Peripheral and central auditory dysfunction in tinnitus with clinically normal hearing

Tinnitus is the perception of ringing in the ear without an external source and occurs even in individuals with clinically normal hearing thresholds. This suggests there may be an undetected auditory dysfunction present. Two main mechanisms that could explain this phenomenon are ultra-high frequency hearing loss (> 8 kHz) and cochlear synaptopathy, which can disrupt both peripheral and central auditory processing. While ultrahigh frequency (UHF) audiometry is increasingly used in tinnitus assessment, the study aims to bridge the gap by systematic integration of measures of central auditory processing (TFS-AF and AMD) with clinically valid peripheral assessment (UHF) to characterise both peripheral and central deficits in tinnitus with normal hearing. The case-control study compared 28 patients with tinnitus and 28 age- and gender-matched controls. The individuals with tinnitus were assessed for tinnitus severity using the Tinnitus Functional Index (TFI). The measures included UHF audiometry (9-20 kHz), TFS-AF, and AMD tasks. The diagnostic accuracy was evaluated using the Receiver Operating Characteristic (ROC) curve, along with regression and Bland-Altman analyses. Tinnitus individuals differed across all measures (TFS-AF, AMD, and UHF) from the control group. indicating a disrupted temporal processing ability. Bland-Altman plots revealed systematic biases: TFS-AF values were consistently higher than UHF thresholds, while AMD scores were lower. UHF audiometry demonstrated superior diagnostic accuracy in classifying individuals with normal hearing who have tinnitus (96.43%). In terms of clinical utility, UHF may offer higher sensitivity in detecting tinnitus in individuals with normal hearing. Systemic biases between measures suggest the presence of independent peripheral/central deficits in individuals with normal hearing who have tinnitus.