Effect of peri-modiolar cochlear implant positioning on auditory nerve responses: A neural response telemetry study

Abstract

Removal of the stylet had no significant effect on the threshold and growth rate of NRT responses. It caused a reduction in the spread of excitation for electrodes 1, 6 and 20, but not for electrodes 11 and 16.

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

“…Based on their observations, the use of a range of stimulus levels may be most appropriate to evaluate electrode interactions. Van Weert et al [12] observed that the spread of excitation in intra-operative NRT measures was larger than that in postoperative measurements. They inferred that this difference related to their high stimulus level in the intra-operative testing procedure.…”

“…An important goal in the design of cochlear implants is to optimize stimulation strategies or electrode arrays to minimize electrode interactions. In accordance with the hypothesis that an electrode array positioned close to the modiolus will allow more effective and efficient stimulation of the spiral ganglion cells, the Nucleus Contour peri-modiolar electrode array is expected to provide more discrete stimulation and has the potential for better frequency resolution with more selective stimulation of target auditory nerve fibers [11,12] . The purpose of the present study is to verify the difference between the electrode interactions produced by traditional 'straight' and peri-modiolar electrode arrays.…”

“…Van Weert et al [12] first investigated the effect of modiolar electrode placement on the spatial spread of neural excitation within individual subjects. All NRT measurements were performed intra-operatively, both before and after peri-modiolar placement of the electrode by removal of the surgical stylet.…”

“…Unfortunately, it is not always possible to successfully record NRT responses at lower levels [3,10] . The masker and probe current levels used in other research [9,12] cally in the upper part of the dynamic range, close to the MCL. Therefore, this study has adopted a method in which the maskers were presented at a fixed current level across the 3 target electrodes relative to the minimum LAPL among 22 electrodes during NRT trials for each individual (250-Hz stimulation rate).…”

“…The CI24R(CS) implant is fitted with the modiolar-hugging (Contour) electrode array, which comprises 22 half-banded electrode contacts without stiffening rings [12] . The CI24R(CS) implant is built on the 'family likeness' by the same integrated circuit as the CI24M (electrically equivalent) and the inter-electrode spacing is not uniform and ranges between 0.57 and 0.81 mm.…”