Increased [18F]Fluorodeoxyglucose Uptake in the Left Pallidum in Military Veterans with Blast-Related Mild Traumatic Brain Injury: Potential as an Imaging Biomarker and Mediation with Executive Dysfunction and Cognitive Impairment

Blast-related mild traumatic brain injury (blast-mTBI) can result in a spectrum of persistent symptoms leading to substantial functional impairment and reduced quality of life. Clinical evaluation and discernment from other conditions common to military service can be challenging and subject to patient recall bias and the limitations of available assessment measures. The need for objective biomarkers to facilitate accurate diagnosis, not just for symptom management and rehabilitation but for prognostication and disability compensation purposes is clear. Toward this end, we compared regional brain [18F]fluorodeoxyglucose-positron emission tomography ([18F]FDG-PET) intensity-scaled uptake measurements and motor, neuropsychological, and behavioral assessments in 79 combat Veterans with retrospectively recalled blast-mTBI with 41 control participants having no lifetime history of TBI. Using an agnostic and unbiased approach, we found significantly increased left pallidum [18F]FDG-uptake in Veterans with blast-mTBI versus control participants, p < 0.0001; q = 3.29 × 10-9 [Cohen's d, 1.38, 95% confidence interval (0.96, 1.79)]. The degree of left pallidum [18F]FDG-uptake correlated with the number of self-reported blast-mTBIs, r2 = 0.22; p < 0.0001. Greater [18F]FDG-uptake in the left pallidum provided excellent discrimination between Veterans with blast-mTBI and controls, with a receiver operator characteristic area under the curve of 0.859 (p < 0.0001) and likelihood ratio of 21.19 (threshold:SUVR ≥ 0.895). Deficits in executive function assessed using the Behavior Rating Inventory of Executive Function-Adult Global Executive Composite T-score were identified in Veterans with blast-mTBI compared with controls, p < 0.0001. Regression-based mediation analyses determined that in Veterans with blast-mTBI, increased [18F]FDG-uptake in the left pallidum-mediated executive function impairments, adjusted causal mediation estimate p = 0.021; total effect estimate, p = 0.039. Measures of working and prospective memory (Auditory Consonant Trigrams test and Memory for Intentions Test, respectively) were negatively correlated with left pallidum [18F]FDG-uptake, p < 0.0001, with mTBI as a covariate. Increased left pallidum [18F]FDG-uptake in Veterans with blast-mTBI compared with controls did not covary with dominant handedness or with motor activity assessed using the Unified Parkinson's Disease Rating Scale. Localized increased [18F]FDG-uptake in the left pallidum may reflect a compensatory response to functional deficits following blast-mTBI. Limited imaging resolution does not allow us to distinguish subregions of the pallidum; however, the significant correlation of our data with behavioral but not motor outcomes suggests involvement of the ventral pallidum, which is known to regulate motivation, behavior, and emotions through basal ganglia-thalamo-cortical circuits. Increased [18F]FDG-uptake in the left pallidum in blast-mTBI versus control participants was consistently identified using two different PET scanners, supporting the generalizability of this finding. Although confirmation of our results by single-subject-to-cohort analyses will be required before clinical deployment, this study provides proof of concept that [18F]FDG-PET bears promise as a readily available noninvasive biomarker for blast-mTBI. Further, our findings support a causative relationship between executive dysfunction and increased [18F]FDG-uptake in the left pallidum.

Pilot study protocol of a randomized controlled trial for the potential effects of creatine monohydrate on persistent post-concussive symptoms

Background

Mild traumatic brain injury or concussion is a global public concern, with an estimated annual incidence between 48 million and 96 million worldwide. It is a socioeconomical problem, and almost one-third of individuals with concussion suffer from severe persistent post-concussive symptoms (PPCS), with an increased risk of unemployment or terminating their studies. To date, no single treatment is available with guaranteed success. Creatine monohydrate (CrM) has shown potential as a treatment for post-concussive symptoms, having a positive impact on cognitive function, chronic fatigue, depression, and anxiety. The aim of this study is to examine the effect of CrM on PPCS assessed using the Rivermead Post-Concussion Symptoms Questionnaire (RPQ).

Methods

The study is designed as a double-blinded randomised controlled trial. Study participants are found through neurological outpatient clinics in Denmark or through social media. They will be between 25 and 35 years of age, will have suffered from PPCS for 6-12 months prior to inclusion, and will have no comorbidities. The participants will be randomly allocated to either an intervention group (INT), placebo group (PLA), or control group (CG). Baseline data will be collected immediately after inclusion, and the study period will be 7 weeks. Follow-up data will be collected 1 week after the end of the study period. The primary outcome of the study is changes in RPQ score. Changes in weight and training status will be adjusted for as potential confounders.

Ethics and dissemination

This protocol is approved by the National Committee on Health Research (97508) and by the Danish Data Protection Agency 11.651. The investigators intend to submit their study findings for publication in peer-reviewed journals and disseminate the findings via presentation at academic meetings/conferences.Clinical Trial registration: NCT05562232, registered September 30, 2022.

Cortical and cerebellar structural correlates of cognitive-motor integration performance in females with and without persistent concussion symptoms

INTRODUCTION

Fifteen percent of individuals who sustain a concussion develop persistent concussion symptoms (PCS). Recent literature has demonstrated atrophy of the frontal, parietal, and cerebellar regions following acute concussive injury. The frontoparietal-cerebellar network is essential for the performance of visuomotor transformation tasks requiring cognitive-motor integration (CMI), important for daily function.

PURPOSE

We investigated cortical and subcortical structural differences and how these differences are associated with CMI performance in those with PCS versus healthy controls.

METHODS

Twenty-six age-matched  female participants (13 PCS, 13 healthy) completed four visuomotor tasks.  Additionally, MR-images were analyzed for cortical thickness and volume, and cerebellar lobule volume.

RESULTS

No statistically significant group differences were found in CMI performance. However, those with PCS demonstrated a significantly thicker and larger precuneus, and significantly smaller cerebellar lobules (VIIIa, VIIIb, X) compared to controls. When groups were combined, volumes of both the cerebellar lobules and cortical regions were associated with CMI task performance.

CONCLUSION

The lack of behavioral differences combined with the structural differences may reflect a compensatory mechanism for those with PCS. In addition, this study highlights the effectiveness of CMI tasks in estimating the structural integrity of the frontoparietal-cerebellar network and is among the first to demonstrate structural correlates of PCS.

Association of Concussion History and Prolonged Recovery in Youth

OBJECTIVE

To determine the number of prior concussions associated with increased incidence of persistent postconcussive symptoms (PPCS) in a cohort of acutely concussed pediatric patients.

DESIGN

Prospective observational cohort study.

SETTING

Three university-affiliated concussion clinics.

PARTICIPANTS

Two hundred seventy participants (14.9 ± 1.9 years, 62% male, 54% with prior concussion) were assessed within 14 days of concussion and followed to clinical recovery. Participants with a second head injury before clinical recovery were excluded.

MEASURES AND MAIN OUTCOME

Concussion history, current injury characteristics, recovery time, and risk for prolonged recovery from current concussion.

RESULTS

There was no statistically significant change in PPCS risk for participants with 0, 1 or 2 prior concussions; however, participants with 3 or more prior concussions had a significantly greater risk of PPCS. Twelve participants sustained a subsequent concussion after clinical recovery from their first injury and were treated as a separate cohort. Our secondary analysis found that these participants took longer to recover and had a greater incidence of PPCS during recovery from their latest concussion.

CONCLUSION

Pediatric patients with a history of 3 or more concussions are at greater risk of PPCS than those with fewer than 3 prior concussions.

Salivary miRNA Expression in Children With Persistent Post-concussive Symptoms

Background

Up to one-third of concussed children develop persistent post-concussive symptoms (PPCS). The identification of biomarkers such as salivary miRNAs that detect concussed children at increased risk of PPCS has received growing attention in recent years. However, whether and how salivary miRNA expression levels differ over time between concussed children with and without PPCS is unknown.

Aim

To identify salivary MicroRNAs (miRNAs) whose expression levels differ over time post-concussion in children with vs. without PPCS.

Methods

We conducted a prospective cohort study with saliva collection at up to three timepoints: (1) within one week of injury; (2) one to two weeks post-injury; and (3) 4-weeks post-injury. Participants were children (ages 11 to 17 years) with a physician-diagnosed concussion from a single hospital center. We collected participants' daily post-concussion symptom ratings throughout their enrollment using the Post-concussion Symptom Scale, and defined PPCS as a total symptom score of ≥ 5 at 28 days post-concussion. We extracted salivary RNA from the saliva samples and measured expression levels of 827 salivary miRNAs. We then compared the longitudinal expression levels of salivary miRNAs in children with vs. without PPCS using linear models with repeated measures.

Results

A total of 135 saliva samples were collected from 60 children. Of the 827 miRNAs analyzed, 91 had expression levels above the calculated background threshold and were included in the differential gene expression analyses. Of these 91 miRNAs, 13 had expression levels that differed significantly across the three timepoints post-concussion between children with and without PPCS (i.e., hsa-miR-95-3p, hsa-miR-301a-5p, hsa-miR-626, hsa-miR-548y, hsa-miR-203a-5p, hsa-miR-548e-5p, hsa-miR-585-3p, hsa-miR-378h, hsa-miR-1323, hsa-miR-183-5p, hsa-miR-200a-3p, hsa-miR-888-5p, hsa-miR-199a-3p+hsa-miR-199b-3p). Among these 13 miRNAs, one (i.e., hsa-miR-203a-5p) was also identified in a prior study, with significantly different expression levels between children with and without PPCS.

Conclusion

Our results from the longitudinal assessment of miRNAs indicate that the expression levels of 13 salivary miRNAs differ over time post-injury in concussed children with vs. without PPCS. Salivary miRNAs may be a promising biomarker for PPCS in children, although replication studies are needed.

The impact of the COVID-19 pandemic on the well-being of individuals with persistent post-concussive symptoms: a qualitative study

Background

In response to the COVID‐19 pandemic, public health measures were implemented that closed essential businesses, mandated social distancing, and imposed substantial changes to the routine care experienced by patients with mild traumatic brain injury (mTBI) and persistent postconcussive symptoms (PPCS). Patients with PPCS often rely on a comprehensive care team, requiring in‐person treatments and consistent care. Little information exists regarding how access to these services have been affected by public health measures and what outcome the measures have had on the recovery of patients with PPCS.

Objective

To explore the impact of the restriction of in‐person treatments, shifts to virtual care, and global public health measures on the recovery and psychological well‐being of patients with PPCS.

Design

Qualitative interviews were recorded, transcribed, and analyzed using a reflexive thematic analysis approach to identify the main impacts of the public health measures on participants with PPCS.

Setting

Participant interviews were completed remotely via telephone or video‐calling software during province‐wide shutdowns.

Participants

20 individuals with PPCS who attended the institution's Brain Injury Program consented to participate.

Interventions

Not applicable.

Results

The impacts of the public health measures emerged most prominently in three main categories: (1) day‐to‐day lived experiences, (2) personal health status, and (3) health service experiences and barriers.

Conclusions

This in‐depth investigation of the lived experiences of patients with PPCS outlines how the COVID‐19 public health measures negatively affected their care and well‐being. The analysis identified that through increasing social support systems, providing better access to standard or remote treatment, and developing more effective telehealth strategies, this population could be better supported in the event of future public health measures.

Neurophysiological Biomarkers of Persistent Post-concussive Symptoms: A Scoping Review

Background and Objectives: Persistent post-concussive symptoms (PCS) consist of neurologic and psychological complaints persisting after a mild traumatic brain injury (mTBI). It affects up to 50% of mTBI patients, may cause long-term disability, and reduce patients' quality of life. The aim of this review was to examine the possible use of different neuroimaging modalities in PCS.

Methods: Articles from Pubmed database were screened to extract studies that investigated the relationship between any neuroimaging features and symptoms of PCS. Descriptive statistics were applied to report the results.

Results: A total of 80 out of 939 papers were included in the final review. Ten examined conventional MRI (30% positive finding), 24 examined diffusion weighted imaging (54.17% positive finding), 23 examined functional MRI (82.61% positive finding), nine examined electro(magneto)encephalography (77.78% positive finding), and 14 examined other techniques (71% positive finding).

Conclusion: MRI was the most widely used technique, while functional techniques seem to be the most sensitive tools to evaluate PCS. The common functional patterns associated with symptoms of PCS were a decreased anti-correlation between the default mode network and the task positive network and reduced brain activity in specific areas (most often in the prefrontal cortex).

Significance: Our findings highlight the importance to use functional approaches which demonstrated a functional alteration in brain connectivity and activity in most studies assessing PCS.

Neuromodulation for Mild Traumatic Brain Injury Rehabilitation: A Systematic Review

Background: Mild traumatic brain injury (mTBI) results from an external force to the head or body causing neurophysiological changes within the brain. The number and severity of symptoms can vary, with some individuals experiencing rapid recovery, and others having persistent symptoms for months to years, impacting their quality of life. Current rehabilitation is limited in its ability to treat persistent symptoms and novel approaches are being sought to improve outcomes following mTBI. Neuromodulation is one technique used to encourage adaptive neuroplasticity within the brain.

Objective: To systematically review the literature on the efficacy of neuromodulation in the mTBI population.

Method: A systematic review was conducted using Medline, Embase, PsycINFO, PsycARTICLES and EBM Review. Preferred Reporting Items for Systematic Reviews and the Synthesis Without Meta-analysis reporting guidelines were used and a narrative review of the selected studies was completed. Fourteen articles fulfilled the inclusion criteria which were published in English, investigating an adult sample and using a pre- and post-intervention design. Studies were excluded if they included non-mild TBI severities, pediatric or older adult populations.

Results: Thirteen of fourteen studies reported positive reductions in mTBI symptomatology following neuromodulation. Specifically, improvements were reported in post-concussion symptom ratings, headaches, dizziness, depression, anxiety, sleep disturbance, general disability, cognition, return to work and quality of life. Normalization of working memory activation patterns, vestibular field potentials, hemodynamics of the dorsolateral prefrontal cortex and excessive delta wave activity were also seen. The studies reviewed had several methodological limitations including small, heterogenous samples and varied intervention protocols, limiting generalisability. Further research is required to understand the context in which neuromodulation may be beneficial.

Conclusions: While these positive effects are observed, limitations included unequal representation of neuromodulation modalities in the literature, and lack of literature describing the efficacy of neuromodulation on the development or duration of persistent mTBI symptoms. Better clarity regarding neuromodulation efficacy could have a significant impact on mTBI patients, researchers, clinicians, and policy makers, facilitating a more productive post-mTBI population. Despite the limitations, the literature indicates that neuromodulation warrants further investigation. PROSPERO registration number: CRD42020161279.

Changes in attentional processing following neurofeedback in patients with persistent post-concussive symptoms: a pilot study

OBJECTIVE

Persistent post-concussive symptoms (PPCS) often include attention deficits, particularly orienting and executive attention. Research in other clinical populations has demonstrated that neurofeedback therapy (NFT) is effective at improving orienting and executive attention, although its effects on attentional networks in patients with PPCS are unknown.

METHOD

In this single-group pilot study, we examined attention-related event-related potentials (ERPs) - N1 and P3 - and cognitive outcomes following Live Z-score training (LZT), a variant of NFT.

RESULTS

No changes in early selective attention, as indexed by N1 amplitude, were observed; however, P3 amplitude, which indexes neural resource allocation, increased following LZT and returned to baseline by 3 months. Cognitive performance improved following treatment, which was sustained at 3 months. The magnitude of change in P3 and ANT performance did not differ between orienting or executive attention, suggesting LZT improved general attentional processing efficiency.

CONCLUSION

Our results suggest that LZT may positively affect attention globally, but does not target specific attention networks. These pilot data warrant the initiation of a clinical trial evaluating the effectiveness of LZT for treating attention deficits in patients with PPCS.

Effects of Interval-Training Exercise on People Who Have Had Persistent Post-Concussive Symptoms for Less Than One Year: A Pilot Study

This study is to examine the effects of a 12-session moderate intensity-interval-training program with blood flow restriction (BFR) and body cooling (BC) on people who have had persistent post-concussive symptoms (PPCS) for <1 year. A single-blind randomized controlled trial of interval-training exercise with BFR and BC was conducted. Twenty-five adults with PPCS were assigned to the experimental group (n = 14) or the control group (n = 11). Both groups rode a recumbent elliptical machine for 21 min at moderate intensity (65% predicted maximum heart rate) twice a week for 6 weeks, but only the experimental group received BFR and BC while riding. The variances of overall PPCS scale scores and their sub-domain scores for individuals during the 6-week intervention and 6-week follow-up period were calculated. During the intervention, the fluctuation of overall symptom severity, severity in the cognitive domain and severity in the mood domain were significantly less in the experimental group (p = 0.03; p = 0.02; p = 0.02). During the follow-up period, the number of symptoms remained more stable in the experimental group (p = 0.02), and a trend toward less fluctuation of symptom severity (p = 0.05) was also observed. The reduced number of symptoms in the cognitive and sleep domains remained more stable in the experimental group following the intervention (p = 0.007; p = 0.02). The severity of mood and sleep symptoms also remained more stable during the follow-up period in the experimental group (p = 0.04). More stable recovery was found in individuals who exercised using BFR and BC than in those who underwent exercise without BFR and BC. Moderate intensity-interval-training exercise with BFR and BC alleviated post-concussive symptoms in people who have had PPCS <1 year.

Characteristics and Outcomes for Delayed Diagnosis of Concussion in Pediatric Patients Presenting to the Emergency Department

BACKGROUND

Concussions are common pediatric injuries. Previous studies have found concussed youth may be underdiagnosed in the emergency department (ED), but outcomes for those with delayed diagnosis have yet to be described.

OBJECTIVE

Our aim was to compare visit characteristics and outcomes of patients who present to the ED with head injury who receive immediate vs. delayed diagnosis.

METHODS

Retrospective chart review of patients aged 6 to 18 years diagnosed with concussion on their first ED or urgent care (UC) visit and patients requiring a second visit for diagnosis between July 1, 2017 and June 20, 2019. We compared demographic information, ED or UC visit features, and recovery outcomes using χ² tests, Student's t-tests, and Wilcoxon rank-sum tests.

RESULTS

Overall, we included 85 patients with delayed concussion diagnosis and 159 with immediate diagnosis. Those with immediate diagnosis had more symptoms inquired at initial visit (5 vs. 4; p = 0.003) and a higher likelihood of receiving concussion-specific physical examinations (80% vs. 36.5%; p < 0.001); 76.5% of delayed diagnosis patients had at least 1 symptom at follow-up visit that was not inquired about at initial visit. Those with delayed diagnosis had more medical visits during recovery (3 vs. 2; p < 0.001), longer average time to symptom resolution (21 vs. 11 days; p = 0.004), and a higher likelihood of having persistent concussion symptoms (odds ratio 2.9; 95% confidence interval 1.4-5.9).

CONCLUSIONS

Concussed children evaluated acutely for head injury who do not receive an immediate diagnosis may be at risk for persistent symptoms. Performance of a concussion-specific physical examination and use of a standardized symptom scale may aid in identification of concussed youth acutely.

Comparison of Methods for Classifying Persistent Post-Concussive Symptoms in Children

Pediatric mild traumatic brain injury (pmTBI) has received increased public scrutiny over the past decade, especially regarding children who experience persistent post-concussive symptoms (PPCS). However, several methods for defining PPCS exist in clinical and scientific literature, and even healthy children frequently exhibit non-specific, concussive-like symptoms. Inter-method agreement (six PPCS methods), observed misclassification rates, and other psychometric properties were examined in large cohorts of consecutively recruited adolescent patients with pmTBI (n = 162) 1 week and 4 months post-injury and in age/sex-matched healthy controls (HC; n = 117) at equivalent time intervals. Six published PPCS methods were stratified into Simple Change (e.g., International Statistical Classification of Diseases and Related Health Problems, 10th revision [ICD-10]) and Standardized Change (e.g., reliable change indices) algorithms. Among HC, test-retest reliability was fair to good across the 4-month assessment window, with evidence of bias (i.e., higher symptom ratings) during retrospective relative to other assessments. Misclassification rates among HC were higher (>30%) for Simple Change algorithms, with poor inter-rater reliability of symptom burden across HC and their parents. A 49% spread existed in terms of the proportion of pmTBI patients "diagnosed" with PPCS at 4 months, with superior inter-method agreement among standardized change algorithms. In conclusion, the self-reporting of symptom burden is only modestly reliable in typically developing adolescents over a 4-month period, with additional evidence for systematic bias in both adolescent and parental ratings. Significant variation existed for identifying pmTBI patients who had "recovered" (i.e., those who did not meet individual criteria for PPCS) from concussion across the six definitions, representing a considerable challenge for estimating the true incidence rate of PPCS in published literature. Although relatively straightforward to obtain, current findings question the utility of the most commonly used Simple Change scores for diagnosis of PPCS in clinical settings.

Longitudinal study of hyperbaric oxygen intervention on balance and affective symptoms in military service members with persistent post-concussive symptoms

BACKGROUND

Dizziness and imbalance are common after mild traumatic brain injury (mTBI). Hyperbaric oxygen (HBO2) has been proposed for persistent post-concussive symptoms after mTBI, but its effect on vestibular function is unknown.

OBJECTIVE

To describe balance function in military service-members before and after intervention, and to explore the influence of post-traumatic stress disorder (PTSD), anxiety, and depression on vestibular outcomes.

METHODS

Seventy-one participants with mTBI and seventy-five healthy adults without brain injury were enrolled (NCT01611194 and NCT01925963). mTBI participants were randomized to 40 HBO2 sessions or 40 sham chamber sessions over 12 weeks. Normative controls received no intervention. Balance and neuropsychological function were measured at baseline, 13 weeks, and 6 months.

RESULTS

The mTBI cohort performed worse than healthy controls on balance and gait measures and reported more affective symptoms. Some within-group improvements were noted at 13 weeks and 6 months. Significant between-intervention differences on balance measures were minimal but effects on postural control generally favored HBO2. Those with affective symptoms, particularly PTSD, had the most improvement in postural control and otolith function following 13 weeks of HBO2.

CONCLUSION

HBO2 may influence balance function after mTBI, particularly in those with affective symptoms.

Longitudinal Assessment of Cortical Excitability in Children and Adolescents With Mild Traumatic Brain Injury and Persistent Post-concussive Symptoms

Introduction: Symptoms following a mild traumatic brain injury (mTBI) usually resolve quickly but may persist past 3 months in up to 15% of children. Mechanisms of mTBI recovery are poorly understood, but may involve alterations in cortical neurophysiology. Transcranial Magnetic Stimulation (TMS) can non-invasively investigate such mechanisms, but the time course of neurophysiological changes in mTBI are unknown. Objective/Hypothesis: To determine the relationship between persistent post-concussive symptoms (PPCS) and altered motor cortex neurophysiology over time. Methods: This was a prospective, longitudinal, controlled cohort study comparing children (8-18 years) with mTBI (symptomatic vs. asymptomatic) groups to controls. Cortical excitability was measured using TMS paradigms at 1 and 2 months post injury. The primary outcome was the cortical silent period (cSP). Secondary outcomes included short interval intracortical inhibition (SICI) and facilitation (SICF), and long-interval cortical inhibition (LICI). Generalized linear mixed model analyses were used to evaluate the effect of group and time on neurophysiological parameters. Results: One hundred seven participants (median age 15.1, 57% female) including 78 (73%) with symptomatic PPCS and 29 with asymptomatic mTBI, were compared to 26 controls. Cortical inhibition (cSP and SICI) was reduced in the symptomatic group compared to asymptomatic group and tended to increase over time. Measures of cortical facilitation (SICF and ICF) were increased in the asymptomatic group and decreased over time. TMS was well tolerated with no serious adverse events. Conclusions: TMS-assessed cortical excitability is altered in children following mild TBI and is dependent on recovery trajectory. Our findings support delayed return to contact sports in children even where clinical symptoms have resolved.