Outcomes of unilateral, bimodal and bilateral cochlear implant users versus normal-hearing listeners on a real-life test battery

Abstract

Binaural hearing is important for spatial hearing in real-life listening situations, e.g., speech perception in noise, sound localisation, and tracking of moving sounds. Adults with bilateral severe and profound sensorineural hearing loss typically receive one cochlear implant (CI) due to cost constraints. To compensate for this, a hearing aid (HA) in the non-implanted ear is often recommended. HAs use a different processing strategy and thus sound different from CI which makes them challenging for some CI users to use. Integrated bimodal technology has been introduced with the view of allowing the two devices to work together on the same platform. Preliminary studies have suggested better bimodal benefits with integrated bimodal technology. However, further, and independent investigation is needed to substantiate these reported benefits. In addition, there is a need to compare outcomes with integrated bimodal technology versus bilateral CI in real-life listening situations to guide best practice and clinical decision making. The aim of this thesis is to investigate the outcomes of adult unilateral, integrated bimodal and bilateral CI users versus normal-hearing listeners on a real-life test battery. To realise this aim, five studies were carried out. The first study assessed bimodal and bilateral CI service provision for adults worldwide using an online questionnaire that was sent to CI professionals in 75 countries (n=62). In the second study, a real-life test battery comprising of performance tests and subjective rating scales was developed. The measurement precision and reference data of the newly developed tests were assessed using a group of adults with normal hearing (n=45). The third study measured the outcomes and experiences of unilateral CI users when using the integrated bimodal technology (CI + Naida Link HA) versus the CI only using the real-life test battery (n=26). The fourth study compared the outcomes and experiences of bilateral CI users when they used one versus two implants on the real-life test battery (n=16). The fifth study compared the outcomes of integrated bimodal and bilateral CI users with those of normal-hearing participants. Results from the international survey showed that binaural hearing for adult unilateral CI users is not well supported in terms of funding for a second implant or HA, and that there is no clear practice guidance for fitting and maintaining the contralateral HA in most world regions. However, CI professionals recognise the value of fitting contralateral HAs at CI services, with audiology departments and private HA dispensers playing an ongoing role in general maintenance and support. The survey also showed that CI professionals are unsure of the benefit of integrated bimodal technology. Results from the second study demonstrated that the new speech- in-noise tests developed showed good reliability and validity. In addition, the new speech-in-noise, localisation and modified tracking tests are feasible and easily administered using the AB-York Crescent of Sound. The third and fourth studies indicated that using integrated bimodal technology and bilateral CI significantly improved performance compared with one CI for speech-in-noise perception, localisation, tracking of moving sounds and the SSQ questionnaire. The last study showed that the benefit provided by a second CI was significantly higher than that provided by the integrated bimodal technology in the spatial-listening tests (localisation and tracking) and the self-reported questionnaire (SSQ). The study also showed that the performance of CI users, including integrated bimodal and bilateral cochlear implant users, is significantly poorer compared than normal-hearing listeners. This underscores the importance of using assistive listening technology and support for CI users. Finally, the results suggest that using a test battery that includes tests more representative of real-life listening situations offers a better understanding of the performance of CI users

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Identifiers

ORCID for Manal Nasser Alfakhri: orcid.org/0000-0003-1837-4863

ORCID for Nicole Campbell: orcid.org/0000-0001-6895-5434

ORCID for Ben Lineton: orcid.org/0000-0003-4784-7762

ORCID for Daniel Rowan: orcid.org/0000-0002-7190-9997

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