Optimised transcranial direct current stimulation (tDCS) for fibromyalgia-targeting the endogenous pain control system: a randomised, double-blind, factorial clinical trial protocol

Brain compensatory mechanisms in depression and memory complaints in fibromyalgia: the role of theta oscillatory activity

BACKGROUND

The different clinical presentations of fibromyalgia syndrome (FMS) might play independent roles in the unclear etiology of cognitive impairments and depressive symptoms seen in patients with FMS. Understanding how these clinical presentations are associated with the clinical and neurophysiological aspects of FMS is important for the development of effective treatments.

AIM

To explore the relationship of memory complaints and depressive symptoms with the different clinical and neurophysiological characteristics of FMS.

METHODS

Cross-sectional data analysis from a randomized clinical trial. Baseline demographics and data on physical fitness, sleep, anxiety, depression, cortical excitability, and pain (clinical and mechanistic) from 63 subjects with FMS were used. Multiple linear and logistic association models were constructed.

RESULTS

Final regression models including different sets of predictions were statistically significant (P < .001), explaining approximately 50% of the variability in cognitive complaints and depression status. Older subjects had higher levels of anxiety, poorer sleep quality, lower motor threshold, and higher relative theta power in the central area and were more likely to have clinical depression. Higher anxiety, pain, and theta power were associated with a higher likelihood of memory complaints.

CONCLUSION

Depression symptoms seem to be associated with transcranial magnetic stimulation-indexed motor threshold and psychosocial variables, whereas memory complaints are associated with pain intensity and higher theta oscillations. These mechanisms might be catalyzed or triggered by some behavioral and clinical features, such as older age, sleep disruption, and anxiety. The correlation with clinical variables suggests that the increasing of theta oscillations is a compensatory response in patients with FMS, which can be explored in future studies to improve the treatment of FMS.

TRIAL REGISTRATION

ClinicalTrials.gov ID NCT03371225.

Adaptive and Compensatory Neural Signatures in Fibromyalgia: An Analysis of Resting-State and Stimulus-Evoked EEG Oscillations

This study aimed to investigate clinical and physiological predictors of brain oscillatory activity in patients with fibromyalgia (FM), assessing resting-state power, event-related desynchronization (ERD), and event-related synchronization (ERS) during tasks. We performed a cross-sectional analysis, including clinical and neurophysiological data from 78 subjects with FM. Multivariate regression models were built to explore predictors of electroencephalography bands. Our findings show a negative correlation between beta oscillations and pain intensity; fibromyalgia duration is positively associated with increased oscillatory power at low frequencies and in the beta band; ERS oscillations in the theta and alpha bands seem to be correlated with better symptoms of FM; fatigue has a signature in the alpha band-a positive relationship in resting-state and a negative relationship in ERS oscillations. Specific neural signatures lead to potential clusters of neural adaptation, in which beta oscillatory activity in the resting state represents a more adaptive activity when pain levels are low and stimulus-evoked oscillations at lower frequencies are likely brain compensatory mechanisms. These neurophysiological changes may help to understand the impact of long-term chronic pain in the central nervous system and the descending inhibitory system in fibromyalgia subjects.

Factors influencing clinical trial participation of women with fibromyalgia across the United States: a cross-sectional survey

Although fibromyalgia is a widespread chronic pain condition where 90 percent of patients are women, they are underrepresented in Randomized Clinical Trials (RCTs). We aim to describe the willingness to participate, assess different factors, and explore the impact of sociodemographic and clinical characteristics on perceived barriers to trial participation. This is a cross-sectional survey targeting women with fibromyalgia. Univariate and multivariate logistic regression were performed. Of the 436 women with fibromyalgia, 56 percent were very likely to participate in RCTs. Minorities expressed less interest than non-minorities, while higher pain scores, previous participation, and younger patients reported a higher interest. Barriers significantly associated with a reduced willingness were: the participant's perception (side effects, distance, potential negative impact), the center (reputation), the trial protocol (number of visits, placebo), and trial awareness by their physician. In a multivariate analysis, older age, low education, lower income, and higher pain scores were associated with perceived barriers to RCT participation. Despite the high interest to participate, factors such as side effects, the center's distance, number of visits, placebo treatments, and the institution's reputation must be considered in clinical trials for women with fibromyalgia.

The role of symptoms severity, heart rate, and central sensitization for predicting sleep quality in patients with fibromyalgia

BACKGROUND

Clinical predictors of sleep quality in patients with fibromyalgia syndrome (FMS) are still unknown. By identifying these factors, we could raise new mechanistic hypotheses and guide management approaches. We aimed to describe the sleep quality of FMS patients and to explore the clinical and quantitative sensory testing (QST) predictors of poor sleep quality and its subcomponents.

METHODS

This study is a cross-sectional analysis of an ongoing clinical trial. We performed linear regression models between sleep quality (Pittsburgh Sleep Quality Index [PSQI]) and demographic, clinical, and QST variables, controlling for age and gender. Predictors for the total PSQI score and its seven subcomponents were found using a sequential modeling approach.

RESULTS

We included 65 patients. The PSQI score was 12.78 ± 4.39, with 95.39% classified as poor sleepers. Sleep disturbance, use of sleep medications, and subjective sleep quality were the worst subdomains. We found poor PSQI scores were highly associated with symptom severity (FIQR score and PROMIS fatigue), pain severity, and higher depression levels, explaining up to 31% of the variance. Fatigue and depression scores also predicted the subjective sleep quality and daytime dysfunction subcomponents. Heart rate changes (surrogate of physical conditioning) predicted the sleep disturbance subcomponent. QST variables were not associated with sleep quality or its subcomponents.

CONCLUSIONS

Symptom severity, fatigue, pain, and depression (but no central sensitization) are the main predictors of poor sleep quality. Heart rate changes independently predicted the sleep disturbance subdomain (the most affected one in our sample), suggesting an essential role of physical conditioning in modulating sleep quality in FMS patients. This underscores the need for multidimensional treatments targeting depression and physical activity to improve the sleep quality of FMS patients.

Non-invasive brain stimulation on clinical symptoms in multiple sclerosis patients: A systematic review and meta-analysis

BACKGROUND

Non-invasive brain stimulation (NIBS) has demonstrated mixed effects on the clinical symptoms of multiple sclerosis. This systematic review and meta-analysis aimed to evaluate the effects of NIBS techniques on the most common symptoms of MS.

METHODS

A literature search was performed until October 2022 which included randomized controlled trials and quasi-experimental studies that used sham-controlled NIBS in patients with MS. We calculated the Hedge's effect sizes of each domain of interest and their 95% confidence intervals (95% CIs) and performed random effects meta-analyses.

RESULTS

A total of 49 studies were included in the systematic review (944 participants). Forty-four eligible studies were included for quantitative analysis, of which 33 applied transcranial direct current stimulation (tDCS), 9 transcranial magnetic stimulation (TMS), and 2 transcranial random noise stimulation (tRNS). We found a significant decrease in fatigue (ES:  - 0.86, 95% CI:  - 1.22 to - 0.51, p < 0.0001), pain (ES: - 1.91, 95% CI, - 3.64 to - 0.19, p=  0.03) and psychiatric symptoms (ES: - 1.44, 95% CI - 2.56 to - 0.32, p = 0.01) in favor of tDCS compared with the sham. On the other hand, there was no strong evidence showing tDCS effectiveness on motor performance and cognition (ES: - 0.03, 95% CI - 0.35 to 0.28, p = 0.83 and ES: 0.71, 95% CI, - 0.09 to 1.52, p = 0.08, respectively). Regarding TMS, we found a significant decrease in fatigue (ES: - 0.45, 95% CI: - 0.84 to -0.07, p = 0.02) and spasticity levels (ES: - 1.11, 95% CI: - 1.48 to - 0.75, p < 0.00001) compared to the sham. However, there was no strong evidence of the effectiveness of TMS on motor performance (ES: - 0.39, 95% CI - 0.95 to 0.16, p = 0.16). Finally, there was no significant evidence showing the effectiveness of tRNS on fatigue levels (ES: - 0.28, 95% CI: - 1.02 to 0.47, p = 0.46) and cognitive improvement (ES: - 0.04, 95% CI: - 0.6, 0.52, p = 0.88) compared with the sham.

CONCLUSIONS

Overall, most studies have investigated the effects of tDCS on MS symptoms, particularly fatigue. The symptom that most benefited from NIBS was fatigue, while the least to benefit was motor performance. In addition, we found that disability score was associated with fatigue improvement. Thus, these findings support the idea that NIBS could have some promising effects on specific MS symptoms. It is also important to underscore that studies are very heterogeneous regarding the parameters of stimulation, and this may also have influenced the effects on some specific behavioral domains.

The Analgesic Effect of Transcranial Direct Current Stimulation in Fibromyalgia: A Systematic Review, Meta-Analysis, and Meta-Regression of Potential Influencers of Clinical Effect

BACKGROUND

There is tentative evidence to support the analgesic effect of transcranial direct current stimulation (tDCS) in fibromyalgia (FM), with large variability in the effect size (ES) encountered in different clinical trials. Understanding the source of the variability and exploring how it relates to the clinical results could characterize effective neuromodulation protocols and ultimately guide care in FM pain. The primary objective of this study was to determine the effect of tDCS in FM pain as compared with sham tDCS. The secondary objective was to explore the relationship of methodology, population, and intervention factors and the analgesic effect of tDCS in FM.

MATERIALS AND METHODS

For the primary objective, a systematic review was conducted according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Randomized clinical trials (RCTs) investigating tDCS as an intervention for FM pain were searched in MEDLINE, Embase, and the Web Of Science. Studies were excluded if they used cross-over designs or if they did not use tDCS as an intervention for pain or did not measure clinical pain. Analysis for the main outcome was performed using a random-effects model. Risk of bias and evidence certainty were assessed for all studies using Cochrane Risk of Bias and Grading of Recommendations Assessment, Development, and Evaluation tools. For the secondary objective, a meta-regression was conducted to explore methodology, population, and intervention factors potentially related to the ES.

RESULTS

Sixteen RCTs were included. Six studies presented a high risk of bias. Significant reduction in pain scores were found for FM (standardized mean difference = 1.22, 95% CI = 0.80-1.65, p < 0.001). Subgroup analysis considering tDCS as a neural target revealed no differences between common neural sites. Meta-regression revealed that the duration of the tDCS protocol in weeks was the only factor associated with the ES, in which protocols that lasted four weeks or longer reported larger ES than shorter protocols.

CONCLUSIONS

Results suggest an analgesic effect of tDCS in FM. tDCS protocols that last four weeks or more may be associated with larger ESs. Definite conclusions are inadequate given the large heterogeneity and limited quality of evidence of the included studies.

Motor Cortex Inhibition and Facilitation Correlates with Fibromyalgia Compensatory Mechanisms and Pain: A Cross-Sectional Study

The role of transcranial magnetic stimulation (TMS) measures as biomarkers of fibromyalgia syndrome (FMS) phenotypes is still unclear. We aimed to determine the clinical correlates of TMS measures in FMS patients. We conducted a cross-sectional analysis that included 58 patients. We performed standardized TMS assessments, including resting motor threshold (MT), motor-evoked potential (MEP), short intracortical inhibition (SICI), and intracortical facilitation (ICF). Sociodemographic, clinical questionnaires, and quantitative sensory testing were collected from all of the patients. Univariate and multivariate linear regression models were built to explore TMS-associated factors. We found that SICI did not significantly correlate with pain levels but was associated with sleepiness, comorbidities, disease duration, and anxiety. On the other hand, ICF showed a positive correlation with pain levels and a negative correlation with body mass index (BMI). BMI was a negative effect modifier of the ICF and pain association. The clinical correlates of MT and MEP were scarce. Our results suggest that SICI and ICF metrics are potential phenotyping biomarkers in FMS related to disease compensation and levels of pain perception, respectively. The clinical translation of TMS paired-pulse protocols represents an opportunity for a mechanistic understanding of FMS and the future development of precision treatments.

Modulation of central pain mechanisms using high-definition transcranial direct current stimulation: A double-blind, sham-controlled study

BACKGROUND

The use of high-definition transcranial direct current stimulation (HD-tDCS) has shown analgesic effects in some chronic pain patients, but limited anti-nociceptive effects in healthy asymptomatic subjects.

METHODS

This double-blinded sham-controlled study assessed the effects of HD-tDCS applied on three consecutive days on central pain mechanisms in healthy participants with (N = 40) and without (N = 40) prolonged experimental pain induced by intramuscular injection of nerve growth factor into the right hand on Day 1. Participants were randomly assigned to Sham-tDCS (N = 20 with pain, N = 20 without) or Active-tDCS (N = 20 with pain, N = 20 without) targeting simultaneously the primary motor cortex and dorsolateral prefrontal cortex for 20 min with 2 mA stimulation intensity. Central pain mechanisms were assessed by cuff algometry on the legs measuring pressure pain sensitivity, temporal summation of pain (TSP) and conditioned pain modulation (CPM), at baseline and after HD-tDCS on Day 2 and Day 3. Based on subject's assessment of received HD-tDCS (sham or active), they were effectively blinded.

RESULTS

Compared with Sham-tDCS, Active-tDCS did not significantly reduce the average NGF-induced pain intensity. Tonic pain-induced temporal summation at Day 2 and Day 3 was significantly lower in the NGF-pain group under Active-tDCS compared to the pain group with Sham-tDCS (p ≤ 0.05). No significant differences were found in the cuff pressure pain detection/tolerance thresholds or CPM effect across the 3 days of HD-tDCS in any of the four groups.

CONCLUSION

HD-tDCS reduced the facilitation of TSP caused by tonic pain suggesting that efficacy of HD-tDCS might depend on the presence of sensitized central pain mechanisms.

Temporal Summation in Fibromyalgia Patients: Comparing Phasic and Tonic Paradigms

Introduction

Fibromyalgia (FM) is associated with dysfunctional pain modulation mechanisms, including central sensitization. Experimental pain measurements, such as temporal summation (TS), could serve as markers of central sensitization and have been previously studied in these patients, with conflicting results. Our objective in this study was to explore the relationships between two different protocols of TS (phasic and tonic) and test the associations between these measures and other clinical variables.

Materials and Methods

In this cross-sectional analysis of a randomized clinical trial, patients were instructed to determine their pain-60 test temperature, then received one train of 15 repetitive heat stimuli and rated their pain after the 1st and 15th stimuli: TSPS-phasic was calculated as the difference between those. We also administered a tonic heat test stimulus at the same temperature continuously for 30 s and asked them to rate their pain levels after 10 s and 30 s, calculating TSPS-tonic as the difference between them. We also collected baseline demographic data and behavioral questionnaires assessing pain, depression, fatigue, anxiety, sleepiness, and quality of life. We performed univariable analyses of the relationship between TSPS-phasic and TSPS-tonic, and between each of those measures and the demographic and clinical variables collected at baseline. We then built multivariable linear regression models to find predictors for TSPS-phasic and TSPS-tonic, while including potential confounders and avoiding collinearity.

Results

Fifty-two FM patients were analyzed. 28.85% developed summation during the TSPS-phasic protocol while 21.15% developed summation during the TSPS-tonic protocol. There were no variables associated TSPS phasic or tonic in the univariable analyses and both measures were not correlated. On the multivariate model for the TSPS-phasic protocol, we found a weak association with pain variables. BPI-pain subscale was associated with more temporal summation in the phasic protocol (ß = 0.38, p = 0.029), while VAS for pain was associated with less summation in the TSPS-tonic protocol (ß = −0.5, p = 0.009).

Conclusion

Our results suggest that, using heat stimuli with pain-60 temperatures, a TSPS-phasic protocol and a TSPS-tonic protocol are not correlated and could index different neural responses in FM subjects. Further studies with larger sample sizes would be needed to elucidate whether such responses could help differentiating subjects with FM into specific phenotypes.

Motor cortex inhibition as a fibromyalgia biomarker: a meta-analysis of transcranial magnetic stimulation studies

Fibromyalgia (FM) is a common and refractory chronic pain condition with multiple clinical phenotypes. The current diagnosis is based on a syndrome identification which can be subjective and lead to under or over-diagnosis. Therefore, there is a need for objective biomarkers for diagnosis, phenotyping, and prognosis (treatment response and follow-up) in fibromyalgia. Potential biomarkers are measures of cortical excitability indexed by transcranial magnetic stimulation (TMS). However, no systematic analysis of current evidence has been performed to assess the role of TMS metrics as a fibromyalgia biomarker. Therefore, this study aims to evaluate evidence on corticospinal and intracortical motor excitability in fibromyalgia subjects and to assess the prognostic role of TMS metrics as response biomarkers in FM. We conducted systematic searches on PubMed/Medline, Embase, and Cochrane Central databases for observational studies and randomized controlled trials on fibromyalgia subjects that used TMS as an assessment. Three reviewers independently selected and extracted the data. Then, a random-effects model meta-analysis was performed to compare fibromyalgia and healthy controls in observational studies. Also, to compare active versus sham treatments, in randomized controlled trials. Correlations between changes in TMS metrics and clinical improvement were explored. The quality and evidence certainty were assessed following standardized approaches. We included 15 studies (696 participants, 474 FM subjects). The main findings were: (1) fibromyalgia subjects present less intracortical inhibition (mean difference (MD) = -0.40, 95% confidence interval (CI) -0.69 to -0.11) and higher resting motor thresholds (MD = 6.90 μV, 95% CI 4.16 to 9.63 μV) when compared to controls; (2) interventions such as exercise, pregabalin, and non-invasive brain stimulation increased intracortical inhibition (MD = 0.19, 95% CI 0.10 to 0.29) and cortical silent period (MD = 14.92 ms, 95% CI 4.86 to 24.98 ms), when compared to placebo or sham stimulation; (3) changes on intracortical excitability are correlated with clinical improvements - higher inhibition moderately correlates with less pain, depression, and pain catastrophizing; lower facilitation moderately correlates with less fatigue. Measures of intracortical inhibition and facilitation indexed by TMS are potential diagnostic and treatment response biomarkers for fibromyalgia subjects. The disruption in the intracortical inhibitory system in fibromyalgia also provides additional evidence that fibromyalgia has some neurophysiological characteristics of neuropathic pain. Treatments inducing an engagement of sensorimotor systems (e.g., exercise, motor imagery, and non-invasive brain stimulation) could restore the cortical inhibitory tonus in FM and induce clinical improvement.

Recruitment characteristics and non-adherence associated factors of fibromyalgia patients in a randomized clinical trial: A retrospective survival analysis

INTRODUCTION

Fibromyalgia is a complex pain condition that affects mostly women. Given the disease's lack of understanding, patients report poor adherence to medication and mistrust of medical services. This study aims to describe the recruitment characteristics and non-adherence associated factors of fibromyalgia patients to an RCT.

METHODS

We performed a retrospective longitudinal analysis with data from our ongoing RCT. We investigated characteristics of subjects recruited, consented, and randomized. Adherence was studied using survival analysis techniques, and its associated factors were identified using Cox proportional hazards regression model.

RESULTS

524 subjects were contacted, 269 were eligible, 61 consented and 40 subjects were randomized. Thirty-eight percent were non-adherent to the protocol with a median of visits of five. The recruitment survey reported that 90% would likely participate in RCTs, 52% had previous participation, and 19% were aware of RCTs by their physicians. Some barriers were investigator-related (staff's friendliness and receiving the results of their trial participation) and center-related (privacy-confidentiality issues and the institution's reputation), without difference between adherent and non-adherent participants. We report significant factors for non-adherence as VAS anxiety score of 5 or more (5.3 HR, p = 0.01), Body Mass Index (BMI) (0.91 HR, p = 0.041) and Quality of Life (QoL) - Personal development subdomain (0.89 HR, p = 0.046).

CONCLUSION

Recruitment and adherence of fibromyalgia patients is a challenge; however, they seem eager to participate in RCTs. We recommend creating a comfortable, friendly and trusting environment to increase the recruitment rate. Higher anxiety, lower BMI and lower quality of life were associated with a higher attrition rate.

Transcranial Direct Current Stimulation Associated With Functional Exercise Program for Treating Fibromyalgia: A Randomized Controlled Trial

OBJECTIVE

To investigate the effects of transcranial direct current stimulation (tDCS) associated with functional exercise on pain, functional performance, psychological symptoms, and quality of life of patients with fibromyalgia (FM).

DESIGN

Randomized controlled trial. Participants were randomized by blocks into 2 groups: tDCS associated with functional exercise (n=17) and sham-tDCS associated with functional exercise (n=14).

SETTING

Laboratory of neuromuscular performance in the department of physical therapy.

PARTICIPANTS

Women with FM (N=31) according to American College of Rheumatology-2010 criteria.

INTERVENTIONS

Anodal tDCS or sham-tDCS was applied over the left motor cortex for 5 consecutive days during the first week of intervention (2 mA; 20min). All volunteers also engaged in 8 weeks of functional exercises 3 times per week.

MAIN OUTCOME MEASURES

Pain intensity, functional performance, psychological symptoms, and quality of life were assessed pre-exercise and immediately after the first, fourth, and eighth weeks of intervention.

RESULTS

Pain intensity, functional performance, psychological symptoms, and quality of life increased significantly in both groups (P<.05); however, no significant differences between groups were found in all outcomes (P>.05).

CONCLUSION

tDCS associated with functional exercises did not enhance the effects of physical exercise on pain, functional performance, psychological symptoms, and quality of life of patients with FM.

Deficit of Inhibition as a Marker of Neuroplasticity (DEFINE Study) in Rehabilitation: A Longitudinal Cohort Study Protocol

Background: Brain plasticity is an intrinsic property of the nervous system, which is modified during its lifetime. This is one mechanism of recuperation after injuries with an important role in rehabilitation. Evidence suggests that injuries in the nervous system disturb the stability between inhibition and excitability essential for the recuperation process of neuroplasticity. However, the mechanisms involved in this balance are not completely understood and, besides the advancement in the field, the knowledge has had a low impact on the rehabilitation practice. Therefore, the understanding of the relationship between biomarkers and functional disability may help to optimize and individualize treatments and build consistent studies in the future.

Methods: This cohort study, the deficit of inhibition as a marker of neuroplasticity study, will follow four groups (stroke, spinal cord injury, limb amputation, and osteoarthritis) to understand the neuroplasticity mechanisms involved in motor rehabilitation. We will recruit 500 subjects (including 100 age- and sex-matched controls). A battery of neurophysiological assessments, transcranial magnetic stimulation, electroencephalography, functional near-infrared spectroscopy, and magnetic resonance imaging, is going to be used to assess plasticity on the motor cortex before and after rehabilitation. One of the main hypotheses in this cohort is that the level of intracortical inhibition is related to functional deficits. We expect to develop a better understanding of the neuroplasticity mechanisms involved in the rehabilitation, and we expect to build neurophysiological “transdiagnostic” biomarkers, especially the markers of inhibition, which will have great relevance in the scientific and therapeutic improvement in rehabilitation. The relationship between neurophysiological and clinical outcomes will be analyzed using linear and logistic regression models.

Discussion: By evaluating the reliability of electroencephalography, functional near-infrared spectroscopy, transcranial magnetic stimulation, and magnetic resonance imaging measures as possible biomarkers for neurologic rehabilitation in different neurologic disorders, this study will aid in the understanding of brain plasticity mechanisms in rehabilitation, allowing more effective approaches and screening methods to take place.

Medial Prefrontal High-Definition Transcranial Direct Current Stimulation to Improve Pain Modulation in Chronic Low Back Pain: A Pilot Randomized Double-blinded Placebo-Controlled Crossover Trial

Chronic low back pain (CLBP) is highly disabling, but often without identifiable source. Focus has been on impaired anti-nociceptive mechanisms contributing to pain maintenance, though methods of targeting this impairment remain limited. This randomised-controlled cross-over pilot trial used active versus sham medial prefrontal cortex (mPFC) high-definition transcranial direct current stimulation (HD-tDCS) for 3-consecutive days to improve descending pain inhibitory function. Twelve CLBP patients were included with an average visual analogue scale (VAS) pain intensity of 3.0 ± 1.5 and pain duration of 5.3 ± 2.6 years. Pressure pain thresholds (PPTs), conditioned pain modulation (CPM), and temporal summation of pain (TSP) assessed by cuff algometry, as well as pain symptomatology (intensity, unpleasantness, quality, disability) and related psychological features (pain catastrophizing, anxiety, affect), were assessed on Day1 before 3 consecutive days of HD-tDCS sessions (each 20 minutes), at 24-hours (Day 4) and 2-weeks (Day 21) following final HD-tDCS. Blinding was successful. No significant differences in psychophysical (PPT, CPM, TSP), symptomatology or psychological outcomes were observed between active and sham HD-tDCS on Day4 and Day21. CPM-effects at Day 1 negatively correlated with change in CPM-effect at Day4 following active HD-tDCS (P = .002). Lack of efficacy was attributed to several factors, not least that patients did not display impaired CPM at baseline. TRIAL REGISTRATION: : ClinicalTrials.gov (NCT03864822). PERSPECTIVE: Medial prefrontal HD-tDCS did not alter pain, psychological nor psychophysical outcomes, though correlational analysis suggested response may depend on baseline pain inhibitory efficacy, with best potential effects in patients with severe impairments in descending pain inhibitory mechanisms. Future work should focus on appropriate patient selection and optimising stimulation targeting.

Barriers and facilitators for clinical trial participation of underrepresented and non-underrepresented fibromyalgia patients: A cross-sectional internet survey

BACKGROUND

There is a need of well-powered randomized clinical trials in fibromyalgia. However, challenges for recruitment are presented. This study aims to describe and assess the perception of barriers and facilitators and the associated factors for the participation of underrepresented and non-underrepresented fibromyalgia patients.

METHODS

We performed an online survey through REDCap (Research Electronic Data Capture) targeting fibromyalgia patients from April 7 to July 3, 2020 during the COVID-19 stay home mandate and it was restricted to the United States of America. We described and compared the survey characteristics between underrepresented and non-underrepresented participants, and we performed logistic regression models to assess the associated factors with clinical trial participation.

RESULTS

In total, 481 completed the survey including 168 underrepresented fibromyalgia patients. Only (1) 11.09 % reported previous participation in clinical trials and the significant perceived barriers were investigator-related (lack of friendliness of research staff and the opportunity to receive the results) and center-related (privacy and confidentiality policies, and the institution's reputation); (2) the participation rate and perceived barriers and facilitators were similar between underrepresented and non-underrepresented patients; and was positively associated with low income, higher age, and clinical trial awareness from their physician; and negatively associated with the perception of investigator-related barriers; and (4) for the underrepresented population, the presence of emotional support.

CONCLUSION

Our findings suggest low rates of participation, regardless of underrepresented population status. Strategies as involving their physician as liaison to increase the awareness of clinical trials, as well as improving patient-researcher communication should be considered in this population.

Prospective, Single-Center Comparison of Transcranial Direct Current Stimulation Plus Electroacupuncture and Standard Analgesia in Patients After Total Knee Arthroplasty: Effect on Rehabilitation and Functional Recovery

Background

The aim of this prospective study was to compare transcranial direct current stimulation (tDCS) plus electroacupuncture with standard analgesia in patients after total knee arthroplasty (TKA) to determine the effects on rehabilitation and functional recovery.

Material/Methods

Eighty patients with osteoarthritis of the knee who underwent TKA were included in the study. They were divided into experimental (n=40) and control groups (n=40) according to postoperative analgesia method. The control group received multimodal analgesia after TKA and the experimental group received additional tDCS plus electroacupuncture. Postoperative pain, knee function, and quality of life were compared between the 2 groups.

Results

Compared with the control group, the experimental group had significantly lower visual analog scale scores at 3 and 7 days and 3 and 6 weeks after TKA (P<0.05). At 6 weeks after TKA, knee injury and osteoarthritis outcome and Hospital for Special Surgery scores and maximum knee flexion in the experimental group were significantly better than those in the control group (P<0.05). In the experimental group compared with the control group, the Short Form-36 Health Survey score also was significantly increased (P<0.05).

Conclusions

The findings from this study showed that tDCS plus electroacupuncture effectively reduced pain after TKA and improved rehabilitation and functional recovery.

New Approaches Based on Non-Invasive Brain Stimulation and Mental Representation Techniques Targeting Pain in Parkinson's Disease Patients: Two Study Protocols for Two Randomized Controlled Trials

Pain is an under-reported but prevalent symptom in Parkinson’s Disease (PD), impacting patients’ quality of life. Both pain and PD conditions cause cortical excitability reduction and non-invasive brain stimulation. Mental representation techniques are thought to be able to counteract it, also resulting effectively in chronic pain conditions. We aim to conduct two independent studies in order to evaluate the efficacy of transcranial direct current stimulation (tDCS) and mental representation protocol in the management of pain in PD patients during the ON state: (1) tDCS over the Primary Motor Cortex (M1); and (2) Action Observation (AO) and Motor Imagery (MI) training through a Brain-Computer Interface (BCI) using Virtual Reality (AO + MI-BCI). Both studies will include 32 subjects in a longitudinal prospective parallel randomized controlled trial design under different blinding conditions. The main outcomes will be score changes in King’s Parkinson’s Disease Pain Scale, Brief Pain Inventory, Temporal Summation, Conditioned Pain Modulation, and Pain Pressure Threshold. Assessment will be performed pre-intervention, post-intervention, and 15 days post-intervention, in both ON and OFF states.

Methods and strategies of tDCS for the treatment of pain: current status and future directions

INTRODUCTION

Transcranial direct current stimulation (tDCS) is a noninvasive neuromodulation technique that has been widely studied for the treatment of chronic pain. It is considered a promising and safe alternative pain therapy. Different targets have been tested, each having their own particular mechanisms for modulating pain perception.

AREAS COVERED

We discuss the current state of the art of tDCS to manage pain and future strategies to optimize tDCS' effects. Current strategies include primary motor cortex tDCS, prefrontal tDCS and tDCS combined with behavioral interventions while future strategies, on the other hand, include high-intensity tDCS, transcutaneous spinal direct current stimulation, cerebellar tDCS, home-based tDCS, and tDCS with extended number of sessions.

EXPERT COMMENTARY

It has been shown that the stimulation of the prefrontal and primary motor cortex is efficient for pain reduction while a few other new strategies, such as high-intensity tDCS and network-based tDCS, are believed to induce strong neuroplastic effects, although the underlying neural mechanisms still need to be fully uncovered. Hence, conventional tDCS approaches demonstrated promising effects to manage pain and new strategies are under development to enhance tDCS effects and make this approach more easily available by using, for instance, home-based devices.

Decreased neural inhibitory state in fibromyalgia pain: A cross-sectional study

OBJECTIVES

Chronic pain is one of the most common and challenging symptoms in fibromyalgia (FM). Currently, self-reported pain is the main criterion used by clinicians assessing patients with pain. However, it is subjective, and multiple factors can affect pain levels. In this study, we investigated the neural correlates of FM pain using conditioned pain modulation (CPM), electroencephalography (EEG), and transcranial magnetic stimulation (TMS).

METHODS

In this cross-sectional neurophysiological analysis of a randomized, double-blind controlled trial, 36 patients with fibromyalgia were included. We analyzed CPM, EEG variables and TMS measures and their correlation with pain levels as measured by a visual analog scale. Univariate and multivariate linear regression analyses were performed to identify the predictors of pain severity.

RESULTS

We found: (1) no association between pain levels and CPM; (2) an association between reduced alpha and beta power over the central region in resting-EEG and higher pain levels; (3) an association between smaller event-related desynchronization (ERD) responses in theta and delta bands over the central region and higher pain levels; (4) an association between smaller ERD responses in theta and delta bands and smaller intracortical inhibition and higher intracortical facilitation ratios; (5) an association between smaller ERD responses in delta band and reduced CPM.

CONCLUSIONS

Our results do not support CPM as a biomarker for pain intensity in FM. However, our specific EEG findings showing the relationship between pain, CPM and TMS measures suggest that FM leads to a disruption of inhibitory neural modulators and thus support CPM as a likely predictive marker of disrupted pain modulation system. These neurophysiological markers need to be further explored in potential future trials as to find novel targets for the treatment of FM.

Noninvasive brain stimulation combined with exercise in chronic pain: a systematic review and meta-analysis

Background: The use of noninvasive brain stimulation (NIBS) combined with exercise could produce synergistic effects on chronic pain conditions. This study aims to evaluate the efficacy and safety of NIBS combined with exercise to treat chronic pain as well as to describe the parameters used to date in this combination.Methods: The search was carried out in Medline, Central, Scopus, Embase, and Pedro until November 2019. Randomized clinical trials (RCTs) and quasi-experimental studies reporting the use of noninvasive brain stimulation and exercise on patients with chronic pain were selected and revised.Results: The authors included eight studies (RCTs), reporting eight comparisons (219 participants). Authors found a significant and homogeneous pain decrease (ES: -0.62, 95% CI:-0.89 to -0.34; I2 = 0.0%) in favor of the combined intervention compared to sham NIBS + exercise, predominantly by excitatory (anodal tDCS/rTMS) motor cortex stimulation. Regarding NIBS techniques, the pooled effect sizes were significant for both tDCS (ES: -0.59, 95% CI: -0.89 to -0.29, I2 = 0.0%) and rTMS (ES: -0.76, 95% CI: -1.41 to -0.11, I2 = 0.0%).Conclusions: This meta-analysis suggests a significant moderate to large effects of the NIBS and exercise combination in chronic pain. The authors discuss the potential theoretical framework for this synergistic effect.