Cochlear Implantation in Adults with Asymmetric Hearing Loss: Benefits of Bimodal Stimulation

Objective: This study addresses the outcome of cochlear implantation in addition to hearing aid use in patients with asymmetric sensorineural hearing loss. Study Design: Prospective longitudinal study. Setting: Tertiary referral center. Patients: Seven adults with asymmetric sensorineural hearing loss, i.e., less than 30% aided speech recognition in their worst hearing ear and 60 to 85% speech recognition in their best hearing ear. All patients had a postlingual onset of their hearing loss and less than 20 years of auditory deprivation of their worst hearing ear. Intervention: Cochlear implantation in the functionally deaf ear. Main Outcome Measures: Speech recognition in quiet, speech recognition in noise, spatial speech recognition, localization abilities, music appreciation, and quality of life. Measurements were performed before cochlear implantation and 3, 6, and 12 months after cochlear implantation. Results: Before cochlear implantation, the average speech recognition of the ear fitted with a hearing aid was 74%. Cochlear implantation eventually resulted in an average speech recognition of 75%. Bimodal stimulation yielded speech recognition scores of 82, 86, and 88% after 3, 6, and 12 months, respectively. At all time intervals, bimodal stimulation resulted in a significantly better speech recognition as compared with stimulation with only hearing aid or only cochlear implant (CI). Speech recognition in noise and spatial speech recognition significantly improved as well as the ability to localize sounds and the quality of life. Conclusion: This study demonstrated that patients are able to successfully integrate electrical stimulation with contralateral acoustic amplification and benefit from bimodal stimulation. Therefore, we think that cochlear implantation should be considered in this particular group of patients, even in the presence of substantial residual hearing on the contralateral side.