What is the evidence for transcranial magnetic stimulation (TMS) as a tinnitus treatment in clinical trials?
Executive summary
Repetitive transcranial magnetic stimulation (rTMS) has been studied as a treatment for chronic tinnitus for roughly two decades, producing a mixed clinical-trial record with some trials and pooled analyses reporting benefit while others show no clear effect; methodological heterogeneity and small sample sizes prevent a definitive conclusion that rTMS is an established, reliably effective treatment [1] [2] [3]. Safety signals in the literature are limited: no serious adverse events were reported in the small trials pooled by reviewers, but investigators repeatedly call for large, multisite randomized trials to resolve which protocols, targets and patient subgroups — if any — derive clinically meaningful benefit [4] [1] [5].
1. The evidence base is substantial but inconsistent
Systematic reviews and meta-analyses find an extensive but heterogeneous literature: some randomized controlled trials (RCTs) report positive results (for example Folmer et al.’s randomized trial), while other large RCTs have failed to show efficacy, and pooled estimates over small trials yield uncertain conclusions because studies differ in protocol, targets and outcome measures [2] [6] [3]. A Cochrane-type synthesis and earlier pooled analyses noted statistically significant reductions in tinnitus loudness when data from a small number of trials were combined, but those results rested on few studies with wide confidence intervals and limited follow‑up [4].
2. Why trial results diverge: technical and clinical heterogeneity
Authors point to multiple unresolved technical variables — stimulation frequency, coil position, current direction, number of sessions, and whether prefrontal as well as auditory cortex sites are stimulated — as plausible reasons studies disagree; these parameters vary widely across trials and likely alter physiological effects, undermining simple cross-trial comparisons [3] [1]. Clinical heterogeneity — patient age, duration of tinnitus, degree of hearing loss, and comorbid depression — is also implicated: different study populations may respond differently, which could partly explain why Folmer’s positive results contrast with the lower efficacy reported in other large trials such as Landgrebe et al. [1] [6].
3. Newer approaches and subgroup signals deserve attention but are preliminary
More recent work explores multilocus sequential rTMS (targeting dorsolateral prefrontal cortex then auditory cortex) and extended session courses; observational series and small controlled studies report significant improvement in some patients and suggest that those without comorbid major depressive disorder may improve faster, while patients with depression sometimes require longer courses to see benefit — but these are not definitive RCT confirmations and remain subject to selection and design limitations [7] [8] [9].
4. Mechanistic and preclinical support exists but doesn’t prove clinical utility
Animal models and neuroimaging studies support a plausible mechanism — modulation of hyperactive auditory cortical networks and induction of cortical plasticity — which gives a biological rationale for rTMS in tinnitus, and preclinical work has shown changes consistent with symptom improvement; however, mechanistic plausibility alone cannot substitute for large, well-controlled clinical trials demonstrating clinically meaningful patient‑centred outcomes [10] [3].
5. Safety, measurement and the path forward
Across the randomized and controlled trials reviewed, no serious adverse effects were reported, which supports a favorable safety profile in the short term, but uncommon harms could be missed in small samples [4]. Investigators and review authors uniformly call for large-scale, multisite randomized clinical trials using standardized stimulation parameters and core outcome measures (for example the Tinnitus Functional Index) and for efforts to identify predictors of response so clinicians can match patients to the right protocol; until such trials are completed, rTMS remains experimental for tinnitus — promising for some individuals but unproven as a broadly effective therapy [1] [11] [5].