Bone conduction/middle ear implants

 

If you have bilateral (both ears) or unilateral (one ear) conductive or mixed hearing loss and you're not accessing speech easily through conventional hearing aids or bone conduction hearing aids, you may be referred for a bone conduction implant and middle ear implant assessment.

  • How does the ear work?

    The ear is made up of three parts, the outer (external) ear, the middle ear and the inner ear.

    Diagram showing how the ear works

    Image © Scott Maskell

    1. The part we can see is the outer ear, which also includes the ear canal. It functions to capture sound energy and funnel it to the ear drum. When the sound energy reaches the ear drum it causes the ear drum to move and vibrate. 
    2. There are three tiny middle ear bones connected to the ear drum. When the ear drum vibrates, it causes the three bones to vibrate as well.
    3. As these bones vibrate, they push against the inner ear (cochlea). The cochlea is a fluid filled organ which contains many sensory cells called hair cells. As the three bones push against the cochlea the fluid inside the cochlea begins to move, which causes the hair cells to move and bend. The hair cells contact the hearing nerve (auditory nerve) and as they move and bend they stimulate the nerve. The nerve then sends the message to the brain for processing.

    In the case of severe to profound deafness, the hair cells and part of the hearing nerve are affected. This is called sensorineural hearing loss. This damage prevents the sound signals from being transmitted to the brain.

    More information

    Watch a video explanation of how the ear works.

    See more useful information.

  • Types of hearing loss

    Conductive hearing loss

    This is caused when a problem in the outer or middle ear stops sounds reaching the inner ear.

    These problems may include:

    • an absence or abnormal shape of the outer ear (microtia)
    • a closed ear canal (atresia)
    • abnormalities of the middle ear structures
    • long standing difficulties with ear infections.

    Sensori-neural hearing loss

    This is caused when there is a problem in the inner ear, for example the hair cells in the cochlea or the hearing nerve.

    This damage prevents the sound signals from being transmitted to the brain. The loss can be mild, moderate, severe or profound. If the sensori-neural hearing loss is in the severe to profound range, bone conduction and middle ear implants are not powerful enough to help.

    Mixed hearing loss

    This is caused when there is both a conductive hearing loss and a sensori-neural hearing loss.

    Unilateral hearing loss

    Unilateral hearing loss when you lose hearing in one ear and still have normal hearing in the other. The loss can be sensori-neural, conductive or mixed.

    More information

    Watch a video explanation of how we hear:

    See more useful information.

What is a bone conduction implant?

‘Bone conduction’ is the transmission of sound through bone in the skull.

A bone conduction implant (BCI) is a medical aid that bypasses any abnormalities of the outer ear, ear canal or middle ear by directly stimulating the inner ear.

How does it work?

  1. A microphone picks up sounds and sends the signal to the sound processor. 
  2. The sound processor converts these sounds into vibrational energy
  3. The vibrations are then transmitted through the bone in the skull, which vibrates the inner ear directly.
  4. The inner ear is stimulated which in turn stimulates the auditory nerve. 
  5. Nerve impulses are sent to the brain where they are interpreted as sound.
  • Benefits

    The outcomes for each implant recipient will vary and depend on many factors, such as:

    • duration of deafness
    • age at implantation
    • anatomical abnormalities or additional difficulties
    • support received.

    We will discuss your expected outcomes with you during the assessment.

  • Risks

    You will have a general anaesthetic and therefore be asleep for the cochlear implant surgery.

    General anaesthetic information:

    Every operation carries risks and possible side effects. The chances of these occurring are very small and many only last a short time following surgery. These may include:

    • infection
    • bleeding
    • dizziness/nausea/vomiting
    • tinnitus (ringing in the ears)
    • weakness in facial muscles
    • taste disturbances
    • leak of cerebrospinal fluid (the fluid surrounding the brain)

    We are able to monitor many of these during surgery or to treat them immediately afterwards.

Your options

There are a number of bone conduction implants available.

  • Percutaneous implant

    This type of implant penetrates the skin, which is why it is called 'percutaneous'.

    Also known as a bone anchored hearing aid (BAHA), this traditional bone conduction implant works by directly connecting an internal implant and external speech processor through the skin.

    Diagram showing how a percutaneous bone conduction implant works
    Image © Scott Maskell

    There are three parts:

    • sound processor
    • abutment (connector)
    • titanium implant.

    The procedure involves:

    1. an operation to place a small titanium implant in the bone behind the ear.
    2. a titanium abutment is attached to the implant and protrudes through the skin.
    3. the sound processor connects directly to the abutment and is worn externally. The sound processor can be taken on or off at any time, but sound is only transmitted when the processor is being worn.

    More information

    Watch video explanations of how percutaneous implants work:

    See more useful information.

  • Transcutaneous implant

    This type of implant communicates across the skin, which is why it is called 'transcutaneous'.

    The external equipment communicates with the internal implant across the skin using a magnet.

    There are currently two types of transcutaneous implant:

    Attract system

    Diagram showing how a transcutaneous bone conduction implant works
    Image © Scott Maskell

    This implant has four parts:

    • sound processor
    • external magnet
    • internal magnet
    • implant.

    The procedure involves:

    1. An operation to place a small implant and internal magnet in the bone behind the ear. These components are completely under the skin.
    2. An external magnet is attached to the externally worn sound processor, with a soft pad for comfort when wearing.
    3. These magnets create an invisible connection between the external sound processor and the implant.
    4. The sound processor converts sounds to vibrations and transmits these to the implant using the magnets.

    More information

    Watch a video explanation of how the attract system works:

    See more useful information.

    Bonebridge system

    Diagram showing how a transcutaneous bonebridge bone conduction implant works
    Image © Scott Maskell

    This implant has two parts:

    • external sound processor with magnet
    • internal implant with magnet

    The procedure involves:

    1. An operation to place the internal implant in the bone behind the ear. This contains an active vibratory mechanism and an internal magnet. These components are completely under the skin.
    2. The magnet inside the externally worn sound processor is attracted to the magnet inside the internal equipment.
    3. These magnets create an invisible connection between the external sound processor and the implant.
    4. The sound processor captures sound signals and sends them through the skin to the internal implant.
    5. The implant converts the sounds into vibrations and sends them through the bone to the inner ear.

    More information

    Watch a video explanation of how the bonebridge system works:

    See more useful information.

  • Middle ear implant (MEI)

    A middle ear implant (MEI) bypasses the abnormal outer ear and/or abnormal ear canal to directly stimulate the bones of the middle ear.

    You may be referred for a MEI assessment if you have bilateral or unilateral conductive or mixed hearing loss and you are not accessing speech easily through conventional hearing aids.

    How does it work?

    1. A microphone picks up sounds and sends the signal to the sound processor.
    2. The sound processor sends the signal across the skin to the internal implant.
    3. The internal implant converts the signal into vibrations and transmits them to the middle ear bones, which then vibrate the inner ear directly.
    4. The inner ear is stimulated, stimulating the auditory nerve.
    5. Nerve impulses are sent to the brain where they are interpreted as sound.

    Diagram showing how a middle ear implant works

    Image © Scott Maskell

    This implant has four parts:

    • sound processor
    • external magnet
    • internal magnet
    • implant.

    The procedure involves:

    1. An operation to place the internal implant in the middle ear. This contains an active vibratory mechanism and an internal magnet. These components are completely under the skin.
    2. The magnet inside the externally worn sound processor is attracted to the magnet inside the internal equipment.
    3. These magnets create an invisible connection between the external sound processor and the implant.
    4. The sound processor captures sound signals and sends them through the skin to the internal implant.
    5. The implant converts the sounds into vibrations and sends them to the bones in the middle ear.

    More information

    Watch a video explanation of how middle ear implants work:

    See more useful information.

Which implant is best for me?

Following a thorough assessment, we will make a recommendation about which bone conduction implant is best for you based on a variety of factors.

At St Thomas’ Hearing Implant Centre we offer three different brands of implants: Oticon, Cochlear, and Med-el. If possible we will try to offer you and your family the choice, but the final decision will be made by the implant team so that you get the implant best suited to you.

Will I be able to hear normally?

Bone Conduction Implants do not restore normal hearing, but you should be able to hear sounds you weren't able to hear with hearing aids.

You will need time to adjust to the new sounds. It's not possible to predict how successfully your listening skills will develop, but we will provide you with the appropriate training and support to have the best chance of success.

Are there other options?

With specialist teaching and support you could continue to wear hearing aids and make the most of limited access to speech. Sign language can be used to support your language skills.

 

 

Contacts

Tel: 020 7188 6245 

Fax: 020 7188 8905 

Email: gst-tr.hearing
implants@nhs.net

Repairs and spares
Tel: 020 7188 6245
Email: 

How to find us

St Thomas' Hospital
2nd floor, Lambeth Wing
Westminster Bridge Road
London SE1 7EH

Lambeth Wing

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