Is Contralateral Suppression of Otoacoustic Emission Observable in Unilateral Cochlear Implant Users With Auditory Neuropathy Spectrum Disorder?

PURPOSE: This study aims to explore the presence of contralateral suppression of otoacoustic emissions (CS-OAEs) in unilateral cochlear implant (CI) users with auditory neuropathy spectrum disorder (ANSD).

METHOD: We enrolled three unilateral CI users with bilateral ANSD and stable otoacoustic emissions in the nonimplanted ear, exhibiting diverse postsynaptic ANSD backgrounds including cerebellar ataxia, areflexia, pes cavus, optic atrophy, sensorineural hearing loss syndrome, Optic Atrophy Plus Syndrome, and Spinocerebellar Ataxia. Measurements of transient-evoked otoacoustic emissions (TEOAEs) were conducted both with and without contralateral electrical stimulation (CES) across five frequency bands. CES was delivered via a CI using a direct audio input cable connected to a computer. In order to elicit a response, broad-band noise is applied and presented at a comfortable level.

RESULTS

Minor amplitude reductions (between 0.2 and 0.6 dB SPL) were observed in TEOAEs with CES across different frequencies for each subject. Despite these changes, there was no prominent suppression effect observed, which emphasizes the differences in CS-OAE responses among individuals with postsynaptic ANSD.

CONCLUSIONS

The absence of significant CS-OAE suppression suggests that direct electrical stimulation through CES may not consistently engage the efferent auditory system in patients with postsynaptic ANSD characteristics. It is essential to broaden the study population to encompass a more diverse range of ANSD presentations in order to confirm the effectiveness of CES in stimulating efferent pathways.