PP808 - Interference in Combined Cochlear Implant and Hearing Aid Use: A Scoping Review 

Abstract:
Advancements in cochlear implant (CI) and hearing aid (HA) technology have enabled the combination of acoustic and electric stimulation for bimodal hearing and electro-acoustic stimulation (EAS). While some users experience benefits like enhanced speech or music perception and improved localization, others face interference between CI and HA signals, potentially leading to HA discontinuation. This scoping review explores the underlying causes of interference, maps existing evidence, and identifies potential research gaps. The insights gained on interference from this review will help foresee and mitigate such scenarios, thereby improving speech and music perception in users of bimodal hearing and EAS.

Summary:
Rationale
The combination of hearing aid (HA) and cochlear implant (CI) technologies, either in the same ear (electroacoustic stimulation, EAS) or across ears (bimodal hearing), offers numerous benefits for users. These include enhanced speech perception in noise, improved localization, and better music perception compared to using HA or CI alone. These bimodal or EAS benefits result from successfully integrating electrical and acoustic signals from the CI and HA. However, the signals may compete in some users, resulting in poorer performance in combined conditions (CI+HA) than HA or CI alone, known as interference. Interference in bimodal users often leads to discontinuation of the HA due to the perceived lack of benefit when used with a CI. Similar interference in EAS users can also result in negative perceptual consequences. Considering the impact of interference, it is crucial to explore its underlying causes to improve the overall auditory experience of bimodal and EAS users. The current knowledge about this interference is limited. Hence, a comprehensive scoping review was conducted to gather existing evidence and identify potential research gaps.

Methods
This scoping review followed the PRISMA-ScR guidelines, and it was registered on protocols.io (can access online at dx.doi.org/10.17504/protocols.io.dm6gp37xdvzp/v2). Inclusion criteria were peer-reviewed articles written in English and published between 2000 and 2023, reported adverse performance outcomes with combined CI and HA use in adults or children compared to CI or HA alone. The exclusion criteria were review articles, case studies, editorials, editor letters, commentaries, and the articles that focused only on bilateral cochlear implants or bilateral hearing aids. Relevant articles were searched using specific keywords and Boolean operators across multiple databases, including Google Scholar, PubMed, and Science Direct. All reviewers independently screened titles, abstracts, and full texts based on the inclusion and exclusion criteria. Conflicts were resolved through discussion and consensus. A data charting form was developed and completed to extract relevant information from included studies.

Results
The database searches yielded 2081 articles, which were reduced to 1055 after removing duplicates. Title and abstract screening resulted in 121 articles for full-text review. After excluding 111 articles, the final scoping review included 15 articles published across 13 scientific journals. These articles originated from nine countries and will undergo narrative analysis to extract insights on interference in combined CI and HA use.

Conclusion
This scoping review will provide valuable insights into the prevalence, causes, and assessment of interference in combined CI and HA use. The findings will be crucial for audiologists in preventing, assessing, and managing interference in bimodal and EAS users. Additionally, the results could guide the development of improved speech processing strategies and bimodal fitting techniques to minimize interference and maximize benefits for these users. By addressing these issues, we can work towards enhancing the overall auditory experience and quality of life of bimodal and EAS users.