A comparison of bilateral cochlear implantation and bimodal aiding in severely-profoundly hearing-impaired adults: head movements, clinical outcomes, and cost-effectiveness

Under current guidelines in the UK, eligible adults can receive a single cochlear implant through the National Health Service. Should they wish to aid their non-implanted ear they can either use an acoustic hearing aid and have ‘bimodal aiding’ or elect to pay for a second cochlear implant and have ‘bilateral cochlear implants’. The experiments reported in this thesis sought to inform this choice by establishing which option provides the greater benefit. It was found that both options offered listening and self-reported benefits over listening with a single cochlear implant. However a greater clinical benefit was found from bilateral cochlear implantation, with better localisation and speech perception in noise abilities. A series of experiments investigated whether head movements could improve listening performance. It was found that cochlear implant users made more complex head movements than normally hearing listeners. Whilst head movements by bilateral cochlear implant users improved localisation performance by reducing the number of front back confusions made, users of a single cochlear implant were unable to accurately locate sounds when head movements were permitted. Finally experiments demonstrated that current generic health related quality of life instruments are limited in their sensitivity to binaural hearing benefits. These instruments are used to inform the ‘effectiveness’ component in cost-effective analyses. Therefore a new questionnaire sensitive to benefits in binaural hearing was developed and its validity and sensitivity were demonstrated. Using this self-report instrument, bimodal aiding and bilateral cochlear implantation were shown to have the potential to be a cost-effective use of resources resulting in improvements to ‘hearing-related quality of life’ compared to a single cochlear implant.