[Bone conduction hearing aids with fluid medium].

In patients with chronic otorrhoea or middle ear pathology, traditional hearing aids which depend on air conduction are of little use. In these situations a bone conduction hearing aid is preferable. Such devices by-pass the middle ear cleft and ossicular chain by conducting sound waves through bone to the cochlea. To date, bone conduction hearing aids have transmitted sound via a vibrating transducer applied either to skin (transcutaneous) or to bone (percutaneous). Unfortunately, these hearing aids possess a number of disadvantages, which include: cost, aesthetic appeal, a general anaesthetic for percutaneous aids, and most notably pressure discomfort to the side of the head. To overcome some of these problems a new bone conducting hearing aid is being developed which differs from conventional aids in that sound transmission is through a liquid medium. This has been tentatively named the "Hydro-Hearing Aid" and a prototype is now being tested.