Middle ear implants
Middle ear implants are used where conventional hearing aids or bone conduction hearing devices are not an option due to medical reasons.
The devices are surgically implanted hearing aids. They send a signal to the middle ear which mechanically vibrates the middle ear bones. This increases the sound vibrations entering the cochlea where the vibrations are converted into electrical signals sent to the brain.
They can be an option for children (five years and above) who have conductive, sensorineural or mixed hearing loss and are unable to use conventional hearing aids.
These implants are quite a new technology and only a small number children in the UK have them.
How do middle ear implants work?
There are different types of middle ear implant but they all work in similar ways. The implant is surgically inserted into the middle ear and the transducer is either attached to one of the middle-ear bones (ossicles) or to the round window between the middle ear and the cochlea (inner ear).
Middle ear implants have a microphone that picks up sound and a sound processor which converts the acoustic signals received by the microphone into electrical signals. The electrical signals are then processed and amplified to take into account the wearer's type and level of deafness.
The electrical signals are converted into a mechanical vibration that is delivered directly to the middle ear, this enhances the transmission of sound waves to the inner ear (cochlea). In the cochlea, the sound waves are detected by hair cells and perceived as sound.
Middle ear implants can be:
- fully implantable – all parts of the device under the skin, meaning there is no need for an external audio sound processor, or
- semi-implantable – part of the device is worn on the ear externally and part placed in the middle ear allowing the ear canal to remain open.
What are the different types of middle ear implant?
Fully implantable middle ear implants (Cochlear Carina, Envoy Esteem)
This type of device is implanted completely under the skin with no external parts. The microphone of the Cochlear Carina is implanted under the skin behind the pinna of the ear (outer part) whereas the Envoy Esteem uses the movement of the eardrum as a microphone. A sound processor is implanted in the bone behind the ear which converts sound vibrations into electrical signals. The processor then amplifies these signals which create intensified mechanical vibrations in the middle ear. The increased sound vibrations then enter the inner ear as they usually would and are converted into electrical signals which are sent to the brain.
Having a fully implantable device means there are no external parts to worry about. It can be worn all day and night as well as in the shower, when washing your hair or swimming.
Semi-implantable middle ear implants (MED-EL Vibrant Soundbridge)
This type consists of an external audio processor which sits behind the ear and contains a magnet. The processor is held in place by magnetic attraction to the implant under the skin.
The sound processor of the Vibrant Soundbridge can also be made fully waterproof with a protective cover.
Your child’s audio processor should be upgraded every five years to keep up with any new technological advances.
Is a middle ear implant suitable for your child?
Your child may be considered for a middle ear implant if they have a medical reason which prevents them from being able to wear a conventional hearing aid or a bone conduction hearing device.
Middle ear implants are suitable for children who:
- have previously had surgery on their ears which makes using a conventional hearing aid difficult (for example mastoid cavity problems following surgery for cholesteatoma).
- were born with underdeveloped outer ears (microtia, atresia)
- aren’t able to wear their bone conduction hearing aid due to medical problems of the soft tissues or loss of fixture
- aren’t able to wear conventional earmoulds due to allergies, eczema or recurrent outer ear infections (otitis externa).
They are also suitable for children who can’t use conventional hearing aids and have:
- stable (non-progressive) hearing loss
- unilateral or bilateral (affecting both ears) deafness
- moderate to severe deafness
- hearing loss that can be conductive, sensorineural or mixed
- no middle ear infections
- stable bone conduction thresholds with less than 15dB deterioration in 2 years
Process for getting a middle ear implant
Your local audiology service should provide a full and comprehensive assessment of your child’s hearing and your child will normally be fitted with a conventional hearing aid for a minimum of four weeks.
A hearing aid may not be beneficial for your child or they might not be able to wear one due to a medical condition. If this is the case and your child meets the criteria set by implant manufacturers you should be given the option of being referred to the Hearing Implant Service for further assessment.
The assessment process for a middle ear implant will be similar to the one for getting a bone conduction hearing device and your child may be seen by a number of different people from the multidisciplinary team.
Surgery
The operation is usually done under general anaesthetic and can take between one and two hours. The implant is then activated around six to eight weeks later. A follow-up appointment will be made after the initial activation to fine tune the processor with further appointments as required.
Technology
At present the Cochlear Carina middle ear implant isn’t compatible with any assistive listening devices, such as loop systems or radio aids.
The Medel Soundbridge middle ear implant does not have a telecoil, however, the audio processor is able to connect to the loop and other wireless devices via a streamer. A streamer sends signals digitally to your child’s hearing device and links with other products using Bluetooth such as mobile phones, laptops or tablets.
Find out about other products and technology that may help your child at home or school.
Find more information on funding and lost equipment as well as transferring care to another service and service standards.
Batteries
Middle ear implant batteries work in various different ways depending on the make and model. Check the supplier's websites to find out more about how long your child's battery should last, how to charge it and how to get hold of replacements.
Support groups
Contact support groups and other organisations, or read blogs written by people who use middle ear implants.
Middle ear implant centres in the UK
Guy's & St Thomas' Hearing Implant Centre, London
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