What randomized clinical trials exist testing TMS specifically for chronic tinnitus and what were their outcomes?

1. The landscape: dozens of randomized trials, many small, a few large

Since the 2000s investigators have conducted multiple randomized, sham‑controlled trials of rTMS in chronic tinnitus patients, with individual trial sizes typically between about 19 and 62 participants and some larger trials enrolling around 70 patients; systematic reviews identified roughly 29 randomized trials encompassing more than 1,200 patients in aggregate by 2020 ^{[1] [2] [4]}.

2. Representative randomized trials and their outcomes

Several high‑visibility randomized trials illustrate the mixed findings: Folmer et al. ran a randomized, participant‑ and observer‑blinded, placebo‑controlled clinical trial at a VA center that screened hundreds and randomized 70 subjects to active or placebo rTMS and used the Tinnitus Functional Index as a primary outcome ^{[4] [5] [6]}; Lehner and colleagues conducted a randomized triple‑site rTMS trial published in Scientific Reports (the triple‑site study is explicitly cited in reviews of parameter effects) ^{[7] [8]}; Plewnia and coauthors tested theta burst stimulation in a randomized controlled trial (reported in systematic reviews) ^[1]; Hoekstra et al. performed a randomized, controlled two‑arm trial of bilateral low‑frequency rTMS that found no efficacy ^[2]; Khedr et al. compared ipsilateral vs contralateral and low vs high frequency arms in a multi‑arm randomized design ^[2]. Outcomes across these trials vary: some trials reported statistically significant and sometimes medium‑to‑large effect sizes on tinnitus severity measures, while others reported no benefit compared with sham ^{[3] [1] [2]}.

3. What the meta‑analyses say: a signal amid heterogeneity

Systematic reviews and meta‑analyses summarize a pattern of promise mixed with caution: one meta‑analysis reported medium‑to‑large effect sizes across included rTMS studies, supporting clinical efficacy, while other reviews emphasize contradictory results and call the overall support limited or inconsistent because of heterogeneity in methods and outcomes ^{[3] [1] [7]}.

4. Why trials disagree: parameters, populations, endpoints

A consistent critique in the literature is that rTMS trials differ markedly in stimulation frequency (low‑frequency 1 Hz versus high‑frequency or theta burst), number of pulses and sessions, coil placement (auditory cortex, temporoparietal or prefrontal sites, unilateral versus bilateral or multi‑site), patient selection (duration and etiology of tinnitus, hearing status), and outcome measures—differences that likely explain discordant trial outcomes and complicate pooling of evidence ^{[3] [7] [2]}.

5. Safety, duration of benefit, and research gaps

Trials report that rTMS is generally well tolerated with mostly mild adverse events such as scalp discomfort and headaches, but long‑term durability of benefit is uncertain and larger, multi‑site randomized trials with standardized protocols are repeatedly called for to define optimal stimulation parameters, target populations, and long‑term efficacy ^{[9] [3] [7]}.

6. Bottom line: promising but not definitive

Randomized trials of rTMS for chronic tinnitus exist in substantial number and include both positive and null results; systematic reviews detect signals of benefit but underline heterogeneity and methodological limitations, and leading voices in the field recommend larger, standardized, multi‑site randomized controlled trials before rTMS can be endorsed as a reliable, generalizable treatment for chronic tinnitus ^{[1] [2] [3]}.