Anatomy-Based Frequency Allocation in Cochlear Implantation: The Importance of Cochlear Coverage

Abstract

Objectives/hypothesis: This study aimed to compare the predicted anatomy-based frequency allocation of cochlear implant electrodes with the default standard frequencies.

Study design: Retrospective study.

Methods: A retrospective analysis was performed using computed tomography (CT) images of patients who received cochlear implants at a tertiary referral center. Patients were excluded if they had any congenital or acquired cochlear anatomical anomalies. The CT images of the patients were uploaded to the surgical planning software. Two independent reviewers allocated the anatomical parameters of the cochlea. The software then used these parameters to calculate the frequency allocation for each electrode according to the type of electrode and the length of the organ of Corti (OC) in each patient. These anatomy-based frequency allocations were compared with the default frequency settings.

Main outcome measure: Frequency-to-place mismatch in semitones.

Results: A total of 169 implanted ears in 102 patients were included in this study. The readings of the two reviewers were homogenous, with a Cronbach's alpha of 0.98. The mean anatomy-based frequency allocation was 487.3 ± 202.9 Hz in electrode 1; 9,298.6 ± 490.6 Hz in electrode 12. The anatomy-based frequency allocations were found to be significantly higher than the frequencies of the default frequencies for each corresponding electrode (one-sample t-test, P < .001). The frequency-to-place mismatch was negatively correlated with cochlear coverage and positively correlated with the cochlear duct length (Pearson correlation > 0.65, P < .003).

Conclusions: The anatomy-based frequency allocation of each electrode is significantly different from the default frequency setting. This frequency-to-place mismatch was affected mainly by the cochlear coverage.

Level of evidence: 3 Laryngoscope, 132:2224-2231, 2022.

Keywords: Cochlear implant; anatomy-based; frequency; frequency-to-place mismatch; organ of corti.