Predicting TMS Success for Tinnitus via Brain Scans

A two-week course of repetitive transcranial magnetic stimulation (rTMS) reduces tinnitus for just over half of patients, leaving clinicians with a persistent question: who will it help? New research provides a potential answer by identifying a specific brain structure that appears to predict a patient’s likelihood of benefiting from the treatment.

Identifying a Predictive Brain Signature

To find a reliable biomarker, researchers led by Zhongling Ding, Bo Peng, and Mengfang Gong conducted a prospective study. They recruited 64 patients with subjective tinnitus and 18 healthy controls. All patients underwent a two-week rTMS protocol, and their response was measured using standard tinnitus handicap (THI) and loudness (VAS) scales. High-resolution structural MRI (sMRI) scans were taken before treatment began.

The team extracted 242 distinct measurements of brain morphology from these scans. Using a combination of statistical analysis and machine learning, they compared the brains of the 36 patients (56.25%) who were classified as responders to the 28 who were non-responders. Their goal was to find structural features present before treatment that could separate the two groups.

The Right Frontal Lobe Emerges as a Key Predictor

The analysis identified ten regional brain features that differed between responders and non-responders. These features spanned networks involved in executive function, emotion, sensory processing, and attention. To determine which were most important for prediction, the researchers built a machine learning model, ExtraTreesGini_BAG_L1.

This model was highly effective. Evaluated through rigorous cross-validation, it achieved an area under the curve (AUC) of 0.85, with an accuracy of 77%. Most notably, it had a recall of 0.97, meaning it correctly identified nearly all patients who would end up being responders.

A SHAP analysis, which interprets the model’s decisions, pinpointed a single feature as the top contributor: the gray matter volume (GMV) of the right pars triangularis of the inferior frontal gyrus (IFGtriang-R). A larger volume in this region was strongly associated with a positive treatment outcome.

A Specific Structural Signature for Treatment Success

The researchers then performed a three-way comparison to understand this finding’s context. They found that responders had a significantly larger IFGtriang-R GMV (0.90 ± 0.08) than both healthy controls (0.86 ± 0.06) and non-responders (0.86 ± 0.07). This pattern indicates that successful responders possess a distinct, pre-existing brain structure. It is not simply a case of having a “normal” or “healthy” brain volume; responders had a relative enlargement in this specific area.

Further correlation analyses showed that the size of this region was not linked to how much a patient’s tinnitus improved (ΔVAS or ΔTHI), nor was it related to how severe their tinnitus was at the start. This suggests the IFGtriang-R volume is not a marker of current symptom burden but may instead reflect an individual’s inherent capacity for neuroplastic change—a “neuroplastic reserve” that reaches a threshold conducive to rTMS efficacy.

Practical Implications for Precision Neuromodulation

This research, published in Frontiers in Neurology (DOI: 10.3389/fneur.2026.1808769), moves the field toward more personalized tinnitus management. The variable success rate of neuromodulation treatments like rTMS is a significant clinical challenge. An objective, pre-treatment biomarker could dramatically improve decision-making.

In practice, a structural MRI scan could be used to assess a candidate’s IFGtriang-R volume. For patients with the identified structural signature, rTMS could be presented as a treatment with a higher probability of success. For others, clinicians might prioritize alternative approaches first, such as manual therapy and jaw exercises for tinnitus linked to temporomandibular dysfunction, or other forms of sound therapy and counseling.

This stratification aligns with a broader shift toward precision medicine in auditory health, where treatment is increasingly guided by individual patient characteristics, from integrated auditory health assessments to targeted pharmacological research for conditions like hyperacusis.

Future Directions and Cautions

The study’s model requires validation in larger, independent patient groups. The rTMS protocol was specific, and it is unknown if this biomarker predicts response to different stimulation parameters or to other neuromodulation treatments. Furthermore, the biological reason why a larger right pars triangularis facilitates rTMS benefit remains a subject for investigation. This region is involved in cognitive control, inhibitory processes, and attention—functions that are often altered in tinnitus.

Ultimately, this work provides a concrete, anatomical starting point. By identifying a brain structure that indicates a readiness to respond to magnetic stimulation, researchers have provided a tool that could make rTMS a more efficient and targeted option for the subset of tinnitus patients most likely to gain relief.