Cochlear implants (CI)


A cochlear implant may be an option if you have severe, permanent hearing loss that isn't helped by hearing aids.

  • 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.

What is a cochlear implant?

A cochlear implant is an electronic device used to bypass the damaged hair cells in the inner ear. Adults receive one cochlear implant on the NHS and children are entitled to two implants.

It is made up of two parts:

  • the internal implant
     The internal implant from a cochlear implant

    Image © Cochlear

  • the external sound processor
     The external sound processor from a cochlear implant

    Image © Cochlear

We offer three different brands of implants: Advanced Bionics, Cochlear, and MED-EL. If possible we try to offer patients and their families the choice.

Examples of the different processors available.

How does a cochlear implant work?

  1. Sounds in the environment are picked up by the microphone which sends the signal to the speech processor. 
  2. The speech processor filters the sound into coded signals. 
  3. The coded signals are then sent to the transmitting coil which sends the signal through the skin to the implanted receiver.
  4. The receiver electrically activates the electrode array which in turn stimulates the auditory nerve. 
  5. Nerve impulses are sent to the brain where they are interpreted as sound.

A cochlear implant does not restore normal hearing, but it should help you to hear sounds that you were not able to hear with a hearing aid. You will need to be trained to use and understand these sounds. Receiving a cochlear implant is the first step in a very long process.

More information

Watch video explanations of how cochlear implants work:

See more useful information.

  • 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.

    There is also a small chance that not all the electrodes of the implant can be inserted or that the device may fail and need removing or replacing.

    Watch three videos explaining the risks of cochlear implant surgery.

    Before cochlear implant surgery During cochlear implant surgery After cochlear implant surgery
    Before cochlear implant surgery During cochlear implant surgery After cochlear implant surgery

Electro acoustic simulation (EAS)

EAS uses a cochlear implant and natural hearing together. The device can consist of a cochlear implant combined with a hearing aid.

If you have more hearing in the low to mid pitches you can use the hearing aid for acoustic amplification, and use the cochlear implant to stimulate the high pitches that you're not able to hear as well.

More information

Watch video explanations of how EAS cochlear implants work.

See more useful information.

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.



Tel: 020 7188 6245

Email: gst-tr.hearing

Repairs and spares
Tel: 020 7188 6245

How to find us

Ear, nose and throat (ENT) department
St Thomas' Hospital
2nd floor, Lambeth Wing
Westminster Bridge Road
London SE1 7EH

Lambeth Wing

Download map to the Hearing Implant Centre (PDF 33Kb)