Contralateral suppression of transient evoked otoacoustic emissions: Normative data for a clinical test set-up

Hypothesis: Contralateral suppression of transient evoked otoacoustic emiss ions (TEOAEs) can be used in a clinical setup using a procedure based on a unique and robust parameter to quantify the magnitude of suppression for a subject. Background: TEOAEs can be suppressed by delivering contralateral white nois e (WN). This suppression is thought to be mediated via the efferent nerve f ibers that innervate the outer hair cells, The ipsilateral TEOAE-eliciting click stimulus level and the contralateral WN Level have a strong impact on the recorded level of suppression. Methods: TEOAEs were recorded using the nonlinear stimulation mode in two c onditions (with and without contralateral WN). An optimal TEOAE-eliciting c lick stimulus level and contralateral WN level were defined to obtain a uni que and robust parameter to quantify the magnitude of suppression. Results: Suppression of TEOAEs with contralateral WN can be measured in a c linical set-up using nonlinear stimulation, and the level of suppression is of the same order of magnitude as measures using the linear stimulation re cording mode. The level of suppression appears to be "locked" to the intera ural difference between ipsilateral TEOAE-eliciting broadband click stimulu s level and the contralateral WN level. Conclusions: A procedure is proposed to record contralateral suppression in a clinical set-up, and normative data are given for a normal-hearing popul ation (n = 60).