Evaluation of Objective Test Techniques in Cochlear Implant Users With Inner Ear Malformations

Abstract

The aim of the study was to compare results of objective test techniques in cochlear implant users with inner ear malformations and incomplete partition anomalies with types I and II and to show which techniques should be used in the evaluation and fitting of cochlear implant users with inner ear malformations. Retrospective clinical study. The subjects in the control group were selected randomly from cochlear implant users with normal cochlea. Inclusion criteria for patients group were having inner ear malformation for the study group and at least 1 year cochlear implants use for both groups. For each individual subject, electrically evoked compound action potentials (ECAPs), electrically evoked stapedius reflex threshold (ESRT), and electrically evoked auditory brainstem response (EABR) thresholds were determined. These tests were applied after a normal cochlear implant fitting session. There were 20 subjects in inner ear malformation group and 15 subjects in the control group. For each subject, 6 intracochlear electrodes, representing apical, middle, and basal array of intracochlear electrode, were used. In the cochlear malformation group, percentage of acquired ECAP thresholds was 25%. However, in the control group, percentage of ECAP was 74%. Similarly with ECAP, percentage of ESRT in the cochlear malformation group was 17.5%, and that in the control group was 90%. The difference between these percentages was statistically significant. Both current levels and latencies of EABR wave V were significantly different from each other for the inner ear malformation group and the control group. For statistical analysis, Mann-Whitney U test for 2 independent samples, Kruskal-Wallis analysis and Dunn's Z test were used. For the inner ear malformation group, EABR is a more applicable objective test technique when compared with ECAP and ESRT.