Anatomy-based fitting versus standard mapping of cochlear implants: A study on speech perception and hearing quality

The study aims to investigate the speech intelligibility and sound quality rating of adults who have been fitted with a cochlear implant (CI) for the first time with two different frequency distributions of the filter bank of the CI audio processor. A patient-specific anatomy-based filter bank setting is compared with the standard filter bank setting specified by the manufacturer. The study is being conducted as a prospective, randomized, and single-blinded crossover study with each subject taking part over a period of 9 months. To date, 53 adults who have been fitted with a cochlear implant for the first time were included in the study, which is still ongoing. The patients were randomly assigned to groups with two different starting conditions at the beginning of the study: anatomy-based frequency allocation (ABF) and standard group (STD). Postoperative cone beam tomography (CBT) images were analyzed using Otoplan® software (Cascination, Bern, Switzerland) to determine the insertion angle and the corresponding center frequencies of the intracochlear electrode contacts and to create an “anatomy-based” frequency allocation of the center frequencies of the filter bank. A total of three visits are planned in a 3-month cycle. In the first visit after 3 months, the alternative frequency allocation is set (crossover), in the second visit both settings are made available to the subjects, and in the third visit, the results are evaluated with both variants. Speech comprehension in quiet (Freiburg monosyllables) and in background noise (Oldenburg sentence test) was tested and hearing quality assessed using questionnaires. The results so far show that there is no statistically significant difference between the two frequency allocations at any visit (p>0.5). On the first and last visits, there was a trend toward better hearing quality with ABF, while this trend was reversed at the second visit after the program was changed. The preliminary results indicate that the anatomically determined frequency allocation of the bandpass filter center frequency setting may facilitate enhanced hearing quality while maintaining unimpaired speech perception in quiet.