Other Types of Implants and Hearing Aids
We receive sound in two ways – by air conduction via the ear canal and by bone conduction transmitted through the jaws and skull bone. A hearing loss can be caused if sounds are not conducted effectively through the air or bones to the organ of hearing (cochlea) and this is called a conductive hearing loss. A sensorineural (permanent) hearing loss is caused when the sounds are conducted effectively but the cochlea itself does not respond to sounds normally. A mixed loss involves both of these problems occurring at the same time.
However, some people are unable to wear conventional hearing aids because they suffer from recurrent ear infections preventing wearing of earmoulds or they have anatomical malformations in the external or middle ear. MEIs are implantable devices that are used to overcome conductive or mixed hearing losses within the mild, moderate and severe hearing loss ranges. MEIs are only suitable for patients unable to wear conventional hearing aids. The device is surgically implanted in the middle ear and takes over the job of the middle ear structures to transmit sounds to the cochlea. MEIs are typically used with an external audio processor which is worn behind the ear and held in place by a magnetic connection across the skin.
For further information: www.medel.com
Some people have a damaged or deficient nerve of hearing and so they cannot benefit from either conventional hearing aids or a cochlear implant. An Auditory Brainstem Implant (ABI) provides the brain with electrical signals, bypassing the cochlear and nerve of hearing. It is an electronic device that attempts to replace the function of the damaged auditory nerve by electrically stimulating the brain stem to produce a sensation of sound. Since it is positioned in the brainstem itself, it involves a much more complex and longer operation and the recovery period is therefore much longer too.
The ABI is a highly specialised device and is only suitable for patients who would not be able to use a Cochlear Implant or any other implantable device due to a damaged auditory nerve and who have no other option for hearing.
The ABI can help a totally deafened person to become more aware of everyday sounds and improve speech understanding with lip reading. There are only a small number of highly specialist Implant centres offering an ABI in the UK.
A bone anchored hearing aid (BAHA) is an alternative to a regular hearing aid for those with problems in their outer or middle ears. It transfers sound by bone vibration directly to the cochlea, bypassing the outer and the middle ear. This means it is useful for conductive or mixed hearing losses. A BAHA relies on a working cochlea to send sound to the brain.
The implant fixture sits in the bone behind the ear. This receives vibrations from the processor on the outside. The bone vibrations trigger a response in the cochlea. A bone anchored hearing aid may be considered when a conventional hearing aid cannot be worn, (for example due to irritated or collapsed ear canals), or when a hearing aid does not give effective benefit.