The effect of perimodiolar placement on speech perception and frequency discrimination by cochlear implant users

Conclusion. Neither speech understanding nor frequency discrimination ability was better in Nucleus Contour (TM) users than in Nucleus 24 straight electrode users. Furthermore, perimodiolar electrode placement does not result in better frequency discrimination. Objectives. We addressed three questions related to perimodiolar electrode placement. First, do patients implanted with the Contour (TM) electrode understand speech better than with an otherwise identical device that has a straight electrode? Second, do these groups have different frequency discrimination abilities? Third, is the distance of the electrode from the modiolus related to frequency discrimination ability? Subjects and methods. Contour (TM) and straight electrode users were matched on four important variables. We then tested these listeners on CNC word and HINT sentence identification tasks, and on a formant frequency discrimination task. We also examined X-rays and measured the distance of the electrodes from the modiolus to determine whether there is a relationship between this factor and frequency discrimination ability. Results. Both speech understanding and frequency discrimination abilities were similar for listeners implanted with the Contour (TM) vs a straight electrode. Furthermore, there was no linear relationship between electrode - modiolus distance and frequency discrimination ability. However, we did note a second-order relationship between these variables, suggesting that frequency discrimination is worse when the electrodes are either too close or too far away from the modiolus.