Contralateral suppression of otoacoustic emissions in tinnitus patients

Abstract

Objective: To compare the functioning of the medial olivocochlear efferent system between tinnitus patients and control subjects.

Study design: Prospective, nonrandomized controlled analysis of suppression of otoacoustic emissions with contralateral acoustic stimulation.

Setting: Tertiary referral center.

Patients: Initial analysis of 97 tinnitus patients and 44 control subjects with click-evoked otoacoustic emission measurement. If subjects had reproducible otoacoustic emissions at 80 dB SPL, suppression of otoacoustic emission with contralateral acoustic stimulation was measured with a 65-dB click stimulus. This resulted in inclusion of 44 ears of tinnitus patients and 57 ears of control subjects.

Intervention: Suppression of the otoacoustic emissions generated by the 65-dB click stimulus was tested using contralateral broadband noise at 70 dB SPL. Suppression was calculated in half-octave frequency bands centered at 1.0, 1.4, 2.0, 2.8, and 4.0 kHz.

Main outcome measure: The amount of suppression of the OAE, calculated in half-octave frequency bands.

Results: Otoacoustic emission amplitudes were equal in both groups. Contralateral suppression of the signal was found in both patients and controls. The amount of suppression was equal, except for the 2.0- and 2.8-kHz frequency bands in the right ear (p value of 0.03, 0.008, respectively), for which the patients had less suppression.

Conclusion: The suppression of otoacoustic emissions with CAS seems equally effective in tinnitus patients and healthy controls. The minor differences between both groups suggest subtle differences in the function of the medial olivocochlear efferent system.