Injury Cohort

Structural segmentation of T1-weighted (T1w) MRI has shown morphometric differences, both compared to controls and longitudinally, following a traumatic brain injury (TBI). While many patients with TBI present with abnormalities on structural MRI images, most neuroimaging software packages have not been systematically evaluated for accuracy in the presence of these pathology-related MRI abnormalities. The current study aimed to assess whether acute MRI lesions (MRI acquired 7–71 days post-injury) cause error in the estimates of brain volume produced by the semi-automated segmentation tool, Freesurfer. More specifically, to investigate whether this error was global, the presence of lesion-induced error in the contralesional hemisphere, where no abnormal signal was present, was measured. A dataset of 176 simulated lesion cases was generated using actual lesions from 16 pediatric TBI (pTBI) cases recruited from the emergency department and 11 typically-developing controls. Simulated lesion cases were compared to the “ground truth” of the non-lesion control-case T1w images. Using linear mixed-effects models, results showed that hemispheric measures of cortex volume were significantly lower in the contralesional-hemisphere compared to the ground truth. Interestingly, however, cortex volume (and cerebral white matter volume) were not significantly different in the lesioned hemisphere. However, percent volume difference (PVD) between the simulated lesion and ground truth showed that the magnitude of difference of cortex volume in the contralesional-hemisphere (mean PVD = 0.37%) was significantly smaller than that in the lesioned hemisphere (mean PVD = 0.47%), suggesting a small, but systematic lesion-induced error. Lesion characteristics that could explain variance in the PVD for each hemisphere were investigated. Taken together, these results suggest that the lesion-induced error caused by simulated lesions was not focal, but globally distributed. Previous post-processing approaches to adjust for lesions in structural analyses address the focal region where the lesion was located however, our results suggest that focal correction approaches are insufficient for the global error in morphometric measures of the injured brain.

Developmental divergence of structural brain networks as an indicator of future cognitive impairments in childhood brain injury: Executive functions

Brain insults during childhood can perturb the already non-linear trajectory of typical brain maturation. The diffuse effects of injury can be modelled using structural covariance networks (SCN), which change as a function of neurodevelopment. However, SCNs are estimated at the group-level, limiting applicability to predicting individual-subject outcomes. This study aimed to measure the divergence of the brain networks in paediatric traumatic brain injury (pTBI) patients and controls, and investigate relationships with executive functioning (EF) at 24 months post-injury. T1-weighted MRI acquired acutely in 78 child survivors of pTBI and 33 controls underwent 3D-tissue segmentation to estimate cortical thickness (CT) across 68 atlas-based regions-of-interest (ROIs). Using an 'add-one-patient' approach, we estimate a developmental divergence index (DDI). Our approach adopts a novel analytic framework in which age-appropriate reference networks to calculate the DDI were generated from control participants from the ABIDE dataset using a sliding-window approach. Divergence from the age-appropriate SCN was related to reduced EF performance and an increase in behaviours related to executive dysfunctions. The DDI measure showed predictive value with regard to executive functions, highlighting that early imaging can assist in prognosis for cognition.

Longitudinal Neuroimaging in Pediatric Traumatic Brain Injury: Current State and Consideration of Factors That Influence Recovery

Traumatic brain injury (TBI) is a leading cause of death and disability for children and adolescents in the U.S. and other developed and developing countries. Injury to the immature brain varies greatly from that of the mature, adult brain due to numerous developmental, pre-injury, and injury-related factors that work together to influence the trajectory of recovery during the course of typical brain development. Substantial damage to brain structure often underlies subsequent functional limitations that persist for years following pediatric TBI. Advances in neuroimaging have established an important role in the acute management of pediatric TBI, and magnetic resonance imaging (MRI) techniques have a particular relevance for the sequential assessment of long-term consequences from injuries sustained to the developing brain. The present paper will discuss the various factors that influence recovery and review the findings from the present neuroimaging literature to assess altered development and long-term outcome following pediatric TBI. Four MR-based neuroimaging modalities have been used to examine recovery from pediatric TBI longitudinally: (1) T1-weighted structural MRI is sensitive to morphological changes in gray matter volume and cortical thickness, (2) diffusion-weighted MRI is sensitive to changes in the microstructural integrity of white matter, (3) MR spectroscopy provides a sensitive assessment of metabolic and neurochemical alterations in the brain, and (4) functional MRI provides insight into the functional changes that occur as a result of structural damage and typical developmental processes. As reviewed in this paper, 13 cohorts have contributed to only 20 studies published to date using neuroimaging to examine longitudinal changes after TBI in pediatric patients. The results of these studies demonstrate considerable heterogeneity in post-injury outcome; however, the existing literature consistently shows that alterations in brain structure, function, and metabolism can persist for an extended period of time post-injury. With larger sample sizes and multi-site cooperation, future studies will be able to further examine potential moderators of outcome, such as the developmental, pre-injury, and injury-related factors discussed in the present review.

Best Practices for Obtaining Genomic Consent in Pediatric Traumatic Brain Injury Research

BACKGROUND

Precision health relies on large sample sizes to ensure adequate power, generalizability, and replicability; however, a critical first step to any study is the successful recruitment of participants.

OBJECTIVES

This study seeks to explore how the enrollment strategies used in a parent study contributed to the high consent rates, establish current best practices that can be used in future studies, and identify additional factors that contribute to consent into pediatric traumatic brain injury biobanks.

METHODS

Retrospective secondary analysis of data from a parent study with high consent rates was examined to explore factors affecting consent into biobanking studies.

RESULTS

Of the 76 subjects who were approached, met the eligibility criteria, and reviewed the consent form, only 16 (21.1%) declined to participate. The consented group (n = 60) represents 64.5% of those who met the eligibility criteria upon initial screening (n = 93) and 78.9% of those with confirmed eligibility (n = 76). Analysis of screening data suggested there were no major barriers to consenting individuals into this pediatric traumatic brain injury biobank.

DISCUSSION

There were no demographic or research-related characteristics that significantly explained enrollment. Ethically, to obtain true informed consent, parents need to understand only their child's diagnosis, prognosis, and medical care, as well as the purpose of the proposed research and its risks and benefits. Researchers need to implement best practices, including a comprehensive review of census data to identify eligible participants to approach, a prescreening protocol, and effective consenting process to obtain informed consent so that precision care initiatives can be pursued.

Functional Brain Hyperactivations Are Linked to an Electrophysiological Measure of Slow Interhemispheric Transfer Time after Pediatric Moderate/Severe Traumatic Brain Injury

Increased task-related blood oxygen level dependent (BOLD) activation is commonly observed in functional magnetic resonance imaging (fMRI) studies of moderate/severe traumatic brain injury (msTBI), but the functional relevance of these hyperactivations and how they are linked to more direct measures of neuronal function remain largely unknown. Here, we investigated how working memory load (WML)-dependent BOLD activation was related to an electrophysiological measure of interhemispheric transfer time (IHTT) in a sample of 18 msTBI patients and 26 demographically matched controls from the UCLA RAPBI (Recovery after Pediatric Brain Injury) study. In the context of highly similar fMRI task performance, a subgroup of TBI patients with slow IHTT had greater BOLD activation with higher WML than both healthy control children and a subgroup of msTBI patients with normal IHTT. Slower IHTT treated as a continuous variable was also associated with BOLD hyperactivation in the full TBI sample and in controls. Higher WML-dependent BOLD activation was related to better performance on a clinical cognitive performance index, an association that was more pronounced within the patient group with slow IHTT. Our previous work has shown that a subgroup of children with slow IHTT after pediatric msTBI has increased risk for poor white matter organization, long-term neurodegeneration, and poor cognitive outcome. BOLD hyperactivations after msTBI may reflect neuronal compensatory processes supporting higher-order capacity demanding cognitive functions in the context of inefficient neuronal transfer of information. The link between BOLD hyperactivations and slow IHTT adds to the multi-modal validation of this electrophysiological measure as a promising biomarker.

Bridging the gap: Mechanisms of plasticity and repair after pediatric TBI

Traumatic brain injury is the leading cause of death and disability in the United States, and may be associated with long lasting impairments into adulthood. The multitude of ongoing neurobiological processes that occur during brain maturation confer both considerable vulnerability to TBI but may also provide adaptability and potential for recovery. This review will examine and synthesize our current understanding of developmental neurobiology in the context of pediatric TBI. Delineating this biology will facilitate more targeted initial care, mechanism-based therapeutic interventions and better long-term prognostication and follow-up.

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.

A Tilted Axis: Maladaptive Inflammation and HPA Axis Dysfunction Contribute to Consequences of TBI

Each year approximately 1.7 million people sustain a traumatic brain injury (TBI) in the US alone. Associated with these head injuries is a high prevalence of neuropsychiatric symptoms including irritability, depression, and anxiety. Neuroinflammation, due in part to microglia, can worsen or even cause neuropsychiatric disorders after TBI. For example, mounting evidence demonstrates that microglia become “primed” or hyper-reactive with an exaggerated pro-inflammatory phenotype following multiple immune challenges. Microglial priming occurs after experimental TBI and correlates with the emergence of depressive-like behavior as well as cognitive dysfunction. Critically, immune challenges are various and include illness, aging, and stress. The collective influence of any combination of these immune challenges shapes the neuroimmune environment and the response to TBI. For example, stress reliably induces inflammation and could therefore be a gateway to altered neuropathology and behavioral decline following TBI. Given the increasing incidence of stress-related psychiatric disorders after TBI, the degree in which stress affects outcome is of particular interest. This review aims to highlight the role of the hypothalamic-pituitary-adrenal (HPA) axis as a key mediator of stress-immune pathway communication following TBI. We will first describe maladaptive neuroinflammation after TBI and how stress contributes to inflammation through both anti- and pro-inflammatory mechanisms. Clinical and experimental data describing HPA-axis dysfunction and consequences of altered stress responses after TBI will be discussed. Lastly, we will review common stress models used after TBI that could better elucidate the relationship between HPA axis dysfunction and maladaptive inflammation following TBI. Together, the studies described in this review suggest that HPA axis dysfunction after brain injury is prevalent and contributes to the dynamic nature of the neuroinflammatory response to brain injury. Experimental stressors that directly engage the HPA axis represent important areas for future research to better define the role of stress-immune pathways in mediating outcome following TBI.

Stressful Life Events, ADHD Symptoms, and Brain Structure in Early Adolescence

Despite a growing understanding that early adversity in childhood broadly affects risk for psychopathology, the contribution of stressful life events to the development of symptoms of attention-deficit/hyperactivity disorder (ADHD) is not clear. In the present study, we examined the association between number of stressful life events experienced and ADHD symptoms, assessed using the Attention Problems subscale of the Child Behavior Checklist, in a sample of 214 children (43% male) ages 9.11-13.98 years (M = 11.38, SD = 1.05). In addition, we examined whether the timing of the events (i.e., onset through age 5 years or after age 6 years) was associated with ADHD symptoms. Finally, we examined variation in brain structure to determine whether stressful life events were associated with volume in brain regions that were found to vary as a function of symptoms of ADHD. We found a small to moderate association between number of stressful life events and ADHD symptoms. Although the strength of the associations between number of events and ADHD symptoms did not differ as a function of the age of occurrence of stressful experiences, different brain regions were implicated in the association between stressors and ADHD symptoms in the two age periods during which stressful life events occurred. These findings support the hypothesis that early adversity is associated with ADHD symptoms, and provide insight into possible brain-based mediators of this association.

Magnetic resonance spectroscopy of fiber tracts in children with traumatic brain injury: A combined MRS - Diffusion MRI study

Traumatic brain injury can cause extensive damage to the white matter (WM) of the brain. These disruptions can be especially damaging in children, whose brains are still maturing. Diffusion magnetic resonance imaging (dMRI) is the most commonly used method to assess WM organization, but it has limited resolution to differentiate causes of WM disruption. Magnetic resonance spectroscopy (MRS) yields spectra showing the levels of neurometabolites that can indicate neuronal/axonal health, inflammation, membrane proliferation/turnover, and other cellular processes that are on-going post-injury. Previous analyses on this dataset revealed a significant division within the msTBI patient group, based on interhemispheric transfer time (IHTT); one subgroup of patients (TBI-normal) showed evidence of recovery over time, while the other showed continuing degeneration (TBI-slow). We combined dMRI with MRS to better understand WM disruptions in children with moderate-severe traumatic brain injury (msTBI). Tracts with poorer WM organization, as shown by lower FA and higher MD and RD, also showed lower N-acetylaspartate (NAA), a marker of neuronal and axonal health and myelination. We did not find lower NAA in tracts with normal WM organization. Choline, a marker of inflammation, membrane turnover, or gliosis, did not show such associations. We further show that multi-modal imaging can improve outcome prediction over a single modality, as well as over earlier cognitive function measures. Our results suggest that demyelination plays an important role in WM disruption post-injury in a subgroup of msTBI children and indicate the utility of multi-modal imaging.

Neuroimaging of the Injured Pediatric Brain: Methods and New Lessons

Traumatic brain injury (TBI) is a significant public health problem in the United States, especially for children and adolescents. Current epidemiological data estimate over 600,000 patients younger than 20 years are treated for TBI in emergency rooms annually. While many patients experience a full recovery, for others there can be long-lasting cognitive, neurological, psychological, and behavioral disruptions. TBI in youth can disrupt ongoing brain development and create added family stress during a formative period. The neuroimaging methods used to assess brain injury improve each year, providing researchers a more detailed characterization of the injury and recovery process. In this review, we cover current imaging methods used to quantify brain disruption post-injury, including structural magnetic resonance imaging (MRI), diffusion MRI, functional MRI, resting state fMRI, and magnetic resonance spectroscopy (MRS), with brief coverage of other methods, including electroencephalography (EEG), single-photon emission computed tomography (SPECT), and positron emission tomography (PET). We include studies focusing on pediatric moderate-severe TBI from 2 months post-injury and beyond. While the morbidity of pediatric TBI is considerable, continuing advances in imaging methods have the potential to identify new treatment targets that can lead to significant improvements in outcome.

Prevalence of low test scores in a pediatric psychiatric inpatient population: Applying multivariate base rate analyses

The understanding of neuropsychological functioning in pediatric psychiatric inpatient populations is growing, but limited, resulting in interpretive challenges. This study examined the application of multivariate base rate (MVBR) analysis in a clinical sample to appraise its utility in characterizing the frequency of low scores, as well as predictors of low scores, when using a flexible test battery. Participants included 99 children from a psychiatric inpatient unit referred for neuropsychological testing. Children hospitalized with psychiatric disorders exhibited high rates of low scores at varying criteria across the battery of tests. Hierarchical multiple regression analyses revealed that after accounting for demographic and psychiatric factors, intellectual functioning accounted for approximately 26% of the variance in observed low scores. The results suggest that a substantial percentage of this population produces low scores on neuropsychological testing and, consistent with prior research, intellectual functioning is strongly associated with low score frequency. To our knowledge, this is the first study to examine the clinical application of MVBR analysis in a pediatric psychiatric inpatient population using a flexible test battery. Taken together, this investigation highlights the potential clinical utility of MVBR analysis when interpreting neuropsychological performance in clinical pediatric populations.

Conditioned Medium of Human Adipose Mesenchymal Stem Cells Increases Wound Closure and Protects Human Astrocytes Following Scratch Assay In Vitro

Astrocytes perform essential functions in the preservation of neural tissue. For this reason, these cells can respond with changes in gene expression, hypertrophy, and proliferation upon a traumatic brain injury event (TBI). Different therapeutic strategies may be focused on preserving astrocyte functions and favor a non-generalized and non-sustained protective response over time post-injury. A recent strategy has been the use of the conditioned medium of human adipose mesenchymal stem cells (CM-hMSCA) as a therapeutic strategy for the treatment of various neuropathologies. However, although there is a lot of information about its effect on neuronal protection, studies on astrocytes are scarce and its specific action in glial cells is not well explored. In the present study, the effects of CM-hMSCA on human astrocytes subjected to scratch assay were assessed. Our findings indicated that CM-hMSCA improved cell viability, reduced nuclear fragmentation, and preserved mitochondrial membrane potential. These effects were accompanied by morphological changes and an increased polarity index thus reflecting the ability of astrocytes to migrate to the wound stimulated by CM-hMSCA. In conclusion, CM-hMSCA may be considered as a promising therapeutic strategy for the protection of astrocyte function in brain pathologies.