Transcutaneous Electrical Nerve Stimulation for Subjective Tinnitus: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

OBJECTIVE: To evaluate the efficacy and safety of transcutaneous electrical nerve stimulation (TENS) for the treatment of subjective tinnitus in adults. DATA SOURCES: Cochrane Library, PubMed, EMBASE, Web of Science, VIP, WanFang, CNKI, SinoMed, and ClinicalTrials.gov. STUDY SELECTION: Randomized controlled trials (RCTs) comparing TENS with sham or active controls for subjective tinnitus were included. DATA EXTRACTION: Data were extracted and synthesized according to PRISMA guidelines. The primary outcomes evaluated were the change in Tinnitus Handicap Inventory (THI) and Visual Analog Scale (VAS) scores for loudness and annoyance. DATA SYNTHESIS: Seven RCTs (N=342 patients) were included in the random-effects meta-analysis. TENS produced a clinically meaningful reduction in THI scores compared with controls [Mean Difference (MD) =-8.60, 95% CI: -13.39 to -3.81], but with substantial heterogeneity ( I2 =62%). TENS did not significantly affect tinnitus loudness or annoyance. Sensitivity analysis identified a single active-control trial as the source of heterogeneity; after its removal, the effect of TENS versus sham control on THI was larger and more consistent (MD=-10.48, 95% CI: -13.42 to -7.54; I2 =11%). The certainty of evidence was rated "Very Low." No severe adverse events were reported. CONCLUSIONS: Based on very low-certainty evidence, TENS safely provides a clinically meaningful reduction in THI but not in perceived loudness or annoyance. This effect is clearest against placebo controls. Further high-quality RCTs with larger sample sizes are necessary to substantiate these findings.