Electrode Interaction in Cochlear Implant Recipients: Comparison of Straight and Contour Electrode Arrays

Abstract

The degree of overlap among cochlear nerve fibers stimulated by different electrodes results in electrode interaction, which has been shown to have a significantly deleterious effect on speech recognition performance in multi-electrode cochlear implant users. The Nucleus CI24R(CS) Contour array, which lies substantially closer to the modiolus than the CI24M straight array, is expected to exhibit narrower excitation patterns. The neural response telemetry (NRT) 3.0 software provides a method of measuring the spread of neural excitation by presenting the masker and probe pulses on different intra-cochlear electrode bands. Nine pairs of children, using Nucleus CI24M/CI24R(CS) cochlear implants with a similar etiology and duration of deafness, insertion depth, age of implantation and loudest acceptable presentation level (LAPL) in NRT sessions, participated in the study. Profiles of the spread of neural excitation stimulated at the LAPL at 3 probe locations were examined for each pair of the 2 types of electrode array. The spread of neural excitation with respect to array type and location revealed significant effects (p < 0.001; p = 0.002) and no interaction between array type and probe location (p = 0.559). The results demonstrated that the Contour array improved electrode discrimination, especially for the electrodes at the basal end of the cochlea. The findings have implications for future electrode array design and current implant mapping strategies.

Modeling of Auditory Neuron Response Thresholds with Cochlear Implants

“…Some authors recommend the use of perimodiolar arrays instead of straight arrays to favor a reduced NRT threshold. However, previous studies showed that perimodiolar placement of electrodes has no effect on NRT thresholds [ 24 , 25 ], an observation consistent with our study.…”

Is Electrode-Modiolus Distance a Prognostic Factor for Hearing Performances after Cochlear Implant Surgery?

“…This might have clinical implications, since a medial array position is associated not only with lower stimulation currents but also with lower psychophysical thresholds and comfortable levels [Runge-Samuelson et al, 2009]. Contour arrays were designed to reduce the distance between the electrodes and the nerve endings and to maximize the quality of electrophysiological interaction be-tween these two structures [Xi et al, 2009]. This concept was supported by reports showing a relation between array location in the cochlea and its insertion depth on the one hand and speech recognition performance on the other [Finley et al, 2008].…”

Challenging aspects of contemporary cochlear implant electrode array design

“…Other studies comparing perimodiolar and lateral wall electrode arrays in terms of eCAP measurements often failed to confirm lower eCAP thresholds for the perimodiolar electrode arrays. 19 , 20 , 21 , 22 The differences in the current amplitude or the distance between the electrode and the cochlear middle wall were often not statistically significant. One reason is a small patient size in such studies.…”