Investigation of the effect of cochlear implant electrode length on speech comprehension in quiet and noise compared with the results with users of electro-acoustic-stimulation, a retrospective analysis

by Andreas Büchner, Angelika Illg, Omid Majdani, Thomas Lenarz

Objectives

This investigation evaluated the effect of cochlear implant (CI) electrode length on speech comprehension in quiet and noise and compare the results with those of EAS users.

Methodes

91 adults with some degree of residual hearing were implanted with a FLEX²⁰, FLEX²⁴, or FLEX²⁸ electrode. Some subjects were postoperative electric-acoustic-stimulation (EAS) users; the other subjects were in the groups of electric stimulation-only (ES-only).Speech perception was tested in quiet and noise at 3 and 6 months of ES or EAS use. Speech comprehension results were analyzed and correlated to electrode length.

Results

While the FLEX²⁰ ES and FLEX²⁴ ES groups were still in their learning phase between the 3 to 6 months interval, the FLEX²⁸ ES group was already reaching a performance plateau at the three months appointment yielding remarkably high test scores. EAS subjects using FLEX²⁰ or FLEX²⁴ electrodes outscored ES-only subjects with the same short electrodes on all 3 tests at each interval, reaching significance with FLEX²⁰ ES and FLEX²⁴ ES subjects on all 3 tests at the 3-months interval and on 2 tests at the 6- months interval. Amongst ES-only subjects at the 3- months interval, FLEX²⁸ ES subjects significantly outscored FLEX²⁰ ES subjects on all 3 tests and the FLEX²⁴ ES subjects on 2 tests. At the-6 months interval, FLEX²⁸ ES subjects still exceeded the other ES-only subjects although the difference did not reach significance.

Conclusions

Among ES-only users, the FLEX²⁸ ES users had the best speech comprehension scores, at the 3- months appointment and tendentially at the 6 months appointment. EAS users showed significantly better speech comprehension results compared to ES-only users with the same short electrodes.

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