Intra-Cochlear Current Spread Correlates with Speech Perception in Experienced Adult Cochlear Implant Users.

Charles-Alexandre Joly,Ruben Hermann,Samar Idriss,Hung Thai-Van,Pierre Reynard,Stéphane Gallego,Fabien Seldran

doi:10.3390/jcm10245819

Abstract

Broader intra-cochlear current spread (ICCS) implies higher cochlear implant (CI) channel interactions. This study aimed to investigate the relationship between ICCS and speech intelligibility in experienced CI users. Using voltage matrices collected for impedance measurements, an individual exponential spread coefficient (ESC) was computed. Speech audiometry was performed to determine the intelligibility at 40 dB Sound Pressure Level (SPL) and the 50% speech reception threshold: I40 and SRT50 respectively. Correlations between ESC and either I40 or SRT50 were assessed. A total of 36 adults (mean age: 50 years) with more than 11 months (mean: 34 months) of CI experience were included. In the 21 subjects for whom all electrodes were active, ESC was moderately correlated with both I40 (r = −0.557, p = 0.009) and SRT50 (r = 0.569, p = 0.007). The results indicate that speech perception performance is negatively affected by the ICCS. Estimates of current spread at the closest vicinity of CI electrodes and prior to any activation of auditory neurons are indispensable to better characterize the relationship between CI stimulation and auditory perception in cochlear implantees.

Highlights

Cochlear implants (CI) are implantable biomedical devices used for auditory rehabilitation among patients with severe to profound sensorineural deafness.The CI audio processor performs a spectral decomposition of the signal into different frequency bands or channels, the number of which varies from 12 to 24 depending on the CI system
exponential spread coefficient (ESC) was positively correlated with SRT50 and negatively correlated with intelligibility measured at 40 dB HL (I40)
Since the development of multi-channel CI in the late 1990s, researchers have investigated the potential impact of channel interaction on speech perception abilities in cochlear implanted subjects

Summary

Introduction

Cochlear implants (CI) are implantable biomedical devices used for auditory rehabilitation among patients with severe to profound sensorineural deafness. The CI audio processor performs a spectral decomposition of the signal into different frequency bands or channels, the number of which varies from 12 to 24 depending on the CI system. The intensity modulation of each acoustic band is converted into electrical amplitude modulation and transmitted to an electrode array which is equipped with as many electrodes as channels generated by the processor. With respect to cochlear tonotopy, the electrical stimulation of each channel is distributed to a unique electrode according to its insertion depth in the cochlea. Tonotopy is partially restored supplying sufficient auditory information and allowing implanted patients to perceive and understand speech from one interlocutor in a quiet environment

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