Is transcranial direct current stimulation (tDCS) effective for chronic low back pain? A systematic review and meta-analysis

The effects of combined transcranial direct Current stimulation with physiotherapy for physical function in subjects with knee osteoarthritis: a systematic review and meta-analysis

BACKGROUND

Transcranial Direct Current Stimulation (tDCS) emerges as a promising therapeutic intervention for knee osteoarthritis (KOA), yet its impact on physical function remains insufficiently explored.

OBJECTIVES

To evaluate the relative effects of tDCS for physical function in patients with KOA.

METHODS

Pubmed, Web of Science, Scopus and Cochrane Database were explored as of August 2023 to identify studies to be included in the current systematic review and metaanalysis. Randomized controlled trials in patients with KOA comparing tDCS with placebo were included. The outcomes defined were measures of physical function (questionnaires, gait, or physical performance). The Risk of Bias tool was used to assess bias in the randomized controlled trials, whereas the PEDro scale was applied for methodological quality, and the certainty of evidence for each outcome was assessed through GRADE. Results for each outcome were synthesized using meta-analysis (random-effects model, I2-test for heterogeneity) and a subgroup analysis was performed to improve the sensitivity of the results and to explore potential moderating factors of the effect sizes.

RESULTS

Ten studies with good to excellent quality were included, analyzing a total of 628 participants. Regarding physical function, tDCS showed a favorable effect (ES: -0.58; 95%CI -0.82, -0.33; I2: 52.1%) with a low risk of bias and low to moderate certainty of evidence. The concurrent application of physiotherapy interventions and tDCS improved the effects on pain and function. Applying physiotherapy interventions, as well as adding peripheral currents, increased the effect sizes (ES: -0.95, k = 3, p = .018; ES: -0.95, k = 4 p = .001, respectively). The pattern of application of the tDCS, either daily or in alternate days, did not moderate the effect size (p = .619). Meta-regression revealed that the number of tDCS sessions did not moderate the effect size either (p = .242).

CONCLUSION

The tDCS might be a promising therapeutic approach to enhance physical function in subjects affected with KOA. However, further systematic reviews with meta-analyses should be performed with standardized and proven-efficacy physiotherapy programs, as well as with long-term results, to ascertain whether the improvement may be sustained over time. This study provides valuable insights into optimizing tDCS interventions for enhanced outcomes in the management of KOA.Protocol available via PROSPERO [CRD42023440676].

Anatomo-physiological basis and applied techniques of electrical neuromodulation in chronic pain

Chronic pain, a complex and debilitating condition, poses a significant challenge to both patients and healthcare providers worldwide. Conventional pharmacological interventions often prove inadequate in delivering satisfactory relief while carrying the risks of addiction and adverse reactions. In recent years, electric neuromodulation emerged as a promising alternative in chronic pain management. This method entails the precise administration of electrical stimulation to specific nerves or regions within the central nervous system to regulate pain signals. Through mechanisms that include the alteration of neural activity and the release of endogenous pain-relieving substances, electric neuromodulation can effectively alleviate pain and improve patients' quality of life. Several modalities of electric neuromodulation, with a different grade of invasiveness, provide tailored strategies to tackle various forms and origins of chronic pain. Through an exploration of the anatomical and physiological pathways of chronic pain, encompassing neurotransmitter involvement, this narrative review offers insights into electrical therapies' mechanisms of action, clinical utility, and future perspectives in chronic pain management.

Efficacy of Transcranial Direct Current Stimulation on Pain Intensity and Functionality in Patients With Knee Osteoarthritis: A Systematic Review and Meta-analysis

OBJECTIVE

The aim of the study is to investigate whether transcranial direct current stimulation is superior to control groups or other interventions for pain relief and improving functionality in knee osteoarthritis patients.

METHODS

PubMed, the Physiotherapy Evidence Database, the Cochrane Library, ProQuest, and Scopus databases were searched from inception to July 2022 to identify randomized clinical trials. The main outcomes were subjective perception of pain intensity measured either with the visual analog scale or with the numeric rating scale; and the functionality, assessed with the Western Ontario and McMaster Universities Osteoarthritis Index. As secondary outcomes, pressure pain threshold, conditioned pain modulation, and its safety were evaluated.

RESULTS

We identified 10 randomized clinical trials (634 participants). The results showed an important effect favoring transcranial direct current stimulation for pain relief (mean difference = -1.1 cm, 95% confident interval = -2.1 to -0.2) and for improving functionality (standardized mean difference = -0.6, 95% confident interval = -1.02 to -0.26). There was also a significant improvement in pressure pain threshold (mean difference = 0.9 Kgf/cm 2 , 95% confident interval = 0.1 to 1.6). The certainty of evidence according to Grades of Recommendation Assessment, Development and Evaluation was generally moderate.

CONCLUSIONS

Our findings suggest that transcranial direct current stimulation is a safe treatment for reducing pain intensity, improving functionality, and the pressure pain thresholds in patients with knee osteoarthritis.

The effects of virtual reality neuroscience-based therapy on clinical and neuroimaging outcomes in patients with chronic back pain: a randomized clinical trial

ABSTRACT

Chronic pain remains poorly managed. The integration of immersive technologies (ie, virtual reality [VR]) with neuroscience-based principles may provide effective pain treatment by targeting cognitive and affective neural processes that maintain pain and therefore potentially changing neurobiological circuits associated with pain chronification and amplification. We tested the effectiveness of a novel VR neuroscience-based therapy (VRNT) to improve pain-related outcomes in n = 31 participants with chronic back pain, evaluated against usual care (waitlist control; n = 30) in a 2-arm randomized clinical trial (NCT04468074). We also conducted pre-treatment and post-treatment MRI to test whether VRNT affects brain networks previously linked to chronic pain and treatment effects. Compared with the control condition, VRNT led to significantly reduced pain intensity (g = 0.63) and pain interference (g = 0.84) at post-treatment vs pre-treatment, with effects persisting at 2-week follow-up. These improvements were partially mediated by reduced kinesiophobia and pain catastrophizing. Several secondary clinical outcomes were also improved by VRNT, including disability, quality of life, sleep, and fatigue. In addition, VRNT was associated with increases in dorsomedial prefrontal functional connectivity with the superior somatomotor, anterior prefrontal and visual cortices, and decreased white matter fractional anisotropy in the corpus callosum adjacent to the anterior cingulate, relative to the control condition. Thus, VRNT showed preliminary efficacy in significantly reducing pain and improving overall functioning, possibly through changes in somatosensory and prefrontal brain networks.

Transcranial Direct Current Stimulation for Orthopedic Pain: A Systematic Review with Meta-Analysis

(1) Background: Transcranial direct current stimulation (tDCS) appears to alleviate chronic pain via a brain-down mechanism. Although several review studies have examined the effects of tDCS on patients with chronic pain, no systematic review or meta-analysis has comprehensively analyzed the effects of tDCS on chronic orthopedic joint pain in one study. We aim to evaluate the effectiveness of tDCS for pain reduction in chronic orthopedic patients; (2) Methods: A comprehensive search of five electronic databases (Medline, Embase, Web of Science, CINAHL, and Cochrane) was performed. Only randomized controlled trials that compared tDCS with a control intervention were included. Eighteen studies met our inclusion criteria. We identified four categories of chronic orthopedic pain: knee (k = 8), lower back (k = 7), shoulder (k = 2), and orofacial pain (k = 1). Random effect models were utilized, and a sensitivity analysis was conducted in the presence of significant heterogeneity. Studies within each pain condition were further classified according to the number of treatment sessions: 1-5 sessions, 6-10 sessions, and >10 sessions.; (3) Results: Significant reductions in chronic orthopedic joint pain were observed following tDCS compared to controls for knee (g = 0.59, p = 0.005), lower back (g = 1.14, p = 0.005), and shoulder (g = 1.17, p = 0.020). Subgroup analyses showed pain reductions after 6-10 tDCS sessions for knee pain and after 1-5 and >10 sessions for lower back pain; (4) Conclusions: tDCS could be considered a potential stand-alone or supplemental therapy for chronic knee and lower back pain. The effectiveness of tDCS treatment varies depending on the number of treatment sessions. Our findings suggest the importance of implementing individualized treatment plans when considering tDCS for chronic pain conditions.

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

INTRODUCTION

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

METHODS AND ANALYSIS

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

ETHICS AND DISSEMINATION

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

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov (NCT05467566).

Efficacy of transcranial direct current stimulation in patients with knee osteoarthritis: A systematic review

OBJECTIVE

Transcranial direct current stimulation (tDCS) has demonstrated its efficacy in alleviating pain among individuals with musculoskeletal disorders. This review focuses on the application of tDCS as a therapeutic intervention for managing knee osteoarthritis (OA), a prevalent musculoskeletal condition. The primary objective is to assess the effectiveness of tDCS(add-on tDCS and /or stand-alone tDCS), whether as an add-on to existing treatments or as a standalone therapy, in reducing pain and enhancing functional capacity in patients with knee OA.

METHODS

A comprehensive search was conducted across multiple databases, including PubMed, Science Direct, OVID, MEDLINE, CINAHL, EMBASE, ProQuest, and Google Scholar, and Web of Science. The search terms employed were "Transcranial direct current stimulation" or "tDCS" in combination with "Osteoarthritis" or "OA" and "knee." After eliminating duplicates and studies that did not meet the inclusion criteria, a total of 14 relevant articles were identified for review.

RESULTS

Among the included studies, twelve reported statistically significant improvements in pain levels when comparing the active tDCS group to the sham tDCS group. Only two studies reported no significant difference in pain intensity between the active tDCS and sham tDCS groups. Findings regarding functional abilities were diverse, with some studies demonstrating a significant enhancement in functional outcomes in the active tDCS group, while others observed no statistically significant differences.

CONCLUSION

The results of this review suggest that tDCS holds promise as a pain management intervention for individuals with knee OA. Notably, anodal tDCS applied over the primary motor cortex (M1) appears to be particularly effective in alleviating pain in patients with knee OA. However, the impact of tDCS on functional performance appears to be limited.

Do Electrical Stimulation Devices Reduce Pain and Improve Function?-A Comparative Review

BACKGROUND

Multiple forms of electrical stimulation (ES) potentially offer widely varying clinical benefits. Diminished function commonly associated with acute and chronic pain lessens productivity and increases medical costs. This review aims to compare the relative effects of various forms of ES on functional and pain outcomes.

METHODS

A comprehensive literature search focused on studies of commonly marketed forms of ES used for treatment of pain and improvement of function. Peer-reviewed manuscripts were categorized as "Important" (systematic review or meta-analysis, randomized controlled trial, observational cohort study) and "Minor" (retrospective case series, case report, opinion review) for each identified form of ES.

RESULTS AND DISCUSSION

Varying forms of ES have markedly different technical parameters, applications, and indications, based on clinically meaningful impact on pain perception, function improvement, and medication reduction. Despite being around for decades, there is limited quality evidence for most forms of ES, although there are several notable exceptions for treatment of specific indications. Neuromuscular electrical stimulation (NMES) has well-demonstrated beneficial effects for rehabilitation of selective spinal cord injured (SCI), post-stroke, and debilitated inpatients. Functional electrical stimulation (FES) has similarly shown effectiveness in rehabilitation of some stroke, SCI, and foot drop outpatients. H-Wave® device stimulation (HWDS) has moderate supportive evidence for treatment of acute and refractory chronic pain, consistently demonstrating improvements in function and pain measures across diverse populations. Interestingly, transcutaneous electrical nerve stimulation (TENS), the most widely used form of ES, demonstrated insignificant or very low levels of pain and functional improvement.

CONCLUSION

Ten of 13 reviewed forms of ES have only limited quality evidence for clinically significant reduction of pain or improvement of function across different patient populations. NMES and FES have reasonably demonstrated effectiveness, albeit for specific clinical rehabilitation indications. HWDS was associated with the most clinically significant outcomes, in terms of functional improvement combined with reduction of pain and medication use. More rigorous long-term clinical trials are needed to further validate appropriate use and specific indications for most forms of ES.

LEVEL OF EVIDENCE

II.

Current Neurostimulation Therapies for Chronic Pain Conditions

PURPOSE OF REVIEW

Neurostimulation treatment options have become more commonly used for chronic pain conditions refractory to these options. In this review, we characterize current neurostimulation therapies for chronic pain conditions and provide an analysis of their effectiveness and clinical adoption. This manuscript will inform clinicians of treatment options for chronic pain.

RECENT FINDINGS

Non-invasive neurostimulation includes transcranial direct current stimulation and repetitive transcranial magnetic stimulation, while more invasive options include spinal cord stimulation (SCS), peripheral nerve stimulation (PNS), dorsal root ganglion stimulation, motor cortex stimulation, and deep brain stimulation. Developments in transcranial direct current stimulation, repetitive transcranial magnetic stimulation, spinal cord stimulation, and peripheral nerve stimulation render these modalities most promising for the alleviating chronic pain. Neurostimulation for chronic pain involves non-invasive and invasive modalities with varying efficacy. Well-designed randomized controlled trials are required to delineate the outcomes of neurostimulatory modalities more precisely.

Chronic pain outcomes of patients receiving electroconvulsive therapy: A systematic review and case series

INTRODUCTION

The potential benefits of electroconvulsive therapy (ECT) in chronic pain and several theories for its mechanism have been reported in the past, but mixed findings have also been reported. In the current systematic review and case series, our primary aim was to assess whether pain and functional outcomes are improved after ECT in patients with chronic pain. Secondary objectives included examining whether psychiatric improvement, specific pain diagnoses, and demographic or medical characteristics were associated with differences in pain treatment response.

METHODS

We performed a retrospective chart review to identify patients with chronic pain diagnoses for more than 3 months prior to the initiation of ECT and a systematic literature search on electronic databases for studies on chronic pain outcomes after ECT.

RESULTS

Eleven patients with various chronic pain diagnoses and comorbid psychiatric conditions were identified in the case series. Six patients reported improvement in pain while 10 patients reported improvement in mood following ECT. Systematic review identified 22 articles reporting a total of 109 cases. Eighty-five (78%) of cases reported reduction in pain while 96.3% of the patients with a comorbid psychiatric diagnosis reported improvement in mood symptoms post-ECT. While there was an association between improvement in mood and pain in studies with numeric ratings in both outcomes (r = 0.61; p < 0.001), some patients reported pain improvement without improvement in mood in both the case series and the pooled analysis of cases in the review. Certain pain diagnoses such as CRPS, phantom limb pain, neuropathic pain, and low back pain have consistently reported benefits and should be further studied in future studies with matched case controls.

CONCLUSION

ECT may be offered to patients with certain pain conditions who have not responded sufficiently to conventional therapies, particularly when comorbid mood symptoms are present. Improved documentation practices on the outcomes in chronic pain patients receiving ECT will help generate more studies that are needed on this topic.

Diagnosis and Management of Neuropathic Pain in Spine Diseases

Neuropathic pain is generally defined as a non-physiological pain experience caused by damage to the nervous system. It can occur spontaneously, as a reaction to a given stimulus, or independently of its action, leading to unusual pain sensations usually referred to as firing, burning or throbbing. In the course of spine disorders, pain symptoms commonly occur. According to available epidemiological studies, a neuropathic component of pain is often present in patients with spinal diseases, with a frequency ranging from 36% to 55% of patients. Distinguishing between chronic nociceptive pain and neuropathic pain very often remains a challenge. Consequently, neuropathic pain is often underdiagnosed in patients with spinal diseases. In reference to current guidelines for the treatment of neuropathic pain, gabapentin, serotonin and norepinephrine reuptake inhibitors and tricyclic antidepressants constitute first-line therapeutic agents. However, long-term pharmacologic treatment often leads to developing tolerance and resistance to used medications. Therefore, in recent years, a plethora of therapeutic methods for neuropathic pain have been developed and investigated to improve clinical outcomes. In this review, we briefly summarized current knowledge about the pathophysiology and diagnosis of neuropathic pain. Moreover, we described the most effective treatment approaches for neuropathic pain and discussed their relevance in the treatment of spinal pain.

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

INTRODUCTION

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

AREAS COVERED

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

EXPERT OPINION

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

Is transcranial direct current stimulation beneficial for treating pain, depression, and anxiety symptoms in patients with chronic pain? A systematic review and meta-analysis

BACKGROUND

Chronic pain is often accompanied by emotional dysfunction. Transcranial direct current stimulation (tDCS) has been used for reducing pain, depressive and anxiety symptoms in chronic pain patients, but its therapeutic effect remains unknown.

OBJECTIVES

To ascertain the treatment effect of tDCS on pain, depression, and anxiety symptoms of patients suffering from chronic pain, and potential factors that modulate the effectiveness of tDCS.

METHODS

Literature search was performed on PubMed, Embase, Web of Science, and Cochrane Library from inception to July 2022. Randomized controlled trials that reported the effects of tDCS on pain and depression and anxiety symptoms in patients with chronic pain were included.

RESULTS

Twenty-two studies were included in this review. Overall pooled results indicated that the use of tDCS can effectively alleviate short-term pain intensity [standard mean difference (SMD): -0.43, 95% confidence interval (CI): -0.75 to -0.12, P = 0.007] and depressive symptoms (SMD: -0.31, 95% CI, -0.47 to -0.14, P < 0.001), middle-term depressive symptoms (SMD: -0.35, 95% CI: -0.58 to -0.11, P = 0.004), long-term depressive symptoms (ES: -0.38, 95% CI: -0.64 to -0.13, P = 0.003) and anxiety symptoms (SMD: -0.26, 95% CI: -0.51 to -0.02, P = 0.03) compared with the control group.

CONCLUSION

tDCS may be an effective short-term treatment for the improvement of pain intensity and concomitant depression and anxiety symptoms in chronic pain patients. Stimulation site, stimulation frequency, and type of chronic pain were significant influence factors for the therapeutic effect of tDCS.

SYSTEMATIC REVIEW REGISTRATION

https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=297693, identifier: CRD42022297693.

Non-invasive brain neuromodulation techniques for chronic low back pain

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

Neuromodulation of somatosensory pain thresholds of the neck musculature using a novel transcranial direct current stimulation montage: a randomized double-blind, sham controlled study

OBJECTIVES

Anodal transcranial direct current stimulation (tDCS) of primary motor cortex (M1) and cathodal of the primary sensory cortex (S1) have previously shown to modulate the sensory thresholds when administered with the reference electrode located over the contralateral supraorbital area (SO). Combining the two stimulation paradigms into one with simultaneous stimulation of the two brain areas (M1 + S1 - tDCS) may result in a synergistic effect inducing a prominent neuromodulation, noticeable in the pain thresholds. The aim of this study is to assess the efficacy of the novel M1 + S1 - tDCS montage compared to sham-stimulation in modulating the pain thresholds in healthy adults.

METHODS

Thirty-nine (20 males) subjects were randomly assigned to either receiving 20 min. active M1 + S1 - tDCS or sham tDCS in a double-blinded single session study. Thermal and mechanical pain thresholds were assessed before and after the intervention.

RESULTS

There were no significant differences in the pain thresholds within either group, or between the M1 + S1 - tDCS group and the Sham-tDCS group (p>0.05), indicating that the intervention was ineffective in inducing a neuromodulation of the somatosensory system.

CONCLUSIONS

Experimental investigations of novel tDCS electrode montages, that are scientifically based on existing studies or computational modelling, are essential to establish better tDCS protocols. Here simultaneous transcranial direct current stimulation of the primary motor cortex and primary sensory cortex showed no effect on the pain thresholds of the neck musculature in healthy subjects. This tDCS montage may have been ineffective due to how the electrical field reaches the targeted neurons, or may have been limited by the design of a single tDCS administration. The study adds to the existing literature of the studies investigating effects of new tDCS montages with the aim of establishing novel non-invasive brain stimulation interventions for chronic neck pain rehabilitation. North Denmark Region Committee on Health Research Ethics (VN-20180085) ClinicalTrials.gov (NCT04658485).

Modulation Of Experimental Prolonged Pain and Sensitization Using High-Definition Transcranial Direct Current Stimulation: A Double-Blind, Sham-Controlled Study

High definition transcranial direct current stimulation (HD-tDCS) targeting brain areas involved in pain processing has shown analgesic effects in some chronic pain conditions, but less modulatory effect on mechanical and thermal pain thresholds in asymptomatic subjects. This double-blinded study assessed the HD-tDCS effects on experimental pain and hyperalgesia maintained for several days in healthy participants. Hyperalgesia and pain were assessed during three consecutive days following provocation of experimental pain (nerve growth factor injected into the right-hand muscle) and daily HD-tDCS sessions (20-minutes). Forty subjects were randomly assigned to Active-tDCS targeting primary motor cortex and dorsolateral prefrontal cortex simultaneously or Sham-tDCS. Tactile and pressure pain sensitivity were assessed before and after each HD-tDCS session, as well as the experimentally-induced pain intensity scored on a numerical rating scale (NRS). Subjects were effectively blinded to the type of HD-tDCS protocol. The Active-tDCS did not significantly reduce the NGF-induced NRS pain score (3.5±2.4) compared to Sham-tDCS (3.9±2.0, P > .05) on day 3 and both groups showed similarly NGF-decreased pressure pain threshold in the right hand (P < .001). Comparing Active-tDCS with Sham-tDCS, the manifestation of pressure hyperalgesia was delayed on day 1, and an immediate (pre-HD-tDCS to post-HD-tDCS) reduction in pressure hyperalgesia was found across all days (P < .05). PERSPECTIVE: The non-significant differences between Active-tDCS and Sham-tDCS on experimental prolonged pain and hyperalgesia suggest that HD-tDCS has no effect on moderate persistent experimental pain. The intervention may still have a positive effect in more severe pain conditions, with increased intensity, more widespread distribution, or increased duration and/or involving stronger affective components.

Non-invasive Brain Stimulation for Chronic Pain: State of the Art and Future Directions

As a technique that can guide brain plasticity, non-invasive brain stimulation (NIBS) has the potential to improve the treatment of chronic pain (CP) because it can interfere with ongoing brain neural activity to regulate specific neural networks related to pain management. Treatments of CP with various forms of NIBS, such as repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS), using new parameters of stimulation have achieved encouraging results. Evidence of moderate quality indicates that high-frequency rTMS of the primary motor cortex has a clear effect on neuropathic pain (NP) and fibromyalgia. However, evidence on its effectiveness regarding pain relief in other CP conditions is conflicting. Concerning tDCS, evidence of low quality supports its benefit for CP treatment. However, evidence suggesting that it exerts a small treatment effect on NP and headaches is also conflicting. In this paper, we describe the underlying principles behind these commonly used stimulation techniques; and summarize the results of randomized controlled trials, systematic reviews, and meta-analyses. Future research should focus on a better evaluation of the short-term and long-term effectiveness of all NIBS techniques and whether they decrease healthcare use, as well as on the refinement of selection criteria.

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

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

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

OBJECTIVE

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

MATERIALS AND METHODS

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

RESULTS

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

DISCUSSION

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

Neuromodulation for chronic pain

Neuromodulation is an expanding area of pain medicine that incorporates an array of non-invasive, minimally invasive, and surgical electrical therapies. In this Series paper, we focus on spinal cord stimulation (SCS) therapies discussed within the framework of other invasive, minimally invasive, and non-invasive neuromodulation therapies. These therapies include deep brain and motor cortex stimulation, peripheral nerve stimulation, and the non-invasive treatments of repetitive transcranial magnetic stimulation, transcranial direct current stimulation, and transcutaneous electrical nerve stimulation. SCS methods with electrical variables that differ from traditional SCS have been approved. Although methods devoid of paraesthesias (eg, high frequency) should theoretically allow for placebo-controlled trials, few have been done. There is low-to-moderate quality evidence that SCS is superior to reoperation or conventional medical management for failed back surgery syndrome, and conflicting evidence as to the superiority of traditional SCS over sham stimulation or between different SCS modalities. Peripheral nerve stimulation technologies have also undergone rapid development and become less invasive, including many that are placed percutaneously. There is low-to-moderate quality evidence that peripheral nerve stimulation is effective for neuropathic pain in an extremity, low quality evidence that it is effective for back pain with or without leg pain, and conflicting evidence that it can prevent migraines. In the USA and many areas in Europe, deep brain and motor cortex stimulation are not approved for chronic pain, but are used off-label for refractory cases. Overall, there is mixed evidence supporting brain stimulation, with most sham-controlled trials yielding negative findings. Regarding non-invasive modalities, there is moderate quality evidence that repetitive transcranial magnetic stimulation does not provide meaningful benefit for chronic pain in general, but conflicting evidence regarding pain relief for neuropathic pain and headaches. For transcranial direct current stimulation, there is low-quality evidence supporting its benefit for chronic pain, but conflicting evidence regarding a small treatment effect for neuropathic pain and headaches. For transcutaneous electrical nerve stimulation, there is low-quality evidence that it is superior to sham or no treatment for neuropathic pain, but conflicting evidence for non-neuropathic pain. Future research should focus on better evaluating the short-term and long-term effectiveness of all neuromodulation modalities and whether they decrease health-care use, and on refining selection criteria and treatment variables.

Pharmacological and non-pharmacological treatment approaches to chronic lumbar back pain

Low back pain is a common and important cause of disability. Chronic pain increases disability and cost. In this review, we discuss pharmacological and non-pharmacological treatment approaches for chronic low back pain in the light of current data and guidelines.