Cochlear Implant Outcomes: A Comparison between Irradiated and Non-irradiated Ears

OBJECTIVES Radiotherapy for head and neck tumors is known to potentially induce sensorineural hearing loss, which is possibly due to damage to the cochlear and/or auditory pathways. Since the success of cochlear implantation depends on a functional auditory nerve, this paper aims to study the hearing outcomes of cochlear implantation in irradiated ears. METHODS A retrospective study of cochlear implant recipients from our institution who had previously received radiotherapy for head and neck cancers was performed. A control group with cochlear implants who did not receive radiotherapy was recruited. A review of case records, speech discrimination scores (SDS), and a validated subjective questionnaire in the form of the Abbreviated Profile of Hearing Aid Benefit (APHAB) was administered to the study group who fulfilled the inclusion criteria. Global and category scores in both groups were averaged and statistically compared via non-inferiority (NI) testing. RESULTS With the control group (n=8) as the reference, the -ΔNI was defined, and a one-tailed lower 95% confidence interval was used for the irradiated group (n=8). The APHAB degree of improvement (%) results were as follows: global, 28.9% (19.32%, -ΔNI=16.3%); ease of communication, 67.0% (58.36%, -ΔNI=37.5%); background noise, 53.2% (44.14%, -ΔNI=26.8%); reverberation, 41.7% (28.85%, -ΔNI=32.7%); and aversiveness, -46.2% (-67.80%, -ΔNI=-56.9%). The SDS was 66.9% (56.02%, -ΔNI=51.0%). From the results, lower 95% confidence interval limits of global APHAB, SDS, ease of communication, and background noise scores of the irradiated group were within the defined -ΔNI boundary and hence are not inferior to the control. The categories of reverberation and aversiveness could not be proven, however. CONCLUSION This study demonstrated marked improvements in hearing measured both objectively and subjectively. The overall hearing outcomes after cochlear implantation for post-irradiated patients were not worse than patients who have had no prior irradiation to ear structures.