Hearing preservation and efficacy outcomes in CI632 recipients with sloping high-frequency hearing loss: Multicenter trial results.

Introduction: Adults with substantial residual low‑frequency (LF) hearing are increasingly considered for cochlear implantation. This study evaluated hearing preservation and speech performance outcomes using a slim perimodiolar electrode (CI632) in adults under expanded indications.

Methods: In a prospective, open label, single arm feasibility trial at three U.S. tertiary centers, ten adults with LF thresholds ≤50 dB HL at 500 Hz, sloping high frequency loss, and aided CNC scores ≤60% in the ear to be implanted received the CI632 device. Participants were followed for 12 months postactivation. Assessments included air and bone conduction audiometry, electrode impedances, unilateral and bilateral CNC in quiet and AzBio sentences in noise, patient reported outcomes, and postoperative CT imaging.

Results: The LF pure tone average (125-500 Hz) showed a mean shift of 19.3 dB at activation and remained stable at 22.4 dB at 12 months. Impedances were stable across visits. Due to preserved acoustic hearing, all participants utilized electric-acoustic stimulation in the implant ear. Speech recognition improved significantly across all measures, with an average improvement at 12 months ranging from 22 to 54 percentage points, depending on the test. Patient reported outcomes also improved. CT imaging confirmed scala tympani placement for all electrodes, with a mean angular insertion depth of 406.6°.

Conclusion: The slim perimodiolar electrode can preserve LF acoustic hearing in adults implanted under expanded indications, supporting meaningful objective and subjective benefit. Hearing preservation outcomes in this cohort exceeded those typically reported for perimodiolar arrays, and preserved LF hearing contributed strongly to improved speech understanding in noise.