Transcutaneous electrical nerve stimulation (TENS) for fibromyalgia in adults

Effectiveness of transcutaneous electrical nerve stimulation improves pain intensity, disability and quality of life in patients with fibromyalgia syndrome: a systematic review with meta-analysis

PURPOSE

The transcutaneous electrical nerve stimulation (TENS) is one of the most frequently electrophysical agents employed in reducing the impact of FMS. This meta-analysis intended to determine the effectiveness of TENS on pain, disability, and quality of life (QoL) in patients with FMS.

METHODS

According to PRISMA, we performed a meta-analysis (CRD42023456439), searching in PubMed Medline, PEDro, CINAHL Complete, Web of Science, and Scopus, since inception up to October 2023. This review focused on controlled clinical trials evaluating the effect of TENS on pain, disability, and QoL in patients with FMS. The pooled effect was estimated using Cohen's standardized mean difference (SMD) and its 95% confidence interval (95%CI).

RESULTS

Twelve studies, providing data from 944 patients, were included (PEDro score of 5.6 points). Meta-analyses showed that TENS interventions are effective in improving pain (SMD = -0.61; 95%CI -1 to -0.16); disability (SMD = -0.27; 95%CI -0.41 to -0.12); and physical dimension of QoL (SMD = 0.26; 95%CI 0.08 to 0.44). Additionally, when TENS is used as a unique therapy, it represents the best therapeutic option for improving pain, disability, and QoL.

CONCLUSIONS

This meta-analysis, including the largest number of studies, showed that TENS intervention is an effective therapy to reduce pain and disability and increase QoL in FMS patients.

Efficacy and Safety of Transcutaneous Electrical Nerve Stimulation in Patients Undergoing Inguinal Hernia Repair: A Systematic Review and Meta-analysis

Background

Postoperative pain is a major cause of delayed recovery following inguinal hernia repair. Transcutaneous electrical nerve stimulation (TENS) is a simple, low-cost method of noninvasive analgesia. This study aimed to assess the efficacy and safety of TENS for pain management following inguinal hernia repair.

Methods

We searched nine electronic databases and trial registries to identify randomized controlled trials (RCTs). The primary outcomes were postoperative pain and the use of rescue analgesics. The Risk of Bias 2 tool was used to evaluate the risk of bias in the included trials. The certainty of the evidence was assessed using Grading of Recommendations, Assessment, Development, and Evaluations (GRADE). Subgroup analyses were conducted based on the anesthesia type or TENS dose and frequency. This study is registered with PROSPERO (CRD42022353932).

Results

Eleven RCTs, with a total of 559 patients, were included. The overall risk of bias was concerning due to the lack of information about concealment or published protocols. TENS may reduce pain on postoperative day (POD) 0 (standardized mean difference [SMD], -2.14; 95% confidence interval [CI], -3.54 to -0.73; moderate certainty of the evidence), POD 1 (SMD, -1.22; 95% CI, -1.92 to -0.52; moderate certainty of the evidence), and POD 2 (SMD, -0.97; 95% CI, -2.04 to 0.10; low certainty of the evidence). According to the subgroup analyses, postoperative pain was reduced, particularly with local anesthesia or repetitive and frequent TENS (P < 0.05). TENS may result in little-to-no difference in rescue analgesic use (risk ratio, 0.75; 95% CI, 0.47-1.18; low certainty of the evidence). No serious adverse events occurred (moderate certainty of the evidence).

Conclusions

TENS may reduce pain in patients who have undergone inguinal hernia repair. Further trials are warranted to confirm our findings.

Beyond the Pain: A Systematic Narrative Review of the Latest Advancements in Fibromyalgia Treatment

Fibromyalgia is a complex chronic pain disorder that significantly impacts the quality of life of affected individuals. The etiology of fibromyalgia remains elusive, necessitating effective treatment options. This review aims to provide an overview of current treatment options for fibromyalgia and highlight recent updates in managing the condition. The methodology employed in this systematic review comprised the following key steps. We conducted a comprehensive search across various databases to identify pertinent studies published between 2000 and 2023. Inclusion criteria were defined to specifically target studies involving adult individuals diagnosed with fibromyalgia, with a focus on both pharmacological and non-pharmacological interventions for managing the condition. The review encompassed a range of study types, including randomized controlled trials, observational studies, and systematic reviews. To ensure the quality of the selected studies, we employed appropriate assessment tools, and data extraction and synthesis adhered to established guidelines. This rigorous approach allowed for a robust analysis of the literature on fibromyalgia management. In the course of our review, it became evident that a spectrum of treatment approaches holds significant promise in the management of fibromyalgia. Specifically, pharmacological interventions, including selective serotonin-norepinephrine reuptake inhibitors, anticonvulsants, cannabinoids, tropisetron, and sodium oxybate, have exhibited substantial potential in alleviating fibromyalgia symptoms. Concurrently, non-pharmacological strategies, such as cognitive-behavioral therapy, exercise regimens, and complementary and alternative therapies, have yielded positive outcomes in improving the condition's management. Recent developments in the field have introduced innovative pharmacological agents like milnacipran and pregabalin, in addition to non-pharmacological interventions like mindfulness-based stress reduction and aquatic exercise, expanding the array of options available to enhance fibromyalgia care and alleviating patient symptoms. Fibromyalgia necessitates a multidisciplinary approach to treatment, encompassing both pharmacological and non-pharmacological interventions. Recent updates in fibromyalgia management offer additional options to alleviate symptoms and improve the quality of life for individuals with fibromyalgia. Healthcare professionals should remain informed about these advancements to provide evidence-based care, addressing the complex symptoms associated with fibromyalgia and enhancing patient outcomes.

Multimodal non-invasive non-pharmacological therapies for chronic pain: mechanisms and progress

BACKGROUND

Chronic pain conditions impose significant burdens worldwide. Pharmacological treatments like opioids have limitations. Non-invasive non-pharmacological therapies (NINPT) encompass diverse interventions including physical, psychological, complementary and alternative approaches, and other innovative techniques that provide analgesic options for chronic pain without medications.

MAIN BODY

This review elucidates the mechanisms of major NINPT modalities and synthesizes evidence for their clinical potential across chronic pain populations. NINPT leverages peripheral, spinal, and supraspinal mechanisms to restore normal pain processing and limit central sensitization. However, heterogeneity in treatment protocols and individual responses warrants optimization through precision medicine approaches.

CONCLUSION

Future adoption of NINPT requires addressing limitations in standardization and accessibility as well as synergistic combination with emerging therapies. Overall, this review highlights the promise of NINPT as a valuable complementary option ready for integration into contemporary pain medicine paradigms to improve patient care and outcomes.

Salivary stimulatory effect of novel low level transcutaneous electro neurostimulator in geriatric patients with xerostomia

BACKGROUND

Xerostomia (dryness of the mouth) is one of the most common long-term consequences of ageing, and it causes a tremendous impact on the function and morphology of the salivary ductal system. As a consequence, it leads to a decrease in the amount of salivary output and also affects the overall quality of life. The purpose of this study was to determine whether electrostimulation using a custom designed transcutaneous electrical nerve stimulation (TENS) device will help to improve the quality of secreted saliva following electrostimulation.

METHODS

One hundred thirty-five participants underwent the intervention for three months, twice daily (80 Hz). Pre-intervention and post-intervention unstimulated saliva were collected. Parameters such as salivary pH, cortisol level, salivary antioxidants, total protein, the viscosity of saliva, and microbial carriage were analysed.

RESULTS

Salivary pH, cortisol, microbial cultures, viscosity, and antioxidants showed a significant difference at the end of the 3rd month (p < 0.05). Irrespective of the patient's age, gender, and common underlying systemic illnesses (diabetes and hypertension), a significant change in the quality of the salivary analytes was observed.

CONCLUSION

The study emphasises the use of a custom designed TENS device in improving the quality of secreted saliva among old patients with oral dryness.

The Effect of Transcutaneous Electrical Nerve Stimulation in Peripheral and Central Hemodynamic Parameters on Resistant Hypertension: A Case Report

Resistant hypertension (RH) is characterized by being difficult to control, even with the use of various antihypertensive drugs and is associated with target organ lesions and other comorbidities. Thus, new treatment alternatives such as transcutaneous electrical nerve stimulation (TENS) can offer benefits to resistant hypertensive patients by reducing blood pressure (BP) in a non-invasive way and without the need for the association of more antihypertensive drugs. In this case, a patient with RH was submitted to three weekly applications of TENS on the stellate ganglion lasting 40 min each for 1 month. Peripheral and central hemodynamic assessments were performed by 24-h ambulatory BP monitoring (ABPM) before and after TENS applications. After completion of the TENS applications, significant reductions in office systolic (SBP) and diastolic BP (DBP) were observed. There was also a decrease in peripheral SBP and DBP in the 24-h ABPM and sleep and SBP during wakefulness. Additionally, central parameters including central SBP and pulse wave velocity presented a significant reduction in the 24-h ABPM, during the wakefulness and sleep. TENS is able to attenuate the sympathetic hyperactivity present in RH cases and decrease the peripheral and central hemodynamic parameters of a resistant hypertensive patient.

The immunomodulatory mechanisms for acupuncture practice

The system physiology approaches that emerge in western countries in recent years echo the holistic view of ancient Traditional Chinese Medicine (TCM) practices that deal with the root, rather than only the symptoms of diseases. Particularly, TCM practices, including acupuncture, emphasize the mobilization of self-healing mechanisms to bring back body homeostasis. Acupuncture has been practiced for over two thousand years to modulate body physiology via stimulation at specific body regions (acupoints). With the development of various research on acupuncture therapy, its regulatory effect on the immune system has been gradually recognized, especially on immunological diseases, including infectious and allergic diseases. In this study, we reviewed the immunomodulatory mechanism of acupuncture and systematically integrates existing research to respectively elucidate the modulatory mechanisms of acupuncture on the innate immune system, adaptive immune system, and well-known neuroanatomical mechanisms, including intact somatosensory-autonomic reflex pathway. With the advances made in recent systems physiology studies, we now have a great opportunity to gain insight into how acupuncture modulates immunity, and subsequently improves its efficacy.

A Review of Chronic Pain and Device Interventions: Benefits and Future Directions

Chronic pain is a debilitating condition with a growing prevalence both in the USA and globally. The complex nature of this condition necessitates a multimodal approach to pain management that extends beyond the established pharmaceutical interventions currently employed. A variety of devices comprising both invasive and noninvasive approaches are available to patients, serving as adjuvants to existing regimens. The benefits of these interventions are notable for their lack of addiction potential, potential for patient autonomy regarding self-administration, minimal to no drug interaction, and overall relative safety. However, there remains a need for further research and more robust clinical trials to assess the true efficacy of these interventions and elucidate if there is an underlying physiological mechanism to their benefit in treating chronic pain or if their effect is predominantly placebo in nature. Regardless, the field of device-based intervention and treatment remains an evolving field with much promise for the future chronic pain management.

Electrical stimulation therapy for peripheral nerve injury

Peripheral nerve injury is common and frequently occurs in extremity trauma patients. The motor and sensory impairment caused by the injury will affect patients' daily life and social work. Surgical therapeutic approaches don't assure functional recovery, which may lead to neuronal atrophy and hinder accelerated regeneration. Rehabilitation is a necessary stage for patients to recover better. A meaningful role in non-pharmacological intervention is played by rehabilitation, through individualized electrical stimulation therapy. Clinical studies have shown that electrical stimulation enhances axon growth during nerve repair and accelerates sensorimotor recovery. According to different effects and parameters, electrical stimulation can be divided into neuromuscular, transcutaneous, and functional electrical stimulation. The therapeutic mechanism of electrical stimulation may be to reduce muscle atrophy and promote muscle reinnervation by increasing the expression of structural protective proteins and neurotrophic factors. Meanwhile, it can modulate sensory feedback and reduce neuralgia by inhibiting the descending pathway. However, there are not many summary clinical application parameters of electrical stimulation, and the long-term effectiveness and safety also need to be further explored. This article aims to explore application methodologies for effective electrical stimulation in the rehabilitation of peripheral nerve injury, with simultaneous consideration for fundamental principles of electrical stimulation and the latest technology. The highlight of this paper is to identify the most appropriate stimulation parameters (frequency, intensity, duration) to achieve efficacious electrical stimulation in the rehabilitation of peripheral nerve injury.

Additional effect of transcutaneous electrical nerve stimulation in a therapeutic exercise program for sedentary with chronic neck pain: A double-blind randomized controlled trial

PURPOSE

To evaluate the additional effect of high frequency (HF) or low frequency (LF) transcutaneous electrical nerve stimulation (TENS) in a specific therapeutic exercise program for the treatment of patients with chronic neck pain.

METHODS

A randomized controlled trial. Sixty participants of both sexes and with chronic neck pain were randomized into three groups: therapeutic exercise group + placebo TENS (n = 20), therapeutic exercise group + HF TENS (n = 20) and therapeutic exercise group + low TENS frequency (n = 20). The following assessment instruments were used: Numerical Pain Rating Scale, Neck Disability Index, Pain-Related Catastrophizing Thoughts Scale and Tampa Scale for Kinesiophobia. Participants were evaluated before the interventions, after eight treatment sessions and 1 month after the end of treatment. Primary outcome was disability measured after the eight treatment sessions. Secondary outcomes were pain intensity, catastrophizing, and kinesiophobia after eight treatment sessions and pain intensity 4 weeks after the end of the treatment sessions.

RESULTS

The three groups were similar at baseline for personal and clinical characteristics. Regarding the main study analyses, there were no significant (p > 0.05) or clinical (d < 0.80) differences between the groups for the main variable (disability), nor for the secondary variables (pain intensity, catastrophizing and kinesiophobia).

CONCLUSION

HF or LF TENS, compared to placebo TENS, does not provide additional clinical benefits to an exercise program for patients with chronic neck pain.

Comparative efficacy and acceptability of non-pharmacological interventions in fibromyalgia: Protocol for a network meta-analysis

INTRODUCTION

Although several non-pharmacological interventions have been tested in the management of Fibromyalgia (FM), there is little consensus regarding the best options for the treatment of this health condition. The purpose of this network meta-analysis (NMA) is to investigate the comparative efficacy and acceptability of non-pharmacological interventions for FM, in order to assist clinical decision making through a ranking of interventions in relation to the most important clinical outcomes in these patients.

METHODS AND ANALYSIS

We will perform a systematic search to identify randomised controlled trials of non-pharmacological interventions endorsed in guidelines and systematic reviews. Information sources searched will include major bibliographic databases without language or date restrictions (MEDLINE, Cochrane Library, EMBASE, AMED, PsycINFO and PEDro). Our primary outcomes will be pain intensity, patient-reported quality of life (QoL), and acceptability of treatment will be our secondary outcome. Risk of bias of the included trials will be assessed using the Cochrane risk of bias tool (RoB2). For each pairwise comparison between the different interventions, we will present mean differences (MDs) for pain intensity and QoL outcomes and Relative Risks (RRs) for acceptability, both with respective 95% confidence intervals (CIs). Initially, standard pairwise meta-analyses will be performed using a DerSimonian-Laird random effects model for all comparisons with at least two trials and then we will perform a frequentist NMA using the methodology of multivariate meta-analysis assuming a common heterogeneity parameter, using the mvmeta command and network suite in STATA. In the NMA, two different types of control group, such as placebo/sham and no intervention/waiting list will be combined as one node called "Control". The competing interventions will be ranked using the P-score, which is the frequentist analogue of surface under the cumulative ranking curve (SUCRA) for the outcomes of interest at immediate- (intervention duration of up to 2 weeks), short- (over 2 weeks up to 12 weeks) and long-terms (over 12 weeks). The confidence in the results from NMA will be assessed using the Confidence in Network Meta-analysis (CINeMA) framework.

ETHICS AND DISSEMINATION

This work synthesises evidence from previously published studies and does not require ethics review or approval. A manuscript describing the findings will be submitted for publication in a peer-reviewed scientific journal.

REGISTRATION

OSF (DOI: 10.17605/OSF.IO/7MS25) and registered in the PROSPERO database (CRD42020216374).

Using TENS for Pain Control: Update on the State of the Evidence

Transcutaneous electrical nerve stimulation (TENS) is a non-pharmacological intervention used in the treatment of acute and chronic pain conditions. The first clinical studies on TENS were published over 50 years ago, when effective parameters of stimulation were unclear and clinical trial design was in its infancy. Over the last two decades, a better understanding of the mechanisms underlying TENS efficacy has led to the development of an adequate dose and has improved outcome measure utilization. The continued uncertainty about the clinical efficacy of TENS to alleviate pain, despite years of research, is related to the quality of the clinical trials included in systematic reviews. This summary of the evidence includes only trials with pain as the primary outcome. The outcomes will be rated as positive (+), negative (-), undecided (U), or equivalent to other effective interventions (=). In comparison with our 2014 review, there appears to be improvement in adverse events and parameter reporting. Importantly, stimulation intensity has been documented as critical to therapeutic success. Examinations of the outcomes beyond resting pain, analgesic tolerance, and identification of TENS responders remain less studied areas of research. This literature review supports the conclusion that TENS may have efficacy for a variety of acute and chronic pain conditions, although the magnitude of the effect remains uncertain due to the low quality of existing literature. In order to provide information to individuals with pain and to clinicians treating those with pain, we suggest that resources for research should target larger, high-quality clinical trials including an adequate TENS dose and adequate timing of the outcome and should monitor risks of bias. Systematic reviews and meta-analyses should focus only on areas with sufficiently strong clinical trials that will result in adequate sample size.

Low-energy Pulsed Electromagnetic Field Therapy Reduces Pain in Fibromyalgia: A Randomized Single-blind Controlled Pilot Study

OBJECTIVES

Fibromyalgia symptoms have a significant impact on the quality of life and respond poorly to medications. It has been hypothesized that the use of low-energy pulsed electromagnetic field (PEMF) induces neuroprotective effects that may interfere with pain perception. We explored the efficacy of PEMF in patients affected by fibromyalgia.

METHODS

Twenty-one females (median age 59 years, interquartile range [IQR] 16.5) affected by fibromyalgia were randomized to receive pulsed electromagnetic field-triple energy pain treatment (PEMF-TEPT) or placebo at T0 and at 4 weeks and 8 weeks. Fibromyalgia impact questionnaire (FIQ), widespread pain index (WPI), visual analog score (VAS) pain, symptom severity (SS) scale, and short form 36 (SF-36) health survey questionnaire have been evaluated.

RESULTS

Patients in the PEMF-TEPT group had a significantly higher reduction of WPI compared to placebo (mean difference -12.90 ± standard deviation [SD] 5.32 vs. -1.91 ± 4.55, difference in difference [DD] of -10.99; P < 0.001), of SS score (-4.10 ± 4.85 vs. -2.00 ± 2.32; DD = -2.1; P < 0.05), of VAS pain (-48 ± 30.75 vs. -16.82 ± 23.69; DD = -31.18; P < 0.01). They also reported a higher improvement of FIQ and SF-36, albeit not reaching statistical significance.

CONCLUSION

In our pilot controlled study, PEMF-TEPT appeared to be safe and improved fibromyalgia symptoms.

Sensorimotor effects of plasticity-inducing percutaneous peripheral nerve stimulation protocols

BACKGROUND

Electrical stimulation of skin afferents can induce somatosensory plasticity in humans. Nevertheless, it is unknown if this is possible to do through percutaneous stimulation of a peripheral nerve, which will allow for regional anaesthesia interventions. Furthermore, potentiation protocols applied over mainly non-nociceptive fibers inhibit nociception in rodents, but this has not been tested in humans.

OBJECTIVE

to determine whether a protocol aiming to depress the nociceptive circuit and another aiming to potentiate non-nociceptive circuits produce regional hypoalgesia and changes in motor function, applied through percutaneous peripheral nerve stimulation (pPNS), and to assess which of them is more promising for pain relief, immediately and 24 hours after intervention.

METHODS

PT-cLF protocol aims to depress the nociceptive pathway through Pain Threshold, continuous Low Frequency stimulation and ST-bHF aims to produce potentiation of the non-nociceptive pathway, through Sensory Threshold burst stimulation at High Frequency. All subjects (n=29) went through both protocols and a control condition in a randomized and blinded crossover design.

RESULTS

Compared to control, ST-bHF induced distal hypoalgesia, towards electrical (p=0.04) and mechanical stimuli (p=0.02) and produced mechanical hypoesthesia (p=0.02). Contrarily, hypoalgesia was not observed after PT-cLF (p>0.05) but increased electrical motor threshold (p=0.04), reduced motor recruitment (p=0.03), and the subjects reported feeling reduced strength (p<0.01).

CONCLUSION

This works provides evidence that is possible to induce antinociceptive plasticity in a wide territory using pPNS. Moreover, it demonstrates for the first time in humans that a protocol aiming to produce long-term potentiation applied predominantly over non-nociceptive afferents induces hypoesthesia and hypoalgesia.

Effects of Transcutaneous Electrical Nerve Stimulation on Pain and Chemotherapy-Induced Peripheral Neuropathy in Cancer Patients: A Systematic Review

Transcutaneous electrical nerve stimulation (TENS) is the usage of a mild electrical current through electrodes that stimulate nerves. Patients with malignancies experience pain and chemotherapy-induced peripheral neuropathy. A systematic review was performed to find research evaluating the effect of TENS on these two common symptoms decreasing the quality of life in cancer patients. PubMed, the Cochrane Central Register of Controlled Trials and EMBASE were searched. Original studies, namely randomized controlled trials, quasi-randomized controlled trials and controlled clinical trials, published between April 2007 and May 2020, were considered. The quality of the selected studies was assessed. Seven papers were incorporated in a qualitative synthesis, with 260 patients in total. The studies varied in terms of design, populations, endpoints, quality, treatment duration, procedures and follow-up period. Based on the results, no strict recommendations concerning TENS usage in the cancer patient population could be issued. However, the existing evidence allows us to state that TENS is a safe procedure that may be self-administered by the patients with malignancy in an attempt to relieve different types of pain. There is a need for multi-center, randomized clinical trials with a good methodological design and adequate sample size.

Does TENS Reduce the Intensity of Acute and Chronic Pain? A Comprehensive Appraisal of the Characteristics and Outcomes of 169 Reviews and 49 Meta-Analyses

Background and Objectives: Uncertainty about the clinical efficacy of transcutaneous electric nerve stimulation (TENS) to alleviate pain spans half a century. There has been no attempt to synthesise the entire body of systematic review evidence. The aim of this comprehensive review was to critically appraise the characteristics and outcomes of systematic reviews evaluating the clinical efficacy of TENS for any type of acute and chronic pain in adults. Materials and Methods: We searched electronic databases for full reports of systematic reviews of studies, overviews of systematic reviews, and hybrid reviews that evaluated the efficacy of TENS for any type of clinical pain in adults. We screened reports against eligibility criteria and extracted data related to the characteristics and outcomes of the review, including effect size estimates. We conducted a descriptive analysis of extracted data. Results: We included 169 reviews consisting of eight overviews, seven hybrid reviews and 154 systematic reviews with 49 meta-analyses. A tally of authors' conclusions found a tendency toward benefits from TENS in 69/169 reviews, no benefits in 13/169 reviews, and inconclusive evidence in 87/169 reviews. Only three meta-analyses pooled sufficient data to have confidence in the effect size estimate (i.e., pooled analysis of >500 events). Lower pain intensity was found during TENS compared with control for chronic musculoskeletal pain and labour pain, and lower analgesic consumption was found post-surgery during TENS. The appraisal revealed repeated shortcomings in RCTs that have hindered confident judgements about efficacy, resulting in stagnation of evidence. Conclusions: Our appraisal reveals examples of meta-analyses with 'sufficient data' demonstrating benefit. There were no examples of meta-analyses with 'sufficient data' demonstrating no benefit. Therefore, we recommend that TENS should be considered as a treatment option. The considerable quantity of reviews with 'insufficient data' and meaningless findings have clouded the issue of efficacy. We offer solutions to these issues going forward.

Effects of Wearable Transcutaneous Electrical Nerve Stimulation on Fibromyalgia: A Randomized Controlled Trial

Purpose

Fibromyalgia is a chronic condition characterized by widespread pain and interference with daily activities. The aim of this study is to assess the benefit of transcutaneous electrical nerve stimulation (TENS) for persons diagnosed with fibromyalgia.

Patients and Methods

Adults meeting diagnostic criteria for fibromyalgia were randomized in a double-blind trial to receive either an active (n=62) or sham (n=57) wearable TENS device for 3-months. Subjects were classified as having lower or higher pain sensitivity by Quantitative Sensory Testing (QST). Patient Global Impression of Change (PGIC, primary outcome) and secondary efficacy measures including Fibromyalgia Impact Questionnaire (FIQR), Brief Pain Inventory (BPI) and painDETECT questionnaire (PDQ) were assessed at baseline, 6-weeks and 3-months. Treatment effects were determined by a mixed model for repeated measures (MMRM) analysis of the intention-to-treat (ITT) population (N=119). A pre-specified subgroup analysis of pain sensitivity was conducted using an interaction term in the model.

Results

No differences were found between active and sham treatment on PGIC scores at 3-months (0.34, 95% CI [−0.37, 1.04], p=0.351) in the ITT population. However, in subjects with higher pain sensitivity (n=60), PGIC was significantly greater for active treatment compared to sham (1.19, 95% CI [0.24, 2.13], p=0.014). FIQR total score (−7.47, 95% CI [−12.46, −2.48], p=0.003), FIQR pain item (−0.62, 95% CI [−1.17, −0.06], p=0.029), BPI Interference (−0.70, 95% CI [−1.30, −0.11], p=0.021) and PDQ (−1.69, 95% CI [−3.20, −0.18], p=0.028) exhibited significant improvements for active treatment compared to sham in the ITT population. Analgesics use was stable and comparable in both groups.

Conclusion

This study demonstrated modest treatment effects of reduced disease impact, pain and functional impairment from wearable TENS in individuals with fibromyalgia. Subjects with higher pain sensitivity exhibited larger treatment effects than those with lower pain sensitivity. Wearable TENS may be a safe treatment option for people with fibromyalgia.

Clinicaltrials.gov Registration

NCT03714425.

Resolving Long-Standing Uncertainty about the Clinical Efficacy of Transcutaneous Electrical Nerve Stimulation (TENS) to Relieve Pain: A Comprehensive Review of Factors Influencing Outcome

Pain is managed using a biopsychosocial approach and pharmacological and non-pharmacological treatments. Transcutaneous electrical nerve stimulation (TENS) is a technique whereby pulsed electrical currents are administered through the intact surface of the skin with the intention of alleviating pain, akin to 'electrically rubbing pain away'. Despite over 50 years of published research, uncertainty about the clinical efficacy of TENS remains. The purpose of this comprehensive review is to critically appraise clinical research on TENS to inform future strategies to resolve the 'efficacy-impasse'. The principles and practices of TENS are described to provide context for readers unfamiliar with TENS treatment. The findings of systematic reviews evaluating TENS are described from a historical perspective to provide context for a critical evaluation of factors influencing the outcomes of randomized controlled trials (RCTs); including sample populations, outcome measures, TENS techniques, and comparator interventions. Three possibilities are offered to resolve the impasse. Firstly, to conduct large multi-centered RCTs using an enriched enrolment with randomized withdrawal design, that incorporates a 'run-in phase' to screen for potential TENS responders and to optimise TENS treatment according to individual need. Secondly, to meta-analyze published RCT data, irrespective of type of pain, to determine whether TENS reduces the intensity of pain during stimulation, and to include a detailed assessment of levels of certainty and precision. Thirdly, to concede that it may be impossible to determine efficacy due to insurmountable methodological, logistical and financial challenges. The consequences to clinicians, policy makers and funders of this third scenario are discussed. I argue that patients will continue to use TENS irrespective of the views of clinicians, policy makers, funders or guideline panel recommendations, because TENS is readily available without prescription; TENS generates a pleasant sensory experience that is similar to easing pain using warming and cooling techniques; and technological developments such as smart wearable TENS devices will improve usability in the future. Thus, research is needed on how best to integrate TENS into existing pain management strategies by analyzing data of TENS usage by expert-patients in real-world settings.

Pain in Women: A Perspective Review on a Relevant Clinical Issue that Deserves Prioritization

Introduction

Gender equity and gender medicine are opportunities not to be missed, and this Expert Group Opinion Paper on pain in women aims to review the treatment of pain conditions mainly affecting women, as well as the fundamental aspects of the different clinical response to drug treatment between the genders, and what can be done for gender-specific rehabilitation.

Methods

Perspective review.

Results

Genotypic and phenotypic differences in pain between the sexes are conditioned by anatomical, physiological, neural, hormonal, psychological, social, and cultural factors, such as the response to pharmacological treatment to control pain. The examination of these factors shows that women are affected by pain diseases more frequently and severely than men and that they report pain more frequently and with a lower pain threshold than men. Some forms of pain are inherently related to gender differences, such as pain related to the genitourinary system. However, other forms of chronic pain are seen more frequently in women than men, such as migraine, rheumatological, and musculoskeletal pain, in particular fibromyalgia.

Discussion

Research is needed into the pathophysiological basis for gender differences in the generation of acute pain and maintenance of chronic pain, including the factors that put women at higher risk for developing chronic pain. In addition, different specialties need to collaborate to develop gender-related diagnostic and therapeutic guidelines, and healthcare professionals need to upskill themselves in the appropriate management of pain using existing diagnostic tools and therapeutic options.

Association of Therapies With Reduced Pain and Improved Quality of Life in Patients With Fibromyalgia: A Systematic Review and Meta-analysis

IMPORTANCE

Fibromyalgia is a chronic condition that results in a significant burden to individuals and society.

OBJECTIVE

To investigate the effectiveness of therapies for reducing pain and improving quality of life (QOL) in people with fibromyalgia.

DATA SOURCES

Searches were performed in the MEDLINE, Cochrane, Embase, AMED, PsycInfo, and PEDro databases without language or date restrictions on December 11, 2018, and updated on July 15, 2020.

STUDY SELECTION

All published randomized or quasi-randomized clinical trials that investigated therapies for individuals with fibromyalgia were screened for inclusion.

DATA EXTRACTION AND SYNTHESIS

Two reviewers independently extracted data and assessed risk of bias using the 0 to 10 PEDro scale. Effect sizes for specific therapies were pooled using random-effects models. The quality of evidence was assessed using the Grading of Recommendations Assessment (GRADE) approach.

MAIN OUTCOMES AND MEASURES

Pain intensity measured by the visual analog scale, numerical rating scales, and other valid instruments and QOL measured by the Fibromyalgia Impact Questionnaire.

RESULTS

A total of 224 trials including 29 962 participants were included. High-quality evidence was found in favor of cognitive behavioral therapy (weighted mean difference [WMD], -0.9; 95% CI, -1.4 to -0.3) for pain in the short term and was found in favor of central nervous system depressants (WMD, -1.2 [95% CI, -1.6 to -0.8]) and antidepressants (WMD, -0.5 [95% CI, -0.7 to -0.4]) for pain in the medium term. There was also high-quality evidence in favor of antidepressants (WMD, -6.8 [95% CI, -8.5 to -5.2]) for QOL in the short term and in favor of central nervous system depressants (WMD, -8.7 [95% CI, -11.3 to -6.0]) and antidepressants (WMD, -3.5 [95% CI, -4.5 to -2.5]) in the medium term. However, these associations were small and did not exceed the minimum clinically important change (2 points on an 11-point scale for pain and 14 points on a 101-point scale for QOL). Evidence for long-term outcomes of interventions was lacking.

CONCLUSIONS AND RELEVANCE

This systematic review and meta-analysis suggests that most of the currently available therapies for the management of fibromyalgia are not supported by high-quality evidence. Some therapies may reduce pain and improve QOL in the short to medium term, although the effect size of the associations might not be clinically important to patients.

The Importance of Daily Activity for Reducing Fibromyalgia Symptoms: A Retrospective "Real World" Data Comparison of two Multimodal Treatment Programs

Objectives

This study aims to evaluate the effectiveness of two multidisciplinary fibromyalgia programs with different intensities.

Materials and methods

In this retrospective real-world comparison of patient data, pre- and post-program datasets of Short Form 36 (SF36) and Fibromyalgia Impact Questionnaire (FIQ) were obtained from a total of 210 female patients in two fibromyalgia multidisciplinary day hospital programs including one intensive program with daily treatments summing up to 20 treatment days during four weeks (P20, n=70) versus a less intensive program with 12 treatment days during four weeks (P12, n=140).

Results

Multiple subscales of SF36 and FIQ were improved in the pre-post comparison in both groups. In the comparison between the two groups, a statistically significantly higher improvement was found in the P20 group compared to the P12 group for the FIQ subscales of stiffness (p=0.001) and the number of days during which the patient felt “good” (p=0.007).

Conclusion

An intensive program of daily treatments and activity seems to be more effective in reducing fibromyalgia-associated stiffness and improving the number of days during which patients feel good than a less intensive program.

Effects of Monopolar Dielectric Radiofrequency Signals on the Symptoms of Fibromyalgia: A Single-Blind Randomized Controlled Trial

Monopolar dielectric radiofrequency (MDR) is a non-invasive treatment for pain based on the local application of electromagnetic signals. The study’s goal was to analyze the effects of MDR on the symptoms of fibromyalgia. For this aim, a randomized controlled trial was conducted on 66 female participants (aged 47 ± 17.7) diagnosed with fibromyalgia. Participants were randomly allocated to either an experimental group (n = 23), which received eight 20-minute sessions of MDR; a sham group, which received the same number of sessions of a sham MDR therapy (n = 22); or a control group (n = 21), which received usual care. The outcome variables included pain measured by the visual analogue scale (VAS), score on the hospital anxiety and depression scale (HADS) and quality of life measured by the combined index of fibromyalgia severity (ICAF). A large effect size was observed for the local pain (R² = 0.46), total ICAF (R² = 0.42) and ICAF physical factor scores (R² = 0.38). Significant mean differences were found for the local pain (p = 0.025) and ICAF physical factor (p = 0.031) scores of the experimental group in comparison with the sham group. No statistically significant differences between groups were found in HADS. In conclusion, MDR is more effective than either sham treatment or usual care in the short-term improvement of pain and the physical wellbeing of participants with fibromyalgia.

Transcutaneous Electrical Nerve Stimulation Reduces Movement-Evoked Pain and Fatigue: A Randomized, Controlled Trial

Objective

Fibromyalgia (FM) is characterized by pain and fatigue, particularly during physical activity. Transcutaneous electrical nerve stimulation (TENS) activates endogenous pain inhibitory mechanisms. This study was undertaken to investigate if using TENS during activity would improve movement‐evoked pain and other patient‐reported outcomes in women with FM.

Methods

Participants were randomly assigned to receive active TENS (n = 103), placebo TENS (n = 99), or no TENS (n = 99) and instructed to use it at home during activity 2 hours each day for 4 weeks. TENS was applied to the lumbar and cervicothoracic regions using a modulated frequency (2–125 Hz) at the highest tolerable intensity. Participants rated movement‐evoked pain (primary outcome measure) and fatigue on an 11‐point scale before and during application of TENS. The primary outcome measure and secondary patient‐reported outcomes were assessed at baseline (time of randomization) and at 4 weeks.

Results

After 4 weeks, a greater reduction in movement‐evoked pain was reported in the active TENS group versus the placebo TENS group (group mean difference –1.0 [95% confidence interval –1.8, –0.2]; P = 0.008) and versus the no TENS group (group mean difference –1.8 [95% confidence interval –2.6, –1.0]; P < 0.0001). A reduction in movement‐evoked fatigue was also reported in the active TENS group versus the placebo TENS group (group mean difference –1.4 [95% confidence interval –2.4, –0.4]; P = 0.001) and versus the no TENS group (group mean difference –1.9 [95% confidence interval –2.9, –0.9]; P = <0.0001). A greater percentage of the patients in the active TENS group reported improvement on the global impression of change compared to the placebo TENS group (70% versus 31%; P < 0.0001) and the no TENS group (9%; P < 0.0001). There were no TENS‐related serious adverse events, and <5% of participants experienced minor adverse events from TENS.

Conclusion

Among women who had FM and were on a stable medication regimen, 4 weeks of active TENS use compared to placebo TENS or no TENS resulted in a significant improvement in movement‐evoked pain and other clinical outcomes. Further research is needed to examine effectiveness in a real‐world setting to establish the clinical importance of these findings.

A Multicenter, Prospective, Randomized, Placebo-Controlled, Double-Blind Study of a Novel Pain Management Device, AT-02, in Patients with Fibromyalgia

Objectives

Existing treatments for fibromyalgia have limited efficacy, and only a minority of individuals clinically respond to any single intervention. This study was a prospective, multicenter, randomized, double-blind, controlled clinical trial to evaluate the feasibility of alternating magnetic field therapy in fibromyalgia patients by comparing the Angel Touch device (AT-02) with a sham control (S-01).

Methods

Two sites enrolled 44 subjects with diagnosed fibromyalgia. After informed consent, subjects taking prohibited concomitant drugs underwent a washout period of two or more weeks. All subjects then began a one-week run-in period. Numerical rating scale (NRS) pain scores were collected without device intervention for one day, followed by S-01 application to four or more painful sites for 10 minutes at each site, twice daily for six days. Subjects were then randomized to AT-02 or S-01, applied to four or more painful sites for 10 minutes at each site, twice daily for eight weeks. NRS scores were obtained twice daily during the entire treatment period.

Results

The primary end point (change in NRS ± SD at week 8 vs baseline) was –0.94 ± 1.33 in the AT-02 group and –0.22 ± 1.38 in the S-01 group. A trend toward a between-group difference in eight-week NRS scores favored the AT-02 group (–0.73, 95% confidence interval = –1.56 to 0.11, P = 0.086). An adjusted repeated measure analysis detected a significant difference in NRS scores (P = 0.039).

Conclusions

The reduction in NRS scores for AT-02 relative to sham was comparable to reductions observed in meta-analyses of fibromyalgia drug therapy. The unadjusted results and the persistence of the pain score reductions remain encouraging.

Transcutaneous electrical nerve stimulation (TENS) for chronic neck pain

BACKGROUND

Chronic neck pain is a highly prevalent condition, affecting 10% to 24% of the general population. Transcutaneous electrical nerve stimulation (TENS) is the noninvasive, transcutaneous use of electrical stimulation to produce analgesia. It is a simple, low-cost and safe intervention used in clinical practice as an adjunct treatment for painful musculoskeletal conditions that have a considerable impact on daily activities, such as chronic neck pain. This review is a split from a Cochrane Review on electrotherapy for neck pain, published in 2013, and focuses specifically on TENS for chronic neck pain.

OBJECTIVES

To evaluate the effectiveness of transcutaneous electrical nerve stimulation (TENS) (alone or in association with other interventions) compared with sham and other clinical interventions for the treatment of chronic neck pain.

SEARCH METHODS

We searched Cochrane Back and Neck Trials Register, CENTRAL, MEDLINE, Embase, five other databases and two trials registers to 9 November 2018. We also screened the reference lists of relevant studies to identify additional trials. There were no language, source, or publication date restrictions.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) involving adults (≥ 18 years of age) with chronic neck pain (lasting > 12 weeks) that compared TENS alone or in combination with other treatments versus active or inactive treatments. The primary outcomes were pain, disability and adverse events.

DATA COLLECTION AND ANALYSIS

Two independent review authors selected the trials, extracted data and assessed the risk of bias of included studies. A third review author was consulted in case of disagreements. We used the Cochrane 'Risk of bias' tool (adapted by Cochrane Back and Neck), to assess the risk of bias of individual trials and GRADE to assess the certainty of evidence. We used risk ratios (RRs) to measure treatment effects for dichotomous outcomes, and mean differences (MDs) for continuous outcomes, with their respective 95% confidence intervals (CIs).

MAIN RESULTS

We included seven RCTs with a total of 651 participants, mean age 31.7 to 55.5 years, conducted in three different countries (Turkey, Jordan and China). The length of follow-up ranged from one week to six months. Most RCTs used continuous TENS, with a frequency of 60 Hz to 100 Hz, pulse width of 40 μs to 250 μs and tolerable intensity, described as a tingling sensation without contraction, in daily sessions lasting 20 to 60 minutes. Due to heterogeneity in interventions and outcomes, we did not pool individual study data into meta-analyses. Overall, we judged most studies as being at low risk for selection bias and high risk for performance and detection bias. Based on the GRADE approach, there was very low-certainty evidence from two trials about the effects of conventional TENS when compared to sham TENS at short-term (up to 3 months after treatment) follow-up, on pain (assessed by the Visual Analogue Scale (VAS)) (MD -0.10, 95% CI -0.97 to 0.77) and the percentage of participants presenting improvement of pain (RR 1.57, 95% CI 0.84 to 2.92). None of the included studies reported on disability or adverse events.

AUTHORS' CONCLUSIONS

This review found very low-certainty evidence of a difference between TENS compared to sham TENS on reducing neck pain; therefore, we are unsure about the effect estimate. At present, there is insufficient evidence regarding the use of TENS in patients with chronic neck pain. Additional well-designed, -conducted and -reported RCTs are needed to reach robust conclusions.

The clinical efficacy of transcutaneous electrical nerve stimulation (TENS) for acute and chronic pain: a protocol for a meta-analysis of randomised controlled trials (RCTs)

INTRODUCTION

The aim of this systematic review with meta-analysis is to evaluate the clinical efficacy of transcutaneous electrical nerve stimulation (TENS) for any type of acute and chronic pain in adults.

METHODS AND ANALYSIS

We intend to search electronic databases (Cochrane Library, MEDLINE, Embase, CINAHL, PsycINFO, LILACS, PEDRO, Web of Science, AMED and SPORTDiscus) from inception to the present day to identify all randomised controlled trials (RCT) on the use of TENS in adults for any type of pain including acute pain, chronic pain and cancer-related pain. We will screen the RCTs against eligibility criteria for inclusion in our review. Two reviewers will independently undertake RCT selection, data extraction and risk of bias assessment. Primary outcomes will be: (i) participant-reported pain relief of ≥30% expressed as frequency (dichotomous) data; and (ii) participant-reported pain intensity expressed as mean (continuous) data. We will conduct meta-analyses to determine risk ratio for dichotomous data, and mean difference (MD) or standardised MD for continuous data for TENS versus placebo TENS, no treatment or waiting list control, standard of care, and other treatments. Subgroup analyses will include different pain conditions (eg, acute vs chronic), TENS intensity, during versus after TENS, TENS as a sole treatment versus TENS in combination with other treatments and TENS administered as a single dose versus repetitive dose.

ETHICS AND DISSEMINATION

This systematic review will not use data from individual participants, and the results will be disseminated in a peer-reviewed publication and presented at a conference.

PROSPERO REGISTRATION NUMBER

CRD42019125054.

Neurostimulation methods in the treatment of chronic pain

The goal of this narrative review was to give an up-to-date overview of the peripheral and central neurostimulation methods that can be used to treat chronic pain. Special focus has been given to three pain conditions: neuropathic pain, nociplastic pain and primary headaches. Both non-invasive and invasive techniques are briefly presented together with their pain relief potentials. For non-invasive stimulation techniques, data concerning transcutaneous electrical nerve stimulation (TENS), transcranial direct current stimulation (tDCS), repetitive transcranial magnetic stimulation (rTMS), remote electrical neuromodulation (REN) and vagus nerve stimulation (VNS) are provided. Concerning invasive stimulation techniques, occipital nerve stimulation (ONS), vagus nerve stimulation (VNS), epidural motor cortex stimulation (EMCS), spinal cord stimulation (SCS) and deep brain stimulation (DBS) are presented. The action mode of all these techniques is only partly understood but can be very different from one technique to the other. Patients' selection is still a challenge. Recent consensus-based guidelines for clinical practice are presented when available. The development of closed-loop devices could be of interest in the future, although the clinical benefit over open loop is not proven yet.

Transcutaneous electrical nerve stimulation (TENS) for chronic pain - an overview of Cochrane Reviews

BACKGROUND

Chronic pain, considered to be pain lasting more than three months, is a common and often difficult to treat condition that can significantly impact upon function and quality of life. Treatment typically includes pharmacological and non-pharmacological approaches. Transcutaneous electrical nerve stimulation (TENS) is an adjunct non-pharmacological treatment commonly recommended by clinicians and often used by people with pain.

OBJECTIVES

To provide an overview of evidence from Cochrane Reviews of the effectiveness of TENS to reduce pain in adults with chronic pain (excluding headache or migraine).To provide an overview of evidence from Cochrane Reviews of the safety of TENS when used to reduce pain in adults with chronic pain (excluding headache or migraine).To identify possible sources of inconsistency in the approaches taken to evaluating the evidence related to TENS for chronic pain (excluding headache or migraine) in the Cochrane Library with a view to recommending strategies to improve consistency in methodology and reporting.To highlight areas of remaining uncertainty regarding the effectiveness of TENS for chronic pain (excluding headache or migraine) with a view to recommending strategies to reduce any uncertainty.

METHODS

Search methodsWe searched the Cochrane Database of Systematic Reviews (CDSR), in the Cochrane Library, across all years up to Issue 11 of 12, 2018.Selection of reviewsTwo authors independently screened the results of the electronic search by title and abstract against inclusion/exclusion criteria. We included all Cochrane Reviews of randomised controlled trials (RCTs) assessing the effectiveness of TENS in people with chronic pain. We included reviews if they investigated the following: TENS versus sham; TENS versus usual care or no treatment/waiting list control; TENS plus active intervention versus active intervention alone; comparisons between different types of TENS; or TENS delivered using different stimulation parameters.Data extraction and analysisTwo authors independently extracted relevant data, assessed review quality using the AMSTAR checklist and applied GRADE judgements where required to individual reviews. Our primary outcomes included pain intensity and nature/incidence of adverse effects; our secondary outcomes included disability, health-related quality of life, analgesic medication use and participant global impression of change.

MAIN RESULTS

We included nine reviews investigating TENS use in people with defined chronic pain or in people with chronic conditions associated with ongoing pain. One review investigating TENS for phantom or stump-associated pain in people following amputation did not have any included studies. We therefore extracted data from eight reviews which represented 51 TENS-related RCTs representing 2895 TENS-comparison participants entered into the studies.The included reviews followed consistent methods and achieved overall high scores on the AMSTAR checklist. The evidence reported within each review was consistently rated as very low quality. Using review authors' assessment of risk of bias, there were significant methodological limitations in included studies; and for all reviews, sample sizes were consistently small (the majority of studies included fewer than 50 participants per group).Six of the eight reviews presented a narrative synthesis of included studies. Two reviews reported a pooled analysis.Primary and secondary outcomes One review reported a beneficial effect of TENS versus sham therapy at reducing pain intensity on a 0 to 10 scale (MD -1.58, 95% CI -2.08 to -1.09, P < 0.001, I² = 29%, P = 0.22, 5 studies, 207 participants). However the quality of the evidence was very low due to significant methodological limitations and imprecision. A second review investigating pain intensity performed a pooled analysis by combining studies that compared TENS to sham with studies that compared TENS to no intervention (SMD -0.85, 95% CI -1.36 to -0.34, P = 0.001, I² = 83%, P < 0.001). This pooled analysis was judged as offering very low quality evidence due to significant methodological limitations, large between-trial heterogeneity and imprecision. We considered the approach of combining sham and no intervention data to be problematic since we would predict these different comparisons may be estimating different true effects. All remaining reviews also reported pain intensity as an outcome measure; however the data were presented in narrative review form only.Due to methodological limitation and lack of useable data, we were unable to offer any meaningful report on the remaining primary outcome regarding nature/incidence of adverse effects, nor for the remaining secondary outcomes: disability, health-related quality of life, analgesic medication use and participant global impression of change for any comparisons.We found the included reviews had a number of inconsistencies when evaluating the evidence from TENS studies. Approaches to assessing risk of bias around the participant, personnel and outcome-assessor blinding were perhaps the most obvious area of difference across included reviews. We also found wide variability in terms of primary and secondary outcome measures, and inclusion/exclusion criteria for studies varied with respect to including studies which assessed immediate effects of single interventions.

AUTHORS' CONCLUSIONS

We found the methodological quality of the reviews was good, but quality of the evidence within them was very low. We were therefore unable to conclude with any confidence that, in people with chronic pain, TENS is harmful, or beneficial for pain control, disability, health-related quality of life, use of pain relieving medicines, or global impression of change. We make recommendations with respect to future TENS study designs which may meaningfully reduce the uncertainty relating to the effectiveness of this treatment in people with chronic pain.

Transcutaneous electrical nerve stimulation (TENS) for chronic pain - an overview of Cochrane Reviews

BACKGROUND

Chronic pain, considered to be pain lasting more than three months, is a common and often difficult to treat condition that can significantly impact upon function and quality of life. Treatment typically includes pharmacological and non-pharmacological approaches. Transcutaneous electrical nerve stimulation (TENS) is an adjunct non-pharmacological treatment commonly recommended by clinicians and often used by people with pain.

OBJECTIVES

To provide an overview of evidence from Cochrane Reviews of the effectiveness of TENS to reduce pain in adults with chronic pain (excluding headache or migraine).To provide an overview of evidence from Cochrane Reviews of the safety of TENS when used to reduce pain in adults with chronic pain (excluding headache or migraine).To identify possible sources of inconsistency in the approaches taken to evaluating the evidence related to TENS for chronic pain (excluding headache or migraine) in the Cochrane Library with a view to recommending strategies to improve consistency in methodology and reporting.To highlight areas of remaining uncertainty regarding the effectiveness of TENS for chronic pain (excluding headache or migraine) with a view to recommending strategies to reduce any uncertainty.

METHODS

Search methodsWe searched the Cochrane Database of Systematic Reviews (CDSR), in the Cochrane Library, across all years up to Issue 11 of 12, 2018.Selection of reviewsTwo authors independently screened the results of the electronic search by title and abstract against inclusion/exclusion criteria. We included all Cochrane Reviews of randomised controlled trials (RCTs) assessing the effectiveness of TENS in people with chronic pain. We included reviews if they investigated the following: TENS versus sham; TENS versus usual care or no treatment/waiting list control; TENS plus active intervention versus active intervention alone; comparisons between different types of TENS; or TENS delivered using different stimulation parameters.Data extraction and analysisTwo authors independently extracted relevant data, assessed review quality using the AMSTAR checklist and applied GRADE judgements where required to individual reviews. Our primary outcomes included pain intensity and nature/incidence of adverse effects; our secondary outcomes included disability, health-related quality of life, analgesic medication use and participant global impression of change.

MAIN RESULTS

We included nine reviews investigating TENS use in people with defined chronic pain or in people with chronic conditions associated with ongoing pain. One review investigating TENS for phantom or stump-associated pain in people following amputation did not have any included studies. We therefore extracted data from eight reviews which represented 51 TENS-related RCTs representing 2895 TENS-comparison participants entered into the studies.The included reviews followed consistent methods and achieved overall high scores on the AMSTAR checklist. The evidence reported within each review was consistently rated as very low quality. Using review authors' assessment of risk of bias, there were significant methodological limitations in included studies; and for all reviews, sample sizes were consistently small (the majority of studies included fewer than 50 participants per group).Six of the eight reviews presented a narrative synthesis of included studies. Two reviews reported a pooled analysis.Primary and secondary outcomes One review reported a beneficial effect of TENS versus sham therapy at reducing pain intensity on a 0 to 10 scale (MD -1.58, 95% CI -2.08 to -1.09, P < 0.001, I² = 29%, P = 0.22, 5 studies, 207 participants). However the quality of the evidence was very low due to significant methodological limitations and imprecision. A second review investigating pain intensity performed a pooled analysis by combining studies that compared TENS to sham with studies that compared TENS to no intervention (SMD -0.85, 95% CI -1.36 to -0.34, P = 0.001, I² = 83%, P < 0.001). This pooled analysis was judged as offering very low quality evidence due to significant methodological limitations, large between-trial heterogeneity and imprecision. We considered the approach of combining sham and no intervention data to be problematic since we would predict these different comparisons may be estimating different true effects. All remaining reviews also reported pain intensity as an outcome measure; however the data were presented in narrative review form only.Due to methodological limitation and lack of useable data, we were unable to offer any meaningful report on the remaining primary outcome regarding nature/incidence of adverse effects, nor for the remaining secondary outcomes: disability, health-related quality of life, analgesic medication use and participant global impression of change for any comparisons.We found the included reviews had a number of inconsistencies when evaluating the evidence from TENS studies. Approaches to assessing risk of bias around the participant, personnel and outcome-assessor blinding were perhaps the most obvious area of difference across included reviews. We also found wide variability in terms of primary and secondary outcome measures, and inclusion/exclusion criteria for studies varied with respect to including studies which assessed immediate effects of single interventions.

AUTHORS' CONCLUSIONS

We found the methodological quality of the reviews was good, but quality of the evidence within them was very low. We were therefore unable to conclude with any confidence that, in people with chronic pain, TENS is harmful, or beneficial for pain control, disability, health-related quality of life, use of pain relieving medicines, or global impression of change. We make recommendations with respect to future TENS study designs which may meaningfully reduce the uncertainty relating to the effectiveness of this treatment in people with chronic pain.

Transcutaneous electrical nerve stimulation (TENS) for neuropathic pain in adults

BACKGROUND

Neuropathic pain, which is due to nerve disease or damage, represents a significant burden on people and society. It can be particularly unpleasant and achieving adequate symptom control can be difficult. Non-pharmacological methods of treatment are often employed by people with neuropathic pain and may include transcutaneous electrical nerve stimulation (TENS). This review supersedes one Cochrane Review 'Transcutaneous electrical nerve stimulation (TENS) for chronic pain' (Nnoaham 2014) and one withdrawn protocol 'Transcutaneous electrical nerve stimulation (TENS) for neuropathic pain in adults' (Claydon 2014). This review replaces the original protocol for neuropathic pain that was withdrawn.

OBJECTIVES

To determine the analgesic effectiveness of TENS versus placebo (sham) TENS, TENS versus usual care, TENS versus no treatment and TENS in addition to usual care versus usual care alone in the management of neuropathic pain in adults.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, PsycINFO, AMED, CINAHL, Web of Science, PEDro, LILACS (up to September 2016) and various clinical trials registries. We also searched bibliographies of included studies for further relevant studies.

SELECTION CRITERIA

We included randomised controlled trials where TENS was evaluated in the treatment of central or peripheral neuropathic pain. We included studies if they investigated the following: TENS versus placebo (sham) TENS, TENS versus usual care, TENS versus no treatment and TENS in addition to usual care versus usual care alone in the management of neuropathic pain in adults.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened all database search results and identified papers requiring full-text assessment. Subsequently, two review authors independently applied inclusion/exclusion criteria to these studies. The same review authors then independently extracted data, assessed for risk of bias using the Cochrane standard tool and rated the quality of evidence using GRADE.

MAIN RESULTS

We included 15 studies with 724 participants. We found a range of treatment protocols in terms of duration of care, TENS application times and intensity of application. Briefly, duration of care ranged from four days through to three months. Similarly, we found variation of TENS application times; from 15 minutes up to hourly sessions applied four times daily. We typically found intensity of TENS set to comfortable perceptible tingling with very few studies titrating the dose to maintain this perception. Of the comparisons, we had planned to explore, we were only able to undertake a quantitative synthesis for TENS versus sham TENS. Insufficient data and large diversity in the control conditions prevented us from undertaking a quantitative synthesis for the remaining comparisons.For TENS compared to sham TENS, five studies were suitable for pooled analysis. We described the remainder of the studies in narrative form. Overall, we judged 11 studies at high risk of bias, and four at unclear risk. Due to the small number of eligible studies, the high levels of risk of bias across the studies and small sample sizes, we rated the quality of the evidence as very low for the pooled analysis and very low individual GRADE rating of outcomes from single studies. For the individual studies discussed in narrative form, the methodological limitations, quality of reporting and heterogeneous nature of interventions compared did not allow for reliable overall estimates of the effect of TENS.Five studies (across various neuropathic conditions) were suitable for pooled analysis of TENS versus sham TENS investigating change in pain intensity using a visual analogue scale. We found a mean postintervention difference in effect size favouring TENS of -1.58 (95% confidence interval (CI) -2.08 to -1.09, P < 0.00001, n = 207, six comparisons from five studies) (very low quality evidence). There was no significant heterogeneity in this analysis. While this exceeded our prespecified minimally important difference for pain outcomes, we assessed the quality of evidence as very low meaning we have very little confidence in this effect estimate and the true effect is likely to be substantially different from that reported in this review. Only one study of these five investigated health related quality of life as an outcome meaning we were unable to report on this outcome in this comparison. Similarly, we were unable to report on global impression of change or changes in analgesic use in this pooled analysis.Ten small studies compared TENS to some form of usual care. However, there was great diversity in what constituted usual care, precluding pooling of data. Most of these studies found either no difference in pain outcomes between TENS versus other active treatments or favoured the comparator intervention (very low quality evidence). We were unable to report on other primary and secondary outcomes in these single trials (health-related quality of life, global impression of change and changes in analgesic use).Of the 15 included studies, three reported adverse events which were minor and limited to 'skin irritation' at or around the site of electrode placement (very low quality evidence). Three studies reported no adverse events while the remainder did not report any detail with regard adverse events.

AUTHORS' CONCLUSIONS

In this review, we reported on the comparison between TENS and sham TENS. The quality of the evidence was very low meaning we were unable to confidently state whether TENS is effective for pain control in people with neuropathic pain. The very low quality of evidence means we have very limited confidence in the effect estimate reported; the true effect is likely to be substantially different. We make recommendations with respect to future TENS study designs which may meaningfully reduce the uncertainty relating to the effectiveness of this treatment modality.