Imaging in Pediatric Concussion: A Systematic Review

The Concussion, Exercise, and Brain Networks (ConExNet) study: a cohort study aimed at understanding the effects of sub-maximal aerobic exercise on resting state functional brain activity in pediatric concussion

BACKGROUND

Recent scientific evidence has challenged the traditional "rest-is-best" approach for concussion management. It is now thought that "exercise-is-medicine" for concussion, owing to dozens of studies which demonstrate that sub-maximal, graded aerobic exercise can reduce symptom burden and time to symptom resolution. However, the primary neuropathology of concussion is altered functional brain activity. To date, no studies have examined the effects of sub-maximal aerobic exercise on resting state functional brain activity in pediatric concussion. In addition, although exercise is now more widely prescribed following concussion, its cardiopulmonary response is not yet well understood in this population. Our study has two main goals. The first is to understand whether there are exercise-induced resting state functional brain activity differences in children with concussion vs. healthy controls. The second is to profile the physiological response to exercise and understand whether it differs between groups.

METHODS

We will perform a single-center, controlled, prospective cohort study of pediatric concussion at a large, urban children's hospital and academic center. Children with sport-related concussion (aged 12-17 years) will be recruited within 4-weeks of injury by our clinical study team members. Key inclusion criteria include: medical clearance to exercise, no prior concussion or neurological history, and no implants that would preclude MRI. Age- and sex-matched healthy controls will be required to meet the same inclusion criteria and will be recruited through the community. The study will be performed over two visits separated by 24-48 h. Visit 1 involves exercise testing (following the current clinical standard for concussion) and breath-by-breath gas collection using a metabolic cart. Visit 2 involves two functional MRI (fMRI) scans interspersed by 10-minutes of treadmill walking at an intensity calibrated to Visit 1 findings. To address sub-objectives, all participants will be asked to self-report symptoms daily and wear a waist-worn tri-axial accelerometer for 28-days after Visit 2.

DISCUSSION

Our study will advance the growing exercise-concussion field by helping us understand whether exercise impacts outcomes beyond symptoms in pediatric concussion. We will also be able to profile the cardiopulmonary response to exercise, which may allow for further understanding (and eventual optimization) of exercise in concussion management.

TRIAL REGISTRATION

Not applicable.

Executive functioning, behavior, and white matter microstructure in the chronic phase after pediatric mild traumatic brain injury: results from the adolescent brain cognitive development study

BACKGROUND

Mild traumatic brain injury (mTBI) is common in children. Long-term cognitive and behavioral outcomes as well as underlying structural brain alterations following pediatric mTBI have yet to be determined. In addition, the effect of age-at-injury on long-term outcomes is largely unknown.

METHODS

Children with a history of mTBI (n = 406; Mage = 10 years, SDage = 0.63 years) who participated in the Adolescent Brain Cognitive Development (ABCD) study were matched (1:2 ratio) with typically developing children (TDC; n = 812) and orthopedic injury (OI) controls (n = 812). Task-based executive functioning, parent-rated executive functioning and emotion-regulation, and self-reported impulsivity were assessed cross-sectionally. Regression models were used to examine the effect of mTBI on these domains. The effect of age-at-injury was assessed by comparing children with their first mTBI at either 0-3, 4-7, or 8-10 years to the respective matched TDC controls. Fractional anisotropy (FA) and mean diffusivity (MD), both MRI-based measures of white matter microstructure, were compared between children with mTBI and controls.

RESULTS

Children with a history of mTBI displayed higher parent-rated executive dysfunction, higher impulsivity, and poorer self-regulation compared to both control groups. At closer investigation, these differences to TDC were only present in one respective age-at-injury group. No alterations were found in task-based executive functioning or white matter microstructure.

CONCLUSIONS

Findings suggest that everyday executive function, impulsivity, and emotion-regulation are affected years after pediatric mTBI. Outcomes were specific to the age at which the injury occurred, suggesting that functioning is differently affected by pediatric mTBI during vulnerable periods. Groups did not differ in white matter microstructure.

The influence of maturation and sex on intracranial blood velocities during exercise in children

Cerebral blood velocity (CBv) increases in response to moderate exercise in humans, but the magnitude of change is smaller in children compared with postpubertal adolescents and adults. Whether sex differences exist in the anterior or posterior CBv response to exercise across pubertal development remains to be determined. We assessed middle cerebral artery (MCAv) and posterior cerebral artery (PCAv) blood velocity via transcranial Doppler in 38 prepubertal (18 males) and 48 postpubertal (23 males) with cerebrovascular and cardiorespiratory measures compared at baseline and ventilatory threshold. At baseline, MCAv was higher in both sexes pre- versus postpuberty. Females demonstrated a greater MCAv (P < 0.001) than their male counterparts (prepubertal females; 78 ± 11 cm·s-1 vs. prepubertal males; 72 ± 8 cm·s-1, and postpubertal females; 68 ± 10 cm·s-1 vs. postpubertal males; 62 ± 7 cm·s-1). During exercise, MCAv remained higher in postpubertal females versus males (81 ± 15 cm·s-1 vs. 73 ± 11 cm·s-1), but there were no differences in prepuberty. The relative increase in PCAv was greater in post- versus prepubertal females (51 ± 9 cm·s-1 vs. 45 ± 11 cm·s-1; P = 0.032) but was similar in males and females. Our findings suggest that biological sex alters anterior cerebral blood velocities at rest in both pre- and postpubertal youth, but the response to submaximal exercise is only influenced by sex postpuberty.NEW & NOTEWORTHY Cerebral blood velocity (CBv) in the anterior circulation was higher in females compared with males irrespective of maturational stage, but not in the posterior circulation. In response to exercise, females demonstrated a greater CBv compared with males, especially post-peak height velocity (post-PHV) where the CBv response to exercise was more pronounced. Our findings suggest that both CBv at rest and in response to acute submaximal exercise are altered by biological sex in a maturity-dependent manner.

Concussion: Beyond the Cascade

Sport concussion affects millions of athletes each year at all levels of sport. Increasing evidence demonstrates clinical and physiological recovery are becoming more divergent definitions, as evidenced by several studies examining blood-based biomarkers of inflammation and imaging studies of the central nervous system (CNS). Recent studies have shown elevated microglial activation in the CNS in active and retired American football players, as well as in active collegiate athletes who were diagnosed with a concussion and returned to sport. These data are supportive of discordance in clinical symptomology and the inflammatory response in the CNS upon symptom resolution. In this review, we will summarize recent advances in the understanding of the inflammatory response associated with sport concussion and broader mild traumatic brain injury, as well as provide an outlook for important research questions to better align clinical and physiological recovery.

Rethinking recovery in adolescent concussions: Network-level functional connectivity alterations associated with motor deficits

Adolescents who are clinically recovered from concussion continue to show subtle motor impairment on neurophysiological and behavioral measures. However, there is limited information on brain-behavior relationships of persistent motor impairment following clinical recovery from concussion. We examined the relationship between subtle motor performance and functional connectivity of the brain in adolescents with a history of concussion, status post-symptom resolution, and subjective return to baseline. Participants included 27 adolescents who were clinically recovered from concussion and 29 never-concussed, typically developing controls (10-17 years); all participants were examined using the Physical and Neurologic Examination of Subtle Signs (PANESS). Functional connectivity between the default mode network (DMN) or dorsal attention network (DAN) and regions of interest within the motor network was assessed using resting-state functional magnetic resonance imaging (rsfMRI). Compared to controls, adolescents clinically recovered from concussion showed greater subtle motor deficits as evaluated by the PANESS and increased connectivity between the DMN and left lateral premotor cortex. DMN to left lateral premotor cortex connectivity was significantly correlated with the total PANESS score, with more atypical connectivity associated with more motor abnormalities. This suggests that altered functional connectivity of the brain may underlie subtle motor deficits in adolescents who have clinically recovered from concussion. More investigation is required to understand the persistence and longer-term clinical relevance of altered functional connectivity and associated subtle motor deficits to inform whether functional connectivity may serve as an important biomarker related to longer-term outcomes after clinical recovery from concussion.

Prospective Study of Gray Matter Atrophy Following Pediatric Mild Traumatic Brain Injury

BACKGROUND AND OBJECTIVES

The clinical and physiologic time course for recovery following pediatric mild traumatic brain injury (pmTBI) remains actively debated. The primary objective of the current study was to prospectively examine structural brain changes (cortical thickness and subcortical volumes) and age-at-injury effects. A priori study hypotheses predicted reduced cortical thickness and hippocampal volumes up to 4 months postinjury, which would be inversely associated with age at injury.

METHODS

Prospective cohort study design with consecutive recruitment. Study inclusion adapted from American Congress of Rehabilitation Medicine (upper threshold) and Zurich Concussion in Sport Group (minimal threshold) and diagnosed by Emergency Department and Urgent Care clinicians. Major neurologic, psychiatric, or developmental disorders were exclusionary. Clinical (Common Data Element) and structural (3 T MRI) evaluations within 11 days (subacute visit [SA]) and at 4 months (early chronic visit [EC]) postinjury. Age- and sex-matched healthy controls (HC) to control for repeat testing/neurodevelopment. Clinical outcomes based on self-report and cognitive testing. Structural images quantified with FreeSurfer (version 7.1.1).

RESULTS

A total of 208 patients with pmTBI (age = 14.4 ± 2.9; 40.4% female) and 176 HC (age = 14.2 ± 2.9; 42.0% female) were included in the final analyses (>80% retention). Reduced cortical thickness (right rostral middle frontal gyrus; d = -0.49) and hippocampal volumes (d = -0.24) observed for pmTBI, but not associated with age at injury. Hippocampal volume recovery was mediated by loss of consciousness/posttraumatic amnesia. Significantly greater postconcussive symptoms and cognitive deficits were observed at SA and EC visits, but were not associated with the structural abnormalities. Structural abnormalities slightly improved balanced classification accuracy above and beyond clinical gold standards (∆+3.9%), with a greater increase in specificity (∆+7.5%) relative to sensitivity (∆+0.3%).

DISCUSSION

Current findings indicate that structural brain abnormalities may persist up to 4 months post-pmTBI and are partially mediated by initial markers of injury severity. These results contribute to a growing body of evidence suggesting prolonged physiologic recovery post-pmTBI. In contrast, there was no evidence for age-at-injury effects or physiologic correlates of persistent symptoms in our sample.

Multicompartmental models and diffusion abnormalities in paediatric mild traumatic brain injury

The underlying pathophysiology of paediatric mild traumatic brain injury and the time-course for biological recovery remains widely debated, with clinical care principally informed by subjective self-report. Similarly, clinical evidence indicates that adolescence is a risk factor for prolonged recovery, but the impact of age-at-injury on biomarkers has not been determined in large, homogeneous samples. The current study collected diffusion MRI data in consecutively recruited patients (n = 203; 8-18 years old) and age and sex-matched healthy controls (n = 170) in a prospective cohort design. Patients were evaluated subacutely (1-11 days post-injury) as well as at 4 months post-injury (early chronic phase). Healthy participants were evaluated at similar times to control for neurodevelopment and practice effects. Clinical findings indicated persistent symptoms at 4 months for a significant minority of patients (22%), along with residual executive dysfunction and verbal memory deficits. Results indicated increased fractional anisotropy and reduced mean diffusivity for patients, with abnormalities persisting up to 4 months post-injury. Multicompartmental geometric models indicated that estimates of intracellular volume fractions were increased in patients, whereas estimates of free water fractions were decreased. Critically, unique areas of white matter pathology (increased free water fractions or increased neurite dispersion) were observed when standard assumptions regarding parallel diffusivity were altered in multicompartmental models to be more biologically plausible. Cross-validation analyses indicated that some diffusion findings were more reproducible when ∼70% of the total sample (142 patients, 119 controls) were used in analyses, highlighting the need for large-sample sizes to detect abnormalities. Supervised machine learning approaches (random forests) indicated that diffusion abnormalities increased overall diagnostic accuracy (patients versus controls) by ∼10% after controlling for current clinical gold standards, with each diffusion metric accounting for only a few unique percentage points. In summary, current results suggest that novel multicompartmental models are more sensitive to paediatric mild traumatic brain injury pathology, and that this sensitivity is increased when using parameters that more accurately reflect diffusion in healthy tissue. Results also indicate that diffusion data may be insufficient to achieve a high degree of objective diagnostic accuracy in patients when used in isolation, which is to be expected given known heterogeneities in pathophysiology, mechanism of injury and even criteria for diagnoses. Finally, current results indicate ongoing clinical and physiological recovery at 4 months post-injury.

A Scoping Review of Magnetic Resonance Modalities Used in Detection of Persistent Postconcussion Symptoms in Pediatric Populations

Up to 30% of youth with concussion experience PPCSs (PPCS) lasting 4 weeks or longer, and can significantly impact quality of life. Magnetic resonance imaging (MRI) has the potential to increase understanding of causal mechanisms underlying PPCS. However, there are no clear modalities to assist in detecting PPCS. This scoping review aims to synthesize findings on utilization of MRI among children and youth with PPCS, and summarize progress and limitations. Thirty-six studies were included from 4907 identified papers. Many studies used multiple modalities, including (1) structural (n = 27) such as T1-weighted imaging, diffusion weighted imaging, and susceptibility weighted imaging; and (2) functional (n = 23) such as functional MRI and perfusion-weighted imaging. Findings were heterogeneous among modalities and regions of interest, which warrants future reviews that report on the patterns and potential advancements in the field. Consideration of modalities that target PPCS prediction and sensitive modalities that can supplement a biopsychosocial approach to PPCS would benefit future research.

Pediatric Sports-Related Concussion: An Approach to Care

Sports-related concussion (SRC) is a common sports injury in children and adolescents. With the vast amount of youth sports participation, an increase in awareness of concussion and evidence that the injury can lead to consequences for school, sports and overall quality of life, it has become increasingly important to properly diagnose and manage concussion. SRC in the student athlete is a unique and complex injury, and it is important to highlight the differences in the management of child and adolescent concussion compared with adults. This review focuses on the importance of developing a multimodal systematic approach to diagnosing and managing pediatric sports-related concussion, from the sidelines through recovery.

Experiences of Children and Youth With Concussion: A Qualitative Study

IMPORTANCE

Concussions are common among children and youth. To date, the pediatric concussion literature has focused on quantitative reports of the effects of concussion and return-to-activity guidelines. However, the subjective experiences of children and youth returning to occupations postconcussion have largely been ignored. An understanding of these experiences is critical to inform effective concussion management.

OBJECTIVE

To investigate the experiences of children and youth returning to occupations after sustaining a concussion and the impacts on their future engagement in occupation.

DESIGN

Qualitative interpretive description was used for data analysis and interpretation.

SETTING

Community.

PARTICIPANTS

Children and youth ages 11 to 18 yr from a cohort study were recruited to be interviewed about their experiences of engaging in occupations postconcussion.

OUTCOMES AND MEASURES

Interviews were conducted 3 to 24 mo postconcussion, transcribed verbatim, and analyzed using interpretive description to identify themes.

RESULTS

Eight children and youth (5 male, 3 female) were included. Analyses revealed three themes of the experiences of children and youth returning to occupations after concussion: diverse experiences of concussion, knowledge is key to concussion management, and concussions affect occupational engagement.

CONCLUSIONS AND RELEVANCE

This study highlights the importance of considering a person's needs to enable effective concussion treatment plans. The results suggest the need for an occupation-based framework to guide interventions in pediatric concussion management. What This Article Adds: Our findings indicate that children and youth report variable recovery patterns, a lack of knowledge about concussion recovery, and a negative effect of concussion on occupational engagement.

Multisite Harmonization of Structural DTI Networks in Children: An A-CAP Study

The analysis of large, multisite neuroimaging datasets provides a promising means for robust characterization of brain networks that can reduce false positives and improve reproducibility. However, the use of different MRI scanners introduces variability to the data. Managing those sources of variability is increasingly important for the generation of accurate group-level inferences. ComBat is one of the most promising tools for multisite (multiscanner) harmonization of structural neuroimaging data, but no study has examined its application to graph theory metrics derived from the structural brain connectome. The present work evaluates the use of ComBat for multisite harmonization in the context of structural network analysis of diffusion-weighted scans from the Advancing Concussion Assessment in Pediatrics (A-CAP) study. Scans were acquired on six different scanners from 484 children aged 8.00–16.99 years [Mean = 12.37 ± 2.34 years; 289 (59.7%) Male] ~10 days following mild traumatic brain injury (n = 313) or orthopedic injury (n = 171). Whole brain deterministic diffusion tensor tractography was conducted and used to construct a 90 x 90 weighted (average fractional anisotropy) adjacency matrix for each scan. ComBat harmonization was applied separately at one of two different stages during data processing, either on the (i) weighted adjacency matrices (matrix harmonization) or (ii) global network metrics derived using unharmonized weighted adjacency matrices (parameter harmonization). Global network metrics based on unharmonized adjacency matrices and each harmonization approach were derived. Robust scanner effects were found for unharmonized metrics. Some scanner effects remained significant for matrix harmonized metrics, but effect sizes were less robust. Parameter harmonized metrics did not differ by scanner. Intraclass correlations (ICC) indicated good to excellent within-scanner consistency between metrics calculated before and after both harmonization approaches. Age correlated with unharmonized network metrics, but was more strongly correlated with network metrics based on both harmonization approaches. Parameter harmonization successfully controlled for scanner variability while preserving network topology and connectivity weights, indicating that harmonization of global network parameters based on unharmonized adjacency matrices may provide optimal results. The current work supports the use of ComBat for removing multiscanner effects on global network topology.

Longitudinal white matter microstructural changes in pediatric mild traumatic brain injury: An A-CAP study

In the largest sample studied to date, white matter microstructural trajectories and their relation to persistent symptoms were examined after pediatric mild traumatic brain injury (mTBI). This prospective, longitudinal cohort study recruited children aged 8–16.99 years with mTBI or mild orthopedic injury (OI) from five pediatric emergency departments. Children's pre‐injury and 1‐month post‐injury symptom ratings were used to classify mTBI with or without persistent symptoms. Children completed diffusion‐weighted imaging at post‐acute (2–33 days post‐injury) and chronic (3 or 6 months via random assignment) post‐injury assessments. Mean diffusivity (MD) and fractional anisotropy (FA) were derived for 18 white matter tracts in 560 children (362 mTBI/198 OI), 407 with longitudinal data. Superior longitudinal fasciculus FA was higher in mTBI without persistent symptoms relative to OI, d (95% confidence interval) = 0.31 to 0.37 (0.02, 0.68), across time. In younger children, MD of the anterior thalamic radiations was higher in mTBI with persistent symptoms relative to both mTBI without persistent symptoms, 1.43 (0.59, 2.27), and OI, 1.94 (1.07, 2.81). MD of the arcuate fasciculus, −0.58 (−1.04, −0.11), and superior longitudinal fasciculus, −0.49 (−0.90, −0.09) was lower in mTBI without persistent symptoms relative to OI at 6 months post‐injury. White matter microstructural changes suggesting neuroinflammation and axonal swelling occurred chronically and continued 6 months post injury in children with mTBI, especially in younger children with persistent symptoms, relative to OI. White matter microstructure appears more organized in children without persistent symptoms, consistent with their better clinical outcomes.

Structural connectome differences in pediatric mild traumatic brain and orthopedic injury

Sophisticated network‐based approaches such as structural connectomics may help to detect a biomarker of mild traumatic brain injury (mTBI) in children. This study compared the structural connectome of children with mTBI or mild orthopedic injury (OI) to that of typically developing (TD) children. Children aged 8–16.99 years with mTBI (n = 83) or OI (n = 37) were recruited from the emergency department and completed 3T diffusion MRI 2–20 days postinjury. TD children (n = 39) were recruited from the community and completed diffusion MRI. Graph theory metrics were calculated for the binarized average fractional anisotropy among 90 regions. Multivariable linear regression and linear mixed effects models were used to compare groups, with covariates age, hemisphere, and sex, correcting for multiple comparisons. The two injury groups did not differ on graph theory metrics, but both differed from TD children in global metrics (local network efficiency: TD > OI, mTBI, d = 0.49; clustering coefficient: TD < OI, mTBI, d = 0.49) and regional metrics for the fusiform gyrus (lower degree centrality and nodal efficiency: TD > OI, mTBI, d = 0.80 to 0.96; characteristic path length: TD < OI, mTBI, d = −0.75 to −0.90) and in the superior and middle orbital frontal gyrus, paracentral lobule, insula, and thalamus (clustering coefficient: TD > OI, mTBI, d = 0.66 to 0.68). Both mTBI and OI demonstrated reduced global and regional network efficiency and segregation as compared to TD children. Findings suggest a general effect of childhood injury that could reflect pre‐ and postinjury factors that can alter brain structure. An OI group provides a more conservative comparison group than TD children for structural neuroimaging research in pediatric mTBI.

Evidence of altered interhemispheric communication after pediatric concussion

OBJECTIVES: To investigate neurophysiological alterations within the typical symptomatic period after concussion (1-month) and throughout recovery (6-months) in adolescents; and (2) to examine relationships between neurophysiological and upper limb kinematic outcomes.METHODS: 18 adolescents with concussion were compared to 17 healthy controls. Transcranial magnetic stimulation (TMS) was used to assess neurophysiological differences between groups including: short- and long-interval intracortical inhibition, intracortical facilitation, short- and long-latency afferent inhibition, afferent facilitation, and transcallosal inhibition (TCI). Behavioral measures of upper limb kinematics were assessed with a robotic device.RESULTS: Mixed model analysis of neurophysiological data identified two key findings. First, participants with concussion demonstrated delayed onset of interhemispheric inhibition, as indexed by TCI, compared to healthy controls. Second, our exploratory analysis indicated that the magnitude of TCI onset delay in adolescents with concussion was related to upper limb kinematics.CONCLUSIONS: Our findings indicate that concussion in adolescence alters interhemispheric communication. We note relationships between neurophysiological and kinematic data, suggesting an affinity for individuals with less concussion-related physiological change to improve their motor behavior over time. These data serve as an important step in future development of assessments (neurobiological and clinical) and interventions for concussion.

Evaluation and Management of Pediatric Concussion in the Acute Setting

ABSTRACT

Concussion, a type of mild traumatic brain injury, is a common injury encountered by providers caring for pediatric patients in the emergency department (ED) setting. Our understanding of the pathophysiologic basis for symptom and recovery trajectories for pediatric concussion continues to rapidly evolve. As this understanding changes, so do recommendations for optimal management of concussed youth. As more and more children present to EDs across the country for concussion, it is imperative that providers caring for children in these settings remain up-to-date with diagnostic recommendations and management techniques. This article will review the definition, epidemiology, pathophysiology, diagnosis, and management of pediatric concussion in the ED setting.

Neurocognitive Outcomes and Their Diffusion Tensor Imaging Correlates in Children With Mild Traumatic Brain Injury

This study aimed to assess the neurocognitive outcomes and their diffusion tensor imaging correlates in children (aged 6-16 years) with mild traumatic brain injury. This prospective analysis included 74 children with mild traumatic brain injury (52 boys; mean age: 9.5 [±2.7] years). Wechsler Intelligence Scale for Children-Indian adaptation (WISC-IV), Child Behavior Checklist, and Children's Sleep Habits Questionnaire were administered for 57 cases (at 3 months postinjury) and 51 controls of similar age. The findings of diffusion tensor imaging (done within 7 days of injury) were correlated with various WISC-IV indices. The presenting features at the time of injury were loss of consciousness (53%), confusion or disorientation (47%), and post-traumatic amnesia (10%). Other features in the acute phase included drowsiness (86%), headache (78%), balance problems (62%), nausea (47%), fatigue (45%), vomiting (35%), nasal or ear bleed (12%), sensitivity to sound and light (12%), etc. At 3 months postinjury, the children with mild traumatic brain injury performed poorly in terms of Intelligence Quotient, perceptual reasoning index, and processing speed index as compared to controls. Based on the Child Behavior Checklist, 17% of children with mild traumatic brain injury had internalizing behavioral problems in comparison with 4% of controls. Prevalence of poor sleepers in the mild traumatic brain injury cohort and controls was 12.3% and 2% respectively. Headache, reduced attention span, and fatigue were common postconcussion symptoms. There was a positive correlation between right uncinate fasciculus fractional anisotropy and verbal comprehension index (r = 0.32; P < .05).

Impaired motor control after sport-related concussion could increase risk for musculoskeletal injury: Implications for clinical management and rehabilitation

This review presents a conceptual framework and supporting evidence that links impaired motor control after sport-related concussion (SRC) to increased risk for musculoskeletal injury. Multiple studies have found that athletes who are post-SRC have higher risk for musculoskeletal injury compared to their counterparts. A small body of research suggests that impairments in motor control are associated with musculoskeletal injury risk. Motor control involves the perception and processing of sensory information and subsequent coordination of motor output within the central nervous system to perform a motor task. Motor control is inclusive of motor planning and motor learning. If sensory information is not accurately perceived or there is interference with sensory information processing and cognition, motor function will be altered, and an athlete may become vulnerable to injury during sport participation. Athletes with SRC show neuroanatomic and neurophysiological changes relevant to motor control even after meeting return to sport criteria, including a normal neurological examination, resolution of symptoms, and return to baseline function on traditional concussion testing. In conjunction, altered motor function is demonstrated after SRC in muscle activation and force production, movement patterns, balance/postural stability, and motor task performance, especially performance of a motor task paired with a cognitive task (i.e., dual-task condition). The clinical implications of this conceptual framework include a need to intentionally address motor control impairments after SRC to mitigate musculoskeletal injury risk and to monitor motor control as the athlete progresses through the return to sport continuum.

Cortical Volume and Thickness in Youth Several Years After Concussion

OBJECTIVE

The long-term effects of pediatric concussion on brain morphometry remain poorly delineated. This study used magnetic resonance imaging (MRI) to investigate cortical volume and thickness in youth several years after concussion.

METHODS

Participants aged 8-19 years old with a history of concussion (n = 37) or orthopedic injury (n = 20) underwent MRI, rated their postconcussion symptoms, and completed cognitive testing on average 2.6 years (SD = 1.6) after injury. FreeSurfer was used to obtain cortical volume and thickness measurements as well as determine any significant correlations between brain morphometry, postconcussion symptoms (parent and self-report), and cognitive functioning.

RESULTS

No significant group differences were found for either cortical volume or thickness. Youth with a history of concussion had higher postconcussion symptom scores (both parent and self-report Postconcussion Symptom Inventory) than the orthopedic injury group, but symptom ratings did not significantly correlate with cortical volume or thickness. Across both groups, faster reaction time on a computerized neurocognitive test battery (CNS Vital Signs) was associated with a thinner cortex in the left pars triangularis of the inferior frontal gyrus and the left caudal anterior cingulate. Better verbal memory was associated with a thinner cortex in the left rostral middle frontal gyrus.

CONCLUSION

Findings do not support differences in cortical volume or thickness approximately 2.5 years postconcussion in youth, suggesting either long-term cortical recovery or no cortical differences as a result of injury. Further research using a longitudinal study design and larger samples is needed.

Predicting Post-Concussion Symptom Recovery in Adolescents Using a Novel Artificial Intelligence

This pilot study explores the possibility of predicting post-concussion symptom recovery at one week post-injury using only objective diffusion tensor imaging (DTI) data inputs to a novel artificial intelligence (AI) system composed of Genetic Fuzzy Trees (GFT). Forty-three adolescents age 11 to 16 years with either mild traumatic brain injury or traumatic orthopedic injury were enrolled on presentation to the emergency department. Participants received a DTI scan three days post-injury, and their symptoms were assessed by the Post-Concussion Symptom Scale (PCSS) at 6 h and one week post-injury. The GFT system was trained using one-week total PCSS scores, 48 volumetric magnetic resonance imaging inputs, and 192 DTI inputs per participant over 225 training runs. Each training run contained a randomly selected 80% of the total sample followed by a 20% validation run. Over a different randomly selected sample distribution, GFT was also compared with six common classification methods. The cascading GFT structure controlled an effectively infinite solution space that classified participants as recovered or not recovered significantly better than chance. It demonstrated 100% and 62% classification accuracy in training and validation, respectively, better than any of the six comparison methods. Recovery sensitivity and specificity were 59% and 65% in the GFT validation set, respectively. These results provide initial evidence for the effectiveness of a GFT system to make clinical predictions of trauma symptom recovery using objective brain measures. Although clinical and research applications will necessitate additional optimization of the system, these results highlight the future promise of AI in acute care.

Neuroimaging in Pediatric Patients with Mild Traumatic Brain Injury: Relating the Current 2018 Centers for Disease Control Guideline and the Potential of Advanced Neuroimaging Modalities for Research and Clinical Biomarker Development

The Center for Disease Control and Prevention (CDC)'s 2018 Guideline for current practices in pediatric mild traumatic brain injury (mTBI; also referred to as concussion herein) systematically identified the best up-to-date practices based on current evidence and, specifically, identified recommended practices regarding computed tomography (CT), magnetic resonance imaging (MRI), and skull radiograph imaging. In this article, we discuss types of neuroimaging not discussed in the guideline in terms of their safety for pediatric populations, their potential application, and the research investigating the future use of certain modalities to aid in the diagnosis and treatment of mTBI in children. The role of neuroimaging in pediatric mTBI cases should be considered for the potential contribution to children's neural and social development, in addition to the immediate clinical value (as in the case of acute structural findings). Selective use of specific neuroimaging modalities in research has already been shown to detect aspects of diffuse brain injury, disrupted cerebral blood flow, and correlate physiological factors with persistent symptoms, such as fatigue, cognitive decline, headache, and mood changes, following mTBI. However, these advanced neuroimaging modalities are currently limited to the research arena, and any future clinical application of advanced imaging modalities in pediatric mTBI will require robust evidence for each modality's ability to provide measurement of the subtle conditions of brain development, disease, damage, or degeneration, while accounting for variables at both non-injury and time-post-injury epochs. Continued collaboration and communication between researchers and healthcare providers is essential to investigate, develop, and validate the potential of advanced imaging modalities in pediatric mTBI diagnostics and management.

The relationship between fluid biomarkers and clinical outcomes in sports-related concussions: a systematic review

OBJECTIVES

The literature on fluid biomarkers for concussion has primarily focused on comparing athletes with and without a diagnosis of concussion and on examining the relationship between fluid biomarkers and exposure to head trauma. This systematic literature review aims to examine the strength of evidence for fluid biomarkers to be associated with clinically relevant outcomes in sports-related concussion.

METHODS

A systematic literature review was conducted using EmBASE, PubMed, and CINAHL. English-language articles that included athletes participating in organized sports and reported the relationship between at least one fluid biomarker and at least one clinical outcome measure, or provided data that could be used to analyze this relationship, were included.

RESULTS

Studies of the relationship between fluid biomarkers and clinical outcomes of concussion have yielded small or variable effects. There were significant inconsistencies in methodology including duration of time post-injury of biomarker collection, use of control groups, the number of time points post-injury that biomarkers were collected, and what clinical outcomes were utilized.

CONCLUSION

There is currently insufficient evidence to support a relationship between any of the included fluid biomarkers and clinical outcome measures of concussion. Future research including clinical outcome measures and using standardized study design and methodology is necessary.

Neuroimaging in paediatric mild traumatic brain injury: a systematic review

Neuroimaging is being increasingly applied to the study of paediatric mild traumatic brain injury (mTBI) to uncover the neurobiological correlates of delayed recovery post-injury. The aims of this systematic review were to: (i) evaluate the neuroimaging research investigating neuropathology post-mTBI in children and adolescents from 0-18 years, (ii) assess the relationship between advanced neuroimaging abnormalities and PCS in children, (iii) assess the quality of the evidence by evaluating study methodology and reporting against best practice guidelines, and (iv) provide directions for future research. A literature search of MEDLINE, PsycINFO, EMBASE, and PubMed was conducted. Abstracts and titles were screened, followed by full review of remaining articles where specific eligibility criteria were applied. This systematic review identified 58 imaging studies which met criteria. Based on several factors including methodological heterogeneity and relatively small sample sizes, the literature currently provides insufficient evidence to draw meaningful conclusions about the relationship between MRI findings and clinical outcomes. Future research is needed which incorporates prospective, longitudinal designs, minimises potential confounds and utilises multimodal imaging techniques.

Microstructure of the Corpus Callosum Long after Pediatric Concussion

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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

PRIMARY OBJECTIVE

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

RESEARCH DESIGN

Observational, cross-sectional.

METHODS AND PROCEDURES

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

MAIN OUTCOMES AND RESULTS

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

CONCLUSIONS

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

Default mode network functional connectivity after multiple concussions in children and adolescents

Objective

This cross-sectional study aims to elucidate if children and adolescents with multiple concussions demonstrate long-term alterations in DMN functional connectivity (FC).

Method

Participants (N = 57, 27 girls and 30 boys; 8-19 years old, M age = 14.7, SD = 2.8) were divided into three groups (orthopedic injury [OI] n = 20; one concussion n = 16; multiple concussions n = 21, M = 3.2 concussions, SD = 1.7) and seen on average 31.6 months post-injury (range 4.3-130.7 months; SD = 19.4). They underwent a resting-state functional magnetic resonance imaging scan. Parents completed the ADHD rating scale-5 for children and adolescents. Children and parents completed the post-concussion symptom inventory (PCSI).

Results

Anterior and posterior DMN components were extracted from the fMRI data for each participant using FSL’s MELODIC and dual regression. We tested for pairwise group differences within each DMN component in FSL’s Randomize (5000 permutations) using threshold-free cluster enhancement to estimate cluster activation, controlling for age, sex, and symptoms of inattention. FC of the anterior DMN was significantly reduced in the group with multiple concussions compared to the two other groups, whereas there were no significant group differences on FC of the posterior DMN. There were no significant associations between DMN FC and PCSI scores.

Conclusions

These results suggest reduced FC in the anterior DMN in youth with multiple concussions, but no linear association with post-concussive symptoms.

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

INTRODUCTION

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Current Concepts in the Evaluation of the Pediatric Patient with Concussion

PURPOSE OF THE REVIEW

A concussion is a mild traumatic brain injury (mTBI) that results in a change in how a person feels or functions after a force transmitted to the head. Nearly 10% of all sports-related injuries are mild traumatic brain injuries. Concussion/mTBIs have accounted for more than 3 million emergency department visits between 2005 and 2009 and present as an important public health concern.

RECENT FINDINGS

Physical, cognitive, and psychological functioning are known to be affected by concussion/mTBI, and various tools are readily available to guide clinicians through the initial evaluation. Evaluation of patients with concussion/mTBI should include symptom report and balance, vestibular-ocular, and neurocognitive testing. Awareness of past medical history and pre-injury history of social, behavioral, and emotional functioning is essential to better understand the injury and to predict the expected course of recovery. No tool available can be used alone to diagnose concussion/mTBI or evaluate for recovery.

Longitudinal Changes in Magnetic Resonance Spectroscopy in Pediatric Concussion: A Pilot Study

Background: Nearly 20% of US adolescents report at least one lifetime concussion. Pathophysiologic models suggest that traumatic biomechanical forces caused by rotational deceleration lead to shear stress, which triggers a neurometabolic cascade beginning with excitotoxicity and leading to significant energy demands and a period of metabolic crisis for the injured brain. Proton magnetic resonance spectroscopy (¹H MRS) offers a means for non-invasive measurement of neurometabolic changes after concussion.

Objective: Describe longitudinal changes in metabolites measured in vivo in the brains of adolescent patients with concussion.

Methods: We prospectively recruited 9 patients ages 11 to 20 who presented to a pediatric Emergency Department within 24 h of concussion. Patients underwent MRI scanning within 72 h (acute, n = 8), 2 weeks (subacute, n = 7), and at approximately 1 year (chronic, n = 7). Healthy, age and sex-matched controls were recruited and scanned once (n = 9). ¹H MRS was used to measure N-acetyl-aspartate, choline, creatine, glutamate + glutamine, and myo-inositol concentrations in six regions of interest: left and right frontal white matter, posterior white matter and thalamus.

Results: There was a significant increase in total thalamus glutamate+glutamine/choline at the subacute (p = 0.010) and chronic (p = 0.010) time points, and a significant decrease in total white matter myo-inositol/choline (p = 0.030) at the chronic time point as compared to controls.

Conclusion: There are no differences in ¹H MRS measurements in the acute concussive period; however, changes in glutamate+glutamine and myo-inositol concentrations detectable by ¹H MRS may develop beyond the acute period.

Impact of mild traumatic brain injury on cingulate functions

Mild traumatic brain injury (mTBI) is a condition of normal neuroimaging, because conventional MRI is not sensitive to brain lesions. Neurocognitive deficits persist for years after injury in 15% of patients. Persistent TAI can continue after the trauma and contribute to progressive disability. Neuropathologic studies underestimate the total axonal damage, by failure to identify fine-caliber unmyelinated fiber. Swollen axons represent the "tip of the iceberg" of damage. Progression of molecular changes, including mitochondrial dysfunction, leads to secondary injuries. Primary low-intensity "invisible injury" is solely detectable at ultrastructural levels. Over the long term, mTBI is not a static event but a progressive injury, increasing risk of neurodegenerative diseases. Lack of evidence of brain injury has led to the development of more sensitive methods: morphometric MRI (VBM, DTI) and functional techniques (fMRI, PET, SPECT). By deformation of the surface of gray matter cingulate gyrus and disruption of long-coursing WM of CB structures, striking the falx, mTBI causes alteration of cingulate functions. Postconcussion, blast, and whiplash-associated disorders are the main mechanisms providing behavior and cognitive symptoms after mTBI.