Factors Influencing Speech Perception in Adults With a Cochlear Implant.

The study was observational and not randomised, so the electrode groups differed before implantation. Patients with residual hearing were generally given the straight electrode, and patients without residual hearing were given the precurved electrode, creating selection bias. The analysis was limited to two electrode types from one manufacturer, so it may not apply to other CI systems. Some factors that can affect speech perception, such as cognition and brain plasticity, were not measured. The groups were small after stratification, especially the straight electrode group with 44 participants, so some correlations may have been missed. The time since implantation varied from 14 to 92 months. Nine participants were excluded from the main multivariable model because of missing data or poor-quality scans. The duration of severe to profound hearing loss was not evaluated because patients could not reliably recall its onset.

The authors declared no conflicts of interest. The Radboudumc department received an ongoing institutional grant from Cochlear Ltd, and the institutional grant from Cochlear Ltd was used for this study. The department also reported past or ongoing grants from Advanced Bionics Corp, Oticon Corp, and Med-el Corp.

Do not read the 11.8 percentage point difference in the model as proof that the precurved electrode caused better speech perception. The electrode was chosen clinically, not randomly, and the precurved group had poorer preoperative hearing thresholds, so selection and implant position cannot be separated.