Evaluation of the Effects of Caloric Vestibular Stimulations on Distortion Product Otoacoustic Emission Responses.

Abstract

Purpose: Although the effects of the auditory system on the balance system are known, we do not possess sufficient knowledge about the possible effects of the balance system on the auditory system. This study aims to investigate the impact of bithermal caloric stimulation on the outer hair cell functions of the contralateral ear.

Method: Distortion product otoacoustic emissions (DPOAEs) were recorded before, during, and after bithermal caloric stimulation. A repeated-measures multivariate analysis examined the effects of Condition (pre, cold, warm, post) and Frequency (13 f₂ frequencies).

Results: DPOAE amplitudes decreased significantly during caloric-induced nystagmus. A significant effect was observed among DPOAE frequencies. The largest amplitude changes occurred in the midfrequency range, while smaller response changes were seen at both low and high frequencies. This significant frequency interaction indicates that caloric-induced suppression varies across frequencies. Furthermore, both cold and warm irrigation reduced DPOAE amplitudes with warm irrigation, in particular, generally provided greater suppression and showed that this effect was related to the rate of caloric stimulation. Posttest values showed that this reduction persisted, albeit to a lesser extent than during active irrigation.

Conclusions: This study shows a significant decrease in DPOAE results for all frequencies during caloric stimulation, supporting the idea that vestibular inputs affect the auditory system through central mechanisms. These findings contribute to emerging evidence of bidirectional interactions between the vestibular and auditory systems.