Hearing results with deep insertion of cochlear implant electrodes

Objective: This study aimed to investigate the relationship of electrode insertion length and speech recognition in patients using Nucleus-22 cochlear implants. Study Design: The study design was a retrospective review of a consecutive clinical series. Setting: The study was conducted at an academic medical center. Patients: Thirty-one postlingually deafened adults with at least 6 months' experience with a Nucleus-22 cochlear implant using Spectra- 22 processor and SPEAK strategy participated. Main Outcome Measures: Open- set speech recognition scores for words and sentences were measured. Results: Insertion length ranged from 22 rings (estimated 17 mm) to 32 rings (estimated 25 mm). Mean word recognition score was 35%. Mean sentence score was 69.6%. Statistical analysis showed no correlation between insertion depth and word or sentence scores. Conclusion: Insertion of the Nucleus-22 array beyond 22 rings does not improve performance in speech recognition. This finding cannot be generalized to other electrodes or processing strategies.