Structural brain pattern abnormalities in tinnitus with and without hearing loss

Subjective tinnitus often coexists with hearing loss, and they share common pathophysiological mechanisms. This comorbidity induces whole-brain gray matter volume (GMV) alterations, manifesting as distributed structural changes in neural networks rather than isolated regional modifications. Multivariate analysis of structural brain patterns is therefore essential to differentiate their underlying mechanisms.

Fifty tinnitus patients and 50 age-/gender-matched controls underwent structural MRI and audiometry. Patients were stratified by hearing level into 22 with hearing loss (T+HL) and 28 without (T-HL). To investigate structural brain patterns specific to tinnitus and hearing loss, Source-Based Morphometry (SBM), a multivariate analytical approach based on Independent Component Analysis (ICA), was applied to identify covarying patterns of GMV. The associations between these structural covariance patterns and clinical characteristics were examined using Spearman's correlation analysis.

Our results showed that in T-HL patients, structural abnormalities in the medial prefrontal cortex, precuneus, and auditory cortex were negatively correlated with tinnitus distress. In contrast, in T+HL patients, abnormalities in the insular structural brain pattern were negatively associated with depressive symptoms.

Our findings revealed that tinnitus-related structural brain patterns involve regions such as the middle frontal gyrus, supplementary motor area (SMA), and anterior cingulate cortex (ACC), with these changes negatively correlating with tinnitus distress, suggesting adaptive mechanisms in tinnitus perception. Moreover, the structural brain pattern involving the insula, putamen, and superior temporal gyrus appears to be primarily driven by hearing loss. These findings support audiometric-based subgrouping in tinnitus management.