Effectiveness of percutaneous electrical nerve stimulation for musculoskeletal pain: A systematic review and meta-analysis

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.

Percutaneous electrical nerve stimulation in post-mastectomy neuropathic pain: A case report

Post-mastectomy pain syndrome (PMPS) is a type of chronic postsurgical pain that can be severe, debilitating and frequently encountered in clinical practice. Multiple studies have focused on prevention, identifying risk factors and treating this condition. Nonetheless, PMPS remains a complex condition to treat effectively. In this case report, we describe the use of percutaneous electrical nerve stimulation in a breast cancer patient who experienced PMPS refractory to conventional treatments.

Immediate effects of percutaneous electrical nerve stimulation in patients with lateral elbow pain

INTRODUCTION

Ultrasound guided-percutaneous electrical nerve stimulation appears to be effective in the treatment of chronic musculoskeletal pain.

OBJECTIVE

To investigate the immediate effects of one session of percutaneous electrical nerve stimulation on the radial nerve in patients with lateral elbow pain.

METHODS

A randomized clinical trial was conducted. Sixty patients with chronic lateral elbow pain were allocated into real-percutaneous electrical nerve stimulation (n = 30) or sham-percutaneous electrical nerve stimulation (n = 30) where the patients received one-single session of the real or sham percutaneous stimulation on the radial nerve, respectively. Pressure pain thresholds, pain intensity, pain-free grip strength, and the self-perceived improvement were evaluated after the intervention.

RESULTS

Significant differences between groups for pain intensity (-11.55, 95% CI -21.79 to -1.30, p < .028), but not for pressure pain threshold or pain-free grip strength, were found. Patients receiving real-percutaneous stimulation had significant improvement in pain-free grip strength on the treated side. The proportion of individuals reporting moderate to large self-perceived improvement (≥4) was significantly higher (p = .026) after real-percutaneous stimulation than after sham-percutaneous stimulation.

CONCLUSION

A single session of real-percutaneous electrical nerve stimulation targeting the radial nerve in subjects with lateral elbow pain decreased pain intensity between groups and increased pain-free grip strength on the treated side but not between groups.

Intramuscular Electrical Stimulation for the Treatment of Trigger Points in Patients with Chronic Migraine: A Protocol for a Pilot Study Using a Single-Case Experimental Design

Background and Objectives: Trigger points (TrPs) are prevalent in patients with migraine headaches. Needling interventions targeting TrPs in migraine patients may reduce the intensity and frequency of headaches, yet systematic reviews reveal a lack of robust evidence. Intramuscular electrical stimulation (IMES) is a modality that delivers electrical current into muscles and TrPs, with recent studies suggesting it may amplify the therapeutic effects of dry needling peripherally and centrally. This could be advantageous for patients with migraine and symptomatic TrPs. Materials and Methods: This study will implement a multiple baseline single-case experimental design (SCED). In a clinical setting, a SCED study lends itself to conducting research with only a few patients that each serve as their own controls. In this SCED study, four participants with chronic migraine will be enrolled in a non-concurrent manner and randomized to one of four baseline measurement periods (4, 5, 6 or 7 weeks), leading to four potentially different start dates for each participant in the intervention phase. During the intervention phase, patients will receive five sessions of dry needling with IMES, one session per week for five weeks. The primary outcome measure will be headache frequency, i.e., the reduction in the number of headache days over a one-month period using electronic headache diary data from the Migraine Buddy smartphone application. Secondary outcome measures will be changes in mean migraine pain intensity using a numeric pain rating scale (NPRS), migraine disability using the Migraine Disability Assessment Test (MIDAS), the Headache Impact Test (HIT-6), and changes in selected cervical musculoskeletal impairments including pressure pain thresholds (PPTs) over TrPs, the craniocervical flexion test (CCFT), and cervical active range of motion (AROM). Primary and secondary outcome measures will be analyzed separately using both visual and statistical analyses. Results: Actively recruiting participants. This project was approved by the Mass General Brigham Institutional Review Board (protocol #2023P000931) and is registered with ClinicalTrials.gov (NCT05893914). Conclusions: This study will seek to determine the effects of a five-week intervention period of IMES to TrPs in the posterior cervical muscles of subjects with chronic migraine.

Pressure Pain Hypersensitivity and Ultrasound Changes in the Radial Nerve in Patients with Unilateral Lateral Epicondylalgia: A Case-Control Study

Some authors have proposed the potential role of the radial nerve in lateral epicondylalgia. The aims of this study were to investigate the presence of pressure pain hyperalgesia and nerve swelling (increased cross-sectional area) assessed with ultrasound imaging on the radial nerve in people with lateral epicondylalgia, and to investigate if an association exists between pressure pain sensitivity and cross-sectional area. A total of 37 patients with lateral epicondylalgia (43% women, age: 45.5 ± 9.5 years) and 37 age- and sex-matched pain-free controls were recruited for participation. Pressure pain thresholds (PPTs) were assessed bilaterally on the radial nerve at the spiral groove, the arcade of Frohse, and the anatomic snuffbox in a blinded design. Further, the cross-sectional area of the radial nerve at the spiral groove and antecubital fossa was also assessed. The results demonstrated lower PPTs on the radial nerve of the affected side in individuals with lateral epicondylalgia as compared with the unaffected side (p < 0.01) and with both sides in healthy controls (p < 0.001). Additionally, the cross-sectional area of the radial nerve on the affected side in patients was higher compared with the unaffected side (p < 0.01) and both sides in healthy controls (p < 0.001). The cross-sectional area of the radial nerve at the spiral groove was negatively associated with PPTs over the radial nerve at the spiral groove (r = -0.496, p = 0.002) and positively associated with function (r = 0.325, p = 0.045). Our findings revealed generalized pressure pain hyperalgesia and also nerve swelling of the radial nerve in people with lateral epicondylalgia, suggesting the presence of a widespread sensitization of nerve tissues in this population. The radial nerve could represent a potential peripheral drive to initial and maintain altered pain processing in lateral epicondylalgia.

Myths and truths on biophysics-based approach in rehabilitation of musculoskeletal disorders

Musculoskeletal disorders (MSD) are a crucial issue in current literature due to their impact on physical function, social, and economic costs. Rehabilitation plays a pivotal role in the therapeutic management of these disabling conditions with growing evidence underlining positive effects in improving functional outcomes. However, to date, several questions are still open about the mechanisms underpinning functional improvements while recent research is now focusing on a deeper understanding of the biophysical processes underpinning the macroscopical effects of these treatments. Thus, this narrative review aims at providing a comprehensive overview about the state of the art of biophysical dimensions of currently available treatments for MSD. PubMed, Scopus, CENTRAL, PEDro, and Web of Science were searched between March 2022 and October 2022 for in vitro and in vivo studies, clinical trials, systematic reviews, and meta-analysis addressing the issue of biophysics-based approach in rehabilitation of MSD. Our findings showed that a biophysical approach might be integrated into regenerative rehabilitation, aiming at enhancing regenerative processes by mechanical and biophysical stimuli. In addition, a biophysical-based approach has been proposed to improve knowledge about several instrumental physical therapies, including shock wave therapies, low-level laser therapy, ultrasound, short-wave diathermy, electrical stimulation, pulsed electromagnetic field, and vibration therapy. In accordance, emerging research is now focusing on the biophysical properties of several medical procedures to improve pain management in patients with MSD. Taken together, our results showed promising results of the integration of a biophysical-based approach in rehabilitation, albeit several limitations currently limit its implementation in routine clinical setting. Unfortunately, the state of the art is still inconclusive, and the low quality of clinical studies based on the biophysical approach did not provide clear treatment protocols. Further studies are needed to promote a precise rehabilitation approach targeting biological modification and enhancing the functional improvement of patients with MSDs.

Bibliometric and Visual Analysis of the Scientific Literature on Percutaneous Electrical Nerve Stimulation (PENS) for Pain Treatment

Background: Percutaneous electrical nerve stimulation (PENS) is a minimally invasive peripheral neuromodulation approach implemented against chronic neuropathic and mixed pain. This bibliometric study aims to quantitatively evaluate the output of PENS for pain treatment in the scientific literature. The main purpose is to stimulate research in the field and bridge potential scientific gaps. Methods: Articles were retrieved from the Web of Science (WOS) database. The search key term was “percutaneous electrical nerve stimulation (All Fields) and pain (All Fields)”. Year of publication, journal metrics (impact factor and quartile, Q), title, document type, topic, and citations were extracted. The join-point regression was implemented to assess differences in time points for the publication output. The software tool VOSviewer (version 1.6.17) was used for the visual analysis. Results: One thousand three hundred and eighteen articles were included in the knowledge visualization process. A linear upward trend for annual new publications was found. Almost two-thirds of the documents were published in top-ranked journals (Q1 and Q2). The topic “efficacy” was prevalent (12.81%). Concerning article type, the search strategy yielded 307 clinical investigations (23.3%). Articles were cited 36,610 times with a mean of 42.4 citations per article. Approximately one-half of the articles were cited less than 23 times in a range of 21 years. The semantic network analysis for keywords found eight clusters. The analysis of collaborative efforts among researchers showed five thematic clusters including 102 authors with a minimum of five documents produced in collaborations. Most partnerships involved the United States, England, and Germany. Conclusions: despite the upward trend in the number of publications on the subject and the publication of articles in top-ranked journals, there is a need to increase scientific collaborations between researchers and institutions from different countries.

Effect of Ultrasound-Guided Percutaneous Neuromodulation of Sciatic Nerve on Hip Muscle Strength in Chronic Low Back Pain Sufferers: A Pilot Study

Background: Limited hip internal rotation range of motion (IR-ROM) and hip abductor weakness are recognized in low back pain (LBP) sufferers. The main aim was to investigate the effect of a ultrasound (US)-guided percutaneous neuromodulation (PNM) technique on hip strength in people with LBP. A second purpose was to discover whether the location along the sciatic nerve, where percutaneous neuromodulation was applied, could influence the change of strength response in these patients. Methods: Sixty LBP sufferers were recruited and divided randomly into three groups. All participants received an isolated percutaneous electrical stimulation at one of three different locations of the sciatic nerve pathway (proximal, middle, and distal), depending on the assigned group. Pain intensity, hip passive IR-ROM, hip muscle strength, and the Oswestry disability index (ODI) were analyzed. All variables were calculated before the intervention and one week after the intervention. Results: All interventions significantly decreased pain intensity and improved the IR-ROMs, strength, and functionality after one week (p = 0.001). However, between-group (treatment x time) differences were reported for flexion strength in the non-intervention limb (p = 0.029) and ODI (p = 0.021), although the effect size was small (Eta² = 0.1) in both cases. Conclusions: The application of an isolated intervention of the US-guided PNM technique may be a useful therapeutic tool to increase the hip muscle strength in patients with chronic LBP.

Effects of Ultrasound-Guided Nerve Stimulation Targeting Peripheral Nerve Tissue on Pain and Function: A Scoping Review

This paper assesses the effects of percutaneous electrical nerve stimulation (PENS) on pain- and function-related outcomes by means of a scoping review of studies with single cases, case-series, quasi-experimental, and randomized or non-randomized trial designs. We consulted the PubMed, MEDLINE and EMBASE databases. Data were extracted by two reviewers. The methodological quality of studies was assessed using the Physiotherapy Evidence Database (PEDro) scale for experimental studies and the Joanna Briggs Institute (JBI) tool for case reports or cases series. Mapping of the results included: (1), description of included studies; (2), summary of results; and, (3), identification of gaps in the existing literature. Eighteen articles (five randomized controlled trials, one trial protocol, nine case series and three case reports) were included. The methodological quality of the papers was moderate to high. The conditions included in the studies were heterogeneous: chronic low back pain, lower limb pain after lumbar surgery, chronic post-amputation pain, rotator cuff repair, foot surgery, knee arthroplasty, knee pain, brachial plexus injury, elbow pain and ankle instability. In addition, one study included a healthy athletic population. Interventions were also highly heterogeneous in terms of sessions, electrical current parameters, or time of treatment. Most studies observed positive effects of PENS targeting nerve tissue against the control group; however, due to the heterogeneity in the populations, interventions, and follow-up periods, pooling analyses were not possible. Based on the available literature, PENS interventions targeting peripheral nerves might be considered as a potential therapeutic strategy for improving pain-related and functional outcomes. Nevertheless, further research considering important methodological quality issues (e.g., inclusion of control groups, larger sample sizes and comparatives between electric current parameters) are needed prior to recommending its use in clinical practice.

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.

Peripheral Nerve Stimulation for Chronic Pain: A Systematic Review of Effectiveness and Safety

Peripheral nerve stimulation (PNS) was the first application of neuromodulation. Widespread application of PNS was limited by technical concerns. Recent advances now allow the percutaneous placement of leads with ultrasound or fluoroscopic guidance, while the transcutaneous powering of these leads removes the need for leads to cross major joints. This systematic review was written to assess the current status of high-quality evidence supporting the use of PNS for pain conditions treated by interventional pain physicians. The available literature on PNS, limited to conditions treated by interventional pain physicians, was reviewed and the quality assessed. Literature from 1966 to June 2021 was reviewed. The outcome measures were pain relief and functional improvement. One hundred and two studies were identified. Five randomized controlled trials (RCT) and four observational studies, all case series, met the inclusion criteria. One RCT was of high quality and four were of moderate quality; all four case series were of moderate quality. Three of the RCTs and all four case series evaluated peripheral nerve neuropathic pain. Based upon these studies, there is level II evidence supporting the use of PNS to treat refractory peripheral nerve injury. One moderate-quality RCT evaluated tibial nerve stimulation for pelvic pain, providing level III evidence for this indication. One moderate-quality RCT evaluated surgically placed cylindrical leads for cluster headaches, providing level III evidence for this indication. The evidence suggests that approximately two-thirds of patients with peripheral neuropathic pain will have at least 50% sustained pain relief. Adverse events from PNS are generally minor. A major advantage of PNS over spinal cord stimulation is the absence of any risk of central cord injury. The study was limited by the paucity of literature for some indications. No studies dealt with joint-related osteoarthritic pain.

Short-Term Effects of PENS versus Dry Needling in Subjects with Unilateral Mechanical Neck Pain and Active Myofascial Trigger Points in Levator Scapulae Muscle: A Randomized Controlled Trial

Procedures such as dry needling (DN) or percutaneous electrical nerve stimulation (PENS) are commonly proposed for the treatment of myofascial trigger points (MTrP). The aim of the present study is to investigate if PENS is more effective than DN in the short term in subjects with mechanical neck pain. This was an evaluator-blinded randomized controlled trial. Subjects were recruited through announcements and randomly allocated into DN or PENS groups. Pain intensity, disability, pressure pain threshold (PPT), range of motion (ROM), and side-bending strength were measured. The analyses included mixed-model analyses of variance and pairwise comparisons with Bonferroni correction. The final sample was composed of 44 subjects (22 per group). Both groups showed improvements in pain intensity (η_p² = 0.62; p < 0.01), disability (η_p² = 0.74; p < 0.01), PPT (η_p² = 0.79; p < 0.01), and strength (η_p² = 0.37; p < 0.01). The PENS group showed greater improvements in disability (mean difference, 3.27; 95% CI, 0.27–6.27) and PPT (mean difference, 0.88–1.35; p < 0.01). Mixed results were obtained for ROM. PENS seems to produce greater improvements in PPT and disability in the short term.