Electrophysiological characteristics and clinical significance of unilateral tinnitus with normal hearing threshold

Objective To investigate the electrophysiological characteristics and clinical significance of unilateral tinnitus with normal hearing threshold. Methods A total of 34 patients with normal hearing but unilateral tinnitus admitted to our department from May 2022 to February 2023 were recruited as the study subjects. Pure tone hearing threshold detection, distortion product otoacoustic emission (DPOAE), auditory brainstem response (ABR) detection and extended high-frequency pure tone audiometry were performed on both ears (affected side and healthy side) of every patient. The data of the affected side group and those of healthy side group were compared. Results The Ⅰ-wave latency of ABR was significantly shorter (1.60 vs 1.73 ms, P=0.018), and its amplitude was obviously decreased (0.19 vs 0.23 μV, P=0.003) in the affected side group when compared with the healthy side group. In the affected group (34 ears), there were 18 ears (52.94%) having amplitude of wave Ⅲ greater than that of wave Ⅴ, while in the healthy group, no such difference in the amplitude between wave Ⅲ and wave Ⅴ was observed. There was statistical significance between the 2 groups (Chi-square=24.480, P < 0.001). In the 12.5, 14.0, 16.0, 18.0 and 20.0 kHz conditions, the average hearing threshold of extended high-frequency audiometry was all significantly higher in the affected side group than the healthy group (P < 0.05). Conclusion For subjective tinnitus patients with normal hearing threshold, ABR examination is helpful in preliminarily determining whether there are hidden functional changes in the auditory pathway. Decreased Ⅰ-wave amplitude, shortened Ⅰ-wave latency, and wave Ⅲ amplitude greater than wave Ⅴ amplitude can be used as objective reference indicators.