Refined anatomy-based fitting reduces interaural place mismatch and improves speech outcomes, with preliminary...

This study proposes a refined approach to anatomy-based fitting (rfABF) that aims to reduce interaural place mismatch in bilateral cochlear implant (CI) users with asymmetric electrode array insertions between ears, a condition frequently associated with incomplete cochlear coverage.

Prospective monocenter proof-of-concept study comparing rfABF with conventional clinically based fitting (CBF). ABF maps were prepared using two algorithmically derived methods: one scaling inter-electrode spectral spacing (zipped), and another transposing the ratio between clinical and tonotopic frequencies (transposed). These maps were then refined based on user feedback until a natural sound quality was achieved. Assessments consisted of speech perception in quiet and noise, sound localization, subjective sound quality ratings (HISQUI19), and listening effort assessed using pupillometry.

Nine experienced adult bilateral CI users with interaural asymmetry in electrode array insertion depth and/or electrode array type.

Bilateral speech understanding improved significantly with rfABF in quiet (CBF: 77.5% ± 8.1%; rfABF: 83.1% ± 8.0%; p = 0.025) and in noise under both S0N0 (signal and noise from front) and S0Ncontra (signal from front, noise from contralateral ear) configurations. Interaural place-of-stimulation mismatch was substantially reduced from a mean of 33.8° ± 27.3° to 6.4° ± 4.2° with rfABF. Exploratory, descriptive pupillometry indicated reduced listening effort in a subset of participants, reflected by lower event-related pupil dilation (ERPD) amplitudes, particularly in cases where speech intelligibility was preserved or improved.

rfABF shows clinical potential to improve speech understanding and facilitate access to binaural cues in bilateral CI users with asymmetric electrode array insertions, with preliminary evidence for reduced listening effort.