Multidomain Auditory Differences in Tinnitus With a Clinically Normal Audiogram: Accounting for Extended High-Frequency Hearing.

Objective

Tinnitus can occur in individuals with clinically normal audiograms, suggesting that conventional threshold-based measures may not capture subtle auditory-system differences. This study aimed to characterize peripheral and subcortical auditory function in tinnitus using a multidomain, exploratory multivariate framework.

Method

Twenty individuals with tinnitus and clinically normal conventional audiograms (0.125-8 kHz) and 25 age-matched controls underwent a multidomain auditory assessment, including auditory brainstem response (ABR), otoacoustic emission, medial olivocochlear suppression, middle ear muscle reflex, temporal fine structure, and extended high-frequency (EHF) audiometry. Group differences were evaluated using exploratory unadjusted analyses, followed by EHF-adjusted analysis of covariance and exploratory principal component analysis (PCA).

Results

Initial exploratory comparisons showed that the tinnitus group had elevated EHF thresholds, reduced ABR Wave I amplitude, differences in cochlear-output and efferent reflex measures, and poorer temporal-processing performance. However, these differences were no longer significant after adjustment for EHF thresholds, suggesting that the overall pattern was largely related to basal cochlear variability. PCA identified three components explaining 72% of cumulative variance, reflecting afferent auditory contribution and basal cochlear output, efferent reflex regulation, and cochlear-temporal coupling.

Conclusions

Individuals with tinnitus and clinically normal conventional audiograms exhibited subtle differences across multiple auditory domains rather than a single isolated deficit. Several of these differences were attenuated after adjustment for EHF, indicating that EHF hearing should be considered when interpreting auditory findings in this population. These findings support the inclusion of EHF assessment as part of the audiological evaluation of individuals with tinnitus.