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

Abstract

ObjectivesRadiotherapy 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.MethodsA 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.ResultsWith 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.ConclusionThis 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.

Challenges of Hearing Rehabilitation after Radiation and Chemotherapy

“…91 The outcome following CI surgery in RT patients has been reported in only small retrospective series or case reports, including in total 25 patients. [92][93][94][95][96][97][98][99] All the case control series showed good performance in RT patients, which was similar to the control groups. 92,94,95 Pediatric patients treated for medulloblastoma were also found to benefit from CIs.…”

“…[92][93][94][95][96][97][98][99] All the case control series showed good performance in RT patients, which was similar to the control groups. 92,94,95 Pediatric patients treated for medulloblastoma were also found to benefit from CIs. 93 Some authors have suggested preoperative brain imaging to evaluate for the presence of central nervous system pathologies, such as demyelination, which could predict poorer outcome.…”

Treatment of late sequelae after radiotherapy for head and neck cancer

“…As determined in nasopharyngeal cancer survivals, the retro-cochlear auditory pathways are not seriously damaged and remain functionally intact even in the longer term after RT [193]. Overall hearing outcomes after cochlear implantation for post- irradiated patients were found not to be worse than in patients who have had no prior RT to ear structures [194] and related complications are rare, though so far, no study has compared the incidence of complications of post-cochlear implantation in irradiated versus non-irradiated temporal bones [195,196]. Moreover, cochlear implant surgery and cochlear implant activity have not been seen to have harmful effects on vestibular function and balance [197].…”

Microvascular free tissue transfer and cochlear implants: A case series and literature review

“…Postoperatively, surgeons must be prepared to deal with the sequalae of radiation effects on soft tissue including increased tension on wound closure, poorer healing, and potential for increased infection. These arguments further support the role of primary CI placement . Of course, there are potential drawbacks to CI at the time of primary oncologic surgery, which must be considered.…”