Title: Human Feasibility Study of an Implantable Middle-Ear Microphone
Funder: Department of Health and Social Care

Abstract: Cochlear implants have been shown over the decades to provide a highly effective and safe treatment for people with severe to profound hearing impairment. Conventional cochlear implant (CI) systems are partially implantable devices utilizing an external speech processor, worn behind the user s ear, containing the battery and microphone. The processor is used to transmit information and power to the cochlear implant via a transcutaneous coil system. A TICI (Totally Implantable Cochlear Implant) system is fully implantable and invisible i.e. the speech processor, rechargeable battery and microphone components are integrated into or connected to the implant. Extensive market studies with patients, surgeons and audiologists show that there is dissatisfaction that cannot be addressed with a conventional CI system. A totally implantable system will deliver significant safety benefits associated with 24/7 hearing and overall improved quality of life, without the limitations imposed by external parts and cables. Cochlear&trade; has commenced development of a middle-ear microphone which measures the vibrations of the ossicles and benefits from the natural amplification and directionality of the pinna and ear canal. Prototypes of this microphone have been verified on the bench and in human cadaver heads with promising results. To further assess the benefits of a TICI with a middle-ear microphone, this project will assess the clinical feasibility/efficacy of this technology and recruit 6 patients to assess this implant. To do this, we will: Develop a human grade middle-ear microphone - The middle-ear microphone is an experimental device not yet suitable for a clinical trial. A detailed risk analysis will be made, including a hazard analysis and a Failure Mode and Effects Analysis. This will result in a middle-ear microphone design that is regarded as safe for implantation in the human body. Develop an investigational system to be used in a clinical trial - The investigational system involves the human grade middle-ear microphone device connected via a lead to a percutaneous connector that is used to connect the implanted device through the skin to the external sound processor. The implantable microphone signal needs to be matched to the sound processor and subjects might need to use a dedicated fitting map. The complete set up described above will be developed and verified on the bench prior to the start of the study. Develop and optimize the surgical implantation method - The performance of the middle-ear microphone is related to its placement and connection to the ossicular chain. Different coupling methods will be assessed and compared in cadaver heads. Develop and optimize an intraoperative test method - To ensure the middle-ear microphone is properly implanted and to verify the functionality during surgery, an intraoperative test is mandatory. This test will be developed and verified in cadaver heads prior to use during the clinical trial. Compare different preoperative screening methods to guarantee proper patient selection - Only patients with normal middle-ear function are eligible candidates for a middle-ear microphone as performance depends on the mobility of the ossicular chain. Different non-invasive repeatable screening methods will be compared, the most suitable one selected and used during the clinical trial. A short term clinical trial will assess the clinical efficacy of the middle-ear microphone in combination with a cochlear implant. - Eligible subjects are adults that have already had a CI for more than a year with stable audiological results. They will receive the percutaneous plug middle ear microphone implant on the contra-lateral side. During the study the subject will be able to listen, via the implanted microphone, using the investigational system described above. Subjects will be assessed on the presence of body and contact noise.

Lay abstract: Cochlear implants have been used for some time in the treatment of those with severe or profound hearing loss. The use of these implantable devices has enabled those with severe hearing impairment to develop and participate in the day to day life of their families, education and workplace. The current design of the cochlear implant is less cumbersome than the early models, which included a body worn component, with a behind the ear component being the only visible part today. However, the technology now available begs the questions: why does there have to be any external part? Why can't the entire implant be hidden in the ear or under the skin? One of the major challenges of implantable devices for hearing loss is where to position the microphone that collects the sound to send to the processor, to allow the totally implantable device to be developed. Currently, the microphone is part of the behind-the-ear sound processor. The focus of the proposed project is a collaboration between clinicians, academics and a partner in industry to develop a microphone that can be accurately placed in the middle ear, to ensure that the instrument has the best possible outcomes for the patient in terms of sound quality. A further priority for the project will be to work with patients, carers and potential implant candidates in the project patient focus group to ensure there is an informed development of the project from a patient perspective. This will be achieved through regular meetings of the focus group throughout the project timetable.

Research activity codes: 5.3 MEDICAL DEVICES;6.3 MEDICAL DEVICES
Health categories: EAR