Factors Affecting Audiometric and Speech Perception Outcomes in Hybrid Cochlear Implant Recipients.

Objectives: To evaluate the long-term audiometric and speech perception outcomes in Hybrid cochlear implant recipients meeting hybrid or electric-acoustic stimulation (EAS) indications, and to identify factors, including age, sex, and duration of hearing loss, that may contribute to outcome variability. Additionally, the study evaluates the impact of EAS on speech perception.

Methods: Data from two clinical trials and retrospective data from the University of Iowa were combined for a total dataset of 150 Cochlear Nucleus Hybrid L24 (Cochlear Ltd., Sydney, Australia) cochlear implant recipients. Audiometric outcomes, as quantified by low-frequency pure-tone average (LFPTA; 125-500 Hz), and speech perception outcomes, including unilateral and bilateral CNC words in quiet and AzBio +5 dB SNR sentences in noise, were assessed preoperatively and postoperatively up to 5 years postactivation.

Results: Functional low-frequency acoustic hearing (LFPTA < 80 dB HL) was preserved in 72.9% of Hybrid L24 recipients up to 5 years postactivation, with audiometric changes stabilizing around 1 year. Significant improvements were observed in speech perception both in quiet and in noise. Age at implantation was a significant predictor of both audiometric and speech outcomes, with younger recipients demonstrating greater speech-in-noise improvements and a greater likelihood of maintaining functionally aidable hearing. EAS users demonstrated superior speech outcomes compared to electric-only users.

Conclusion: Cochlear implantation for EAS candidates provides long-term preservation of acoustic hearing and improved speech perception outcomes, particularly in younger recipients. These findings support the use of hybrid/EAS cochlear implantation in candidates with low-frequency hearing and highlight the benefit of EAS in enhancing speech understanding.

Level of evidence: 3 Trial Registration: Relevant studies were registered on ClinicalTrials.gov under trial registration numbers NCT00678899 (pivotal study group), NCT02379273 (continuation of pivotal study group), and NCT02379819 (post-approval study group).