Repetitive transcranial magnetic stimulation and transcranial direct-current stimulation in neuropathic pain due to radiculopathy: a randomized sham-controlled comparative study

Motor cortex repetitive transcranial magnetic stimulation in fibromyalgia: a multicentre randomised controlled trial

BACKGROUND

Despite affecting 2-4% of the population worldwide, fibromyalgia often remains refractory to treatment. Here we report the first international randomised double-blind, sham-controlled trial developed to assess the efficacy of repetitive transcranial magnetic stimulation (rTMS) as an add-on therapy for fibromyalgia.

METHODS

Women aged ≥18 yr with fibromyalgia refractory to best available treatment were enrolled in Brazil, France, and Japan, and randomised to 10 Hz motor cortex (M1) rTMS, 3000 pulses day-1, or sham stimulation. This included 10 induction sessions over 2 weeks, followed by weekly maintenance (6 weeks), and fortnightly extended maintenance (8 weeks). Primary outcome was ≥50% pain reduction at week 8 compared with baseline. Secondary outcomes included pain interference, mood, global impression of change, and Fibromyalgia Impact Questionnaire (FIQ) scores at weeks 8 and 16.

RESULTS

We randomised 101 women (mean age 48 [range 25-83] yr) into active (n=52) or sham (n=49) arms. Bayesian analysis revealed a 99.4% probability of ≥50% pain reduction at week 8 in the active group vs sham (odds ratio [OR] 3.04; 95% credible interval [95% CrI] 1.26-8.06), with a number needed to treat of 4.54. Frequentist analysis confirmed that relative pain reduction was higher in the active than in the sham group (40.4% vs 18.4%, P=0.028). At week 16, this probability reduced to 34.2% (OR 0.815; 95% CrI 0.313-2.1), but the likelihood of FIQ score reduction was 79.1%. The intervention appeared safe.

CONCLUSIONS

Add-on M1-repetitive transcranial magnetic stimulation reduced pain intensity up to 8 weeks in women with fibromyalgia. Although analgesic effects waned, functional improvements remained during extended maintenance at week 16.

Non-invasive cerebral and spinal cord stimulation for motor and gait recovery in incomplete spinal cord injury: systematic review and meta-analysis

BACKGROUND

Spinal cord injury (SCI) leads to gait impairment and loss of motor function and can be traumatic or non-traumatic in nature. Recently there has been important progress in the field of non-invasive central nervous stimulation, which can target the brain or spinal cord. In this review we aim to compare the effect of non-invasive cerebral and spinal cord stimulation on gait recovery and motor strength of lower limbs in subjects with SCI.

METHODS

We conducted a search (from September 2022 until March 2024) using the PubMed, Cochrane, and PEDro databases, including all studies published since the year 2000. The protocol of the review followed PRISMA guidelines and only RCTs scoring above 5 on the PEDro scale were selected.

RESULTS

A total of 12 RCTs with 341 participants were included. When all studies were pooled together, non-invasive central nervous system stimulation had significant effects on Lower Extremity Motor Scale (LEMS) score and gait speed. However, data was less apparent when subgrouped by type and level of stimulation. Repetitive transcranial magnetic stimulation (rTMS) showed large effect on LEMS, however transcranial direct current stimulation (tDCS) displayed a small effect on motor strength and gait speed. No meta-analysis could be performed for non-invasive spinal cord stimulation due to a lack of studies.

CONCLUSIONS

When all non-invasive stimulation techniques were pooled together, significant effects on motor strength and gait function were observed. However, subgroup analyses based on stimulation types and levels revealed a significant reduction in these effects, particularly when categorized by stimulation type (rTMS and tDCS). Furthermore, a meta-analysis could not be conducted for non-invasive spinal cord stimulation due to a lack of studies (only one study each on tsDCS and tSCS). Therefore, more randomized controlled trials are needed to evaluate neuromodulation interventions in spinal cord injury, particularly at the spinal cord level. Registration This systematic review with meta-analysis was registered in PROSPERO under the ID 512864.

Repetitive transcranial magnetic stimulation for fibromyalgia: are we there yet?

Repetitive transcranial magnetic stimulation (rTMS) has increasingly been used to modify cortical maladaptive plastic changes shown to occur in fibromyalgia (FM) and to correlate with symptoms. Evidence for its efficacy is currently inconclusive, mainly due to heterogeneity of stimulation parameters used in trials available to date. Here, we reviewed the current evidence on the use of rTMS for FM control in the format of a narrative review, in which a systematic dissection of the different stimulation parameters would be possible. We conducted a search in Medline and Embase for controlled trials on rTMS in people with FM with at least 10 participants in each treatment arm, and treatment/follow-up of at least 3 weeks. The search identified 482 abstracts, of which 45 were screened to full review, and 11 met inclusion criteria. Six out of 11 trials were positive. The dorsolateral prefrontal cortex was the target in 218 patients (49.2%), and the primary motor cortex (M1) in 225 (50.8%). Studies targeting M1 at 10 Hz, with stimulation current delivered in the posterior-anterior, were systematically positive, frequently showing that maintenance sessions delivered weekly, and biweekly were able to maintain the analgesic effects seen after daily induction sessions. Studies assessing the effects of rTMS for FM are still marked by heterogeneity in stimulation petameters, choice of primary outcomes, and inclusion criteria. The selection of the stimulation parameters associated with significant analgesic effects is likely to benefit following larger multicenter trials and improve the overall management of pain and associated symptoms in people with FM.

Combined transcranial direct current stimulation and pain neuroscience education for chronic low back pain: a randomized controlled trial

OBJECTIVE

Priming the neural circuity likely targeted by pain neuroscience education (PNE), using transcranial direct current stimulation (tDCS) may enhance the efficacy of PNE. The aim of this study was to compare the effects of active tDCS + PNE to sham tDCS + PNE on measures of pain, pain behaviors, and cognitive function in participants with chronic low back pain (CLBP) and high pain catastrophizing.

METHODS

20 participants were recruited and randomly allocated into the active tDCS + PNE (n = 10) or sham tDCS + PNE (n = 10) groups. All participants received five sessions of their assigned interventions over a 2-week period. The active tDCS + PNE group received 20 min of 2 mA, anodal current applied to the left dorsolateral prefrontal cortex.

RESULTS

Within groups, both interventions demonstrated significant improvement in NPRS, PCS, and TSK. The active tDCS + PNE group also demonstrated significant improvement in the SCWT, CTMT2-Inhibitory, and CTMT2-Set Shifting. Between groups, the active tDCS + PNE group showed significantly greater improvement on the PCS, SCWT, and CTMT2-Inhibitory.

CONCLUSIONS

The results of this pilot study suggest that active tDCS + PNE appeared to provide greater improvement than sham tDCS + PNE on levels of pain catastrophizing and attentional interference in participants with CLBP and high pain catastrophizing, consistent with both interventions targeting brain regions involved in those processes. Considering the differences between groups, tDCS appears to provide a priming effect on PNE.

PERSPECTIVE

This article presents evidence of a priming effect of transcranial direct current stimulation on pain neuroscience education in participants with chronic low back pain and high pain catastrophizing. The findings support that the combination of interventions improves pain behavior and cognitive function greater than pain neuroscience education alone.

CLINICAL TRIAL REGISTRY

NCT05571215, The Effect of Combining Pain Neuroscience Education and Transcranial Direct Current Stimulation on Pain Catastrophizing, Kinesiophobia, and Pain in Patients With Chronic Low Back Pain, https://classic.clinicaltrials.gov/ct2/show/NCT05571215.

Prediction of the response to repetitive transcranial magnetic stimulation of the motor cortex in peripheral neuropathic pain and validation of a new algorithm

CLINICAL TRIAL REGISTRATION

NCT02010281.

Effects of combining sensory-motor exercises with transcranial direct current stimulation on cortical processing and clinical symptoms in patients with lumbosacral radiculopathy: An exploratory randomized controlled trial

BACKGROUND

Chronic low back pain (CLBP) is linked to reduced excitability in the primary motor (M1) and sensory (S1) cortices. Combining sensory-motor exercises with transcranial direct current stimulation (tDCS) to boost M1 and S1 excitability may improve treatment outcomes. This combined approach aligns with the neurophysiological mechanisms underlying CLBP and may target the neuroplastic changes induced by low back pain. This study aimed to assess whether enhancing M1 and S1 excitability via tDCS, alongside sensory-motor exercises, offers additional benefits for CLBP patients.

METHOD

Participants were randomly assigned to receive either real or sham tDCS alongside sensory-motor exercises. Outcome measures included pain intensity, disability level, motor control ability, amplitudes of N80 and N150, and the amplitude of motor-evoked potential (MEP) and active motor threshold (AMT) for the multifidus (MF) and transversus abdominis/internal oblique (TrA/IO) muscles. A linear mixed-effects model (LMM) analyzed group, time, and interaction effects, while Spearman's correlation assessed relationships between neurophysiological and clinical outcomes.

RESULTS

The results showed significant reductions in pain intensity and disability levels (P < 0.001) and improved motor control (P < 0.001) in both groups. Both groups also exhibited increase in MF MEP amplitude (P = 0.042) and N150 amplitude (P = 0.028). The tDCS group demonstrated a significant decrease in AMT of MF and TrA/IO muscles (P < 0.05) and an increase in N80 amplitude (P = 0.027), with no significant changes in the control group. Additionally, the tDCS group had significantly lower AMT for the TrA/IO muscle in the post-test compared to the sham group (P = 0.001). Increased N150 amplitude was correlated with improved motor control.

CONCLUSIONS

The findings showed that sensory-motor exercises combined with either tDCS or sham tDCS effectively reduced pain intensity, decreased disability, and improved lumbar motor control in lumbosacral radiculopathy patients. No significant differences were observed between groups, indicating no added clinical benefit from tDCS over exercises alone. However, both groups demonstrated increased N150 and MF MEP amplitudes, suggesting enhanced cortical excitability in motor and sensory regions. While clinical outcomes were similar, neurophysiological data indicate that sensory-motor exercises play a central role in boosting cortical excitability, with tDCS further amplifying this effect, as evidenced by a significant AMT reduction in MF and TrA/IO muscles and an increase in N80 amplitude.

H-Coil Repetitive Transcranial Magnetic Stimulation Relieves Pain and Symptoms of Anxiety and Depression in Patients With Chronic Peripheral Neuropathic Pain: A Randomized Sham-Controlled Crossover Study

OBJECTIVES

This study aimed to investigate the analgesic effects of H-coil repetitive transcranial magnetic stimulation (rTMS) primarily targeting the hand area of the primary motor cortex (M1) in patients with peripheral neuropathic pain. Given that the H-coil has a wider reach than conventional coils, there is a possibility that targeting the hand motor cortex also may stimulate prefrontal areas. Thus, we also aimed to examine whether rTMS with an M1 target could produce effects on psychologic outcomes.

MATERIALS AND METHODS

In total, 17 patients were randomly assigned to receive active or sham H-coil rTMS in a counterbalanced order. After a nine-week washout period, they crossed over to either active or sham rTMS, according to a double-blind crossover design. Each treatment period consisted of five daily rTMS sessions and a one- and three-week follow-up visit. The primary outcome was average usual pain intensity. Secondary outcomes included pain unpleasantness, dynamic and static mechanical allodynia, anxiety and depression, sleep, pain catastrophizing, function, and patients' impression of change. Effects of rTMS were investigated using linear mixed model analyses.

RESULTS

We found two significant interactions between treatment and time, indicating that active H-coil rTMS induced significant analgesic effects (t [134] = -2.18; p = .03; d = -0.10) and significant reductions in anxiety and depression compared with sham stimulation over the treatment course (t [73] = -2.14; p = .04; d = -0.09). The analgesic effect occurred two weeks after the treatment, and the effect on anxiety and depression occurred three weeks after treatment. No other significant interactions were found for the secondary variables.

CONCLUSIONS

Five days of H-coil rTMS targeting the hand area of M1 induced statistically significant effects on pain intensity. Moreover, rTMS improved symptoms of anxiety and depression, possibly because of the wide and deep reach of the H-coil.

CLINICAL TRIAL REGISTRATION

The Clinicaltrials.gov registration number for the study is NCT05488808.

Neuromodulation for neuropathic pain

The treatment of neuropathic pain (NeP) often leads to partial or incomplete pain relief, with up to 40 % of patients being pharmaco-resistant. In this chapter the efficacy of neuromodulation techniques in treating NeP is reviewed. It presents a detailed evaluation of the mechanisms of action and evidence supporting the clinical use of the most common approaches like transcutaneous electrical nerve stimulation (TENS), transcranial direct current stimulation (tDCS), repetitive transcranial magnetic stimulation (rTMS), deep brain stimulation (DBS), invasive motor cortex stimulation (iMCS), spinal cord stimulation (SCS), dorsal root ganglion stimulation (DRG-S), and peripheral nerve stimulation (PNS). Current literature suggests that motor cortex rTMS is effective for peripheral and central NeP, and TENS for peripheral NeP. Evidence for tDCS is inconclusive. DBS is reserved for research settings due to heterogeneous results, while iMSC has shown efficacy in a small randomized trial in neuropathic pain due to stroke and brachial plexus avulsion. SCS has moderate evidence for painful diabetic neuropathy and failed back surgery syndrome, but trials were not controlled with sham. DRG-S and PNS have shown positive results for complex regional pain syndrome and post-surgical neuropathic pain, respectively. Adverse effects vary, with non-invasive techniques showing local discomfort, dizziness and headache, and DBS and SCS hardware-related issues. To date, non-invasive techniques have been more extensively studied and some are included in international guidelines, while the evidence level for invasive techniques are less robust, potentially suggesting their use in a case-by-case indication considering patient´s preferences, costs and expected benefits.

Glaucoma Rehabilitation Using ElectricAI Transcranial Stimulation (GREAT)-Optimizing Stimulation Protocol for Vision Enhancement Using an RCT

Purpose

We compared the effect of three different transcranial electrical stimulation (tES) protocols delivered to the occipital lobe on peripheral vision in patients with glaucoma.

Methods

A double-masked, placebo-controlled study was conducted with 35 patients with glaucoma. We compared three different tES protocols: anodal transcranial direct current stimulation (a-tDCS), transcranial alternating current stimulation (tACS), and transcranial random noise stimulation (tRNS) against sham stimulation. Each patient attended four stimulation sessions (a-tDCS, tACS, tRNS, and sham) in a random order with at least 48 hours between visits. Stimulation involved placing an anodal electrode over the occipital lobe (Oz) and cathodal electrode on the cheek for 20 minutes. High-resolution perimetry (HRP) and multifocal visual evoked potential (mfVEP) measurements were made before and immediately after stimulation. Changes in HRP detection accuracy/reaction time and mfVEP signal-to-noise ratio (SNR)/latency were analyzed using linear mixed models.

Results

Compared to sham, HRP detection accuracy was significantly improved after a-tDCS in both the central 20-degree (b = 0.032, P = 0.018) and peripheral analysis (b = 0.051, P = 0.002). Additionally, mfVEP SNR was significantly increased (b = 0.016, P = 0.017) and the latency was shortened (b = -1.405, P = 0.04) by the a-tDCS in the central 20-degree analysis. In the peripheral analysis, there was a trend toward an enhancement of SNR after a-tDCS stimulation (b = 0.014, P = 0.052), but it did not reach statistical significance; latency was increased after tACS (b = 1.623, P = 0.041). No significant effects were found in comparison to other active tES protocols.

Conclusions

A single session of a-tDCS enhances perceptual and electrophysiologic measures of vision in patients with glaucoma. However, the small magnitude of changes observed in HRP (3.2% for accuracy in central and 5.1% in peripheral) did not exceed previous test variability and may not be clinically meaningful.

Translational Relevance

a-tDCS holds promise as a potential treatment for enhancing visual function. However, future studies are needed to evaluate the long-term effects and clinical relevance of this intervention using validated measures of perimetric changes in the visual field.

Assessing the effectiveness of high frequency repetitive transcranial magnetic stimulation for post-mastectomy pain in breast cancer patients: A randomized controlled trial

BACKGROUND

Post-mastectomy pain Syndrome (PMPS), characterized by chronic neuropathic pain stemming from intercostobrachial nerve lesions, presents a formidable clinical challenge. With the incidence of breast cancer surging, effective interventions for PMPS are urgently needed. To address this, we conducted this double-blind, placebo-controlled, randomized clinical trial to study the efficacy of repetitive Transcranial Magnetic Stimulation (rTMS) therapy over the motor cortex on pain, quality of life and thermal sensitivity in PMPS patients.

METHODS

We delivered 15 rTMS sessions over three weeks in a cohort of 34 PMPS patients. These patients were allocated randomly to either rTMS therapy or sham therapy groups. Pain assessments, utilizing the Visual Analogue Scale (VAS) and Short Form McGill Pain Questionnaire (SF-MPQ), alongside quality-of-life evaluations through the Functional Assessment of Cancer Therapy-Breast (FACT-B), were recorded before and after the 15 sessions. Additionally, we assessed thermal sensitivity using Quantitative Sensory Testing (QST).

RESULTS

Our findings demonstrate the superior efficacy of rTMS therapy (over sham therapy) in reducing VAS and SF-MPQ scores (p < 0.0001), improving physical (p = 0.037), emotional (p = 0.033), and functional well-being (p = 0.020) components of quality of life, as quantified by FACT-B. Our investigation also unveiled marked enhancements in thermal sensitivity within the rTMS therapy group, with statistically significant improvements in cold detection threshold (p = 0.0001), warm detection threshold (p = 0.0033), cold pain threshold (p = 0.0078), and hot pain tolerance threshold (p = 0.0078).

CONCLUSION

The study underscores the profound positive impact of rTMS therapy on pain, quality of life, and thermal sensitivity in patients having PMPS, opening new avenues for pain management strategies.

Repetitive transcranial magnetic stimulation focusing on patients with neuropathic pain in the upper limb: a randomized sham-controlled parallel trial

This study aimed to evaluate the efficacy and safety of navigation-guided repetitive transcranial magnetic stimulation (rTMS) over the primary motor cortex in patients with neuropathic pain in the upper limb. This randomized, blinded, sham-controlled, parallel trial included a rTMS protocol (10-Hz, 2000 pulses/session) consisting of five daily sessions, followed by one session per week for the next seven weeks. Pain intensity, as well as pain-related disability, quality of life, and psychological status, were assessed. For the primary outcome, pain intensity was measured daily using a numerical rating scale as a pain diary. Thirty patients were randomly assigned to the active rTMS or sham-stimulation groups. In the primary outcome, the decrease (least square [LS] mean ± standard error) in the weekly average of a pain diary at week 9 compared to the baseline was 0.84 ± 0.31 in the active rTMS group and 0.58 ± 0.29 in the sham group (LS mean difference, 0.26; 95% confidence interval, - 0.60 to 1.13). There was no significant effect on the interaction between the treatment group and time point. Pain-related disability score improved, but other assessments showed no differences. No serious adverse events were observed. This study did not show significant pain relief; however, active rTMS tended to provide better results than sham. rTMS has the potential to improve pain-related disability in addition to pain relief.Clinical Trial Registration number: jRCTs052190110 (20/02/2020).

Field recordings of transcranial magnetic stimulation in human brain postmortem models

Introduction

The ability of repetitive transcranial magnetic stimulation (rTMS) to deliver a magnetic field (MF) in deep brain targets is debated and poorly documented.

Objective

To quantify the decay of MF in the human brain.

Methods

Magnetic field was generated by single pulses of TMS delivered at maximum intensity using a flat or angulated coil. Magnetic field was recorded by a 3D-magnetic probe. Decay was measured in the air using both coils and in the head of 10 postmortem human heads with the flat coil being positioned tangential to the scalp. Magnetic field decay was interpreted as a function of distance to the coil for 6 potential brain targets of noninvasive brain stimulation: the primary motor cortex (M1, mean depth: 28.5 mm), dorsolateral prefrontal cortex (DLPFC: 28 mm), secondary somatosensory cortex (S2: 35.5 mm), posterior and anterior insulae (PI: 38.5 mm; AI: 43.5 mm), and midcingulate cortex (MCC: 57.5 mm).

Results

In air, the maximal MF intensities at coil center were 0.88 and 0.77 T for the flat and angulated coils, respectively. The maximal intracranial MF intensity in the cadaver model was 0.34 T, with a ∼50% decay at 15 mm and a ∼75% MF decay at 30 mm. The decay of the MF in air was similar for the flat coil and significantly less attenuated with the angulated coil (a ∼50% decay at 20 mm and a ∼75% MF decay at 45 mm).

Conclusions

Transcranial magnetic stimulation coil MFs decay in brain structures similarly as in air, attenuation with distance being significantly lower with angulated coils. Reaching brain targets deeper than 20 mm such as the insula or Antérior Cingulate Cortex seems feasible only when using angulated coils. The abacus of MF attenuation provided here can be used to adjust modalities of deep brain stimulation with rTMS in future research protocols.

Optimal Frequency in Repetitive Transcranial Magnetic Stimulation for the Management of Chronic Pain: A Network Meta-Analysis of Randomized Controlled Trials

OBJECTIVE

Repetitive Transcranial Magnetic Stimulation (rTMS) has been shown to be effective for pain modulation in a variety of pathological conditions causing neuropathic pain. The purpose of this study is to conduct a network meta-analysis (NMA) of randomized control trials to identify the most optimal frequency required to achieve chronic pain modulation using rTMS.

METHODS

A comprehensive search was conducted in electronic databases to identify randomized controlled trials investigating the efficacy of rTMS for chronic pain management. A total of 24 studies met the inclusion criteria, and a NMA was conducted to identify the most effective rTMS frequency for chronic pain management.

RESULTS

Our analysis revealed that high frequency rTMS (20 Hz) was the most effective frequency for chronic pain modulation. Patients treated with 20 Hz had lower pain levels than those treated at 5 Hz (mean difference [MD] = -3.11 [95% confidence interval {CI}: -5.61 - -0.61], P = 0.032) and control (MD = -1.99 [95% CI: -3.11 - -0.88], P = 0.023). Similarly, treatment with 10 Hz had lower pain levels compared to 5 Hz (MD = -2.56 [95% CI: -5.05 - -0.07], P = 0.045) and control (MD = -1.44 [95% CI: -2.52 - -0.36], P = 0.031). 20 Hz and 10 Hz were not statistically different.

CONCLUSIONS

This NMA suggests that high frequency rTMS (20 Hz) is the most optimal frequency for chronic pain modulation. These findings have important clinical implications and can guide healthcare professionals in selecting the most effective frequency for rTMS treatment in patients with chronic pain.

Comparison of the analgesic effects of "superficial" and "deep" repetitive transcranial magnetic stimulation in patients with central neuropathic pain: a randomized sham-controlled multicenter international crossover study

ABSTRACT

We directly compared the analgesic effects of "superficial" and 'deep" repetitive transcranial magnetic stimulation (rTMS) of the primary motor cortex in patients with central neuropathic pain. Fifty-nine consecutive patients were randomly assigned to active or sham "superficial" (using a figure-of-8 [F8]-coil) or "deep" (using a Hesed [H]-coil) stimulation according to a double-blind crossover design. Each treatment period consisted of 5 daily stimulation sessions and 2 follow-up visits at 1 and 3 weeks after the last stimulation session. The primary outcome was the comparison of the mean change in average pain intensity over the course of the treatment (group × time interaction). Secondary outcomes included neuropathic symptoms (NPSI), pain interference, patient global impression of change (PGIC), anxiety, depression, and catastrophizing. In total, 51 patients participated in at least one session of both treatments. There was a significant interaction between "treatment" and "time" (F = 2.7; P = 0.0024), indicating that both figure-8 (F8-coil) and H-coil active stimulation induced significantly higher analgesic effects than sham stimulation. The analgesic effects of both types of coils had a similar magnitude but were only moderately correlated ( r = 0.39, P = 0.02). The effects of F8-coil stimulation appeared earlier, whereas the effects of H-coil stimulation were delayed, but tended to last longer (up to 3 weeks) as regards to several secondary outcomes (PGIC and total NPSI score). In conclusion, "deep" and "superficial" rTMS induced analgesic effects of similar magnitude in patients with central pain, which may involve different mechanisms of action.

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.

Beyond trial-and-error: Individualizing therapeutic transcranial neuromodulation for chronic pain

BACKGROUND AND OBJECTIVE

Repetitive transcranial magnetic stimulation (rTMS) applied to the motor cortex provides supplementary relief for some individuals with chronic pain who are refractory to pharmacological treatment. As rTMS slowly enters treatment guidelines for pain relief, its starts to be confronted with challenges long known to pharmacological approaches: efficacy at the group-level does not grant pain relief for a particular patient. In this review, we present and discuss a series of ongoing attempts to overcome this therapeutic challenge in a personalized medicine framework.

DATABASES AND DATA TREATMENT

Relevant scientific publications published in main databases such as PubMed and EMBASE from inception until March 2023 were systematically assessed, as well as a wide number of studies dedicated to the exploration of the mechanistic grounds of rTMS analgesic effects in humans, primates and rodents.

RESULTS

The main strategies reported to personalize cortical neuromodulation are: (i) the use of rTMS to predict individual response to implanted motor cortex stimulation; (ii) modifications of motor cortex stimulation patterns; (iii) stimulation of extra-motor targets; (iv) assessment of individual cortical networks and rhythms to personalize treatment; (v) deep sensory phenotyping; (vi) personalization of location, precision and intensity of motor rTMS. All approaches except (i) have so far low or moderate levels of evidence.

CONCLUSIONS

Although current evidence for most strategies under study remains at best moderate, the multiple mechanisms set up by cortical stimulation are an advantage over single-target 'clean' drugs, as they can influence multiple pathophysiologic paths and offer multiple possibilities of individualization.

SIGNIFICANCE

Non-invasive neuromodulation is on the verge of personalised medicine. Strategies ranging from integration of detailed clinical phenotyping into treatment design to advanced patient neurophysiological characterisation are being actively explored and creating a framework for actual individualisation of care.

Repetitive transcranial magnetic stimulation in central post-stroke pain: current status and future perspective

Central post-stroke pain (CPSP) is an incapacitating disorder that impacts a substantial proportion of stroke survivors and can diminish their quality of life. Conventional therapies for CPSP, including tricyclic antidepressants, anticonvulsants, and opioids, are frequently ineffective, necessitating the investigation of alternative therapeutic strategies. Repetitive transcranial magnetic stimulation (rTMS) is now recognized as a promising noninvasive pain management method for CPSP. rTMS modulates neural activity through the administration of magnetic pulses to specific cortical regions. Trials analyzing the effects of rTMS on CPSP have generated various outcomes, but the evidence suggests possible analgesic benefits. In CPSP and other neuropathic pain conditions, high-frequency rTMS targeting the primary motor cortex (M1) with figure-eight coils has demonstrated significant pain alleviation. Due to its associaton with analgesic benefits, M1 is the most frequently targeted area. The duration and frequency of rTMS sessions, as well as the stimulation intensity, have been studied in an effort to optimize treatment outcomes. The short-term pain relief effects of rTMS have been observed, but the long-term effects (> 3 months) require further investigation. Aspects such as stimulation frequency, location, and treatment period can influence the efficacy of rTMS and ought to be considered while planning the procedure. Standardized guidelines for using rTMS in CPSP would optimize therapy protocols and improve patient outcomes. This review article provides an up-to-date overview of the incidence, clinical characteristics, outcome of rTMS in CPSP patients, and future perspective in the field.

Non-invasive cortical stimulation for drug-resistant pain

PURPOSE OF REVIEW

Neuromodulation techniques are being increasingly used to alleviate pain and enhance quality of life. Non-invasive cortical stimulation was originally intended to predict the efficacy of invasive (neurosurgical) techniques, but has now gained a place as an analgesic procedure in its own right.

RECENT FINDINGS

Repetitive transcranial magnetic stimulation (rTMS): Evidence from 14 randomised, placebo-controlled trials (~750 patients) supports a significant analgesic effect of high-frequency motor cortex rTMS in neuropathic pain. Dorsolateral frontal stimulation has not proven efficacious so far. The posterior operculo-insular cortex is an attractive target but evidence remains insufficient. Short-term efficacy can be achieved with NNT (numbers needed to treat) ~2-3, but long-lasting efficacy remains a challenge.Like rTMS, transcranial direct-current stimulation (tDCS) induces activity changes in distributed brain networks and can influence various aspects of pain. Lower cost relative to rTMS, few safety issues and availability of home-based protocols are practical advantages. The limited quality of many published reports lowers the level of evidence, which will remain uncertain until more prospective controlled studies are available.

SUMMARY

Both rTMS and tDCS act preferentially upon abnormal hyperexcitable states of pain, rather than acute or experimental pain. For both techniques, M1 appears to be the best target for chronic pain relief, and repeated sessions over relatively long periods of time may be required to obtain clinically significant benefits. Patients responsive to tDCS may differ from those improved by rTMS.

Advances and challenges in neuropathic pain: a narrative review and future directions

Over the past few decades, substantial advances have been made in neuropathic pain clinical research. An updated definition and classification have been agreed. Validated questionnaires have improved the detection and assessment of acute and chronic neuropathic pain; and newer neuropathic pain syndromes associated with COVID-19 have been described. The management of neuropathic pain has moved from empirical to evidence-based medicine. However, appropriately targeting current medications and the successful clinical development of drugs acting on new targets remain challenging. Innovative approaches to improving therapeutic strategies are required. These mainly encompass rational combination therapy, drug repurposing, non-pharmacological approaches (such as neurostimulation techniques), and personalised therapeutic management. This narrative review reports historical and current perspectives regarding the definitions, classification, assessment, and management of neuropathic pain and explores potential avenues for future research.

Long-term analgesic effect of trans-spinal direct current stimulation compared to non-invasive motor cortex stimulation in complex regional pain syndrome

The aim of the present study was to compare the analgesic effect of motor cortex stimulation using high-frequency repetitive transcranial magnetic stimulation or transcranial direct current stimulation and transcutaneous spinal direct current stimulation in patients with complex regional pain syndrome. Thirty-three patients with complex regional pain syndrome were randomized to one of the three treatment groups (repetitive transcranial magnetic stimulation, n = 11; transcranial direct current stimulation, n = 10; transcutaneous spinal direct current stimulation, n = 12) and received a series of 12 sessions of stimulation for 3 weeks (induction phase) and 11 sessions for 4 months (maintenance therapy). The primary end-point was the mean pain intensity assessed weekly with a visual numerical scale during the month prior to treatment (baseline), the 5-month stimulation period and 1 month after the treatment. The weekly visual numerical scale pain score was significantly reduced at all time points compared to baseline in the transcutaneous spinal direct current stimulation group, at the last two time points in the repetitive transcranial magnetic stimulation group (end of the 5-month stimulation period and 1 month later), but at no time point in the transcranial direct current stimulation group. A significant pain relief was observed at the end of induction phase using transcutaneous spinal direct current stimulation compared to repetitive transcranial magnetic stimulation (P = 0.008) and to transcranial direct current stimulation (P = 0.003). In this trial, transcutaneous spinal direct current stimulation was more efficient to relieve pain in patients with complex regional pain syndrome compared to motor cortex stimulation techniques (repetitive transcranial magnetic stimulation, transcranial direct current stimulation). This efficacy was found during the induction phase and was maintained thereafter. This study warrants further investigation to confirm the potentiality of transcutaneous spinal direct current stimulation as a therapeutic option in complex regional pain syndrome.

A randomised sham-controlled study evaluating rTMS analgesic efficacy for postherpetic neuralgia

Context

Postherpetic neuralgia (PHN) is a refractory neuropathic pain condition in which new treatment options are being developed. Repetitive transcranial magnetic stimulation (rTMS) may have the potential to reduce pain sensations in patients with postherpetic neuralgia.

Objectives

This study investigated the efficacy on postherpetic neuralgia by stimulating two potential targets, the motor cortex (M1) and the dorsolateral prefrontal cortex (DLPFC).

Methods

This is a double-blind, randomised, sham-controlled study. Potential participants were recruited from Hangzhou First People's Hospital. Patients were randomly assigned to either the M1, DLPFC or Sham group. Patients received ten daily sessions of 10-Hz rTMS in 2 consecutive weeks. The primary outcome measure was visual analogue scale (VAS) assessed at baseline, first week of treatment (week 1), post-treatment (week 2), 1-week (week 4), 1-month (week 6) and 3-month (week 14) follow-up.

Results

Of sixty patients enrolled, 51 received treatment and completed all outcome assessments. M1 stimulation resulted in a larger analgesia during and after treatment compared to the Sham (week 2 - week 14, p < 0.005), as well as to the DLPFC stimulation (week 1 - week 14, p < 0.05). In addition to pain, sleep disturbance was significantly improved and relieved by targeting either the M1 or the DLPFC (M1: week 4 - week 14, p < 0.01; DLPFC: week 4 - week 14, p < 0.01). Moreover, pain sensations following M1 stimulation uniquely predicted improvement in sleep quality.

Conclusion

M1 rTMS is superior to DLPFC stimulation in treating PHN with excellent pain response and long-term analgesia. Meanwhile, M1 and DLPFC stimulation were equally effective in improving sleep quality in PHN.

Clinical trial registration

https://www.chictr.org.cn/, identifier ChiCTR2100051963.

Electrical stimulation methods and protocols for the treatment of traumatic brain injury: a critical review of preclinical research

BACKGROUND

Traumatic brain injury (TBI) is a leading cause of disabilities resulting from cognitive and neurological deficits, as well as psychological disorders. Only recently, preclinical research on electrical stimulation methods as a potential treatment of TBI sequelae has gained more traction. However, the underlying mechanisms of the anticipated improvements induced by these methods are still not fully understood. It remains unclear in which stage after TBI they are best applied to optimize the therapeutic outcome, preferably with persisting effects. Studies with animal models address these questions and investigate beneficial long- and short-term changes mediated by these novel modalities.

METHODS

In this review, we present the state-of-the-art in preclinical research on electrical stimulation methods used to treat TBI sequelae. We analyze publications on the most commonly used electrical stimulation methods, namely transcranial magnetic stimulation (TMS), transcranial direct current stimulation (tDCS), deep brain stimulation (DBS) and vagus nerve stimulation (VNS), that aim to treat disabilities caused by TBI. We discuss applied stimulation parameters, such as the amplitude, frequency, and length of stimulation, as well as stimulation time frames, specifically the onset of stimulation, how often stimulation sessions were repeated and the total length of the treatment. These parameters are then analyzed in the context of injury severity, the disability under investigation and the stimulated location, and the resulting therapeutic effects are compared. We provide a comprehensive and critical review and discuss directions for future research. RESULTS AND CONCLUSION: We find that the parameters used in studies on each of these stimulation methods vary widely, making it difficult to draw direct comparisons between stimulation protocols and therapeutic outcome. Persisting beneficial effects and adverse consequences of electrical simulation are rarely investigated, leaving many questions about their suitability for clinical applications. Nevertheless, we conclude that the stimulation methods discussed here show promising results that could be further supported by additional research in this field.

Application of Repetitive Transcranial Magnetic Stimulation in Neuropathic Pain: A Narrative Review

Neuropathic pain, affecting 6.9-10% of the general population, has a negative impact on patients' quality of life and potentially leads to functional impairment and disability. Repetitive transcranial magnetic stimulation (rTMS)-a safe, indirect and non-invasive technique-has been increasingly applied for treating neuropathic pain. The mechanism underlying rTMS is not yet well understood, and the analgesic effects of rTMS have been inconsistent with respect to different settings/parameters, causing insufficient evidence to determine its efficacy in patients with neuropathic pain. This narrative review aimed to provide an up-to-date overview of rTMS for treating neuropathic pain as well as to summarize the treatment protocols and related adverse effects from existing clinical trials. Current evidence supports the use of 10 Hz HF-rTMS of the primary motor cortex to reduce neuropathic pain, especially in patients with spinal cord injury, diabetic neuropathy and post-herpetic neuralgia. However, the lack of standardized protocols impedes the universal use of rTMS for neuropathic pain. rTMS was hypothesized to achieve analgesic effects by upregulating the pain threshold, inhibiting pain impulse, modulating the brain cortex, altering imbalanced functional connectivity, regulating neurotrophin and increasing endogenous opioid and anti-inflammatory cytokines. Further studies are warranted to explore the differences in the parameters/settings of rTMS for treating neuropathic pain due to different disease types.

Better Fields or Currents? A Head-to-Head Comparison of Transcranial Magnetic (rTMS) Versus Direct Current Stimulation (tDCS) for Neuropathic Pain

While high-frequency transcranial magnetic stimulation (HF-rTMS) is now included in the armamentarium to treat chronic neuropathic pain (NP), direct-current anodal stimulation (a-tDCS) to the same cortical targets may represent a valuable alternative in terms of feasibility and cost. Here we performed a head-to-head, randomized, single-blinded, cross-over comparison of HF-rTMS versus a-tDCS over the motor cortex in 56 patients with drug-resistant NP, who received 5 daily sessions of each procedure, with a washout of at least 4 weeks. Daily scores of pain, sleep, and fatigue were obtained during 5 consecutive weeks, and functional magnetic resonance imaging (fMRI) to a motor task was performed in a subgroup of 31 patients. The percentage of responders, defined by a reduction in pain scores of > 2 SDs from pre-stimulus levels, was similar to both techniques (42.0% vs. 42.3%), while the magnitude of "best pain relief" was significantly skewed towards rTMS. Mean pain ratings in responders decreased by 32.6% (rTMS) and 29.6% (tDCS), with half of them being sensitive to only one technique. Movement-related fMRI showed significant activations in motor and premotor areas, which did not change after 5 days of stimulation, and did not discriminate responders from non-responders. Both HF-rTMS and a-tDCS showed efficacy at 1 month in drug-resistant NP, with magnitude of relief slightly favoring rTMS. Since a significant proportion of patients responded to one procedure only, both modalities should be tested before declaring a patient as unresponsive.

Feasibility and safety of combining repetitive transcranial magnetic stimulation and quadriceps strengthening exercise for chronic pain in knee osteoarthritis: a study protocol for a pilot randomised controlled trial

INTRODUCTION

Knee osteoarthritis is a leading cause of disability, resulting in pain and reduced quality of life. Exercise is the cornerstone of conservative management but effects are, at best, moderate. Early evidence suggests that repetitive transcranial magnetic stimulation (rTMS) applied over the primary motor cortex (M1) may improve the effect of exercise in knee osteoarthritis. This pilot study aims to (1) determine the feasibility, safety and participant-rated response to an intervention adding M1 rTMS to exercise in knee osteoarthritis; (2) elucidate physiological mechanisms in response to the intervention; (3) provide data to conduct a sample size calculation for a fully powered trial.

METHODS AND ANALYSIS

This is a pilot randomised, assessor-blind, therapist-blind and participant-blind, sham-controlled trial. Thirty individuals with painful knee osteoarthritis will be recruited and randomly allocated to receive either: (1) active rTMS+exercise or (2) sham rTMS+exercise intervention. Participants will receive 15 min of either active or sham rTMS immediately prior to 30 min of supervised muscle strengthening exercise (2×/week, 6 weeks) and complete unsupervised home exercises. Outcome measures of feasibility, safety, pain, function and physiological mechanisms will be assessed before and/or after the intervention. Feasibility and safety will be analysed using descriptive analysis. Within-group and between-group comparisons of pain and function will be conducted to examine trends of efficacy.

ETHICS AND DISSEMINATION

This study has been approved by the University of New South Wales Human Research Ethics Committee (HC210954). All participants will provide written informed consent. The study results will be submitted for peer-reviewed publication.

TRIAL REGISTRATION NUMBER

ACTRN12621001712897p.

Transcranial direct current stimulation of 3 cortical targets is no more effective than placebo as treatment for fibromyalgia: a double-blind sham-controlled clinical trial

ABSTRACT

Transcranial direct current stimulation (tDCS) over the primary motor cortex (M1) and the dorsolateral prefrontal cortex seem to improve pain and other symptoms of fibromyalgia (FM), although the evidence on the effectiveness of tDCS and the optimal stimulation target is not robust enough. Our main objective was to establish the optimal area of stimulation, comparing the 2 classical targets and a novel pain-related area, the operculo-insular cortex, in a sham-controlled trial. Using a double-blind design, we randomly assigned 130 women with FM to 4 treatment groups (M1, dorsolateral prefrontal cortex, operculo-insular cortex, and sham), each receiving fifteen 20-minute sessions of 2 mA anodal tDCS over the left hemisphere. Our primary outcome was pain intensity. The secondary outcomes were the other core symptoms of FM (fatigue, mood, cognitive and sleep disorders, and hyperalgesia measured by the pressure pain threshold). We performed the assessment at 3 time points (before, immediately after treatment, and at 6 months follow-up). The linear mixed-model analysis of variances showed significant treatment effects across time for clinical pain and for fatigue, cognitive and sleep disturbances, and experimental pain, irrespective of the group. In mood, the 3 active tDCS groups showed a significantly larger improvement in anxiety and depression than sham. Our findings provide evidence of a placebo effect, support the use of tDCS for the treatment of affective symptoms, and challenge the effectiveness of tDCS as treatment of FM.

Analgesic Effects of Repetitive Transcranial Magnetic Stimulation at Different Stimulus Parameters for Neuropathic Pain: A Randomized Study

OBJECTIVES

The aim of the present study was to investigate the analgesic effects of repetitive transcranial magnetic stimulation over the primary motor cortex (M1-rTMS) using different stimulation parameters to explore the optimal stimulus condition for treating neuropathic pain.

MATERIALS AND METHODS

We conducted a randomized, blinded, crossover exploratory study. Four single sessions of M1-rTMS at different parameters were administered in random order. The tested stimulation conditions were as follows: 5-Hz with 500 pulses per session, 10-Hz with 500 pulses per session, 10-Hz with 2000 pulses per session, and sham stimulation. Analgesic effects were assessed by determining the visual analog scale (VAS) pain intensity score and Short-Form McGill Pain Questionnaire 2 (SF-MPQ2) score immediately before and immediately after intervention.

RESULTS

We enrolled 22 adults (age: 59.8 ± 12.1 years) with intractable neuropathic pain. Linear-effects models showed significant effects of the stimulation condition on changes in VAS pain intensity (p = 0.03) and SF-MPQ2 (p = 0.01). Tukey multiple comparison tests revealed that 10-Hz rTMS with 2000 pulses provided better pain relief than sham stimulation, with greater decreases in VAS pain intensity (p = 0.03) and SF-MPQ2 (p = 0.02).

CONCLUSIONS

The results of this study suggest that high-dose stimulation (specifically, 10-Hz rTMS at 2000 pulses) is more effective than lower-dose stimulation for treating neuropathic pain.

Non-invasive Brain Stimulation for Central Neuropathic Pain

The research and clinical application of the noninvasive brain stimulation (NIBS) technique in the treatment of neuropathic pain (NP) are increasing. In this review article, we outline the effectiveness and limitations of the NIBS approach in treating common central neuropathic pain (CNP). This article summarizes the research progress of NIBS in the treatment of different CNPs and describes the effects and mechanisms of these methods on different CNPs. Repetitive transcranial magnetic stimulation (rTMS) analgesic research has been relatively mature and applied to a variety of CNP treatments. But the optimal stimulation targets, stimulation intensity, and stimulation time of transcranial direct current stimulation (tDCS) for each type of CNP are still difficult to identify. The analgesic mechanism of rTMS is similar to that of tDCS, both of which change cortical excitability and synaptic plasticity, regulate the release of related neurotransmitters and affect the structural and functional connections of brain regions associated with pain processing and regulation. Some deficiencies are found in current NIBS relevant studies, such as small sample size, difficulty to avoid placebo effect, and insufficient research on analgesia mechanism. Future research should gradually carry out large-scale, multicenter studies to test the stability and reliability of the analgesic effects of NIBS.

Cortical stimulation for chronic pain: from anecdote to evidence

Epidural stimulation of the motor cortex (eMCS) was devised in the 1990's, and has now largely supplanted thalamic stimulation for neuropathic pain relief. Its mechanisms of action involve activation of multiple cortico-subcortical areas initiated in the thalamus, with involvement of endogenous opioids and descending inhibition toward the spinal cord. Evidence for clinical efficacy is now supported by at least seven RCTs; benefits may persist up to 10 years, and can be reasonably predicted by preoperative use of non-invasive repetitive magnetic stimulation (rTMS). rTMS first developed as a means of predicting the efficacy of epidural procedures, then as an analgesic method on its own right. Reasonable evidence from at least six well-conducted RCTs favors a significant analgesic effect of high-frequency rTMS of the motor cortex in neuropathic pain (NP), and less consistently in widespread/fibromyalgic pain. Stimulation of the dorsolateral frontal cortex (DLPFC) has not proven efficacious for pain, so far. The posterior operculo-insular cortex is a new and attractive target but evidence remains inconsistent. Transcranial direct current stimulation (tDCS) is applied upon similar targets as rTMS and eMCS; it does not elicit action potentials but modulates the neuronal resting membrane state. tDCS presents practical advantages including low cost, few safety issues, and possibility of home-based protocols; however, the limited quality of most published reports entails a low level of evidence. Patients responsive to tDCS may differ from those improved by rTMS, and in both cases repeated sessions over a long time may be required to achieve clinically significant relief. Both invasive and non-invasive procedures exert their effects through multiple distributed brain networks influencing the sensory, affective and cognitive aspects of chronic pain. Their effects are mainly exerted upon abnormally sensitized pathways, rather than on acute physiological pain. Extending the duration of long-term benefits remains a challenge, for which different strategies are discussed in this review.

A Preliminary Study of the Efficacy of Transcranial Direct Current Stimulation in Trigeminal Neuralgia

The purpose of this study is to assess the efficacy of transcranial direct current stimulation (tDCS) in patients with treatment-refractory trigeminal neuralgia (TN) and examine the utility of neuroimaging methods in identifying markers of such efficacy. Six patients with classical TN refractory to maximal medical treatment, underwent tDCS (three cases inhibitory/cathodic and three cases excitatory/anodic stimulation). All patients underwent pre- and posttreatment functional magnetic resonance imaging (fMRI) during block-design tasks (i.e., Pain, Pain + tDCS, tDCS) as well as single-shell diffusion MRI (dMRI) acquisition. The precise locations of tDCS electrodes were identified by neuronavigation. Five therapeutic tDCS sessions were carried out for each patient with either anodic or cathodic applications. The Numeric Rating Scale of pain (NRS) and the Headache Disability Index (HDI) were used to score the subjective efficacy of treatment. Altered activity of regional sites was identified by fMRI and associated changes in the spinothalamocortical sensory tract (STCT) were measured by the dMRI indices of fractional anisotropy (FA) and mean diffusivity (MD). Fiber counts of the bilateral trigeminal root entry zone (REZ) were performed as an added measure of fiber loss or recovery. All patients experienced a significant reduction in pain scores with a substantial decline in HDI (P value < 0.01). Following a course of anodic tDCS, the ipsilateral caudate, globus pallidus, somatosensory cortex, and the contralateral globus pallidus showed a significantly attenuated activation whereas cathodic tDCS treatment resulted in attenuation of the thalamus and globus pallidus bilaterally, and the somatosensory cortex and anterior cingulate gyrus contralaterally. dMRI analysis identified a substantial increase (>50%) in the number of contralateral sensory fibers in the STCT with either anodic or cathodic tDCS treatment in four of the six patients. A significant reduction in FA (>40%) was observed in the ipsilateral REZ in the posttreatment phase in five of the six patients. Preliminary evidence suggests that navigated tDCS presents a promising method for alleviating the pain of TN. Different patterns of activation manifested by anodic and cathodic stimulation require further elaboration to understand their implication. Activation and attenuation of responses at various sites may provide further avenues for condition treatment.

Evidence Mapping Based on Systematic Reviews of Repetitive Transcranial Magnetic Stimulation on the Motor Cortex for Neuropathic Pain

BACKGROUND AND OBJECTIVE

There is vast published literature proposing repetitive transcranial magnetic stimulation (rTMS) technology on the motor cortex (M1) for the treatment of neuropathic pain (NP). Systematic reviews (SRs) focus on a specific problem and do not provide a comprehensive overview of a research area. This study aimed to summarize and analyze the evidence of rTMS on the M1 for NP treatment through a new synthesis method called evidence mapping.

METHODS

Searches were conducted in PubMed, EMBASE, Epistemonikos, and The Cochrane Library to identify the studies that summarized the effectiveness of rTMS for NP. The study type was restricted to SRs with or without meta-analysis. All literature published before January 23, 2021, was included. Two reviewers independently screened the literature, assessed the methodological quality, and extracted the data. The methodological quality of the included SRs was assessed by using the A Measurement Tool to Assess Systematic Reviews (AMSTAR-2). Data were extracted following a defined population, intervention, comparison, and outcome (PICO) framework from primary studies that included SRs. The same PICO was categorized into PICOs according to interventions [frequency, number of sessions (short: 1-5 sessions, medium: 5-10 sessions, and long: >10 sessions)] and compared. The evidence map was presented in tables and a bubble plot.

RESULTS

A total of 38 SRs met the eligibility criteria. After duplicate primary studies were removed, these reviews included 70 primary studies that met the scope of evidence mapping. According to the AMSTAR-2 assessment, the quality of the included SRs was critically low. Of these studies, 34 SRs scored "critically low" in terms of methodological quality, 2 SR scored "low," 1 SR scored "moderate," and 1 SR scored "high."

CONCLUSION

Evidence mapping is a useful methodology to provide a comprehensive and reliable overview of studies on rTMS for NP. Evidence mapping also shows that further investigations are necessary to highlight the optimal stimulation protocols and standardize all parameters to fill the evidence gaps of rTMS. Given that the methodological quality of most included SRs was "critically low," further investigations are advised to improve the methodological quality and the reporting process of SRs.

Effects of rTMS and tDCS on neuropathic pain after brachial plexus injury: a randomized placebo-controlled pilot study

Neuropathic pain after brachial plexus injury (NPBPI) is a highly disabling clinical condition and is increasingly prevalent due to increased motorcycle accidents. Currently, no randomized controlled trials have evaluated the effectiveness of non-invasive brain stimulation techniques such as repetitive transcranial magnetic stimulation (rTMS) and transcranial direct-current stimulation (tDCS) in patients suffering from NPBPI. In this study, we directly compare the efficacy of 10-Hz rTMS and anodal 2 mA tDCS techniques applied over the motor cortex (5 daily consecutive sessions) in 20 patients with NPBPI, allocated into 2 parallel groups (active or sham). The order of the sessions was randomised for each of these treatment groups according to a crossover design and separated by a 30-day interval. Scores for "continuous" and "paroxysmal" pain (primary outcome) were tabulated after the last stimulation day and 30 days after. Secondary outcomes included the improvement in multidimensional aspects of pain, anxiety state and quality of life from a qualitative and quantitative approach. Active rTMS and tDCS were both superior to sham in reducing continuous (p < 0.001) and paroxysmal (p = 0.002; p = 0.02) pain as well as in multidimensional aspects of pain (p = 0.001; p = 0.002) and anxiety state (p =  < 0.001; p = 0.005). Our results suggest rTMS and tDCS are able to treat NPBPI with little distinction in pain and anxiety state, which may promote the use of tDCS in brachial plexus injury pain management, as it constitutes an easier and more available technique.Clinical Trial Registration: http://www.ensaiosclinicos.gov.br/, RBR-5xnjbc - Sep 3, 2018.

Analgesic Effects of Navigated Repetitive Transcranial Magnetic Stimulation in Patients With Acute Central Poststroke Pain

INTRODUCTION

Central poststroke pain (CPSP) develops commonly after stroke, which impairs the quality of life, mood, and social functioning. Current pharmacological approaches for the treatment of CPSP are not satisfactory. Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive technique which has been recommended for the treatment of chronic CPSP. However, few studies have evaluated the analgesic effects of rTMS in patients with acute neuropathic pain after stroke.

METHODS

We evaluated the analgesic effects of rTMS applied over the upper extremity area of the motor cortex (M1) in patients with acute CPSP. Forty patients were randomized to receive either rTMS (10 Hz, 2000 stimuli) (n = 20) or a sham intervention (n = 20) for 3 weeks. The Numeric Rating Scale (NRS), Short-form McGill Pain Questionnaire-2 (SF-MPQ-2, Chinese version), Hamilton Anxiety Scale (HAM-A), Hamilton Depression Scale (HAM-D), brain-derived neurotrophic factor (BDNF) levels, and motor-evoked potentials (MEP) were analyzed at baseline, 3 days, 1 week, 2 weeks, and 3 weeks.

RESULTS

Significant treatment-time interactions were found for pain intensity. Compared with the sham group, the NRS and SF-MPQ-2 scores were significantly lower on the seventh day of treatment in the rTMS group (P < 0.001, Cohen's d = 1.302) (P = 0.003, Cohen's d = 0.771), and this effect lasted until the third week (P = 0.001, Cohen's d = 0.860) (P = 0.027, Cohen's d = 0.550). The HAM-A and HAM-D scores did not change in the rTMS group when compared with the sham group (P = 0.341, Cohen's d = 0.224) (P = 0.356, Cohen's d = 0.217). The serum BDNF levels were significantly higher in the treated group (P = 0.048, Cohen's d = -0.487), and the resting motor threshold (RMT) decreased by 163.65%.

CONCLUSION

Our findings indicate that rTMS applied over the upper extremity area of the motor cortex can effectively alleviate acute CPSP, possibly by influencing cortical excitability and serum BDNF secretion.

TRIAL REGISTRATION

This trial is registered with Clinical Trial Registry of China: Reg. No. ChiCTR-INR-17012880.

Difference in Analgesic Effects of Repetitive Transcranial Magnetic Stimulation According to the Site of Pain

High-frequency repetitive transcranial magnetic stimulation (rTMS) of the primary motor cortex for neuropathic pain has been shown to be effective, according to systematic reviews and therapeutic guidelines. However, our large, rigorous, investigator-initiated, registration-directed clinical trial failed to show a positive primary outcome, and its subgroup analysis suggested that the analgesic effect varied according to the site of pain. The aim of this study was to investigate the differences in analgesic effects of rTMS for neuropathic pain between different pain sites by reviewing our previous clinical trials. We included three clinical trials in this mini meta-analysis: a multicenter randomized controlled trial at seven hospitals (N = 64), an investigator-initiated registration-directed clinical trial at three hospitals (N = 142), and an exploratory clinical trial examining different stimulation parameters (N = 22). The primary efficacy endpoint (change in pain scale) was extracted for each patient group with pain in the face, upper limb, or lower limb, and a meta-analysis of the efficacy of active rTMS against sham stimulation was performed. Standardized mean difference (SMD) with 95% confidence interval (CI) was calculated for pain change using a random-effects model. The analgesic effect of rTMS for upper limb pain was favorable (SMD = -0.45, 95% CI: -0.77 to -0.13). In contrast, rTMS did not produce significant pain relief on lower limb pain (SMD = 0.04, 95% CI: -0.33 to 0.41) or face (SMD = -0.24, 95% CI: -1.59 to 1.12). In conclusion, these findings suggest that rTMS provides analgesic effects in patients with neuropathic pain in the upper limb, but not in the lower limb or face, under the conditions of previous clinical trials. Owing to the main limitation of small number of studies included, many aspects should be clarified by further research and high-quality studies in these patients.

The Effect of Repetitive Transcranial Magnetic Stimulation on Lower-Limb Motor Ability in Stroke Patients: A Systematic Review

Repetitive transcranial magnetic stimulation (rTMS) is fundamental in inducing neuroplastic changes and promoting brain function restoration. Nevertheless, evidence based on the systematic assessment of the implication of rTMS in stroke patients is inadequate. This study aimed to evaluate the value of rTMS in the treatment of lower-limb motor dysfunction in stroke patients via gait characteristics. The electronic literature search was performed in ScienceDirect, Google Scholar, and PubMed databases using "repetitive transcranial magnetic stimulation," "gait," and "stroke" between 2000 and 2020. By screening all the identified studies, a total of 10 studies covering 257 stroke patients were included by matching the inclusion criteria, involving both rTMS with high (≥5 Hz) and low frequency (<5 Hz). Despite the limited study number and relatively high risk of bias, the results of this review primarily confirmed the enhancing effects of rTMS on the lower-limb motor ability (e.g., gait and balance) of stroke patients. In addition, 15- to 20-min course of rTMS for 2 to 3 weeks was found to be the most common setting, and 1 Hz and 10 Hz were the most commonly used low and high frequencies, respectively. These results might have significant clinical applications for patients with weakened lower-limb mobility after a stroke. Nevertheless, more rigorous studies in this field are much warranted. Systematic Review Registration:https://inplasy.com/, identifier INPLASY202180079.

A Review of the Clinical and Therapeutic Implications of Neuropathic Pain

Understanding neuropathic pain presents several challenges, given the various mechanisms underlying its pathophysiological classification and the lack of suitable tools to assess its diagnosis. Furthermore, the response of this pathology to available drugs is still often unpredictable, leaving the treatment of neuropathic pain still questionable. In addition, the rise of personalized treatments further extends the ramified classification of neuropathic pain. While a few authors have focused on neuropathic pain clustering, by analyzing, for example, the presence of specific TRP channels, others have evaluated the presence of alterations in microRNAs to find tailored therapies. Thus, this review aims to synthesize the available evidence on the topic from a clinical perspective and provide a list of current demonstrations on the treatment of this disease.

Repetitive transcranial magnetic stimulation for neuropathic pain: a randomized multicentre sham-controlled trial

Repetitive transcranial magnetic stimulation (rTMS) has been proposed to treat neuropathic pain but the quality of evidence remains low. We aimed to assess the efficacy and safety of neuronavigated rTMS to the motor cortex (M1) or dorsolateral prefrontal cortex (DLPFC) in neuropathic pain over 25 weeks. We did a randomised double-blind, placebo-controlled trial at four outpatient clinics in France. Patients aged 18-75 years with peripheral neuropathic pain were randomly assigned in a 1:1 ratio to M1 or DLPFC-rTMS and re-randomised in a 2:1 ratio to active or sham rTMS (10 Hz, 3000 pulses/session, 15 sessions over 22 weeks). Patients and investigators were blind to treatment allocation. The primary endpoint was the comparison between active M1-rTMS, active DLPCF-rTMS and sham-rTMS for the change over the course of 25 weeks (group by time interaction) in average pain intensity (from 0 no pain to 10 maximal pain) on the Brief Pain Inventory (BPI), using a mixed model repeated measures analysis in patients who received at least one rTMS session (modified ITT population). Secondary outcomes included other measures of pain intensity and relief, sensory and affective dimensions of pain, quality of pain, self reported pain intensity and fatigue (patients diary), patient and clinician global impression of change (PGIC, CGIC), quality of life, sleep, mood and catastrophizing. This study is registered with ClinicalTrials.gov NCT02010281. A total of 152 patients were randomised and 149 received treatment (49 for M1; 52 for DLPFC; 48 for sham). M1-rTMS reduced pain intensity versus sham-rTMS (estimate for group x session interaction: -0.048 ± 0.02; 95% CI: -0.09 to -0.01; p = 0.01). DLPFC-rTMS was not better than sham (estimate: -0.003 ± 0.01; 95% CI:-0.04 to 0.03, p = 0.9). M1-rRMS, but not DLPFC-rTMS, was also superior to sham-rTMS on pain relief, sensory dimenson of pain, self reported pain intensity and fatigue, PGIC and CGIC. There were no effect on quality of pain, mood, sleep and quality of life as all groups improved similarly over time. Headache was the most common side effect and occurred in 17 (34.7%), 23 (44.2%) and 13 (27.1%) patients from M1, DLPFC and sham groups respectively (p = 0.2). Our results support the clinical relevance of M1-rTMS, but not of DLPFC-rTMS, for peripheral neuropathic pain with an excellent safety profile.

Posterior-superior insular deep transcranial magnetic stimulation alleviates peripheral neuropathic pain - A pilot double-blind, randomized cross-over study

OBJECTIVES

Peripheral neuropathic pain (pNeP) is prevalent, and current treatments, including drugs and motor cortex repetitive transcranial magnetic stimulation (rTMS) leave a substantial proportion of patients with suboptimal pain relief.

METHODS

We explored the intensity and short-term duration of the analgesic effects produced in pNeP patients by 5 days of neuronavigated deep rTMS targeting the posterior superior insula (PSI) with a double-cone coil in a sham-controlled randomized cross-over trial.

RESULTS

Thirty-one pNeP patients received induction series of five active or sham consecutive sessions of daily deep-rTMS to the PSI in a randomized sequence, with a washout period of at least 21 days between series. The primary outcome [number of responders (>50% pain intensity reduction from baseline in a numerical rating scale ranging from 0 to 10)] was significantly higher after real (58.1%) compared to sham (19.4%) stimulation (p = 0.002). The number needed to treat was 2.6, and the effect size was 0.97 [95% CI (0.6; 1.3)]. One week after the 5th stimulation day, pain scores were no longer different between groups, and no difference in neuropathic pain characteristics and interference with daily living were present. No major side effects occurred, and milder adverse events (i.e., short-lived headaches after stimulation) were reported in both groups. Blinding was effective, and analgesic effects were not affected by sequence of the stimulation series (active-first or sham-first), age, sex or pain duration of participants.

DISCUSSION

PSI deep-rTMS was safe in refractory pNeP and was able to provide significant pain intensity reduction after a five-day induction series of treatments. Post-hoc assessment of neuronavigation targeting confirmed deep-rTMS was delivered within the boundaries of the PSI in all participants.

CONCLUSION

PSI deep-rTMS provided significant pain relief during 5-day induction sessions compared to sham stimulation.

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.

A randomized controlled trial of 5 daily sessions and continuous trial of 4 weekly sessions of repetitive transcranial magnetic stimulation for neuropathic pain

Supplemental Digital Content is Available in the Text.

Five daily sessions of repetitive transcranial magnetic stimulation with stimulus conditions were ineffective in neuropathic pain relief. Long-term administration should be investigated for clinical use of repetitive transcranial magnetic stimulation in neuropathic pain.

We conducted a multicenter, randomized, patient- and assessor-blinded, sham-controlled trial to investigate the efficacy of repetitive transcranial magnetic stimulation (rTMS) of the primary motor cortex (M1) in patients with neuropathic pain (NP). Patients were randomly assigned to receive 5 daily sessions of active or sham rTMS of M1 corresponding to the part of the body experiencing the worst pain (500 pulses per session at 5 Hz). Responders were invited to enroll in an open-label continuous trial involving 4 weekly sessions of active rTMS. The primary outcome was a mean decrease in a visual analogue scale of pain intensity (scaled 0-100 mm) measured daily during the daily sessions in an intention-to-treat population. Secondary outcomes were other pain scores, quality-of-life measures, and depression score. One hundred forty-four patients were assigned to the active or sham stimulation groups. The primary outcome, mean visual analogue scale decreases, was not significantly different (P = 0.58) between the active stimulation group (mean, 8.0) and the sham group (9.2) during the daily sessions. The secondary outcomes were not significantly different between 2 groups. The patients enrolled in the continuous weekly rTMS achieved more pain relief in the active stimulation group compared with the sham (P < 0.01). No serious adverse events were observed. Five daily sessions of rTMS with stimulus conditions used in this trial were ineffective in short-term pain relief in the whole study population with various NP. Long-term administration to the responders should be investigated for the clinical use of rTMS on NP in the future trials.

Transcranial Direct Current Stimulation and Mirror Therapy for Neuropathic Pain After Brachial Plexus Avulsion: A Randomized, Double-Blind, Controlled Pilot Study

Introduction: Although transcranial direct current stimulation (tDCS) and mirror therapy (MT) have benefits in combating chronic pain, there is still no evidence of the effects of the simultaneous application of these techniques in patients with neuropathic pain. This study aims to assess the efficacy of tDCS paired with MT in neuropathic pain after brachial plexus injury. Methods: In a sham controlled, double-blind, parallel-group design, 16 patients were randomized to receive active or sham tDCS administered during mirror therapy. Each patient received 12 treatment sessions, 30 min each, during a period of 4 weeks over M1 contralateral to the side of the injury. Outcome variables were evaluated at baseline and post-treatment using the McGill questionnaire, Brief Pain Inventory, and Medical Outcomes Study 36-Item Short-Form Health Survey. Long-term effects of treatment were evaluated at a 3-month follow-up. Results: An improvement in pain relief and quality of life were observed in both groups (p ≤ 0.05). However, active tDCS and mirror therapy resulted in greater improvements after the endpoint (p ≤ 0.02). No statistically significant differences in the outcome measures were identified among the groups at follow-up (p ≥ 0.12). A significant relationship was found between baseline pain intensity and outcome measures (p ≤ 0.04). Moreover, the results showed that state anxiety is closely linked to post-treatment pain relief (p ≤ 0.05). Conclusion: Active tDCS combined with mirror therapy has a short-term effect of pain relief, however, levels of pain and anxiety at the baseline should be considered. Clinical Trial Registration: www.ClinicalTrials.gov, identifier NCT04385030.

Neuromodulation techniques for acute and preventive migraine treatment: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Several neuromodulation methods exists for migraine treatment. The aim of the present study was to perform a systematic review and meta-analysis of randomized controlled trials (RCTs) focusing on migraine treatment using neurostimulation methods.

METHODS

We searched Medline and Embase up to July 1, 2020 for RCTs reporting acute or preventive treatment of migraine with either non-invasive or invasive neurostimulation methods. Two researchers independently assessed the eligibility of the retrieved studies and extracted data. Outcomes for the quantitative synthesis were 2 h pain free for acute treatment and headache days per month for preventive treatment. We performed subgroup analyses by treatment (stimulation method and site of application). Estimates were pooled using random-effects meta-analysis.

RESULTS

Thirty-eight articles were included in the qualitative analysis (7 acute, 31 preventive) and 34 in the quantitative evaluation (6 acute, 28 preventive). Remote electrical neuromodulation (REN) was effective for acute treatment. Data were insufficient to draw conclusions for any other techniques (single studies). Invasive occipital nerve stimulation (ONS) was effective for migraine prevention, with a large effect size but considerable heterogeneity, whereas supra-orbital transcutaneous electrical nerve stimulation (TENS), percutaneous electrical nerve stimulation (PENS), and high-frequency repetitive transcranial magnetic stimulation (rTMS) over the primary motor cortex (M1) were effective, with small to medium effect sizes. Vagus-nerve stimulation, left prefrontal cortex rTMS, and cathodal transcranial direct current stimulation (tDCS) over the M1 had no significant effect and heterogeneity was high.

CONCLUSION

Several neuromodulation methods are of potential interest for migraine management, but the quality of the evidence is very poor. Future large and well-conducted studies are needed and could improve on the present results.

Repetitive transcranial magnetic stimulation of the primary motor cortex in management of chronic neuropathic pain: a systematic review

OBJECTIVES

Repetitive transcranial magnetic stimulation (rTMS) of the primary motor cortex (M1) with frequencies 5-20 Hz is an expanding non-invasive treatment for chronic neuropathic pain (NP). Outcome data, however, show considerable inhomogeneity with concern to the levels of effect due to the great diversity of treated conditions. The aim of this review was to survey the literature regarding the efficacy and safety of M1 rTMS, and the accuracy to predict a positive response to epidural motor cortex stimulation (MCS) which is supposed to give a more longstanding pain relief.

METHODS

A systematic literature search was conducted up to June 2019 in accordance with the PRISMA guidelines. We used the PICO Model to define two specific clinical questions: (1) Does rTMS of M1 relieve NP better than sham treatment? (2) Can the response to rTMS be used to predict the effect of epidural MCS? After article selection, data extraction, and study quality assessment, the certainty of evidence of treatment effect was defined using the GRADE system.

RESULTS

Data on 5-20 Hz (high-frequency) rTMS vs. sham was extracted from 24 blinded randomised controlled trials which were of varying quality, investigated highly heterogeneous pain conditions, and used excessively variable stimulation parameters. The difference in pain relief between active and sham stimulation was statistically significant in 9 of 11 studies using single-session rTMS, and in 9 of 13 studies using multiple sessions. Baseline data could be extracted from 6 single and 12 multiple session trials with a weighted mean pain reduction induced by active rTMS, compared to baseline, of -19% for single sessions, -32% for multiple sessions with follow-up <30 days, and -24% for multiple sessions with follow-up ≥30 days after the last stimulation session. For single sessions the weighted mean difference in pain reduction between active rTMS and sham was 15 percentage points, for multiple sessions the difference was 22 percentage points for follow-ups <30 days, and 15 percentage points for follow-ups ≥30 days. Four studies reported data that could be used to evaluate the accuracy of rTMS to predict response to MCS, showing a specificity of 60-100%, and a positive predictive value of 75-100%. No serious adverse events were reported.

CONCLUSIONS

rTMS targeting M1 can result in significant reduction of chronic NP which, however, is transient and shows a great heterogeneity between studies; very low certainty of evidence for single sessions and low for multiple sessions. Multiple sessions of rTMS can maintain a more longstanding effect. rTMS seems to be a fairly good predictor of a positive response to epidural MCS and may be used to select patients for implantation of permanent epidural electrodes. More studies are needed to manifest the use of rTMS for this purpose. Pain relief outcomes in a longer perspective, and outcome variables other than pain reduction need to be addressed more consistently in future studies to consolidate the applicability of rTMS in routine clinical practice.

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.

Clinical and Neurochemical Effects of Transcranial Magnetic Stimulation (TMS) in Multiple Sclerosis: A Study Protocol for a Randomized Clinical Trial

Background: Transcranial Magnetic Stimulation (TMS) is a technique based on the principles of electromagnetic induction. It applies pulses of magnetic radiation that penetrate the brain tissue, and it is a non-invasive, painless, and practically innocuous procedure. Previous studies advocate the therapeutic capacity of TMS in several neurodegenerative and psychiatric processes, both in animal models and in human studies. Its uses in Parkinson's disease, Alzheimer's disease and in Huntington's chorea have shown improvement in the symptomatology and in the molecular profile, and even in the cellular density of the brain. Consequently, the extrapolation of these TMS results in the aforementioned neurodegenerative disease to other entities with etiopathogenic and clinical analogy would raise the relevance and feasibility of its use in multiple sclerosis (MS). The overall objective will be to demonstrate the effectiveness of the TMS in terms of safety and clinical improvement, as well as to observe the molecular changes in relation to the treatment.

Methods and Design: Phase II clinical trial, unicentric, controlled, randomized, single blind. A total of 90 patients diagnosed with relapsing-remitting multiple sclerosis (RRMS) who meet all the inclusion criteria and do not present any of the exclusion criteria that are established and from which clinically evaluable results can be obtained. The patients included will be assigned under the 1:1:1 randomization formula, constituting three groups for the present study: 30 patients treated with natalizumab + white (placebo) + 30 patients treated with natalizumab + TMS (1 Hz) + 30 patients treated with natalizumab + TMS (5 Hz).

Discussion: Results of this study will inform on the efficiency of the TMS for the treatment of MS. The expected results are that TMS is a useful therapeutic resource to improve clinical status (main parameters) and neurochemical profile (surrogate parameters); both types of parameters will be checked.

Ethics and Dissemination: The study is approved by the Local Ethics Committee and registered in https://clinicaltrials.gov (NCT04062331). Dissemination will include submission to a peer-reviewed journal, patients, associations of sick people and family members, healthcare magazines and congress presentations.

Trial Registration:ClinicalTrials.gov ID: NCT04062331 (registration date: 19^th/ August/2019).

Version Identifier: EMTr-EMRR, ver-3, 21/11/2017.

New Developments in Non-invasive Brain Stimulation in Chronic Pain

Purpose of Review

The goal of this review is to present a summary of the recent literature of a non-invasive brain stimulation (NIBS) to alleviate pain in people with chronic pain syndromes. This article reviews the current evidence for the use of transcranial direct current (tDCS) and repetitive transcranial magnetic stimulation (rTMS) to improve outcomes in chronic pain. Finally, we introduce the reader to novel stimulation methods that may improve therapeutic outcomes in chronic pain.

Recent Findings

While tDCS is approved for treatment of fibromyalgia in Canada and the European Union, no NIBS method is currently approved for chronic pain in the United States. Increasing sample sizes in randomized clinical trials (RCTs) seems the most efficient way to increase confidence in initial promising results. Trends at funding agencies reveal increased interest and support for NIBS such as recent Requests for Application from the National Institutes of Health. NIBS in conjunction with cognitive behavioral therapy and physical therapy may enhance outcomes in chronic pain. Novel stimulation methods, such as transcranial ultrasound stimulation, await rigorous study in chronic pain.

Repetitive Magnetic Stimulation for the Management of Peripheral Neuropathic Pain: A Systematic Review

INTRODUCTION

Repetitive magnetic stimulation (rMS) is a safe and well-tolerated intervention. Transcranial magnetic stimulation (TMS) is used for the treatment of depression and for the treatment and prevention of migraine. Over the last few years, several reports and randomised controlled studies of the use of rMS for the treatment of pain have been published. The aim of this systematic review was to identify the available literature regarding the use of rMS in the treatment of peripheral neuropathic pain.

METHODS

After a systematic Medline search we identified 12 papers eligible to be included in this review.

RESULTS

The majority of the studies were on patients with phantom limb pain, followed by radiculopathy, plexopathy, post-traumatic pain and peripheral neuropathy. The treatment protocols vary significantly from study to study and, therefore, pooling the results together is currently difficult. However, rMS has a definite immediate effect in pain relief which, in the majority of studies, is maintained for a few weeks.

CONCLUSION

rMS seems to be a promising intervention in the treatment of peripheral neuropathic pain. Further research is in the field is needed. Use of neuronavigation might increase the precision of stimulation and subsequently its effectiveness.