Effectiveness of transcranial direct current stimulation preceding cognitive behavioural management for chronic low back pain: sham controlled double blinded randomised controlled trial

Combining Transcranial Direct Current Stimulation With Non-Invasive Interventions for Chronic Primary Pain: A Systematic Review and Meta-Analysis

BACKGROUND

A growing number of studies has combined transcranial direct current stimulation (tDCS) with other non-invasive non-pharmacological therapies (NINPT) to enhance effects in pain reduction. However, the efficacy of these combined approaches in treating chronic primary pain (CPP) warrants thorough investigation.

OBJECTIVE

This study aims to evaluate the efficacy of tDCS in conjunction with other NINPT in alleviating pain severity among CPP patients.

METHODS

We conducted a systematic search for randomized controlled trials (RCTs) comparing the efficacy of tDCS combined with NINPT against control treatments in adult CPP patients. The search spanned multiple databases, including PubMed, EMBASE, LILACS, Scopus, Web of Science, and CENTRAL.

RESULTS

Our systematic review included 11 RCTs with a total of 449 participants. In our meta-analysis, which comprised 228 participants receiving active-tDCS and 221 receiving sham-tDCS, we found a significant reduction in pain intensity (Standard Mean Difference = -0.73; 95% Confidence Interval (CI) = -1.18 to -0.27; P = .002) with the use of active-tDCS combined with NINPT.

CONCLUSION

These findings substantiate the therapeutic potential of combining tDCS with other NINPT, highlighting it as an effective treatment modality for reducing pain intensity in CPP patients.

Effects and safety of transcranial direct current stimulation on multiple health outcomes: an umbrella review of randomized clinical trials

Transcranial direct current stimulation (tDCS), which delivers a direct current to the brain, emerged as a non-invasive potential therapeutic in treating a range of neurological and neuropsychiatric disorders. However, a comprehensive quantitative evidence synthesis on the effects of tDCS on a broad range of mental illnesses is lacking. Here, we systematically assess the certainty of the effects and safety of tDCS on several health outcomes using an umbrella review of randomized controlled trials (RCTs). The methodological quality of each included original meta-analysis was assessed by the A Measurement Tool for Assessing Systematic Reviews 2 (AMSTAR2), and the certainty of the evidence for each effect was evaluated with Grading of Recommendations, Assessment, Development, and Evaluation (GRADE). We followed an a priori protocol (PROSPERO CRD42023458700). We identified 15 meta-analyses of RCTs (AMSTAR 2; high 3, moderate 3, and low 9) that included 282 original articles, covering 22 unique health endpoints across 22 countries and six continents. From meta-analyses of RCTs supported by very low to high certainty of evidence, it was found that tDCS improved symptoms related to post-stroke, including post-stroke depression scale score (equivalent standardized mean difference [eSMD], 1.61 [95% confidence level, 0.72-2.50]; GRADE=moderate), activities of daily living independence (7.04 [3.41-10.67]; GRADE=high), motor recovery of upper and lower extremity (upper extremity: 0.15 [0.06-0.24], GRADE=high; lower extremity: 0.10 [0.03-0.16], GRADE=high), swallowing performance (GRADE=low), and spasticity (GRADE=moderate). In addition, tDCS had treatment effects on symptoms of several neurological and neuropsychiatric disorders, including obsessive-compulsive disorder (0.81 [0.44-1.18]; GRADE=high), pain in fibromyalgia (GRADE=low), disease of consciousness (GRADE=low), insight score (GRADE=moderate) and working memory (0.34 [0.01-0.67]; GRADE=high) in schizophrenia, migraine-related pain (-1.52 [-2.91 to -0.13]; GRADE=high), attention-deficit/hyperactivity disorder (reduction in overall symptom severity: 0.24 [0.04-0.45], GRADE=low; reduction in inattention: 0.56 [0.02-1.11], GRADE=low; reduction in impulsivity: 0.28 [0.04-0.51], GRADE=low), depression (GRADE=low), cerebellar ataxia (GRADE=low), and pain (GRADE=very low). Importantly, tDCS induced an increased number of reported cases of treatment-emergent mania or hypomania (0.88 [0.62-1.13]; GRADE=moderate). We found varied levels of evidence for the effects of tDCS with multiple neurological and neuropsychiatric conditions, from very low to high certainty of evidence. tDCS was effective for people with stroke, obsessive-compulsive disorder, fibromyalgia, disease of consciousness, schizophrenia, migraine, attention-deficit/hyperactivity disorder, depression, cerebellar ataxia, and pain. Therefore, these findings suggest the benefit of tDCS for several neurological and neuropsychiatric disorders; however, further studies are needed to understand the underlying mechanism and optimize its therapeutic potential.

Effectiveness of transcranial direct current stimulation in chronic pain and neurogenic claudication related to lumbar spinal stenosis

OBJECTIVES

Transcranial direct current stimulation (tDCS) is a promising non-invasive brain stimulation technique for treating chronic pain, yet its effectiveness in chronic lower extremity pain due to lumbar spinal stenosis (LSS) has not been studied. This research aimed to investigate the impact of tDCS on pain, walking capacity, functional status, and quality of life in LSS patients.

PATIENTS AND METHODS

In this prospective, randomized, double-blind, sham-controlled study, 32 LSS patients received either real or sham tDCS over the motor cortex contralateral to the patient's painful lower extremity for 10 consecutive weekdays (10 sessions). Evaluations were conducted at baseline, post-session, and 1-3 months later. The pain was evaluated by Visual Analog Scale (VAS), walking duration and distance by Treadmill Walking Test, functional status by Modified Oswestry Disability Questionnaire (MODQ) and quality of life by Short Form-36 (SF-36).

RESULTS

In-group comparisons, active tDCS showed sustained analgesic effects for 3-month post-treatment, distinct from sham. After the final session, active group exhibited significantly better asymptomatic walking distance and duration. Active stimulation led to notably lower MOLBDQ scores after 1 month. Significant improvements in SF-36 subscales were seen after 3 months, especially in pain, physical functioning, and general health. Positive tDCS effects on pain, claudication, and some quality of life aspects were evident at 3 months, while functional status improvements were mainly limited to 1 month.

CONCLUSION

tDCS shows potential as a safe, non-invasive technique for alleviating chronic LSS-related pain, enhancing mobility, functionality, and quality of life.

TRIAL REGISTRATION

Clinicaltrials.gov ID: NCT03958526.

Brain stimulation targets for chronic pain: Insights from meta-analysis, functional connectivity and literature review

Noninvasive brain stimulation (NIBS) techniques have demonstrated their potential for chronic pain management, yet their efficacy exhibits variability across studies. Refining stimulation targets and exploring additional targets offer a possible solution to this challenge. This study aimed to identify potential brain surface targets for NIBS in treating chronic pain disorders by integrating literature review, neuroimaging meta-analysis, and functional connectivity analysis on 90 chronic low back pain patients. Our results showed that the primary motor cortex (M1) (C3/C4, 10-20 EEG system) and prefrontal cortex (F3/F4/Fz) were the most used brain stimulation targets for chronic pain treatment according to the literature review. The bilateral precentral gyrus (M1), supplementary motor area, Rolandic operculum, and temporoparietal junction, were all identified as common potential NIBS targets through both a meta-analysis sourced from Neurosynth and functional connectivity analysis. This study presents a comprehensive summary of the current literature and refines the existing NIBS targets through a combination of imaging meta-analysis and functional connectivity analysis for chronic pain conditions. The derived coordinates (with integration of the international electroencephalography (EEG) 10/20 electrode placement system) within the above brain regions may further facilitate the localization of these targets for NIBS application. Our findings may have the potential to expand NIBS target selection beyond current clinical trials and improve chronic pain treatment.

Effects of transcranial direct current stimulation combined with Pilates-based exercises in the treatment of chronic low back pain in outpatient rehabilitation service in Brazil: double-blind randomised controlled trial protocol

INTRODUCTION

Chronic low back pain may be associated with pathoanatomical, neurophysiological, physical, psychological and social factors; thus, treatments to reduce symptoms are important to improve the quality of life of this population. We aimed to evaluate the effects of transcranial direct current stimulation (tDCS) combined with Pilates-based exercises compared with sham stimulation on pain, quality of life and disability in patients with chronic non-specific low back pain.

METHODS AND ANALYSIS

This is a protocol for a double-blind randomised controlled trial with participants, outcome assessor and statistician blinded. We will include 36 individuals with a history of non-specific chronic low back pain for more than 12 weeks and minimum pain intensity of 3 points on the Numerical Pain Rating Scale. Individuals will be randomised into two groups: (1) active tDCS combined with Pilates-based exercises and (2) sham tDCS combined with Pilates-based exercises. Three weekly sessions of the protocol will be provided for 4 weeks, and individuals will be submitted to three assessments: the first (T0) will be performed before the intervention protocol, the second (T1) immediately after the intervention protocol and the third (T2) will be a follow-up 1 month after the end of the intervention. We will assess pain, disability, central sensitisation, quality of life, pressure pain threshold, global impression of change, adverse events and medication use. The Numerical Pain Rating Scale and the Roland-Morris Disability Questionnaire will be used at T1 to assess pain and disability, respectively, as primary outcome measures.

ETHICS AND DISSEMINATION

This trial was prospectively registered in ClinicalTrials.gov website and ethically approved by the Ethics and Research Committee of the Faculty of Health Sciences of Trairi (report number: 5.411.244) before data collection. We will publish the results in a peer-reviewed medical journal and on institution websites.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov (NCT05467566).

Does Multisession Cathodal Transcranial Direct Current Stimulation of the Left Dorsolateral Prefrontal Cortex Prime the Effects of Cognitive Behavioral Therapy on Fear of Pain, Fear of Movement, and Disability in Patients with Nonspecific Low Back Pain? A Randomized Clinical Trial Study

Many studies have shown that low back pain (LBP) is associated with psychosomatic symptoms which may lead to brain changes. This study aimed to investigate the effect of the concurrent application of cognitive behavioral therapy (CBT) and transcranial direct electrical stimulation (tDCS) over the left dorsolateral prefrontal cortex (DLPFC) on fear of pain, fear of movement, and disability in patients with nonspecific LBP. This study was performed on 45 LBP patients (23 women, 22 men; mean age 33.00 ± 1.77 years) in three groups: experimental (2 mA cathodal tDCS (c-tDCS)), sham (c-tDCS turned off after 30 s), and control (only received CBT). In all groups, CBT was conducted for 20 min per session, with two sessions per week for four weeks. Fear of pain, fear of movement, and disability were evaluated using questionnaires at baseline, immediately after, and one month after completion of interventions. Results indicated that all three different types of intervention could significantly reduce fear and disability immediately after intervention (p > 0.05). However, improvement in the experimental group was significantly higher than in the other groups immediately after and at the one-month follow-up after interventions (p < 0.05). DLPFC c-tDCS can prime the immediate effects of CBT and also the lasting effects on the reduction in the fear of pain, fear of movement, and disability in LBP patients.

Exploring the Frontiers of Neuroimaging: A Review of Recent Advances in Understanding Brain Functioning and Disorders

Neuroimaging has revolutionized our understanding of brain function and has become an essential tool for researchers studying neurological disorders. Functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) are two widely used neuroimaging techniques to review changes in brain activity. fMRI is a noninvasive technique that uses magnetic fields and radio waves to produce detailed brain images. An EEG is a noninvasive technique that records the brain's electrical activity through electrodes placed on the scalp. This review overviews recent developments in noninvasive functional neuroimaging methods, including fMRI and EEG. Recent advances in fMRI technology, its application to studying brain function, and the impact of neuroimaging techniques on neuroscience research are discussed. Advances in EEG technology and its applications to analyzing brain function and neural oscillations are also highlighted. In addition, advanced courses in neuroimaging, such as diffusion tensor imaging (DTI) and transcranial electrical stimulation (TES), are described, along with their role in studying brain connectivity, white matter tracts, and potential treatments for schizophrenia and chronic pain. Application. The review concludes by examining neuroimaging studies of neurodevelopmental and neurological disorders such as autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD), Alzheimer's disease (AD), and Parkinson's disease (PD). We also described the role of transcranial direct current stimulation (tDCS) in ASD, ADHD, AD, and PD. Neuroimaging techniques have significantly advanced our understanding of brain function and provided essential insights into neurological disorders. However, further research into noninvasive treatments such as EEG, MRI, and TES is necessary to continue to develop new diagnostic and therapeutic strategies for neurological disorders.

Transcranial direct current stimulation combined with peripheral stimulation in chronic pain: a systematic review and meta-analysis

INTRODUCTION

The combination of Transcranial Direct Current Stimulation (tDCS) with peripheral stimulation may optimize their effects and bring positive results in treatment of people with chronic pain.

AREAS COVERED

A systematic review with meta-analysis of randomized and non-randomized trials was performed to investigate the combination of tDCS with peripheral stimulation in adults with chronic pain. The primary outcome was pain intensity. Six studies were included in this review (sample of 228 participants), which investigated the combination of tDCS and transcutaneous electrical nerve stimulation, peripheral electrical stimulation, breathing-controlled electrical stimulation and intramuscular electrical stimulation. The conditions studied were knee osteoarthritis, spinal cord injury, chronic low back pain, and neurogenic pain of the arms. Pain intensity, measured by visual analog scale or numerical rating scale, was reduced in all included studies when at least one of the interventions was active, regardless they were combined or alone, with or without tDCS. However, meta-analysis showed superiority of tDCS used in combination with peripheral stimulation.

EXPERT OPINION

This systematic review and meta-analysis suggests positive effects of tDCS combined with peripheral stimulation in chronic pain conditions. However, the evidence of the primary outcome was classified as low quality due to the limited number of studies.

Efficacy of transcranial direct current stimulation (tDCS) on pain and shoulder range of motion in post-mastectomy pain syndrome patients: a randomized-control trial

Background

Post-mastectomy pain syndrome (PMPS) is a highly prevalent complication after surgical treatment for breast cancer, and it affects the patient’s quality of life in aspects of losing shoulder full range of motion, pain, and depression. Transcranial direct current stimulation (tDCS) is non-invasive brain stimulation technique that was used in numerous clinical applications and in pain reduction in cancer patients. However, the effectiveness of tDCS on PMPS has never been evaluated in an experimental study.

Aim

To investigate the effect of bilateral anodal tDCS of motor cortex (M1) on pain, depression, and shoulder range of motion (ROM) in post-mastectomy pain syndrome.

Study design

Randomized controlled trial.

Methods

A total of 30 female patients with post-mastectomy neuropathic pain were randomized into two groups; the intervention group which received bilateral tDCS on motor cortex (M1) and the control group that received sham bilateral tDCS on M1. As pain affects shoulder range of motion (ROM), shoulder ROM was measured by electronic goniometer pre- and post-tDCS application. In addition, the levels of pain and depression have been measured pre and post treatment. Pain has been measured with visual analogue scale (VAS) and depression with Beck-Depression-Inventory-BDI questionnaire (BDI).

Results

A significant difference was noted in group A regarding pain, depression and shoulder ROM (p= 0.001, p= 0.003, and p= 0.003, respectively). Between group comparison revealed a significant difference of VAS scores and shoulder flexion ROM between groups, the study group and the control group (p=0.041 and 0.048, respectively). Pain decreased by 32% and Shoulder flexion increased by 4.8% post-treatment while there were no significant difference in group B (p=0.567 and p=0.866, respectively).

Conclusions

The application of tDCS decreases the severity of pain and improves shoulder range of motion suffered by breast cancer patients after total mastectomy surgery.

Time since onset might be of essence: A recommendation to assess the effects of combination of non-pharmacological neuromodulatory approaches at early stage since symptoms onset

In the past decade researchers began to assess the potential beneficial effects of non-invasive brain stimulation (NIBS) combined with a behavioral task as a treatment approach for various medical conditions. Transcranial direct current stimulation (tDCS) applied to the motor cortex combined with another treatment approach has been assessed as analgesic treatment in neuropathic and non-neuropathic pain conditions, and was found to exert only modest pain relief. Our group results show that combined tDCS and mirror therapy dramatically reduced acute phantom limb pain intensity with long-lasting effects, potentially preventing pain chronification. A review of the scientific literature indicates that our approach differs from that of others: We applied the intervention at the acute stage of the disease, whereas other studies applied the intervention in patients whose disease had already been established. We suggest that the timing of administration of the combined intervention is critical. Unlike in patients with chronic painful condition, in which the maladaptive plasticity associated with pain chronification and chronicity is well-consolidated, early treatment at the acute pain stage may be more successful in counterbalancing the not-yet consolidated maladaptive plasticity. We encourage the research community to test our hypothesis, both in the treatment of pain, and beyond.

Anodal-TDCS over Left-DLPFC Modulates Motor Cortex Excitability in Chronic Lower Back Pain

Chronic pain is associated with abnormal cortical excitability and increased pain intensity. Research investigating the potential for transcranial direct current stimulation (tDCS) to modulate motor cortex excitability and reduce pain in individuals with chronic lower back pain (CLBP) yield mixed results. The present randomised, placebo-controlled study examined the impact of anodal-tDCS over left-dorsolateral prefrontal cortex (left-DLPFC) on motor cortex excitability and pain in those with CLBP. Nineteen participants with CLBP (Mage = 53.16 years, SDage = 14.80 years) received 20-min of sham or anodal tDCS, twice weekly, for 4 weeks. Short interval intracortical inhibition (SICI) and intracortical facilitation (ICF) were assessed using paired-pulse Transcranial Magnetic Stimulation prior to and immediately following the tDCS intervention. Linear Mixed Models revealed no significant effect of tDCS group or time, on SICI or ICF. The interactions between tDCS group and time on SICI and ICF only approached significance. Bayesian analyses revealed the anodal-tDCS group demonstrated higher ICF and SICI following the intervention compared to the sham-tDCS group. The anodal-tDCS group also demonstrated a reduction in pain intensity and self-reported disability compared to the sham-tDCS group. These findings provide preliminary support for anodal-tDCS over left-DLPFC to modulate cortical excitability and reduce pain in CLBP.

An Updated Overview of Low Back Pain Management

We aimed to determine the recommendation level for the treatment of acute and chronic low back pain (LBP). A systematic review (SR) of the literature was performed and all English-language articles that discuss acute and chronic LBP, including MEDLINE and the Cochrane Database of Systematic Reviews, were searched. Of the 873 searched literature reports, 259 articles, including 131 clinical trials, 115 SRs, nine meta-analyses, and four clinical guidelines were analyzed. In these articles, high-quality randomized controlled trials, SRs, and used well-written clinical guidelines were reviewed. The results indicated multiple acute and chronic LBP treatment methods in the literature, and these reports when reviewed included general behavior, pharmacological therapy, psychological therapy, specific exercise, active rehabilitation and educational interventions, manual therapy, physical modalities, and invasive procedures. The Trial conclusions and SRs were classified into four categories of A, B, C, and D. If there were not enough high-quality articles, it was designated as "I" (insufficient). This review and summary of guidelines may be beneficial for physicians to better understand and make recommendations in primary care.

Effect of Single Session of Anodal M1 Transcranial Direct Current Stimulation-TDCS-On Cortical Hemodynamic Activity: A Pilot Study in Fibromyalgia

Transcranial direct current stimulation (TDCS) on the primary motor cortex (M1) has been reported to be effective in fibromyalgia (FM). Our previous works have shown hypometabolism of motor networks in FM using Functional Near Infrared Spectroscopy (fNIRS), which could contribute to pain symptoms. To investigate if a single Transcranial Direct Current Stimulation (TDCS) session can restore the reduced metabolism expected in FM patients, we compared metabolic activity in FM patients and controls during a finger-tapping task in basal condition, sham condition, and under anodal TDCS on M1. During the finger tapping task, a continuous wave 20 channel fNIRS system was placed across the bilateral central-frontal areas in 22 healthy controls and 54 FM patients. Subjects were randomly assigned to real TDCS or sham stimulation. The finger-tapping slowness did not change after real and sham stimulation. After real TDCS stimulation, FM patients showed an increased activation of cortical motor regions (t-statistic = -2.5246, p-value = 0.0125 for the stimulated hemisphere and t-statistic = -4.6638, p-value = 0.0001 for the non-stimulated hemisphere). The basal differences between FM and controls reverted after real TDCS, while this effect was not observed for sham stimulation. A single TDCS session of the cortical motor network seemed able to restore basic cortical hypometabolism in FM patients. Further studies could clarify the long-term effect of M1 stimulation on cortical metabolism, and its relevance in pain processing and clinical features.

Non-invasive brain stimulation and pain neuroscience education in the cognitive-affective treatment of chronic low back pain: Evidence and future directions

Chronic low back pain (CLBP) is among the leading causes of disability worldwide. Beyond the physical and functional limitations, people's beliefs, cognitions, and perceptions of their pain can negatively influence their prognosis. Altered cognitive and affective behaviors, such as pain catastrophizing and kinesiophobia, are correlated with changes in the brain and share a dynamic and bidirectional relationship. Similarly, in the presence of persistent pain, attentional control mechanisms, which serve to organize relevant task information are impaired. These deficits demonstrate that pain may be a predominant focus of attentional resources, leaving limited reserve for other cognitively demanding tasks. Cognitive dysfunction may limit one's capacity to evaluate, interpret, and revise the maladaptive thoughts and behaviors associated with catastrophizing and fear. As such, interventions targeting the brain and resultant behaviors are compelling. Pain neuroscience education (PNE), a cognitive intervention used to reconceptualize a person's pain experiences, has been shown to reduce the effects of pain catastrophizing and kinesiophobia. However, cognitive deficits associated with chronic pain may impact the efficacy of such interventions. Non-invasive brain stimulation (NIBS), such as transcranial direct current stimulation (tDCS) or repetitive transcranial magnetic stimulation (rTMS) has been shown to be effective in the treatment of anxiety, depression, and pain. In addition, as with the treatment of most physical and psychological diagnoses, an active multimodal approach is considered to be optimal. Therefore, combining the neuromodulatory effects of NIBS with a cognitive intervention such as PNE could be promising. This review highlights the cognitive-affective deficits associated with CLBP while focusing on current evidence for cognition-based therapies and NIBS.

Non-invasive brain neuromodulation techniques for chronic low back pain

Structural and functional changes of the brain occur in many chronic pain conditions, including chronic low back pain (CLBP), and these brain abnormalities can be reversed by effective treatment. Research on the clinical applications of non-invasive brain neuromodulation (NIBS) techniques for chronic pain is increasing. Unfortunately, little is known about the effectiveness of NIBS on CLBP, which limits its application in clinical pain management. Therefore, we summarized the effectiveness and limitations of NIBS techniques on CLBP management and described the effects and mechanisms of NIBS approaches on CLBP in this review. Overall, NIBS may be effective for the treatment of CLBP. And the analgesic mechanisms of NIBS for CLBP may involve the regulation of pain signal pathway, synaptic plasticity, neuroprotective effect, neuroinflammation modulation, and variations in cerebral blood flow and metabolism. Current NIBS studies for CLBP have limitations, such as small sample size, relative low quality of evidence, and lack of mechanistic studies. Further studies on the effect of NIBS are needed, especially randomized controlled trials with high quality and large sample size.

High-definition transcranial infraslow pink noise stimulation for chronic low back pain: protocol for a pilot, safety and feasibility randomised placebo-controlled trial

INTRODUCTION

Chronic low back pain (CLBP) is a common disabling health condition. Current treatments demonstrate modest effects, warranting newer therapies. Brain imaging demonstrates altered electrical activities in cortical areas responsible for pain modulation, emotional and sensory components of pain experience. Treatments targeting to change electrical activities of these key brain regions may produce clinical benefits. This pilot study aims to (1) evaluate feasibility, safety and acceptability of a novel neuromodulation technique, high-definition transcranial infraslow pink noise stimulation (HD-tIPNS), in people with CLBP, (2) explore the trend of effect of HD-tIPNS on pain and function, and (3) derive treatment estimates to support sample size calculation for a fully powered trial should trends of effectiveness be present.

METHODS AND ANALYSIS

A pilot, triple-blinded randomised two-arm placebo-controlled parallel trial. Participants (n=40) with CLBP will be randomised to either sham stimulation or HD-tIPNS (targeting somatosensory cortex and dorsal and pregenual anterior cingulate cortex). Primary outcomes include feasibility and safety measures, and clinical outcomes of pain (Brief Pain Inventory) and disability (Roland-Morris disability questionnaire). Secondary measures include clinical, psychological, quantitative sensory testing and electroencephalography collected at baseline, immediately postintervention, and at 1-week, 1-month and 3 months postintervention. All data will be analysed descriptively. A nested qualitative study will assess participants perceptions about acceptability of intervention and analysed thematically.

ETHICS AND DISSEMINATION

Ethical approval has been obtained from Health and Disability Ethics Committee (Ref:20/NTB/67). Findings will be reported to regulatory and funding bodies, presented at conferences, and published in a scientific journal.

TRIAL REGISTRATION NUMBER

ACTRN12620000505909p.

Effects of High-Definition Transcranial Direct Current Stimulation Over the Primary Motor Cortex on Cold Pain Sensitivity Among Healthy Adults

Some clinical studies have shown promising effects of transcranial direct current stimulation (tDCS) over the primary motor cortex (M1) on pain relief. Nevertheless, a few studies reported no significant analgesic effects of tDCS, likely due to the complexity of clinical pain conditions. Human experimental pain models that utilize indices of pain in response to well-controlled noxious stimuli can avoid many confounds that are present in the clinical data. This study aimed to investigate the effects of high-definition tDCS (HD-tDCS) stimulation over M1 on sensitivity to experimental pain and assess whether these effects could be influenced by the pain-related cognitions and emotions. A randomized, double-blinded, crossover, and sham-controlled design was adopted. A total of 28 healthy participants received anodal, cathodal, or sham HD-tDCS over M1 (1 mA for 20 min) in different sessions, in which montage has the advantage of producing more focal stimulation. Using a cold pressor test, several indices reflecting the sensitivity to cold pain were measured immediately after HD-tDCS stimulation, such as cold pain threshold and tolerance and cold pain intensity and unpleasantness ratings. Results showed that only anodal HD-tDCS significantly increased cold pain threshold when compared with sham stimulation. Neither anodal nor cathodal HD-tDCS showed significant analgesic effects on cold pain tolerance, pain intensity, and unpleasantness ratings. Correlation analysis revealed that individuals that a had lower level of attentional bias to negative information benefited more from attenuating pain intensity rating induced by anodal HD-tDCS. Therefore, single-session anodal HD-tDCS modulates the sensory-discriminative aspect of pain perception as indexed by the increased pain threshold. In addition, the modulating effects of HD-tDCS on attenuating pain intensity to suprathreshold pain could be influenced by the participant’s negative attentional bias, which deserves to be taken into consideration in the clinical applications.

Exercise attenuates low back pain and alters epigenetic regulation in intervertebral discs in a mouse model

BACKGROUND CONTEXT

Chronic low back pain (LBP) is a multifactorial disorder with complex underlying mechanisms, including associations with intervertebral disc (IVD) degeneration in some individuals. It has been demonstrated that epigenetic processes are involved in the pathology of IVD degeneration. Epigenetics refers to several mechanisms, including DNA methylation, that have the ability to change gene expression without inducing any change in the underlying DNA sequence. DNA methylation can alter the entire state of a tissue for an extended period of time and thus could potentially be harnessed for long-term pain relief. Lifestyle factors, such as physical activity, have a strong influence on epigenetic regulation. Exercise is a commonly prescribed treatment for chronic LBP, and sex-specific epigenetic adaptations in response to endurance exercise have been reported. However, whether exercise interventions that attenuate LBP are associated with epigenetic alterations in degenerating IVDs has not been evaluated.

PURPOSE

We hypothesize that the therapeutic efficacy of physical activity is mediated, at least in part, at the epigenetic level. The purpose of this study was to use the SPARC-null mouse model of LBP associated with IVD degeneration to clarify (1) if IVD degeneration is associated with altered expression of epigenetic regulatory genes in the IVDs, (2) if epigenetic regulatory machinery is sensitive to therapeutic environmental intervention, and (3) if there are sex-specific differences in (1) and/or (2).

STUDY DESIGN

Eight-month-old male and female SPARC-null and age-matched control (WT) mice (n=108) were assigned to exercise (n=56) or sedentary (n=52) groups. Deletion of SPARC is associated with progressive IVD degeneration and behavioral signs of LBP. The exercise group received a circular plastic home cage running wheel on which they could run freely. The sedentary group received an identical wheel secured in place to prevent rotation. After 6 months, the results obtained in each group were compared.

METHODS

After 6 months of exercise, LBP-related behavioral indices were determined, and global DNA methylation (5-methylcytosine) and epigenetic regulatory gene mRNA expression in IVDs were assessed. This project was supported by the Canadian Institutes for Health Research. The authors have no conflicts of interest.

RESULTS

Lumbar IVDs from WT sedentary and SPARC-null sedentary mice had similar levels of global DNA methylation (%5-mC) and comparable mRNA expression of epigenetic regulatory genes (Dnmt1,3a,b, Mecp2, Mbd2a,b, Tet1-3) in both sexes. Exercise attenuated LBP-related behaviors, decreased global DNA methylation in both WT (p<.05) and SPARC-null mice (p<.01) and reduced mRNA expression of Mecp2 in SPARC-null mice (p<.05). Sex-specific effects of exercise on expression of mRNA were also observed.

CONCLUSIONS

Exercise alleviates LBP in a mouse model. This may be mediated, in part, by changes in the epigenetic regulatory machinery in degenerating IVDs. Epigenetic alterations due to a lifestyle change could have a long-lasting therapeutic impact by changing tissue homeostasis in IVDs.

CLINICAL SIGNIFICANCE

This study confirmed the therapeutic benefits of exercise on LBP and suggests that exercise results in sex-specific alterations in epigenetic regulation in IVDs. Elucidating the effects of exercise on epigenetic regulation may enable the discovery of novel gene targets or new strategies to improve the treatment of chronic LBP.

Effects of transcranial direct current stimulation on experimental pain perception: A systematic review and meta-analysis

OBJECTIVE

Many studies have examined the effectiveness of transcranial direct current stimulation (tDCS) on human pain perception in both healthy populations and pain patients. Nevertheless, studies have yielded conflicting results, likely due to differences in stimulation parameters, experimental paradigms, and outcome measures. Human experimental pain models that utilize indices of pain in response to well-controlled noxious stimuli can avoid many confounds present in clinical data. This study aimed to assess the robustness of tDCS effects on experimental pain perception among healthy populations.

METHODS

We conducted three meta-analyses that analyzed tDCS effects on ratings of perceived pain intensity to suprathreshold noxious stimuli, pain threshold and tolerance.

RESULTS

The meta-analyses showed a statically significant tDCS effect on attenuating pain-intensity ratings to suprathreshold noxious stimuli. In contrast, tDCS effects on pain threshold and pain tolerance were statistically non-significant. Moderator analysis further suggested that stimulation parameters (active electrode size and current density) and experimental pain modality moderated the effectiveness of tDCS in attenuating pain-intensity ratings.

CONCLUSION

The effectiveness of tDCS on attenuating experimental pain perception depends on both stimulation parameters of tDCS and the modality of experimental pain.

SIGNIFICANCE

This study provides some theoretical basis for the application of tDCS in pain management.

The Effect of Noninvasive Brain Stimulation to Reduce Nonspecific Low Back Pain: A Systematic Review and Meta-analysis

OBJECTIVE

We conducted a systematic review/meta-analysis to evaluate noninvasive brain stimulation (NIBS) efficacy to alleviate pain and improve disability in low back pain (LBP).

MATERIALS AND METHODS

A systematic literature search was performed by a librarian in MEDLINE, Embase, EBM Reviews, CINAHL, and Web of Science databases (last search: January 14, 2021). Data were pooled by the number of sessions and follow-up periods. Independent reviewers performed screening, data extraction, and risk of bias. Pain reduction and disability were used as outcomes.

RESULTS

Twelve articles were included in the qualitative synthesis and 8 in the meta-analysis. A single session of NIBS reduced pain compared with sham (standardized mean difference: -0.47; P<0.001; very low-quality evidence). Repeated sessions of NIBS did not impact pain at short-term (mean difference [MD]: -0.31; P=0.23) or midterm (MD: -0.56; P=0.33; moderate quality evidence). Combining NIBS with cointerventions did not influence pain (MD: -0.31; P=0.30; moderate quality evidence). NIBS did not have a statistically significant impact on disability.

DISCUSSION

There is very low-quality evidence suggesting that a single NIBS session reduces LBP intensity. In contrast, there is moderate quality evidence that repeated NIBS sessions or combination with cointervention did not improve pain or disability. Thus, current results do not support NIBS use to treat chronic LBP. Considering that tDCS was tested in 8 of 12 studies with little success, studies focusing on different NIBS techniques or innovative parameters are required to determine their potential to improve pain and disability in chronic LBP.

Evidence-Based Guidelines and Secondary Meta-Analysis for the Use of Transcranial Direct Current Stimulation in Neurological and Psychiatric Disorders

BACKGROUND

Transcranial direct current stimulation has shown promising clinical results, leading to increased demand for an evidence-based review on its clinical effects.

OBJECTIVE

We convened a team of transcranial direct current stimulation experts to conduct a systematic review of clinical trials with more than 1 session of stimulation testing: pain, Parkinson's disease motor function and cognition, stroke motor function and language, epilepsy, major depressive disorder, obsessive compulsive disorder, Tourette syndrome, schizophrenia, and drug addiction.

METHODS

Experts were asked to conduct this systematic review according to the search methodology from PRISMA guidelines. Recommendations on efficacy were categorized into Levels A (definitely effective), B (probably effective), C (possibly effective), or no recommendation. We assessed risk of bias for all included studies to confirm whether results were driven by potentially biased studies.

RESULTS

Although most of the clinical trials have been designed as proof-of-concept trials, some of the indications analyzed in this review can be considered as definitely effective (Level A), such as depression, and probably effective (Level B), such as neuropathic pain, fibromyalgia, migraine, post-operative patient-controlled analgesia and pain, Parkinson's disease (motor and cognition), stroke (motor), epilepsy, schizophrenia, and alcohol addiction. Assessment of bias showed that most of the studies had low risk of biases, and sensitivity analysis for bias did not change these results. Effect sizes vary from 0.01 to 0.70 and were significant in about 8 conditions, with the largest effect size being in postoperative acute pain and smaller in stroke motor recovery (nonsignificant when combined with robotic therapy).

CONCLUSION

All recommendations listed here are based on current published PubMed-indexed data. Despite high levels of evidence in some conditions, it must be underscored that effect sizes and duration of effects are often limited; thus, real clinical impact needs to be further determined with different study designs.

Analgesic Effect of Noninvasive Brain Stimulation for Neuropathic Pain Patients: A Systematic Review

Introduction

The objective of this review is to systematically summarize the consensus on best practices for different NP conditions of the two most commonly utilized noninvasive brain stimulation (NIBS) technologies, repetitive transcranial magnetic stimulation (rTMS), and transcranial direct current stimulation (tDCS).

Methods

PubMed was searched according to the predetermined keywords and criteria. Only English language studies and studies published up to January 31, 2020 were taken into consideration. Meta-analyses, reviews, and systematic reviews were excluded first, and those related to animal studies or involving healthy volunteers were also excluded. Finally, 29 studies covering 826 NP patients were reviewed.

Results

The results from the 24 enrolled studies and 736 NP patients indicate that rTMS successfully relieved the pain symptoms of 715 (97.1%) NP patients. Also, five studies involving 95 NP patients (81.4%) also showed that tDCS successfully relieved NP. In the included studied, the M1 region plays a key role in the analgesic treatment of NIBS. The motor evoked potentials (MEPs), the 10–20 electroencephalography system (EEG 10/20 system), and neuro-navigation methods are used in clinical practice to locate therapeutic targets. Based on the results of the review, the stimulation parameters of rTMS that best induce an analgesic effect are a stimulation frequency of 10–20 Hz, a stimulation intensity of 80–120% of RMT, 1000–2000 pulses, and 5–10 sessions, and the most effective parameters of tDCS are a current intensity of 2 mA, a session duration of 20–30 min, and 5–10 sessions.

Conclusions

Our systematically reviewed the evidence for positive and negative responses to rTMS and tDCS for NP patient care and underscores the analgesic efficacy of NIBS in patients with NP. The treatment of NP should allow the design of optimal treatments for individual patients.

Transcranial direct current stimulation (a-tCDS) after subacromial injections in patients with subacromial pain syndrome: a randomized controlled pilot study

BACKGROUND

Subacromial pain syndrome (SAPS) is a common complaint in orthopaedics. Subacromial corticosteroid injections (CSI) can relieve pain in the short term. Anodal transcranial direct current stimulation (a-tDCS) has been used for symptomatic pain relief in a variety of chronic pain conditions. The aim of this pilot study was to assess whether the application a-tDCS could enhance the symptomatic relief provided by CSI in patients affected by SAPS.

METHODS

Thirty-eight participants (18 to 65-year-old) suffering from SAPS were recruited to have a CSI and randomly allocated to receive, 1 weeks post CSI, real a-tDCS (r-tDCS), sham tDCS (s-tDCS) or no intervention (Control). Upper limb function was measured 1 week prior to the CSI, at the 2- and 4-week follow-ups using self-administered questionnaires and physical measures. Self-reported pain and activity during each day were logged by the participants using visual analog scales (VAS). Differences between groups were tested using repeated-measures ANOVAs.

RESULTS

Pain VAS and the Single Assessment Numeric Evaluation scale (SANE) showed significant improvement from baseline 2 weeks and 4 weeks after CSI in all groups (p < 0.05). There were no significant group X time interaction 2 weeks following tDCS treatment in any of the variables.

CONCLUSION

All groups showed significant improvement in pain VAS and SANE scores following the CSI. One session of a-tDCS treatment 2 weeks following CSI did not result in any additive or potentializing effects when compared to a s-tDCS or a control group.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03967574 . Registered 30 May 2019 - Retrospectively registered.

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.

Transcranial Direct Current Stimulation Combined With Therapeutic Exercise in Chronic Low Back Pain: Protocol of a Randomized Controlled Trial

OBJECTIVE

Although some studies have shown the clinical benefits of therapeutic exercise in chronic nonspecific low back pain, the effect sizes are generally small to moderate and recurrence rates are high. Transcranial direct current stimulation (tDCS) has been used to modulate pain-processing systems and motor outputs and has the potential to optimize the clinical benefits of therapeutic exercise. However, evidence for this combination is still lacking. The purpose of this protocol for a randomized clinical trial is to investigate whether the combination of tDCS and therapeutic exercise is more effective in relieving pain than therapeutic exercise alone.

METHODS

This 2-arm, randomized controlled clinical trial will take place at the Federal University of Piauí, Brazil. Sixty patients will be randomized into 2 groups to receive tDCS (real/sham) + exercise therapies for 12 sessions over a period of 4 weeks. Pain intensity, sensory and affective aspects of pain, physical functioning, kinesiophobia, and global perceived effect will be recorded before treatment and at 4 weeks, 3 months, and 6 months after randomization. Data will be collected by an examiner unaware of (blind to) the treatment allocation.

IMPACT

This trial can potentially provide important information and assist in clinical decision-making on the combined use of tDCS to optimize the clinical benefits of therapeutic exercise in patients with chronic nonspecific low back pain.

No efficacy of transcranial direct current stimulation on chronic migraine with medication overuse: A double blind, randomised clinical trial

Background

Transcranial direct current stimulation was suggested to provide beneficial effects in chronic migraine, a condition often associated with medication overuse for which no long-term therapy is available.

Methods

We conducted a randomised controlled trial to assess long-term efficacy of transcranial direct current stimulation. Adults diagnosed with chronic migraine and medication overuse were assigned to receive in a 1:1:1 ratio anodal, cathodal, or sham transcranial direct current stimulation daily for five consecutive days, along with standardised drug withdrawal protocol. Primary outcome was 50% reduction of days of headache per month at 12 months. Co-secondary outcomes were 50% reduction of days of headache per month at 6 months, reduction of analgesic intake per month, and change in disability and quality of life, catastrophising, depression, state and trait anxiety, dependence attitude and allodynia intensity. Patients were not allowed to take any migraine prophylaxis drug for the entire study period.

Results

We randomly allocated 135 patients to anodal (44), cathodal (45), and sham (46) transcranial direct current stimulation. At 6 and 12 months, the percentage of reduction of days of headache and number of analgesics per month ranged between 48.5% and 64.7%, without differences between transcranial direct current stimulation (cathodal, anodal, or the results obtained from the two arms of treatment, anodal plus cathodal) and sham. Catastrophising attitude significantly reduced at 12 months in all groups. There was no difference for the other secondary outcomes.

Conclusions

Transcranial direct current stimulation did not influence the short and long-term course of chronic migraine with medication overuse after acute drug withdrawal. Behavioral and educational measures and support for patients’ pain management could provide long-term improvement and low relapse rate. Trial registration number NCT04228809

The Analgesic Effect of Transcranial Direct Current Stimulation (tDCS) combined with Physical Therapy on Common Musculoskeletal Conditions: A Systematic Review and Meta-Analysis

BACKGROUND

The analgesic effects of transcranial Direct Current Stimulation (tDCS) combined with physical therapy remain unclear.

OBJECTIVE

To systematically review available evidence comparing tDCS with any physical therapy modality (PTM) to PTM alone or PTM with sham tDCS on pain relief on common musculoskeletal (MSK) conditions, namely knee osteoarthritis (KOA), chronic low back pain (CLBP), myofascial pain syndrome (MPS) and fibromyalgia.

METHODS

EMBASE and MEDLINE were searched from inception to April 2019 for randomized controlled trials. Reviewers independently assessed the studies quality and extracted data according to the PRISMA protocol. The GRADE approach was used to asses quality of evidence and a "Summary of Findings" table was created. The analyses used random-effects model. The primary outcome was pain reduction after treatment.

RESULTS

Eight articles were included. Only one study had low risk of bias. Quality of evidence was considered low or very low. Significant reduction in pain scores were found for fibromyalgia and KOA (Standardized mean difference (SMD) = -1.94 [95% CI: -3.37 to -0.49; I ²=76.4%] and SMD = -2.35 [95% CI: -3.63 to -1.06; I ²=69.7%] respectively). Subgroup analysis considering the type of PTM despite MSK condition revealed significant reduction in pain scores for exercise, SMD = -1.20 [95% CI: -1.683 to -0.717; I ²=10.8%].

CONCLUSIONS

Large heterogeneity and low quality of evidence and limited number of studies were found. Results suggest a potential analgesic effect of tDCS in combination with a PTM for fibromyalgia and KOA. Subgroup analysis suggests a stronger effect of tDCS when combined with an exercise based PTM.

The Effectiveness of Attention Bias Modification with and without Trans Cranial Direct Current Stimulation in Chronic Low Back Pain

Objective: The present study aimed to compare the effect of ABM (attention bias modification) with and without tDCS (transcranial direct current stimulation) on attention bias, pain intensity, and disability due to pain and pain-related psychological consequences, such as depression, anxiety, and stress. Method : Using convenience sampling, 60 individuals who met the criteria for chronic low back pain (LBP) were selected and randomly assigned in to 2 experimental groups and 2 control and sham-tDCS groups. The experimental ABM group received 5 sessions of the dot-probe task, while the second experimental group received 5 sessions of dot-probe task combined with tDCS. Results: The findings indicated that ABM and ABM+tDCS could reduce attention bias and pain-related psychological consequences significantly, compared to the control and sham groups. Also, attention bias and pain outcomes (depression, anxiety, disability due to pain and pain intensity) remained in ABM+tDCS group than in ABM group in a 1-month follow-up. Conclusion: It was found that tDCS + ABM had no additional effects at the end of intervention, but led to more long-lasting effects in 1-month follow-up. Randomized clinical trial registry number: IRCT20171107037306N1.

Targeting the Autonomic Nervous System Balance in Patients with Chronic Low Back Pain Using Transcranial Alternating Current Stimulation: A Randomized, Crossover, Double-Blind, Placebo-Controlled Pilot Study

Background

Chronic low back pain (CLBP) is characterized by an alteration in pain processing by the central nervous system that may affect autonomic nervous system (ANS) balance. Heart rate variability (HRV) reflects the balance of parasympathetic and sympathetic ANS activation. In particular, respiratory sinus arrhythmia (RSA) solely reflects parasympathetic input and is reduced in CLBP patients. Yet, it remains unknown if non-invasive brain stimulation can alter ANS balance in CLBP patients.

Objective

To evaluate if non-invasive brain stimulation modulates the ANS, we analyzed HRV metrics collected in a previously published study of transcranial alternating current stimulation (tACS) for the modulation of CLBP through enhancing alpha oscillations. We hypothesized that tACS would increase RSA.

Methods

A randomized, crossover, double-blind, sham-controlled pilot study was conducted to investigate the effects of 10Hz-tACS on metrics of ANS balance calculated from electrocardiogram (ECG). ECG data were collected for 2 mins before and after 40 mins of 10Hz-tACS or sham stimulation.

Results

There were no significant changes in RSA or other frequency-domain HRV components from 10Hz-tACS. However, exploratory time-domain HRV analyses revealed a significant increase in the standard deviation of normal intervals between R-peaks (SDNN), a measure of ANS balance, for 10Hz-tACS relative to sham.

Conclusion

Although tACS did not significantly increase RSA, we found in an exploratory analysis that tACS modulated an integrated HRV measure of both ANS branches. These findings support the further study of how the ANS and alpha oscillations interact and are modulated by tACS.

ClinicalTrials.gov

Transcranial Alternating Current Stimulation in Back Pain – Pilot Study, NCT03243084.

Transcranial Direct Current Stimulation to Improve the Dysfunction of Descending Pain Modulatory System Related to Opioids in Chronic Non-cancer Pain: An Integrative Review of Neurobiology and Meta-Analysis

Background: Opioid long-term therapy can produce tolerance, opioid-induced hyperalgesia (OIH), and it induces dysfunction in pain descending pain inhibitory system (DPIS). Objectives: This integrative review with meta-analysis aimed: (i) To discuss the potential mechanisms involved in analgesic tolerance and opioid-induced hyperalgesia (OIH). (ii) To examine how the opioid can affect the function of DPIS. (ii) To show evidence about the tDCS as an approach to treat acute and chronic pain. (iii) To discuss the effect of tDCS on DPIS and how it can counter-regulate the OIH. (iv) To draw perspectives for the future about the tDCS effects as an approach to improve the dysfunction in the DPIS in chronic non-cancer pain. Methods: Relevant published randomized clinical trials (RCT) comparing active (irrespective of the stimulation protocol) to sham tDCS for treating chronic non-cancer pain were identified, and risk of bias was assessed. We searched trials in PubMed, EMBASE and Cochrane trials databases. tDCS protocols accepted were application in areas of the primary motor cortex (M1), dorsolateral prefrontal cortex (DLPFC), or occipital area. Results: Fifty-nine studies were fully reviewed, and 24 with moderate to the high-quality methodology were included. tDCS improved chronic pain with a moderate effect size [pooled standardized mean difference; -0.66; 95% confidence interval (CI) -0.91 to -0.41]. On average, active protocols led to 27.26% less pain at the end of treatment compared to sham [95% CI; 15.89-32.90%]. Protocol varied in terms of anodal or cathodal stimulation, areas of stimulation (M1 and DLPFC the most common), number of sessions (from 5 to 20) and current intensity (from 1 to 2 mA). The time of application was 20 min in 92% of protocols. Conclusion: In comparison with sham stimulation, tDCS demonstrated a superior effect in reducing chronic pain conditions. They give perspectives that the top-down neuromodulator effects of tDCS are a promising approach to improve management in refractory chronic not-cancer related pain and to enhance dysfunctional neuronal circuitries involved in the DPIS and other pain dimensions and improve pain control with a therapeutic opioid-free. However, further studies are needed to determine individualized protocols according to a biopsychosocial perspective.

Transcranial direct current stimulation reduces seizure frequency in patients with refractory focal epilepsy: A randomized, double-blind, sham-controlled, and three-arm parallel multicenter study

BACKGROUND

Transcranial direct current stimulation (tDCS) has been explored in epilepsy with limited samples, varied parameters, and inconclusive results. We aimed to study the efficacy of tDCS for patients with refractory focal epilepsy.

METHOD

We conducted a randomized, double-blind, sham-controlled, and three-arm (Group 1 (sham), Group 2 (20-min), and Group 3 (2 × 20-min)) tDCS parallel multicenter study. The primary outcome measurement was seizure frequencies (SFs). The study consisted of 28-days baseline, 14-days treatment, and 56-days follow-up. The cathode was placed over the epileptogenic focus, and the current intensity was 2 mA. The generalized estimating equations model, one-way analysis of variance, chi-square and Kruskal-Wallis test were used for analysis.

RESULTS

Of the 82 enrolled patients, 70 patients were included for final analysis (Group 1, n = 21; Group 2, n = 24; and Group 3, n = 25). There was a significant reduction in SFs for both active tDCS groups compared with the sham group. Patients in Group 2 showed a significantly 50.73-21.91% greater reduction in SFs that lasted for 4 weeks (p = 0.008-0.060). Patients in Group 3 showed a significantly 63.19-49.79% greater reduction in SFs compared with the sham group that lasted for 5 weeks (p = 0.011-0.045). Patients in Group 3 had a 64.98-66.32% greater reduction in SFs at W9-W10, when compared with Group 2 (p = 0.021-0.022).

CONCLUSION

Fourteen consecutive days tDCS significantly decreased SFs in patients with refractory focal epilepsy, with 2 × 20-min daily stimulation protocol being superior to 20-min daily stimulation protocol.

Randomized controlled trial of TDCS on cognition in 201 seniors with mild neurocognitive disorder

OBJECTIVE

To examine the efficacy and safety of combined transcranial direct current stimulation (tDCS) and working memory training (WMT) in enhancing the cognitive functions for individuals with mild neurocognitive disorder due to AD (NCD-AD).

METHODS

In this double-blind, sham-controlled randomized clinical trial (RCT), 201 patients with NCD-AD were randomly assigned for a 4-week intervention of either a combination of tDCS and WMT, sham tDCS and WMT, or tDCS and control cognitive training (CCT). Global cognition and domain-specific cognitive function were assessed before and after the intervention with Alzheimer's disease assessment scale-cognitive subscale (ADAS-Cog), category verbal fluency test, logical memory, digit, and visual span tests.

RESULTS

Study participants did not show intervention group differences in baseline demographics, or cognitive characteristics (ANOVA). Cognitive enhancement was found across three groups after 4 weeks intervention. Combined tDCS-WMT group showed significantly greater improvement compared with single-modality groups in delayed recall (P = 0.043, η²  = 0.036) and working memory capacity (P = 0.04, η²  = 0.038) at 4th week, and logical memory at 12th week (P = 0.042, η²  = 0.037). Adverse events, including skin lesions (2.2%), were similar between groups.

INTERPRETATION

tDCS or WMT could be a safe, feasible, and effective intervention for individuals with NCD-AD. A combination of tDCS and WMT presents greater cognitive enhancement, which may highlight the potential synergistic effects of combined modality intervention on cognition.

Transcranial direct current stimulation for nonspecific low back pain: double-blind randomized sham-controlled trial

Introduction: Low back pain is recognized as a major cause of morbidity worldwide. Between 70 and 80% of adults experience at least one occasion of low back pain with duration of 3 months or longer in their lifetime. Aside from the classic treatment methods, there are other new techniques yet to be clinically investigated. Transcranial direct current stimulation (tDCS) has been reported to alleviate pain by affecting the central nervous system. To date only a small number of studies have been published on the effects of tDCS on chronic low back pain. Some of these were pilot studies and others were low-powered in terms of their inference. Therefore the clinical application of tDCS requires further careful evaluation. Objective: To assess the efficacy of transcranial direct current stimulation for treatment of chronic nonspecific low back pain. Materials and methods: We carried out a double-blind randomized sham-controlled trial in a University Hospital. In total 70 people (15 women) with low back pain were randomized to either active or sham stimulation. The primary outcome was intensity of low back pain on the Visual Analog Scale. We also used the Oswestry Disability Questionnaire to evaluate the effects of back pain on daily activities. For the active stimulation group we administered 2 mA tDCS, 20 minutes for each session, once daily, 5 days per week for 2 weeks, totaling 10 sessions. For the sham stimulation group a similar program was followed with no stimulation. Both groups used analgesic medication. Results: Within-group analysis showed that an initial decrease in pain intensity was significant in both groups (both p < 0.001). However, pain reduction became stable only in the active treatment group. There was a significant difference in the pattern of change in mean pain scores in favor of tDCS (p < 0.001). Active treatment also significantly reduced disability scores (all p values < 0.001), whereas participants in the sham treatment group did not experience functional recovery. Mixed ANOVA indicated that the pattern of change in mean scores of disability differed between the two groups throughout the study course, in favor of active stimulation (p < 0.001). Conclusion: Transcranial direct current stimulation is an effective and safe initial treatment for chronic nonspecific low back pain, and the benefits remain for at least several months.

Conservative Interventions Reduce Fear in Individuals With Chronic Low Back Pain: A Systematic Review

OBJECTIVE

To systematically review and critically appraise the effectiveness of conservative and surgical interventions to reduce fear in studies of people with chronic low back pain, based on the analysis of randomized controlled trials for which fear was a primary or secondary outcome.

DATA SOURCES

Electronic databases PubMed, CINAHL, PsycINFO, PEDro, and CENTRAL, as well as manual searches and grey literature were searched from inception until May 2019.

STUDY SELECTION

Randomized controlled trials analyzing the effectiveness of conservative and surgical interventions to reduce fear were included.

DATA EXTRACTION

Two reviewers independently conducted the search strategy, study selection, data extraction, risk of bias assessment, and quality of the evidence judgment.

DATA SYNTHESIS

Sixty-one studies (n=7201) were included. A large number of fear-related search terms were used but only 3 fear constructs (kinesiophobia, fear-avoidance beliefs, fear of falling) were measured in the included studies. Multidisciplinary and psychological interventions as well as exercise reduced kinesiophobia. Fear-avoidance beliefs were reduced by the aforementioned interventions, manual therapy, and electrotherapy. A multidisciplinary intervention reduced the fear of falling. There was moderate evidence of multidisciplinary interventions and exercise to reduce kinesiophobia. There was moderate evidence of manual therapy and electrotherapy to reduce fear-avoidance beliefs.

CONCLUSIONS

The present systematic review highlights the potential effectiveness of conservative interventions to reduce kinesiophobia and fear-avoidance beliefs in individuals with chronic low back pain. This information can help health professionals to reduce fear when treating patients with this condition.

The Response of the Primary Motor Cortex to Neuromodulation is Altered in Chronic Low Back Pain: A Preliminary Study

Objective

Neuromodulation is increasingly investigated for the treatment of low back pain (LBP). However, the neurophysiological effects of common neuromodulatory techniques (anodal transcranial direct current stimulation [tDCS] and peripheral electrical stimulation [PES]) have not been investigated in people with chronic LBP. Here we aimed to compare the effect of three neuromodulatory protocols (anodal tDCS, high intensity PES, and a priming protocol of combined tDCS/PES) on primary motor cortex (M1) excitability in people with and without chronic LBP.

Design

Cross-sectional.

Setting

University laboratory.

Participants

Ten individuals with chronic LBP and 10 pain-free controls.

Methods

Participants received four interventions in random order across separate sessions: 1) anodal tDCS to M1 + PES to the back muscles; 2) tDCS + sham PES; 3) sham tDCS + PES; or 4) sham tDCS + sham PES. Motor cortical excitability (map volume, discrete map peaks, and cortical silent period [CSP]) was measured before and after each intervention.

Results

Anodal tDCS increased M1 excitability (increased map volume and reduced CSP) in controls but had no effect in the LBP group. PES reduced M1 excitability in both groups. The combined tDCS + PES treatment increased M1 excitability in the LBP group but had no effect in controls.

Conclusions

The neurophysiological response to common neuromodulatory treatments differs between people with and without LBP. This has relevance for the design and tailoring of neuromodulation in pain. Further, if the goal of treatment is to increase M1 excitability, a priming protocol (e.g., combined tDCS + PES) may be more effective than tDCS alone.

Effects of Combining a Brief Cognitive Intervention with Transcranial Direct Current Stimulation on Pain Tolerance: A Randomized Controlled Pilot Study

Objective

Cognitive behavioral therapy has been shown to be effective for treating chronic pain, and a growing literature shows the potential analgesic effects of minimally invasive brain stimulation. However, few studies have systematically investigated the potential benefits associated with combining approaches. The goal of this pilot laboratory study was to investigate the combination of a brief cognitive restructuring intervention and transcranial direct current stimulation (tDCS) over the left dorsolateral prefrontal cortex in affecting pain tolerance.

Design

Randomized, double-blind, placebo-controlled laboratory pilot.

Setting

Medical University of South Carolina.

Subjects

A total of 79 healthy adult volunteers.

Methods

Subjects were randomized into one of six groups: 1) anodal tDCS plus a brief cognitive intervention (BCI); 2) anodal tDCS plus pain education; 3) cathodal tDCS plus BCI; 4) cathodal tDCS plus pain education; 5) sham tDCS plus BCI; and 6) sham tDCS plus pain education. Participants underwent thermal pain tolerance testing pre- and postintervention using the Method of Limits.

Results

A significant main effect for time (pre-post intervention) was found, as well as for baseline thermal pain tolerance (covariate) in the model. A significant time × group interaction effect was found on thermal pain tolerance. Each of the five groups that received at least one active intervention outperformed the group receiving sham tDCS and pain education only (i.e., control group), with the exception of the anodal tDCS + education-only group. Cathodal tDCS combined with the BCI produced the largest analgesic effect.

Conclusions

Combining cathodal tDCS with BCI yielded the largest analgesic effect of all the conditions tested. Future research might find stronger interactive effects of combined tDCS and a cognitive intervention with larger doses of each intervention. Because this controlled laboratory pilot employed an acute pain analogue and the cognitive intervention did not authentically represent cognitive behavioral therapy per se, the implications of the findings on chronic pain management remain unclear.

Effect of Transcranial Direct Current Stimulation of the Motor Cortex on Visceral Pain in Patients with Hepatocellular Carcinoma

Objective

Hepatocellular carcinoma (HCC) is frequently associated with visceral pain. Transcranial direct current stimulation (tDCS) has been proven to reduce chronic pain; however, its effectiveness in malignant visceral pain is unknown. This study aimed to investigate the effects of tDCS in patients with visceral pain due to HCC.

Design

This is a randomized, sham-controlled, double-blind, prospective study. Forty patients with visceral pain due to HCC were enrolled and randomly assigned into two groups: a real and a sham group; tDCS was applied over the primary motor area (M1) for 10 consecutive days (2 mA, 30 minutes). Patient's pain was evaluated by visual analog scale (VAS) and verbal descriptor scale (VDS) and for depression by Hamilton rating scale (HAM-D). Evaluation was done at prestimulation, after the first, fifth, and 10th sessions, and one month after the end of stimulation sessions.

Results

Real tDCS showed a reduction of VDS (P = 0.001, F = 4.01) and VAS (P = 0.001, F = 6.817) for HAM-D (P = 0.012, F = 5,077); the effect started from the fifth session and continued to one month after stimulation, while in the sham group the effect persisted for five days only. Percentage reduction in all scales in the real group after the 10th session was as follows: VDS P = 0.008, VAS P = 0.001, HAM-D = 0.001; for one month after the end of stimulation, it was as follows: VDS P = 0.001, VAS P = 0.037, HAM-D = 0.002.

Conclusions

tDCS proved to be an effective and clinically relevant therapeutic strategy for visceral pain due to HCC.

Effect of 12-Week Whole-Body Vibration Exercise on Lumbopelvic Proprioception and Pain Control in Young Adults with Nonspecific Low Back Pain

BACKGROUND Nonspecific low back pain (NSLBP) accounts for a large proportion of low back pain cases. The present study aimed to investigate the effect of the whole-body vibration (WBV) exercise on lumbar proprioception in NSLBP patients. It was hypothesized that WBV exercise enhances lumbar proprioception. MATERIAL AND METHODS Forty-two patients with NSLBP performed an exercise program 3 times a week for a total of 12 weeks of WBV. The lumbar proprioception was measured by joint position sense. Outcomes were lumbar angle deviation and visual analogue scale (VAS) score. RESULTS After the 12-week WBV exercise, lumbar flexion angle deviation was reduced from 3.65±2.26° to 1.90±1.07° (P=0.0001), and extension angle deviation was reduced from 3.06±1.85° to 1.61±0.75° (P=0.0001), significantly lower than baseline. After participating in the 12-week WBV exercise, a significant pain reduction was observed (P=0.0001). Men in the whole group (n=32) indicated significantly lower angle deviations in flexion and extension, whereas women (n=10) indicated significantly lower flexion angle deviation (P=0.037), and no significant difference was found in extension angle deviation (P=0.052). However, by subdividing the entire group (n=42) into poor and good proprioceptive groups, WBV exercise presented significant enhancement of lumbar proprioceptive ability in the poor flexion proprioception subgroup, poor extension proprioception subgroup, and good extension proprioception subgroup (each P=0.0001), but not in the subgroup with good flexion proprioceptive ability (P=0.165). CONCLUSIONS Lumbar flexion and extension proprioception as measured by joint position sense was significantly enhanced and pain was significantly reduced after 12-week WBV exercise in NSLBP patients. However, the patients with good flexion proprioceptive ability had limited proprioceptive enhancement.

Latin American and Caribbean consensus on noninvasive central nervous system neuromodulation for chronic pain management (LAC2-NIN-CP)

Supplemental Digital Content is Available in the Text.

Introduction:

Chronic pain (CP) is highly prevalent and generally undertreated health condition. Noninvasive brain stimulation may contribute to decrease pain intensity and influence other aspects related to CP.

Objective:

To provide consensus-based recommendations for the use of noninvasive brain stimulation in clinical practice.

Methods:

Systematic review of the literature searching for randomized clinical trials followed by consensus panel. Recommendations also involved a cost-estimation study.

Results:

The systematic review wielded 24 transcranial direct current stimulation (tDCS) and 22 repetitive transcranial magnetic stimulation (rTMS) studies. The following recommendations were provided: (1) Level A for anodal tDCS over the primary motor cortex (M1) in fibromyalgia, and level B for peripheral neuropathic pain, abdominal pain, and migraine; bifrontal (F3/F4) tDCS and M1 high-definition (HD)-tDCS for fibromyalgia; Oz/Cz tDCS for migraine and for secondary benefits such as improvement in quality of life, decrease in anxiety, and increase in pressure pain threshold; (2) level A recommendation for high-frequency (HF) rTMS over M1 for fibromyalgia and neuropathic pain, and level B for myofascial or musculoskeletal pain, complex regional pain syndrome, and migraine; (3) level A recommendation against the use of anodal M1 tDCS for low back pain; and (4) level B recommendation against the use of HF rTMS over the left dorsolateral prefrontal cortex in the control of pain.

Conclusion:

Transcranial DCS and rTMS are recommended techniques to be used in the control of CP conditions, with low to moderate analgesic effects, and no severe adverse events. These recommendations are based on a systematic review of the literature and a consensus made by experts in the field. Readers should use it as part of the resources available to decision-making.

Transcranial Direct Current Stimulation as a Therapeutic Tool for Chronic Pain

Transcranial direct current stimulation (tDCS) modulates spontaneous neuronal activity that can generate long-term neuroplastic changes. It has been used in numerous therapeutic trials showing significant clinical effects especially when combined with other behavioral therapies. One area of intensive tDCS research is chronic pain. Since the initial tDCS trials for chronic pain treatment using current parameters of stimulation, more than 60 clinical trials have been published testing its effects in different pain syndromes. However, as the field moves in the direction of clinical application, several aspects need to be taken into consideration regarding tDCS effectiveness and parameters of stimulation. In this article, we reviewed the evidence of tDCS effects for the treatment of chronic pain and critically analyzed the literature pertaining its safety and efficacy, and how to optimize tDCS clinical effects in a therapeutic setting. We discuss optimization of tDCS effects in 3 different domains: (i) parameters of stimulation, (ii) combination therapies, and (iii) subject selection. This article aims to provide insights for the development of future tDCS clinical trials.

Anodal Transcranial Direct-Current Stimulation to Enhance Rehabilitation in Individuals With Rotator Cuff Tendinopathy: A Triple-Blind Randomized Controlled Trial

Background Anodal transcranial direct-current stimulation (a-tDCS) has been shown to enhance the effects of sensorimotor training in neurological populations. Sensorimotor training leads to reduced pain and increased function in the treatment of rotator cuff tendinopathy. The addition of a-tDCS during a rehabilitation program centered on sensorimotor training may improve treatment outcomes in individuals with rotator cuff tendinopathy. Objective To compare 2 groups of individuals with rotator cuff tendinopathy, one receiving a rehabilitation program centered on sensorimotor training with a-tDCS and the other receiving the same rehabilitation program with sham a-tDCS. Methods In this triple-blind, parallel-group randomized controlled trial, 40 adults with rotator cuff tendinopathy participated in a 6-week rehabilitation program (8 treatments with home exercises and including sensorimotor training, patient education, and strengthening). They were randomly assigned to 1 of 2 groups to receive either real a-tDCS (stimulation, 1.5 mA for 30 minutes) or sham a-tDCS during the first 5 treatments. Symptoms and functional limitations (Disabilities of the Arm, Shoulder and Hand questionnaire, Western Ontario Rotator Cuff index) of all participants were evaluated at baseline and at 3, 6, and 12 weeks. Acromiohumeral distances (ultrasonographic measurement at 0°, 45°, and 60° of arm elevation) were assessed at baseline and 6 weeks. Two-way or 3-way repeated-measures analyses of variance were used for statistical analyses. Results Both groups showed statistically significant improvement in Disabilities of the Arm, Shoulder and Hand questionnaire and Western Ontario Rotator Cuff index scores at 3, 6, and 12 weeks, and in acromiohumeral distance at 45° and 60° at 6 weeks (P<.05). No significant group-by-time interaction was observed for all outcomes (P>.43). Conclusion Results do not demonstrate any improved treatment outcomes from the addition of a-tDCS during a rehabilitation program for individuals with rotator cuff tendinopathy. Level of Evidence Therapy, level 1b. J Orthop Sports Phys Ther 2018;48(7):541-551. Epub 10 May 2018. doi:10.2519/jospt.2018.7871.

Principles of designing a clinical trial: optimizing chances of trial success

PURPOSE OF REVIEW

Clinical trials are essential to advance health care and develop new therapies. In this review we discuss the underlying principles of clinical trial design with an emphasis on assessing design risks that lead to trial failure as well as negative trials. While of general interest, this is perhaps particularly timely for the neuromodulation community, given the paucity of well-designed trials in the field. We give some examples from the phantom limb pain (PLP) literature.

RECENT FINDINGS

It is critical to gather as much preliminary data as possible and to know how to interpret it in order to choose an appropriate trial design. Therefore, the investigator needs to effectively assess the likely trial design risk/benefit ratio with a view to maximizing the chance of a meaningful outcome, whether this outcome rejects or fails to reject the null hypothesis. This analysis is especially important in a complex and heterogeneous disorder such as PLP, which has had many negative trials.

SUMMARY

We discuss the factors pertaining to a strong trial design benefit/risk assessment, how late trial phases require greater support from preliminary data, how to design trials to minimize risks, maximize benefits, and optimize internal validity as well as the chances of a positive outcome. We highlight the need for investigators to incorporate best practice in trial design to increase the chances of success, to always anticipate unexpected challenges during the trial.

The effects of transcranial direct current stimulation (tDCS) combined with group exercise treatment in subjects with chronic low back pain: a pilot randomized control trial

OBJECTIVE

To test the efficacy of transcranial direct current stimulation (tDCS) in addition to group exercise on non-specific chronic low back pain.

DESIGN

Double-blinded randomized control trial.

SUBJECTS

Patients with non-specific chronic low back pain.

METHODS

A total of 35 subjects were recruited and allocated to real- or sham-tDCS followed by a group exercise protocol. Each patient underwent five sessions of brain stimulation followed by 10 sessions of group exercise. Subjects were evaluated before and after tDCS, after group exercise and one month after the combined treatment. Outcome measures were Visual Analog Scale for pain intensity, Roland Morris Disability Questionnaire, EuroQuol-5 Dimension and Patient Health Questionnaire-9.

RESULTS

Significant between-group difference in pain intensity (-27.7 ± 30.4 mm in real-tDCS group compared to -2.2 ± 30.1 mm in sham-tDCS group) and Patient Health Questionnaire-9 (-4.9 ± 4.2 in real-tDCS group compared to -1.1 ± 2.7 in sham-tDCS group) was found one month after the combined treatment ( P < 0.05).

CONCLUSION

Our results showed that real-tDCS can induce significant larger effects on pain and psychological well-being, compared to sham-tDCS, when it is associated with a group exercise program. The effects were observed mostly in the follow-up.

Non-invasive brain stimulation techniques for chronic pain

BACKGROUND

This is an updated version of the original Cochrane Review published in 2010, Issue 9, and last updated in 2014, Issue 4. Non-invasive brain stimulation techniques aim to induce an electrical stimulation of the brain in an attempt to reduce chronic pain by directly altering brain activity. They include repetitive transcranial magnetic stimulation (rTMS), cranial electrotherapy stimulation (CES), transcranial direct current stimulation (tDCS), transcranial random noise stimulation (tRNS) and reduced impedance non-invasive cortical electrostimulation (RINCE).

OBJECTIVES

To evaluate the efficacy of non-invasive cortical stimulation techniques in the treatment of chronic pain.

SEARCH METHODS

For this update we searched CENTRAL, MEDLINE, Embase, CINAHL, PsycINFO, LILACS and clinical trials registers from July 2013 to October 2017.

SELECTION CRITERIA

Randomised and quasi-randomised studies of rTMS, CES, tDCS, RINCE and tRNS if they employed a sham stimulation control group, recruited patients over the age of 18 years with pain of three months' duration or more, and measured pain as an outcome. Outcomes of interest were pain intensity measured using visual analogue scales or numerical rating scales, disability, quality of life and adverse events.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted and verified data. Where possible we entered data into meta-analyses, excluding studies judged as high risk of bias. We used the GRADE system to assess the quality of evidence for core comparisons, and created three 'Summary of findings' tables.

MAIN RESULTS

We included an additional 38 trials (involving 1225 randomised participants) in this update, making a total of 94 trials in the review (involving 2983 randomised participants). This update included a total of 42 rTMS studies, 11 CES, 36 tDCS, two RINCE and two tRNS. One study evaluated both rTMS and tDCS. We judged only four studies as low risk of bias across all key criteria. Using the GRADE criteria we judged the quality of evidence for each outcome, and for all comparisons as low or very low; in large part this was due to issues of blinding and of precision.rTMSMeta-analysis of rTMS studies versus sham for pain intensity at short-term follow-up (0 to < 1 week postintervention), (27 studies, involving 655 participants), demonstrated a small effect with heterogeneity (standardised mean difference (SMD) -0.22, 95% confidence interval (CI) -0.29 to -0.16, low-quality evidence). This equates to a 7% (95% CI 5% to 9%) reduction in pain, or a 0.40 (95% CI 0.53 to 0.32) point reduction on a 0 to 10 pain intensity scale, which does not meet the minimum clinically important difference threshold of 15% or greater. Pre-specified subgroup analyses did not find a difference between low-frequency stimulation (low-quality evidence) and rTMS applied to the prefrontal cortex compared to sham for reducing pain intensity at short-term follow-up (very low-quality evidence). High-frequency stimulation of the motor cortex in single-dose studies was associated with a small short-term reduction in pain intensity at short-term follow-up (low-quality evidence, pooled n = 249, SMD -0.38 95% CI -0.49 to -0.27). This equates to a 12% (95% CI 9% to 16%) reduction in pain, or a 0.77 (95% CI 0.55 to 0.99) point change on a 0 to 10 pain intensity scale, which does not achieve the minimum clinically important difference threshold of 15% or greater. The results from multiple-dose studies were heterogeneous and there was no evidence of an effect in this subgroup (very low-quality evidence). We did not find evidence that rTMS improved disability. Meta-analysis of studies of rTMS versus sham for quality of life (measured using the Fibromyalgia Impact Questionnaire (FIQ) at short-term follow-up demonstrated a positive effect (MD -10.80 95% CI -15.04 to -6.55, low-quality evidence).CESFor CES (five studies, 270 participants) we found no evidence of a difference between active stimulation and sham (SMD -0.24, 95% CI -0.48 to 0.01, low-quality evidence) for pain intensity. We found no evidence relating to the effectiveness of CES on disability. One study (36 participants) of CES versus sham for quality of life (measured using the FIQ) at short-term follow-up demonstrated a positive effect (MD -25.05 95% CI -37.82 to -12.28, very low-quality evidence).tDCSAnalysis of tDCS studies (27 studies, 747 participants) showed heterogeneity and a difference between active and sham stimulation (SMD -0.43 95% CI -0.63 to -0.22, very low-quality evidence) for pain intensity. This equates to a reduction of 0.82 (95% CI 0.42 to 1.2) points, or a percentage change of 17% (95% CI 9% to 25%) of the control group outcome. This point estimate meets our threshold for a minimum clinically important difference, though the lower confidence interval is substantially below that threshold. We found evidence of small study bias in the tDCS analyses. We did not find evidence that tDCS improved disability. Meta-analysis of studies of tDCS versus sham for quality of life (measured using different scales across studies) at short-term follow-up demonstrated a positive effect (SMD 0.66 95% CI 0.21 to 1.11, low-quality evidence).Adverse eventsAll forms of non-invasive brain stimulation and sham stimulation appear to be frequently associated with minor or transient side effects and there were two reported incidences of seizure, both related to the active rTMS intervention in the included studies. However many studies did not adequately report adverse events.

AUTHORS' CONCLUSIONS

There is very low-quality evidence that single doses of high-frequency rTMS of the motor cortex and tDCS may have short-term effects on chronic pain and quality of life but multiple sources of bias exist that may have influenced the observed effects. We did not find evidence that low-frequency rTMS, rTMS applied to the dorsolateral prefrontal cortex and CES are effective for reducing pain intensity in chronic pain. The broad conclusions of this review have not changed substantially for this update. There remains a need for substantially larger, rigorously designed studies, particularly of longer courses of stimulation. Future evidence may substantially impact upon the presented results.

Non-invasive brain stimulation techniques for chronic pain

BACKGROUND

This is an updated version of the original Cochrane Review published in 2010, Issue 9, and last updated in 2014, Issue 4. Non-invasive brain stimulation techniques aim to induce an electrical stimulation of the brain in an attempt to reduce chronic pain by directly altering brain activity. They include repetitive transcranial magnetic stimulation (rTMS), cranial electrotherapy stimulation (CES), transcranial direct current stimulation (tDCS), transcranial random noise stimulation (tRNS) and reduced impedance non-invasive cortical electrostimulation (RINCE).

OBJECTIVES

To evaluate the efficacy of non-invasive cortical stimulation techniques in the treatment of chronic pain.

SEARCH METHODS

For this update we searched CENTRAL, MEDLINE, Embase, CINAHL, PsycINFO, LILACS and clinical trials registers from July 2013 to October 2017.

SELECTION CRITERIA

Randomised and quasi-randomised studies of rTMS, CES, tDCS, RINCE and tRNS if they employed a sham stimulation control group, recruited patients over the age of 18 years with pain of three months' duration or more, and measured pain as an outcome. Outcomes of interest were pain intensity measured using visual analogue scales or numerical rating scales, disability, quality of life and adverse events.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted and verified data. Where possible we entered data into meta-analyses, excluding studies judged as high risk of bias. We used the GRADE system to assess the quality of evidence for core comparisons, and created three 'Summary of findings' tables.

MAIN RESULTS

We included an additional 38 trials (involving 1225 randomised participants) in this update, making a total of 94 trials in the review (involving 2983 randomised participants). This update included a total of 42 rTMS studies, 11 CES, 36 tDCS, two RINCE and two tRNS. One study evaluated both rTMS and tDCS. We judged only four studies as low risk of bias across all key criteria. Using the GRADE criteria we judged the quality of evidence for each outcome, and for all comparisons as low or very low; in large part this was due to issues of blinding and of precision.rTMSMeta-analysis of rTMS studies versus sham for pain intensity at short-term follow-up (0 to < 1 week postintervention), (27 studies, involving 655 participants), demonstrated a small effect with heterogeneity (standardised mean difference (SMD) -0.22, 95% confidence interval (CI) -0.29 to -0.16, low-quality evidence). This equates to a 7% (95% CI 5% to 9%) reduction in pain, or a 0.40 (95% CI 0.53 to 0.32) point reduction on a 0 to 10 pain intensity scale, which does not meet the minimum clinically important difference threshold of 15% or greater. Pre-specified subgroup analyses did not find a difference between low-frequency stimulation (low-quality evidence) and rTMS applied to the prefrontal cortex compared to sham for reducing pain intensity at short-term follow-up (very low-quality evidence). High-frequency stimulation of the motor cortex in single-dose studies was associated with a small short-term reduction in pain intensity at short-term follow-up (low-quality evidence, pooled n = 249, SMD -0.38 95% CI -0.49 to -0.27). This equates to a 12% (95% CI 9% to 16%) reduction in pain, or a 0.77 (95% CI 0.55 to 0.99) point change on a 0 to 10 pain intensity scale, which does not achieve the minimum clinically important difference threshold of 15% or greater. The results from multiple-dose studies were heterogeneous and there was no evidence of an effect in this subgroup (very low-quality evidence). We did not find evidence that rTMS improved disability. Meta-analysis of studies of rTMS versus sham for quality of life (measured using the Fibromyalgia Impact Questionnaire (FIQ) at short-term follow-up demonstrated a positive effect (MD -10.80 95% CI -15.04 to -6.55, low-quality evidence).CESFor CES (five studies, 270 participants) we found no evidence of a difference between active stimulation and sham (SMD -0.24, 95% CI -0.48 to 0.01, low-quality evidence) for pain intensity. We found no evidence relating to the effectiveness of CES on disability. One study (36 participants) of CES versus sham for quality of life (measured using the FIQ) at short-term follow-up demonstrated a positive effect (MD -25.05 95% CI -37.82 to -12.28, very low-quality evidence).tDCSAnalysis of tDCS studies (27 studies, 747 participants) showed heterogeneity and a difference between active and sham stimulation (SMD -0.43 95% CI -0.63 to -0.22, very low-quality evidence) for pain intensity. This equates to a reduction of 0.82 (95% CI 0.42 to 1.2) points, or a percentage change of 17% (95% CI 9% to 25%) of the control group outcome. This point estimate meets our threshold for a minimum clinically important difference, though the lower confidence interval is substantially below that threshold. We found evidence of small study bias in the tDCS analyses. We did not find evidence that tDCS improved disability. Meta-analysis of studies of tDCS versus sham for quality of life (measured using different scales across studies) at short-term follow-up demonstrated a positive effect (SMD 0.66 95% CI 0.21 to 1.11, low-quality evidence).Adverse eventsAll forms of non-invasive brain stimulation and sham stimulation appear to be frequently associated with minor or transient side effects and there were two reported incidences of seizure, both related to the active rTMS intervention in the included studies. However many studies did not adequately report adverse events.

AUTHORS' CONCLUSIONS

There is very low-quality evidence that single doses of high-frequency rTMS of the motor cortex and tDCS may have short-term effects on chronic pain and quality of life but multiple sources of bias exist that may have influenced the observed effects. We did not find evidence that low-frequency rTMS, rTMS applied to the dorsolateral prefrontal cortex and CES are effective for reducing pain intensity in chronic pain. The broad conclusions of this review have not changed substantially for this update. There remains a need for substantially larger, rigorously designed studies, particularly of longer courses of stimulation. Future evidence may substantially impact upon the presented results.