Effectivenessoftranscutaneouselectricalnervestimulation(TENS)modalityfortreatingmyofascialpainsyndrome:Asystematicreviewandmeta-analysis

Myofascial pain syndrome (MPS) is a chronic pain disorder affecting 30-93% of patients with musculoskeletal pain. It involves trigger points in muscles and fascia, primarily affecting the neck, shoulders, and back. Treatment options include medications, injections, and physical modalities like transcutaneous electrical nerve stimulation (TENS). TENS works by stimulating sensory nerves to block pain signals through the gate-control mechanism and by increasing endogenous opioid release.

While TENS is commonly used for various pain conditions, the evidence for its effectiveness in myofascial pain syndrome specifically needed systematic evaluation.

The researchers conducted a comprehensive systematic review and meta-analysis following established guidelines. They searched major medical databases (PubMed, EMBASE, Web of Science, Cochrane Central) from inception to July 2021 for randomized controlled trials comparing TENS to placebo, sham treatments, or exercise in MPS patients. Two reviewers independently screened 422 studies, ultimately selecting 21 articles for systematic review, with 12 trials suitable for detailed analysis and 7 studies providing data for meta-analysis. They assessed study quality using the Cochrane risk of bias tool and extracted data on pain intensity (Visual Analog Scale) and pain pressure threshold measurements.

The meta-analysis included 214 participants across 5 randomized trials. TENS showed significant pain reduction compared to exercise groups, with a mean difference of -1.60 points on the Visual Analog Scale (95% CI: -2.16 to -1.05, P < 0.001). However, TENS did not significantly improve pain pressure threshold scores compared to sham treatments (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). The overall effect on pain pressure threshold was not statistically significant (MD = 0.96, 95% CI: -0.72 to 2.64, P = 0.26).

Study quality was generally moderate to good, though there was significant heterogeneity between studies due to variations in TENS parameters, treatment protocols, and patient populations.

TENS appears to provide some benefit for reducing pain intensity in myofascial pain syndrome, particularly when compared to exercise alone. However, the evidence suggests TENS should be used as an adjuvant (add-on) treatment rather than a standalone therapy. The lack of improvement in pain pressure threshold indicates that while patients may feel less pain, the underlying trigger point sensitivity may not change significantly. Clinicians should consider TENS as part of a comprehensive treatment approach that may include other modalities like manual therapy, exercise, and medications.

The variability in treatment protocols across studies suggests that optimal TENS parameters for MPS still need to be established through larger, high-quality trials.