Contralateral Suppression of Transient Evoked Otoacoustic Emission in the Study of Tinnitus Generation

Objective: Tinnitus is a physiological disorder that can originate from different lesions and from different sites of the auditory system. In this study we investigated the effect of contralateral acoustic stimulation (CAS) using white noise on transient evoked otoacoustic emission (TEOAE) amplitude in tinnitus patients, to determine its usefulness as a clinical test in studying the generation of tinnitus. Methods: The study included 37 (66 ears) normal hearing chronic tinnitus patients and 30 (60 ears) well-matched control subjects with no tinnitus. In all subjects, TEOAE was performed with and without CAS using white noise. Results and Conclusion: There was smaller TEOAE amplitude in tinnitus subjects than non-tinnitus subjects reflecting outer hair cells dysfunction. This difference was statistically significant at the frequency bands of 3, 4, 5 kHz. There was a reduction of the efferent suppression in tinnitus subjects compared to the controls at the frequency bands of 1 2 kHz reflecting medial olivocochlear (efferent cochlear) system dysfunction in tinnitus. But this difference was not statistically significant. There was even a paradoxically greater TEOAE amplitude at 4 kHz. confirming this dysfunction, and this showed borderline significance. TEOAE and its contralateral suppression test is a valuable tool in investigating a possible generation mechanism of tinnitus in some patients.