Association of Hemodynamic and Cerebrovascular Responses to Exercise With Symptom Severity in Adolescents and Young Adults With Concussion

Use of physical exertion to enhance objective testing following mild traumatic brain injury: a systematic review

Background

Assessment of recovery from mild traumatic brain injury (mTBI) is complex and challenging. Post-exertion testing, where individuals undergo objective testing following physical exercise, has shown promise in identifying mTBI-related impairments that may not be evident at rest, but could hinder a safe return to sport.

Objectives

To conduct a systematic review to determine if physical exertion affects objective physiological or sensorimotor tests differently in individuals with mTBI compared with healthy controls.

Methods

A systematic search of 11 databases and five trial registries on 30 May 2024 identified reports that: (i) compared individuals aged 12-65 years within 12 months of mTBI against healthy control participants, (ii) investigated the effects of a single session of physical exertion and (iii) collected before, during or after exertion, objective measures of physiological or sensorimotor function. Risk of bias was assessed with the Risk Of Bias In Non-randomized Studies of Interventions tool. Results were analysed descriptively.

Results

The review included 22 studies with 536 participants wih mTBI. Risk of bias was deemed high. At rest, 8/22 (36%) studies detected differences in physiological responses between participants wih mTBI and healthy control participants. During or after exertion, 21/22 (96%) studies detected differences in physiological responses, including cardiovascular, respiratory and cerebral autoregulation.

Conclusion

The findings indicate that objective testing during or after physical exertion can enhance the ability to detect mTBI-related impairments in various physiological parameters, and this concept could be considered when monitoring recovery and return to sport. Further studies are needed.

PROSPERO registration number

CRD42023411681.

Exploring Molecular Pathways in Exercise-Induced Recovery from Traumatic Brain Injury

Traumatic brain injury (TBI) is functional damage or brain injury due to external forces and is a leading cause of death and disability in children and adults. It causes disruption of the blood-brain barrier (BBB), infiltration of peripheral blood cells, oxidative stress, neuroinflammation and apoptosis, neural excitotoxicity, and mitochondrial dysfunction. Studies have shown that PE can be applied as a non-pharmacological therapy and effectively improve functional recovery from TBI. Recovery from TBI can benefit from both pre- or post-TBI exercise through various mechanisms for neurorepair and rehabilitation of behavior and cognition, including alleviation of TBI-induced oxidative stress, upregulation of heat-shock proteins, reduction of TBI-induced inflammation, promotion of secretion of neurotrophic factors to facilitate neural regeneration, suppression of TBI-induced apoptosis to reduce brain injury, and stabilization of mitochondrial function for better cellular function. This review article provides an overview of the effect of pre- and post-TBI exercise on recovery of neurofunctions and cognition following TBI, summarizes the potential regulatory networks and cellular and biological processes involved in recovery of brain functions, and outlines the molecular mechanisms underlying exercise-induced improvement of TBI, including regulation of gene expression and activation of heat-shock proteins and neurotrophic factors under different exercise schemes. These mechanisms involve TBI-induced oxidative stress, upregulation of heat-shock proteins, inflammation, secretion of neurotrophic factors, and TBI-induced apoptosis. Due to high heterogeneity in human TBI, the outcome of exercise intervention is affected by the injury type and severity of TBI. More studies are needed to investigate the application of various exercise approaches that fits TBI under different circumstances, and to elucidate the detailed pathogenesis mechanisms of TBI to develop more patient-tailored interventions.

Identifying the Cerebral Physiologic Response to Aerobic Exercise Following Concussion: A Scoping Review

OBJECTIVE

The purpose of this study was to identify the cerebral physiologic response to aerobic exercise in individuals with a symptomatic concussion, highlighting available knowledge and knowledge gaps in the literature.

DESIGN

A systematic scoping review was conducted and reported in keeping with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) extension for scoping reviews. A search of EMBASE, MEDLINE, SCOPUS, BIOSIS, and Cochrane libraries was conducted on June 15, 2023 (from database inception). An online systematic/scoping review management system was used to remove duplicates, and the remaining articles were screened for inclusion by 2 researchers. Inclusion criteria required articles to be original research published in peer-reviewed journals. Additionally, studies were required to have an aerobic exercise component, include a measure of cerebral physiology during a bout of aerobic exercise, exclude moderate and/or severe traumatic brain injury (TBI) populations, and be in the English language. Both human and animal studies were included, with participants of any age who were diagnosed with a mild TBI/concussion only (ie, Glasgow Coma Scale score ≥ 13). Studies could be of any design as long as a measure of cerebral physiologic response to a bout of aerobic exercise was included.

RESULTS

The search resulted in 1773 articles to be screened and data from 3 eligible studies were extracted.

CONCLUSIONS

There are currently too few studies investigating the cerebral physiologic response to aerobic exercise following concussion or mild TBI to draw definitive conclusions. Further research on this topic is necessary since understanding the cerebral physiologic response to aerobic exercise in the concussion and mild TBI populations could assist in optimizing exercise-based treatment prescription and identifying other targeted therapies.

Response of Central Nervous System Biomolecules and Systemic Biomarkers to Aerobic Exercise Following Concussion: A Scoping Review of Human and Animal Research

The purpose of this study was to identify the response of biomolecules and biomarkers that are associated with the central nervous system to aerobic exercise in human and pre-clinical models of concussion or mild traumatic brain injury (TBI), and to highlight the knowledge gaps in the literature. A systematic scoping review was conducted following a search of EMBASE, MEDLINE, SCOPUS, BIOSIS, and Cochrane Libraries performed on September 8, 2023 (from data base inception). The scoping review was reported following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) extension for scoping reviews. Duplicates were removed and article screening was performed using an online systematic review management system. The search resulted in a total of 2,449 articles being identified, with 14 articles meeting the inclusion/exclusion criteria and having their data extracted. One study was conducted in humans, while the remainder of identified studies utilized murine models. The current literature is limited and evaluated many different biomolecules and biomarkers with brain-derived neurotrophic factor being the most researched. Further studies on this topic are needed to better understand the biomarker response to exercise after concussion and mild TBI, especially in the human population.

Transcranial Doppler Ultrasound and Concussion-Supplemental Symptoms with Physiology: A Systematic Review

Sport-related concussion (SRC) can impair the cerebrovasculature both acutely and chronically. Transcranial Doppler (TCD) ultrasound assessment has the potential to illuminate the mechanisms of impairment and provide an objective evaluation of SRC. The current systematic review investigated studies employing TCD ultrasound assessment of intracranial arteries across three broad categories of cerebrovascular regulation: neurovascular coupling (NVC), cerebrovascular reactivity (CVR), and dynamic cerebral autoregulation (dCA). The current review was registered in the International Prospective Register of Systematic Reviews (PROSPERO) database (CRD42021275627). The search strategy was applied to PubMed, as this database indexes all biomedical journals. Original articles on TCD for athletes with medically diagnosed SRC were included. Title/abstract and full-text screening were completed by three authors. Two authors completed data extraction and risk of bias using the Methodological Index for Non-Randomized Studies and Scottish Intercollegiate Guideline Network checklists. Of the 141 articles identified, 14 met the eligibility criteria. One article used an NVC challenge, eight assessed CVR, and six investigated dCA. Methodologies varied widely among studies, and results were heterogeneous. There was evidence of cerebrovascular impairment in all three domains roughly 2 days post-SRC, but the magnitude and recovery of these impairments were not clear. There was evidence that clinical symptom resolution occurred before cerebrovascular function, indicating that physiological deficits may persist despite clinical recovery and return to play. Collectively, this emphasizes an opportunity for the use of TCD to illuminate the cerebrovascular deficits caused by SRC. It also highlights that there is need for consistent methodological rigor when employing TCD in a SRC population.

Does early exercise intolerance effect time to return to play, symptom burden, neurocognition, Vestibular-Ocular-Motor (VOM) function and academic ability in acutely concussed student-athletes?

INTRODUCTION

Early Exercise Intolerance (EEI) is associated with delayed recovery and longer time to Return To Play (RTP), but this has not been established.Participants; (n = 52, male n = 30) UK university-aged rugby-union student-athletes.

METHODS

Student-athletes completed baseline screening (July-October 2021 and 2022). The test battery was repeated within 48 h, 4, 8 and 14 days after a Sports-Related Concussion (SRC) with the Buffalo Concussion Bike or Treadmill Test to set sub-symptom heart rate threshold. Student-athletes then completed a controlled early exercise protocol in-between reassessment (days 3, 5-7 and 9-13). Those with EEI were compared to those with early-exercise tolerance.

OUTCOME MEASURES

Post-Concussion Symptom Scale, Immediate Post-Concussion and Cognitive Test, Vestibular-Ocular Motor Screening Tool and the Revised Perceived Academic Impact Tool.

RESULTS

EEI was seen throughout the initial 14-days post-SRC (23.8%, 22.4%, 25.5%. 25.0%). EEI was associated with a slower reaction time within 48 h (-0.01 (-0.030-0.043) Vs 0.06 (0.033-0.24), p = 0.004) and greater VOMS scores within 48 h; (0.00 (0.00-4.00) Vs 5.50 (2.75-9.00), p = 0.016) and 4 days (0.00 (0.00-2.00) Vs 5.00 (0.00-6.00), p = 0.044). RTP was 12.5 days longer in those with EEI at 14-days post-SRC.

CONCLUSION

EEI is prevalent following an SRC in university-aged student-athletes and was associated with delayed recovery and RTP.

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.

Assessment of cardiovascular functioning following sport-related concussion: A physiological perspective

There is still much uncertainty surrounding the approach to diagnosing and managing a sport-related concussion (SRC). Neurobiological recovery may extend beyond clinical recovery following SRC, highlighting the need for objective physiological parameters to guide diagnosis and management. With an increased understanding of the connection between the heart and the brain, the utility of assessing cardiovascular functioning following SRC has gained attention. As such, this review focuses on the assessment of cardiovascular parameters in the context of SRC. Although conflicting results have been reported, decreased heart rate variability, blood pressure variability, and systolic (ejection) time, in addition to increased spontaneous baroreflex sensitivity and magnitude of atrial contraction have been shown in acute SRC. We propose that these findings result from the neurometabolic cascade triggered by a concussion and represent alterations in myocardial calcium handling, autonomic dysfunction, and an exaggerated compensatory response that attempts to maintain homeostasis following a SRC. Assessment of the cardiovascular system has the potential to assist in diagnosing and managing SRC, contributing to a more comprehensive and multimodal assessment strategy.

Does Physiologic Post-Concussion Disorder Cause Persistent Post-Traumatic Headache?

PURPOSE OF REVIEW

One system classifies patients with symptoms after concussion into physiologic, vestibulo-ocular, cervicogenic, and mood/cognition post-concussion disorders (PCD) based upon the preponderance of specific symptoms and physical impairments. This review discusses physiologic PCD and its potential relationship to the development of persistent post-traumatic headaches (PPTH).

RECENT FINDINGS

Headache is the most reported symptom after a concussion. Headaches in physiologic PCD are suspected to be due to abnormal cellular metabolism, subclinical neuroinflammation, and dysfunction of the autonomic nervous system (ANS). These abnormalities have been linked to the development of migraine-like and neuralgia-related PPTH. Physiologic PCD is a potential cause of PPTH after a concussion. Future research should focus on how to prevent PPTH in patients with physiologic PCD.

Cerebral Autoregulation-guided Management of Adult and Pediatric Traumatic Brain Injury

Cerebral autoregulation (CA) plays a vital role in maintaining cerebral blood flow in response to changes in systemic blood pressure. Impairment of CA following traumatic brain injury (TBI) may exacerbate the injury, potentially impacting patient outcomes. This focused review addresses 4 key questions regarding the measurement, natural history of CA after TBI, and potential clinical implications of CA status and CA-guided management in adults and children with TBI. We examine the feasibility and safety of CA assessment, its association with clinical outcomes, and the potential for reversing deranged CA following TBI. Finally, we discuss how the knowledge of CA status may affect TBI management and outcomes.

Neuroimaging to enhance understanding of cardiovascular autonomic changes associated with mild traumatic brain injury: a scoping review

BACKGROUND

Cardiovascular changes, such as altered heart rate and blood pressure, have been identified in some individuals following mild traumatic brain injury (mTBI) and may be related to disturbances of the autonomic nervous system and cerebral blood flow.

METHODS

We conducted a scoping review according to PRISMA-ScR guidelines across six databases (Medline, CINAHL, Web of Science, PsychInfo, SportDiscus and Google Scholar) to explore literature examining both cardiovascular parameters and neuroimaging modalities following mTBI, with the aim of better understanding the pathophysiological basis of cardiovascular autonomic changes associated with mTBI.

RESULTS

Twenty-nine studies were included and two main research approaches emerged from data synthesis. Firstly, more than half the studies used transcranial Doppler ultrasound and found evidence of cerebral blood flow impairments that persisted beyond symptom resolution. Secondly, studies utilizing advanced MRI identified microstructural injury within brain regions responsible for cardiac autonomic function, providing preliminary evidence that cardiovascular autonomic changes are a consequence of injury to these areas.

CONCLUSION

Neuroimaging modalities hold considerable potential to aid understanding of the complex relationship between cardiovascular changes and brain pathophysiology associated with mTBI. However, it is difficult to draw definitive conclusions from the available data due to variability in study methodology and terminology.

Role of biomarkers and emerging technologies in defining and assessing neurobiological recovery after sport-related concussion: a systematic review

OBJECTIVE

Determine the role of fluid-based biomarkers, advanced neuroimaging, genetic testing and emerging technologies in defining and assessing neurobiological recovery after sport-related concussion (SRC).

DESIGN

Systematic review.

DATA SOURCES

Searches of seven databases from 1 January 2001 through 24 March 2022 using keywords and index terms relevant to concussion, sports and neurobiological recovery. Separate reviews were conducted for studies involving neuroimaging, fluid biomarkers, genetic testing and emerging technologies. A standardised method and data extraction tool was used to document the study design, population, methodology and results. Reviewers also rated the risk of bias and quality of each study.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Studies were included if they: (1) were published in English; (2) represented original research; (3) involved human research; (4) pertained only to SRC; (5) included data involving neuroimaging (including electrophysiological testing), fluid biomarkers or genetic testing or other advanced technologies used to assess neurobiological recovery after SRC; (6) had a minimum of one data collection point within 6 months post-SRC; and (7) contained a minimum sample size of 10 participants.

RESULTS

A total of 205 studies met inclusion criteria, including 81 neuroimaging, 50 fluid biomarkers, 5 genetic testing, 73 advanced technologies studies (4 studies overlapped two separate domains). Numerous studies have demonstrated the ability of neuroimaging and fluid-based biomarkers to detect the acute effects of concussion and to track neurobiological recovery after injury. Recent studies have also reported on the diagnostic and prognostic performance of emerging technologies in the assessment of SRC. In sum, the available evidence reinforces the theory that physiological recovery may persist beyond clinical recovery after SRC. The potential role of genetic testing remains unclear based on limited research.

CONCLUSIONS

Advanced neuroimaging, fluid-based biomarkers, genetic testing and emerging technologies are valuable research tools for the study of SRC, but there is not sufficient evidence to recommend their use in clinical practice.

PROSPERO REGISTRATION NUMBER

CRD42020164558.

Autonomic dysfunction and exercise intolerance in concussion: a scoping review

PURPOSE

Concussion commonly results in exercise intolerance, often limiting return to activities. Improved understanding of the underlying mechanisms of post-concussive exercise intolerance could help guide mechanism-directed rehabilitation approaches. Signs of altered cardiovascular autonomic regulation-a potential contributor to exercise intolerance-have been reported following concussion, although it is not clear how these findings inform underlying mechanisms of post-concussive symptoms. Systematic summarization and synthesis of prior work is needed to best understand current evidence, allowing identification of common themes and gaps requiring further study. The purpose of this review was to (1) summarize published data linking exercise intolerance to autonomic dysfunction, and (2) summarize key findings, highlighting opportunities for future investigation.

METHODS

The protocol was developed a priori, and conducted in five stages; results were collated, summarized, and reported according to PRISMA guidelines. Studies including injuries classified as mild traumatic brain injury (mTBI)/concussion, regardless of mechanism of injury, were included. Studies were required to include both autonomic and exercise intolerance testing. Exclusion criteria included confounding central or peripheral nervous system dysfunction beyond those stemming from the concussion, animal model studies, and case reports.

RESULTS

A total of 3116 publications were screened; 17 were included in the final review.

CONCLUSION

There was wide variability in approach to autonomic/exercise tolerance testing, as well as inclusion criteria/testing timelines, which limited comparisons across studies. The reviewed studies support current clinical suspicion of autonomic dysfunction as an important component of exercise intolerance. However, the specific mechanisms of impairment and relationship to symptoms and recovery require additional investigation.