Effectivenessoftranscutaneouselectricalnervestimulation(TENS)modalityfortreatingmyofascialpainsyndrome:Asystematicreviewandmeta-analysis

Myofascial pain syndrome (MPS) is a common chronic pain condition that affects muscles and fascia, with trigger points as its hallmark feature. It impacts a substantial portion of patients with musculoskeletal pain, with estimates ranging from 30% to 93%. Given the variety of treatment options available, including medications, injections, and physical modalities, clinicians need clear evidence to guide their choices. Transcutaneous electrical nerve stimulation (TENS) is a noninvasive electrical therapy that has been proposed as a potential treatment for MPS, with theories suggesting it works through endogenous opioid release, sensory nerve stimulation, and gate-control mechanisms.

However, the actual clinical benefit of TENS for myofascial pain remained unclear, prompting this comprehensive review of the available research.

The researchers conducted a systematic review and meta-analysis following Cochrane Collaboration guidelines and the PRISMA protocol. They searched multiple databases including PubMed, EMBASE, Web of Science, and Cochrane Central Register of Controlled Trials from database inception through July 2021. Two reviewers independently screened articles and extracted data. They included all randomized controlled trials and quasi-randomized trials that evaluated TENS for patients with myofascial pain syndrome.

The primary outcomes were pain reduction measured by the Visual Analog Scale (VAS) and pain pressure threshold (PPT) measured with a pressure algometer. The team assessed risk of bias using the Cochrane appraisal checklist and performed meta-analysis using Review Manager software, applying random-effects or fixed-effects models based on heterogeneity levels.

From 422 initially identified articles, 21 studies met criteria for the systematic review (including 12 trials), and 7 studies with sufficient data were included in the meta-analysis. The included studies were published between 2002 and 2021, with most conducted in Turkey, and used various TENS parameters including continuous, biphasic, and burst modalities.

For pain reduction measured by VAS, five RCTs with seven trials and 214 participants were pooled. The analysis showed a significant decrease in VAS score in the TENS group compared with the exercise group (MD = -1.60, 95% CI: -2.16 to -1.05, P < 0.00001). However, when comparing TENS to sham or control groups overall, or when analyzing TENS versus sham TENS specifically, no statistically significant difference was found (MD = -0.67, 95% CI: -1.70 to 0.36, P = 0.20 for the sham subgroup).

For pain pressure threshold, five RCTs involving 222 participants were analyzed. The results showed no significant decrease in PPT score in the TENS group compared with sham (MD = 1.88, 95% CI: -0.62 to 4.38, P = 0.14) or exercise (MD = 0.19, 95% CI: -0.99 to 1.37, P = 0.75). Overall, TENS therapy did not improve PPT scores (MD = 0.96, 95% CI: -0.72 to 2.64, P = 0.26).

The studies showed considerable heterogeneity (I2 = 88% for VAS, I2 = 99% for PPT), reflecting variability in TENS parameters, treatment protocols, and patient populations across trials.

The findings suggest that TENS may provide some pain relief for myofascial pain syndrome when compared to exercise, but the evidence does not strongly support its effectiveness when compared to sham or placebo treatments. The lack of significant improvement in pain pressure threshold indicates that TENS may not fundamentally alter trigger point sensitivity. The authors conclude that TENS can be utilized as an adjuvant treatment to help alleviate MPS but should not be regarded as a monotherapy. For patients, this means TENS might be worth trying as part of a broader treatment plan that includes other approaches like exercise, manual therapy, or medications, but should not be expected to work as the sole treatment.

For clinicians, the results highlight the importance of using TENS in combination with other evidence-based interventions rather than relying on it alone. The considerable heterogeneity across studies also points to the need for better standardized research protocols to clarify optimal TENS parameters for myofascial pain.