Effects of transcutaneous electrical nerve stimulation (TENS) on proinflammatory cytokines: protocol for systematic review

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 external low intensity focused ultrasound on inflammatory markers in neuropathic pain

BACKGROUND

Changes in inflammatory cytokine levels contribute to the induction and maintenance of neuropathic pain. We have shown that external low intensity focused ultrasound (liFUS) reduces allodynia in a common peroneal nerve injury (CPNI). Here, we investigate an underlying mechanism of action for this treatment and measure the effect of liFUS on inflammatory markers.

METHODS

Male rats were divided into four groups: CPNI/liFUS, CPNI/shamliFUS, shamCPNI/liFUS, and shamCPNI/shamliFUS. Mechanical nociceptive thresholds were measured using Von Frey filaments (VFF) to confirm the absence/presence of allodynia at baseline, after CPNI, and after liFUS. Commercial microarray and ELISA assays were used to assess cytokine expression in the treated L5 dorsal root ganglion (DRG) and dorsal horn (DH) tissue 24 and 72 h after liFUS.

RESULTS

VFF thresholds were significantly reduced following CPNI in both groups that received the injury (p < 0.001). After liFUS, only the CPNI/liFUS cohort showed a significant increase in mechanical thresholds (p < 0.001). CPNI significantly increased TNFa, IL6, CNTF, IL1b (p < 0.05 for all) levels in the DRG and DH, compared to baseline, consistent with previous work in sciatic nerve injury. LiFUS in CPNI rats resulted in a decrease in these cytokines in DRG 72 h post-therapy (TNFa, IL6, CNTF and IL1b, p < 0.001). In the DH, IL1b, CNTF, and TNFa (p < 0.05 for all) decreased 72 h after liFUS.

CONCLUSION

We have demonstrated that liFUS modifies inflammatory cytokines in both DRG and DH in CPNI rats. These data provide evidence that liFUS, reverses the allodynic phenotype, in part, by altering inflammatory cytokine pathways.

Transcutaneous electrical nerve stimulation (TENS): towards the development of a clinic-friendly method for the evaluation of excitatory and inhibitory pain mechanisms

Background: Temporal summation and conditioned pain modulation (CPM) can be measured using a thermode and cold pressor test (CPTest). Unfortunately, these complex and expensive tools are ill-suited for routine clinical assessments.

Aims: We aimed to compare the temporal summation and CPM obtained with the thermode + CPTest paradigm to those obtained with a novel paradigm using transcutaneous electrical nerve stimulation (TENS).

Methods: We assessed temporal summation and CPM in 29 healthy participants, using two paradigms (random order): TENS, and thermode + CPTest. In the TENS paradigm, both the conditioning stimulus (CS) and the test stimulus (TS) were delivered using TENS; in the thermode + CPTest paradigm, the CS consisted of a CPTest and the TS was delivered using a thermode. We compared the average temporal summation and CPM evoked by the two paradigms.

Results: Average temporal summation was similar for both modalities (P = 0.90), and the number of participants showing temporal summation was similar in both paradigms (19 with thermode vs. 18 with TENS; P = 1.00). Average CPM response was larger following the thermode + CPTest than following the TENS (P = 0.005), and more participants showed CPM with the thermode + CPTest paradigm compared to the TENS paradigm (24 vs. 14; P = 0.01).

Conclusions: Both paradigms were roughly equivalent in the ability to evoke temporal summation (although response to one modality did not predict response to the other), but the TENS paradigm appeared to be less apt to induce a CPM response than the thermode + CPTest paradigm.

Efficacy of Transcutaneous Electronic Nerve Stimulation in Postoperative Analgesia After Pulmonary Surgery: A Systematic Review and Meta-Analysis

OBJECTIVE

The aim of the study was to identify the analgesic efficacy and safety of transcutaneous electronic nerve stimulation in postoperative pain after pulmonary surgery.

DESIGN

Electronic databases (PubMed, Embase, Web of Science, and CENTRAL) were systematically searched from their inception to June 2019. The continuous variables were pooled as the weighted mean difference with correlated 95% confidence interval. Results were recognized as significant when a P value is less than 0.05. Subgroup analyses, sensitivity analyses, and quality assessment were performed.

RESULTS

Altogether, 10 studies were included. The pooled results indicated that transcutaneous electronic nerve stimulation group conferred lower pain intensity score on the first postoperative day (weighted mean difference = -0.93, 95% confidence interval = -1.56 to -0.30, P = 0.004), postoperative day 2 (weighted mean difference = -1.00, 95% confidence interval = -1.64 to -0.35, P = 0.002), postoperative day 3 (weighted mean difference = -0.92, 95% confidence interval = -1.76 to -0.09, P = 0.03), postoperative day 4 (weighted mean difference = -0.90, 95% confidence interval = -1.24 to -0.56, P < 0.001), and postoperative day 5 (weighted mean difference = -1.39, 95% confidence interval = -2.20 to -0.57, P < 0.001) compared with the placebo transcutaneous electronic nerve stimulation group. No publication bias was found. No significant discovery was obtained in sensitivity analyses.

CONCLUSIONS

Transcutaneous electronic nerve stimulation might be an effective supplementary analgesic regimen in multimodal analgesia to decrease pain intensity after pulmonary surgery.

Treatment with low-energy shock wave alleviates pain in an animal model of uroplakin 3A-induced autoimmune interstitial cystitis/painful bladder syndrome

Purpose

To investigate whether treatment with low-energy shock wave (LESW) alleviates pain and bladder dysfunction in a mouse model of uroplakin 3A (UPK3A)-induced interstitial cystitis/painful bladder syndrome (IC/PBS).

Materials and Methods

Forty female BALB/c mice were divided into four groups (n=10/group): Sham, Sham+LESW, UPK3A, and UPK3A+LESW. At 6 weeks of age, mice were injected with an emulsion containing water and complete Freund's adjuvant with (UPK3A and UPK3A+LESW groups) or without (Sham and Sham+LESW groups) 200 µg of UPK3A. At 10 weeks, mice received a second dose of Freund's adjuvant to booster immunization. At 12 weeks, mice underwent pain assessment and a frequency volume chart (FVC) test as the pretreatment assessment. LESW treatment and pain assessment were conducted from 13 to 15 weeks. One week after the final treatment, pain assessment and the FVC were conducted again as the post-treatment assessment. Mice were euthanized and sacrificed at 17 weeks.

Results

The presence of tactile allodynia and bladder dysfunction was significant in the UPK3A-injected mice. LESW raised the pain threshold and improved bladder function with decreased urinary frequency and increased mean urine output. Expression and secretion of local and systemic inflammatory markers, including tumor necrosis factor-α (TNF-α) and nerve growth factor (NGF), increased after UPK3A immunization. These markers were significantly decreased after LESW treatment (p<0.05).

Conclusions

LESW treatment attenuated pain and bladder dysfunction in a UPK3A-induced model of IC/PBS. Local and systemic inflammation was partially controlled, with a reduced number of infiltrated inflammatory cells and reduced levels of TNF-α and NGF.

Electrical impulse effects on degenerative human annulus fibrosus model to reduce disc pain using micro-electrical impulse-on-a-chip

Electrical stimulation of cells and tissues for therapeutic benefit is a well-established method. Although animal studies can emulate the complexity of an organism’s physiology, lab-on-a-chip platforms provide a suitable primary model for follow-up animal studies. Thus, inexpensive and easy-to-use platforms for in vitro human cell studies are required. In the present study, we designed a micro-electrical impulse (micro-EI)-on-a-chip (micro-EI-chip), which can precisely control electron density and adjust the frequency based on a micro-EI. The micro-EI-chip can stimulate cells at various micro-EI densities (0–500 mV/mm) and frequencies (0–300 Hz), which enables multiple co-culture of different cell types with or without electrical stimulation. As a proof-of-concept study, a model involving degenerative inflamed human annulus fibrosus (hAF) cells was established in vitro and the effects of micro-EI on inflamed hAF cells were evaluated using the micro-EI-chip. Stimulation of the cells (150 mV/mm at 200 Hz) inhibited the secretion of inflammatory cytokines and downregulated the activities of extracellular matrix-modifying enzymes and matrix metalloproteinase-1. These results show that micro-EI stimulation could affect degenerative diseases based on inflammation, implicating the micro-EI-chip as being useful for basic research of electroceuticals.

Transcutaneous electric nerve stimulation over acupoints for patients with diarrhea-predominant irritable bowel syndrome: Protocol for systematic review and meta-analysis

BACKGROUND

At present, drug therapy for diarrhea-predominant irritable bowel syndrome (IBS-D) has made great progress; however, it does not often produce a satisfying curative effect. Transcutaneous electric nerve stimulation over acupoints (Acu-TENS) might be more effective in improving patient's symptoms and producing fewer side-effects as a result.Although with a great progress of the drug therapy for IBS-D, it is often hard to achieve its satisfactory curative effect. Acu-TENS that may be effective to improve patients' symptoms and fewer side-effects will be sought. There is no systematic review concerning the efficacy of Acu-TENS for IBS-D published. Therefore, this review aims to systematically evaluate the efficacy of Acu-TENS on IBS-D.

METHODS

Four English (PubMed, EMBASE, The Cochrane Library, Web of Science) and 4 Chinese electronic databases (Biomedical Literature Database, CNKI, VIP, Wanfang Database) will be searched from their inception to November 26, 2018. Randomized controlled trials that evaluated the effect of Acu-TENS on patients with IBS-D will be included. The primary outcome measures will include average weekly stool frequency, visual analog scale (VAS), and the Bristol scale. The secondary outcome measures will include the MOS 36-item short-form health survey (SF-36), IBS Quality of Life Questionnaire (IBS-QOL), severity of IBS symptoms (IBS-SSS), and rectal perception. Quality evaluation and data extraction will be independently undertaken, respectively. The data from the eligible trials will be analyzed by RevMan5.3.

RESULTS

For patients with IBS-D, this systematic review will provide evidences related to the efficacy of Acu-TENS in these evaluation aspects, stool frequency, VAS and the Bristol scale, SF-36, IBS-QOL, IBS-SSS, and rectal perception.

CONCLUSION

This evidence may be useful to medical workers with regard to the use of Acu-TENS in the treatment of IBS-D.PROSPERO registration number: PROSPERO CRD442018109294.

Effects of Transcutaneous Electrical Nerve Stimulation on Proinflammatory Cytokines: Systematic Review and Meta-Analysis

The mechanism of pain reduction involves bidirectional processes of pain blocking (nociception) and reductions in the levels of proinflammatory cytokines in the blood. Does transcutaneous electrical nerve stimulation (TENS) reduce blood levels of proinflammatory cytokines? For this systematic review, we searched in six databases to identify randomized controlled trials with the criteria: humans older than 18 years (adults), use of TENS in the experimental group, and having at least one pre- and postintervention blood level of at least one proinflammatory cytokine. The risk of bias and the level of evidence were assessed. Five studies were included involving 240 participants. The heterogeneity of the studies was high (I²: 85%); therefore, we used a random-effects meta-analysis. It was observed through the meta-analysis synthesis measures that there were statistically significant differences following the use of TENS to reduce the general group of cytokines. When grouped by chronic disease, by postoperative settings, or by individual studies in the case of IL-6, it was observed that the significant reduction of cytokines related to the use of TENS was maintained. The use of TENS reduced the blood levels of proinflammatory cytokines (we observed a protective factor of TENS in relation to inflammation). The protocol of the systematic review was registered in PROSPERO, CRD42017060379.