Assessment of Electrically Evoked Stapedius Reflex Threshold (eSRT) for Auditory Mapping in Pulse Width Modulation Cochlear Implants: The Effect of Multielectrode Stimulation.

Objective: This study assesses the electrically evoked stapedius reflex threshold (eSRT) as an objective method for generating auditory maps in individuals with pulse-width-modulation cochlear implants (CIs). It investigates the impact of both single- and multiple-electrode stimulations on eSRT detection rates and their association with patients' comfort loudness levels (C-levels). Despite eSRT exploration by several CI brands incorporating pulse-amplitude-modulation stimulation technology, there is a lack of information on systems using pulse-width modulation.

Approach: The eSRT was measured in 19 ears ipsilaterally and contralaterally in response to stimulations in groups of 1, 3, and 5 electrodes across five distinct cochlear regions, spanning from apical to basal. For each group, the eSRT detection rate and its correlation with the C-levels were analyzed both regionally and overall.

Main Results: In both contralateral and ipsilateral sides, higher electrically evoked stapedius reflex (eSR) detection rates were obtained for multielectrode (67%, 47%) than for single-electrode (41%, 23%) stimulation. Invoking eSR in the apical and basal regions was easier than in the middle region. The multiple stimulation just increased slightly the correlation coefficients between eSRT and C-levels from 0.73 to 0.77 and from 0.77 to 0.85 (p < 0.05) for the contralateral and ipsilateral ears, respectively.

Significance: Our research indicates that using a multielectrode stimulation approach enhances the detection rate of eSRT and slightly improves the correlation coefficient between eSRT and C-levels. It is found preferable to obtain measurements from the contralateral side due to its higher detection rate, although the ipsilateral side yields a marginally higher correlation coefficient. The findings suggest that eSRTs obtained from pulse width modulation implants could aid audiologists in programming the device.