Cognitive and neural effects of exercise following traumatic brain injury: A systematic review of randomized and controlled clinical trials

Aerobic exercise and brain structure among military service members and Veterans with varying histories of mild traumatic brain injury: A LIMBIC-CENC exploratory investigation

OBJECTIVES

To explore associations of recent moderate-to-vigorous aerobic exercise (MVAE) participation and lifetime mild traumatic brain injury (mTBI) history with measures of brain gray matter volumes among military service members and Veterans (SMVs).

METHODS

Participants (n = 1,340; aged 41.3 ± 10.3 years; 13% female) were SMV's who participated in the Long-term Impact of Military-relevant Brain Injury Consortium-Chronic Effects of Neurotrauma Consortium Prospective Longitudinal Study (LIMBIC-CENC PLS). MVAE participation was self-reported via the Behavioral Risk Factor Surveillance System and categorized according to current MVAE recommendations (Inactive, Insufficiently Active, Active, and Highly Active). Lifetime mTBI history was queried via validated structured interview and categorized as 0 mTBI, 1-2 mTBIs, 3 + mTBIs. Structural MRI (T1- and T2-weighted images) were used to measure gray matter volumetrics: ventricle-to-brain ratio (VBR); bilateral volumes of the frontal, parietal, temporal, occipital, cingulate, hippocampus, amygdala, and thalamus regions. Multivariable linear regression models were fit to test associations of MVAE participation, mTBI history, and their interaction on each of the volumetric outcomes while controlling for age, sex, education attainment, and PTSD symptoms. Effects were considered statistically significant if the corresponding unstandardized beta (B) and 95% CI did not include 0.

RESULTS

Regarding main effects, participants in the Inactive MVAE group had significantly larger VBR values (worse outcome) than those in the Insufficiently Active group (B[95%CI] = -0.137[-0.260, -0.014]). Interaction effects showed participants with no lifetime mTBIs in the Highly Active group had larger VBR values (worse outcome) when compared to those in the Inactive and Insufficiently Active groups. SMVs with 3 + lifetime mTBIs who were Highly Active also had smaller VBR values (better outcome) when compared to Highly Active SMVs with fewer lifetime mTBIs. There were no other statistically significant differences for MVAE participation, mTBI history, or their interactions.

CONCLUSIONS

History of one or more lifetime mTBIs was not associated with measures of brain gray matter volumes, suggesting that declines in structural brain health are not expected for the most SMVs with mTBI(s). Although MVAE may benefit brain health, a positive association between self-reported MVAE participation and gray matter volumes was not observed.

Correlations Between Morpho-structural Properties of the Brain and Cognitive and Motor Deficits in Individuals with Traumatic Brain Injury

Traumatic brain injury (TBI) results in changes in brain networks followed by long-lasting behavioral and social impairments. This study explores the relationship between neurobehavioral as well as physical function deficits and structural changes in brain white matter (WM) and gray matter (GM) in individuals with TBI by evaluating morphometric magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) data. The structural MRI-based fractal analysis has emerged as a promising new approach to measure the morphology of the WM and GM. While DTI metrics reflect the microstructural properties of WM, the fractal dimension (FD) is regarded as a measure of morphometric complexity of the system, thus providing complementary information on the brain structure. This study included 10 individuals having moderate-to-severe TBI with balance/postural control deficits and 8 healthy controls. The network-based GM and WM morphologies were measured using FD and structural connectivity metrics, and fractional anisotropy (FA) was assessed using DTI in major WM tracts. The associations between brain structural (FA and FD) measures and a number of neuropsychological assessment and sensorimotor function outcomes were evaluated using partial least square correlation analysis. Our findings showed that the complexity in GM of default mode network, salience network, sensorimotor network, and frontoparietal network is positively correlated with the performance in cognitive and balance outcomes in patients with TBI. On the contrary, in DTI connectivity measures, only few regions including corona radiata, inferior longitudinal fasciculus, and middle cerebellar peduncle were strongly correlated with the behavioral outcomes in the TBI group. Our study suggests that the brain structure complexity measured by FD is a promising and complementary approach to DTI for potentially serving as a biomarker of cognitive and sensorimotor functions in TBI population.

Attrition, adherence, and compliance to exercise training interventions in persons with traumatic brain injury: a systematic review of training studies

BACKGROUND

Exercise training (ET) is a promising rehabilitation approach for long-term negative consequences of traumatic brain injury (TBI). However, little is known regarding overall rates of attrition, adherence, and compliance to ET in TBI.

OBJECTIVE

The purpose of this systematic review was to estimate average attrition, adherence, and compliance rates in ET studies in persons with TBI.

METHODS

Databases were searched from inception to April 15, 2024. Two authors independently extracted data related to attrition, adherence, compliance, and possible moderators identified a priori.

RESULTS

The average rate of attrition from 45 studies was 14.4%, although the majority of studies had small sample sizes (i.e. n < 42). Based on hierarchical linear regression, the most influential predictors of attrition were sample size and study design. A minority of studies reported adherence (44.4%) or compliance (22.2%) but those that did reported good average adherence (85.1%) and compliance (77.7%). These studies support the ability of persons with TBI to complete an ET intervention as prescribed.

CONCLUSIONS

Researchers can use this information to ensure adequate power to detect a true effect of ET in persons with TBI. Researchers conducting ET studies in persons with TBI should clearly and thoroughly report data on attrition, adherence, and compliance.

Cardiorespiratory fitness and working memory in persons with traumatic brain injury: a cross-sectional analysis

INTRODUCTION

Cognitive impairment is a highly impactful consequence of traumatic brain injury (TBI) and there are limited evidence-based treatment practices to combat these impairments. Evidence from other populations suggest that aerobic exercise training (AET) is beneficial for a variety of cognitive deficits, but the research in persons with TBI to date is equivocal. One potential reason is the heterogeneity of exercise prescriptions and outcome measures. This stems from the fact that studies have not been designed based on previous data supporting a specific AET prescription to target a cognitive domain. The primary purpose of this cross-sectional analysis was to examine the relationship between cardiorespiratory fitness (CRF), as a cross-sectional surrogate of AET, and cognition in persons with TBI to inform future research.

METHODS

Cross-sectional analysis was conducted on baseline data of persons with TBI who completed neuropsychological assessments to evaluate several cognitive domains and a cardiopulmonary exercise test (CPET) to measure CRF. Based on the normal distribution of an outcome, Pearson's r or Spearman's ρ was calculated to measure the relationship between CRF and cognition.

RESULTS

Data were analyzed for all participants who demonstrated valid CPETs (n = 21 of 29). Based on the cycle ergometer-based norms of CRF, males in this sample were in the 69th percentile and females in this sample were in the 56th percentile, with high variability across individuals. Higher CRF, as measured by peak power output (Wpeak), was significantly associated with greater working memory (ρ = 0.465, p = 0.017), even after post-hoc corrections.

CONCLUSIONS

These data suggest average and highly variable CRF in persons with TBI of all severity and support cycle ergometry-based CPET testing in this population. Further, these data provide support for future research applying AET to target working memory and possibly other executive functions in persons with TBI. This research is a small step toward large-scale randomized controlled trials that can directly impact clinical care to treat cognitive symptoms post-TBI.

Physical activity and frontoparietal network connectivity in traumatic brain injury

BACKGROUND

Prolonged changes to functional network connectivity as a result of a traumatic brain injury (TBI) may relate to long-term cognitive complaints reported by TBI survivors. No interventions have proven to be effective at treating long-term cognitive complaints after TBI but physical activity has been shown to promote cognitive function and modulate functional network connectivity in non-injured adults. Therefore, the objective of this study was to test if physical activity engagement was associated with functional connectivity of the cognitively relevant frontoparietal control network (FPCN) in adults with a TBI history.

METHODS

In a case-control study design, resting state function magnetic resonance imaging and physical activity data from a subset of participants (18-81 years old) from the Cambridge Centre for Ageing and Neuroscience (Cam-CAN) study was analyzed. Fifty-seven participants reported a prior head injury with loss of consciousness and 57 age and sex matched controls were selected. Seed-based functional connectivity analyses were performed using seeds in the dorsolateral prefrontal cortex and the inferior parietal lobule, to test for differences in functional connectivity between groups, associations between physical activity and functional connectivity within TBI as well as differential associations between physical activity and functional connectivity between TBI and controls.

RESULTS

Seed-based connectivity analyses from the dorsolateral prefrontal cortex showed that those with a history of TBI had decreased positive connectivity between dorsolateral prefrontal cortex and intracalcarine cortex, lingual gyrus, and cerebellum, and increased positive connectivity between dorsolateral prefrontal cortex and cingulate gyrus and frontal pole in the TBI group. Results showed that higher physical activity was positively associated with increased connectivity between the dorsolateral prefrontal cortex and inferior temporal gyrus. Differential associations were observed between groups whereby the strength of the physical activity-functional connectivity association was different between the inferior parietal lobule and inferior temporal gyrus in TBI compared to controls.

DISCUSSION

Individuals with a history of TBI show functional connectivity alterations of the FPCN. Moreover, engagement in physical activity is associated with functional network connectivity of the FPCN in those with a TBI. These findings are consistent with the evidence that physical activity affects FPCN connectivity in non-injured adults; however, this effect presents differently in those with a history of TBI.

Can transcranial photobiomodulation improve cognitive function in TBI patients? A systematic review

Introduction

Transcranial photobiomodulation (tPBM) is a non-invasive neuromodulation technology which has become a promising therapy for treating many brain diseases. Although it has been confirmed in studies targeting neurological diseases including Alzheimer's and Parkinson's that tPBM can improve cognitive function, the effectiveness of interventions targeting TBI patients remains to be determined. This systematic review examines the cognitive outcomes of clinical trials concerning tPBM in the treatment of traumatic brain injury (TBI).

Methods

We conducted a systematic literature review, following the PRISMA guidelines. The PubMed, Web of Science, Scopus, EMBASE, and Cochrane Library databases were searched before October 31, 2023.

Results

The initial search retrieved 131 articles, and a total of 6 studies were finally included for full text-analysis after applying inclusion and exclusion criteria.

Conclusion

Results showed improvements in cognition for patients with chronic TBI after tPBM intervention. The mechanism may be that tPBM increases the volume of total cortical gray matter (GM), subcortical GM, and thalamic, improves cerebral blood flow (CBF), functional connectivity (FC), and cerebral oxygenation, improving brain function. However, due to the significant heterogeneity in application, we cannot summarize the optimal parameters for tPBM treatment of TBI. In addition, there is currently a lack of RCT studies in this field. Therefore, given this encouraging but uncertain finding, it is necessary to conduct randomized controlled clinical trials to further determine the role of tPBM in cognitive rehabilitation of TBI patients.

Effectiveness of aerobic exercise on cognition in individuals with traumatic brain injury: A systematic review

Cognitive deficits are among the most common impairments in individuals with traumatic brain injury (TBI). Aerobic exercise is a repetitive and structured physical activity that influences structural and functional brain alterations differently. This review aims to examine the effects of aerobic exercise on cognition in individuals with TBI. PubMed, CINAHL, EMBASE, SCOPUS, MEDLINE, and Web of Science were searched from inception to December 20, 2023. Studies designed as randomized controlled trials (RCT), clinical controlled trials (CCT), and pilot studies included individuals with a confirmed diagnosis of TBI, comparing aerobic exercise with passive, active, or no control group and included at least one outcome measure assessing any cognitive domain were selected. The quality of the selected studies was assessed using the Physiotherapy Evidence Database (PEDro) scale. Six studies met the eligibility criteria (n = 118), with 53% of participants being female. Four studies were of good quality, fair quality (n = 1), and poor quality (n = 1) on the PEDro. Two of the selected studies showed significant improvements in cognition after moderate and vigorous aerobic exercises, while four studies indicated that moderate and vigorous aerobic exercise did not improve cognition post-TBI. The evidence on the effects of moderate and vigorous aerobic exercise on cognitive function post-TBI remains limited. Additional studies are strongly warranted to understand aerobic exercise's effects on cognition post-TBI.

The Temporal Relationship Between Moderate to Vigorous Physical Activity and Secondary Conditions During the First Year After Moderate to Severe Traumatic Brain Injury

OBJECTIVE

To determine the cross-sectional and temporal relationships between minutes per week of moderate to vigorous physical activity (MVPA) as measured by a wrist-worn accelerometer and secondary conditions in the first year after moderate to severe traumatic brain injury (TBI).

DESIGN

Prospective longitudinal cohort study.

SETTING

Four inpatient rehabilitation centers.

PARTICIPANTS

Individuals (N = 180) with moderate-severe TBI enrolled in the TBI Model Systems Study.

INTERVENTIONS

Participants wore a wrist accelerometer for 7 days immediately post discharge, and for 7 consecutive days at 6- and 12-months post injury.

MAIN OUTCOME MEASURES

Minutes per week of MVPA from daily averages based on wrist worn accelerometer. Secondary conditions included depression (Patient Health Questionnaire-9), fatigue (PROMIS Fatigue), Pain (Numeric Rating Scale), Sleep (Pittsburgh Sleep Quality Index), and cognition (Brief Test of Adult Cognition by Telephone).

RESULTS

At baseline, 6 and 12 months, 61%, 70% and 79% of the sample achieved at least 150 minutes per week of MVPA. The correlations between minutes of MVPA between baseline, 6 and 12 months were significant (r = 0.53-0.73), as were secondary conditions over these time points. However, no significant correlations were observed between minutes of MVPA and any secondary outcomes cross-sectionally or longitudinally at any time point.

CONCLUSIONS

Given the robust relationships physical activity has with outcomes in the general population, further research is needed to understand the effect of physical activity in individuals with moderate-severe TBI.

Effect of stress on the rehabilitation performance of rats with repetitive mild fluid percussion-induced traumatic brain injuries

Animal models of traumatic brain injury (TBI) have shown that impaired motor and cognitive function can be improved by physical exercise. However, not each animal with TBI can be well rehabilitated at the same training intensity due to a high inter-subject variability. Hence, this paper presents a two-stage wheel-based mixed-mode rehabilitation mechanism by which the effect of stress on the rehabilitation performance was investigated. The mixed-mode rehabilitation mechanism consists of a two-week adaptive and a one-week voluntary rehabilitation program as Stages 1 and 2, respectively. In Stage 1, the common over and undertraining problem were completely resolved due to the adaptive design, and rats ran voluntarily over a 30-min duration in Stage 2. The training intensity adapted to the physical condition of all the TBI rats at all times in Stage 1, and then the self-motivated running rats were further rehabilitated under the lowest level of stress in Stage 2. For comparison purposes, another group of rats took a 3-week adaptive rehabilitation program. During the 3-week program, the rehabilitation performance of the rats were assessed using modified neurologic severity score (mNSS) and an 8-arm radial maze. Surprisingly, the group taking the mixed mode program turned out to outperform its counterpart in terms of mNSS. The mixed-mode rehabilitation mechanism was validated as an effective and efficient way to help rats restore motor, neurological and cognitive function after TBI. It was validated that the rehabilitation performance can be optimized under the lowest level of stress.

Mechanisms and treatments of chronic pain after traumatic brain injury

While pain after trauma generally resolves, some trauma patients experience pain for months to years after injury. An example, relevant to both combat and civilian settings, is chronic pain after traumatic brain injury (TBI). Headache as well as pain in the back and extremities are common locations for TBI-related chronic pain to be experienced. TBI-related pain can exist alone or can exacerbate pain from other injuries long after healing has occurred. Consequences of chronic pain in these settings include increased suffering, higher levels of disability, serious emotional problems, and worsened cognitive deficits. The current review will examine recent evidence regarding dysfunction of endogenous pain modulatory mechanisms, neuroplastic changes in the trigeminal circuitry and alterations in spinal nociceptive processing as contributors to TBI-related chronic pain. Key pain modulatory centers including the locus coeruleus, periaqueductal grey matter, and rostroventromedial medulla are vulnerable to TBI. Both the rationales and existing evidence for the use of monoamine reuptake inhibitors, CGRP antagonists, CXCR2 chemokine receptor antagonists, and interventional therapies will be presented. While consensus guidelines for the management of chronic post-traumatic TBI-related pain are lacking, several approaches to this clinically challenging situation deserve focused evaluation and may prove to be viable therapeutic options.

Exercise promotes growth and rescues volume deficits in the hippocampus after cranial radiation in young mice

Human and animal studies suggest that exercise promotes healthy brain development and function, including promoting hippocampal growth. Childhood cancer survivors that have received cranial radiotherapy exhibit hippocampal volume deficits and are at risk of impaired cognitive function, thus they may benefit from regular exercise. While morphological changes induced by exercise have been characterized using magnetic resonance imaging (MRI) in humans and animal models, evaluation of changes across the brain through development and following cranial radiation is lacking. In this study, we used high-resolution longitudinal MRI through development to evaluate the effects of exercise in a pediatric mouse model of cranial radiation. Female mice received whole-brain radiation (7 Gy) or sham radiation (0 Gy) at an infant equivalent age (P16). One week after irradiation, mice were housed in either a regular cage or a cage equipped with a running wheel. In vivo MRI was performed prior to irradiation, and at three subsequent timepoints to evaluate the effects of radiation and exercise. We used a linear mixed-effects model to assess volumetric and cortical thickness changes. Exercise caused substantial increases in the volumes of certain brain regions, notably the hippocampus in both irradiated and nonirradiated mice. Volume increases exceeded the deficits induced by cranial irradiation. The effect of exercise and irradiation on subregional hippocampal volumes was also characterized. In addition, we characterized cortical thickness changes across development and found that it peaked between P23 and P43, depending on the region. Exercise also induced regional alterations in cortical thickness after 3 weeks of voluntary exercise, while irradiation did not substantially alter cortical thickness. Our results show that exercise has the potential to alter neuroanatomical outcomes in both irradiated and nonirradiated mice. This supports ongoing research exploring exercise as a strategy for improving neurocognitive development for children, particularly those treated with cranial radiotherapy.

Mobilization phases in traumatic brain injury

Mobilization in traumatic brain injury (TBI) have shown the improvement of length of stay, infection, long term weakness, and disability. Primary damage as a result of trauma's direct effect (skull fracture, hematoma, contusion, laceration, and nerve damage) and secondary damage caused by trauma's indirect effect (microvasculature damage and pro-inflammatory cytokine) result in reduced tissue perfusion & edema. These can be facilitated through mobilization, but several precautions must be recognized as mobilization itself may further deteriorate patient's condition. Very few studies have discussed in detail regarding mobilizing patients in TBI cases. Therefore, the scope of this review covers the detail of physiological effects, guideline, precautions, and technique of mobilization in patients with TBI.

Rationale and methodology for examining the acute effects of aerobic exercise combined with varying degrees of virtual reality immersion on cognition in persons with TBI

Persons with Traumatic Brain Injury (TBI) commonly present with long-term cognitive deficits in executive function, processing speed, attention, and learning and memory. While specific cognitive rehabilitation techniques have shown significant success for deficits in individual domains, aerobic exercise training represents a promising approach for an efficient and general treatment modality that might improve many cognitive domains concurrently. Existing studies in TBI report equivocal results, however, and are hampered by methodological concerns, including small sample sizes, uncontrolled single-group designs, and the use of suboptimal exercise modalities for eliciting cognitive improvements in this population. One particularly promising modality involves the application of environmental enrichment via virtual reality (VR) during aerobic exercise in persons with TBI, but this has yet to be investigated. One approach for systematically developing an optimal aerobic exercise intervention for persons with TBI involves the examination of single bouts of aerobic exercise (i.e., acute aerobic exercise) on cognition. Acute exercise research is a necessary first step for informing the development of high-quality exercise training interventions that are more likely to induce meaningful beneficial effects. To date, such an acute exercise paradigm has yet to be conducted in persons with TBI. To that end, we propose an acute exercise study that will investigate the acute effects of aerobic exercise with incremental degrees of environmental enrichment (VR) relative to a control comparison condition on executive function (divided attention and working memory) and processing speed in 24 people with TBI.

Acquired Brain Injury Survivor Long-Term Cognitive Exercise Engagement Post-Speech Therapy Discharge

Purpose The purpose of this article is to promote the viewpoint that speech-language pathologists (SLPs) are well positioned to actively encourage individuals with cognitive-communication disorders following acquired brain injury (ABI) to engage in ongoing, long-term, cognitive exercise post-therapy discharge. Method This viewpoint article draws on evidence from the well-researched area of physical exercise, reports findings of early-stage research in the much less studied area of cognitive exercise, and highlights relevant aspects of motivational theory informing exercise participation. Informed by these, an evidence-supported model of cognitive exercise engagement is offered to inform ABI-targeted cognitive wellness empowerment efforts, and a case study illustrates clinical application of the model. Conclusions Exercise provides an opportunity to sustain or improve long-term health, function, and quality of life outcomes. It is within SLP scope of practice to collaborate with family members and other caregivers to empower individuals post-ABI, especially those with decreased self-management skills, to engage in long-term computerized and noncomputerized cognitive exercise following SLP therapy discharge. Ongoing research will further inform the evidence supporting the scholarly opinion presented in this viewpoint.

Aerobic Exercise for Sport-related Concussion: A Systematic Review and Meta-analysis

INTRODUCTION

Approximately 25% of people with sport-related concussion (SRC) experiences persistent symptoms. The 2016 Berlin consensus on SRC recommends symptom-limited aerobic exercise as a rehabilitation option for persistent symptoms after concussion. However, this recommendation is based on a limited body of knowledge because there is uncertainty about the effectiveness of such interventions. The objective of this systematic review is to assess the effects of symptom-limited aerobic exercise programs compared with control interventions on symptom intensity in individuals with SRC.

METHODS

A structured search was conducted in MEDLINE, EMBASE, CINHAL, and EBM reviews. Randomized clinical trials (RCT) including aerobic exercise programs as an intervention for SRC were included. After selection, the risk of bias and Grading of Recommendations, Assessment, Development and Evaluation recommendations were applied to pooled studies for quantitative analysis. Standard mean differences (SMD) and 95% confidence interval (CI) were calculated. A descriptive analysis was also performed.

RESULTS

Seven RCT (326 participants) in adolescent populations were included. Three of seven RCT had a high risk of bias. Symptom-limited aerobic exercise programs have a significant beneficial effect on the perception of symptoms (6 studies, 277 participants, low-quality evidence; pooled SMD, -0.44; 95% CI, -0.68 to -0.19). When introduced in the acute phase, symptom-limited aerobic exercise programs have a significant beneficial effect on symptomatic recovery compared with control interventions (3 studies, 206 participants, moderate quality evidence, pooled SMD, -0.43; 95% CI, -0.71 to -0.15).

CONCLUSIONS

Symptom-limited aerobic exercise programs are beneficial in improving symptoms of adolescents after an SRC. Good-quality studies are needed to determine effects on adults and on other outcomes.