Imaging evaluation of electrode placement and effect on electrode discrimination on different cochlear implant electrode arrays

Abstract

The aim of the present study is to evaluate the effect of electrode discrimination based on electrode to modiolus distance in different cochlear implant models, using image information to estimate the outcomes after an implantation on electrode discrimination METHODS: A descriptive prospective randomized study performed during 16 months. A psychoacoustic platform was used to evaluate patients' electrode discrimination capabilities of patients. For the acquisition of the images, a cone beam computed tomography was used to assess postcochlear implantation of electrodes' position. We considered two other new measurements: the intracochlear position index, which indicates how far is the electrode from the modiolar wall, and the homogeneity factor (HF), which provides us with information about the distance between the electrodes and the modiolus RESULTS: 21 postlingually deaf adults showing different CI models [CI522 (n = 7), CI512 (n = 7), and CI532 (n = 7)] that corresponded to the lateral and perimodiolar array electrodes. The average success rate of the CI522 group was 47%, of the CI512 group was 48%, and of the CI532 group was 77%. There is statistically significant difference between groups CI532-CI522 (p = 0.0033) and CI532-CI512 (p = 0.0027) CONCLUSION: The Nucleus CI532 offers a better perimodiolar placement. HF and IPI measurements provide information about the electrodes location inside the cochlea, being related to electrode discrimination.

Outcomes for a clinically representative cohort of hearing-impaired adults using the Nucleus® CI532 cochlear implant

“…Positioning the cochlear implant electrode contacts close to the stimulation target reduces the current spread and leads to more focused stimulation; thus, lowering the current levels required to produce behavioural thresholds and comfort levels [12][13][14]. This localized stimulation provides superior place-pitch spectral discrimination [15,16], and improved speech perception outcomes [17,18]. However, due to their increased stiffness and size, perimodiolar arrays which use stylets to keep them straight at the point of insertion, have been associated with poorer hearing preservation results and a higher incidence of basilar membrane trauma compared to thin, flexible lateral wall arrays [19,20].…”

Channel discrimination along all contacts of the cochlear implant electrode array and its relation to speech perception

“…In a pitch ranking task, the subject is typically asked to judge which of the stimulating electrode contacts has a higher pitch. Several studies based on pitch ranking tasks showed a positive relationship between the ability to distinguish pitches and speech perception (Nelson et al 1995;Collins, Zwolan, and Wakefield 1997). Furthermore, Kenway et al (2015) found that pitch ranking ability is an independent predictor of overall CI outcome.…”

Simpler and effective radiological evaluations for modiolar proximity of a slim modiolar cochlear implant electrode

“…Recently, cochlear implant recipients with slim modiolar electrodes (i.e., CI532/632) led to either similar or statistically superior audiological results compared with those with straight electrodes (i.e., CI422/522) strictly matched for age and preoperative hearing thresholds 2 . Furthermore, a growing body of evidence suggests that the enhanced modiolar proximity of slim modiolar electrodes would lead to improved place-pitch spectral discrimination 16 , and speech perception outcomes 14 , 17 , as compared with conventional perimodiolar electrodes. However, not all reports in literature fully support this phenomenon 9 , 18 , 19 , probably due to confounding variables such as heterogeneous degrees of modiolar proximity even with slim modiolar electrodes 20 .…”

“…However, not all reports in literature fully support this phenomenon 9 , 18 , 19 , probably due to confounding variables such as heterogeneous degrees of modiolar proximity even with slim modiolar electrodes 20 . Indeed, better modiolar proximity has been proposed to attenuate the substantial overlap (i.e., spread of excitation) in the electrical field between electrode contacts, resulting in better electrode discrimination capability 16 , 21 , and potentially better speech outcomes than conventional electrodes 21 . In addition, positioning of the electrodes close to the spiral ganglion neurons can reduce the effects of neural-electrode interaction by improving channel discrimination 16 , lowering threshold levels 22 , and reduction of power consumption 23 .…”

“…Indeed, better modiolar proximity has been proposed to attenuate the substantial overlap (i.e., spread of excitation) in the electrical field between electrode contacts, resulting in better electrode discrimination capability 16 , 21 , and potentially better speech outcomes than conventional electrodes 21 . In addition, positioning of the electrodes close to the spiral ganglion neurons can reduce the effects of neural-electrode interaction by improving channel discrimination 16 , lowering threshold levels 22 , and reduction of power consumption 23 . Therefore, robust and efficient measurement of modiolar proximity is mandatory for slim modiolar electrodes which were designed to achieve the best modiolar proximity amongst all electrodes.…”