Tonotopic fitting of the sound processor cochlear implant in normal cochlea anatomy

Abstract

Introduction. Cochlear implantation is very effective due to the known tonotopic organization of the cochlea. These data are used in the distribution of signals along the channels of the cochlear implant electrode. The more accurate and natural the stimulation of the auditory nerve fibers, the better the perception of speech, sounds and speech intelligibility.The aim of the study was to compare the clinical and anatomical settings of the cochlear implant processor.Materials and methods. The study included 63 patients aged 2 to 60 years using cochlear implantation system, implants with a standard long electrode array (31.5 mm). All participants underwent computed tomography (CT) of the temporal bones with a step of 0.6 mm or less. CT data were processed using Otoplan and Sliser 3D software. The geometric dimensions of the cochlea, the length of the cochlear canal, the angular position and tonotopic frequency of each electrode were calculated, and a 3D reconstruction of the cochlea and electrode was built.Results. The correction of the frequency filters of the electrodes and the anatomical adjustment of the processor were performed according to the data obtained in the Otoplan program. A comparison was made between the clinical and anatomical setting. After the redistribution of frequency filters, patients noted a more natural sound, improved speech intelligibility. Thus, with anatomical adjustment, an exact correspondence is achieved between the central frequency of each electrode channel and the tonotopic frequency of the cochlear zone, individually determined by computed tomography.Conclusions. A new tool has appeared that allows you to significantly improve the quality and provide an individual approach to setting up processors after cochlear implantation.