What is a cochlear implant?
A cochlear implant provides access to sounds for people with a significant hearing loss who get little or no benefit from hearing aids. It is a highly technical medical device that has internal and external parts and is designed to bypass damaged hair cells in the inner ear and directly stimulate the auditory nerve. The brain experiences this stimulation as sound sensation.
External speech processor captures sound and converts it to digital signals.
Processor sends digital signals to internal implant.
Internal implant turns signals into electrical energy, sending it to an array inside the cochlea.
Electrodes stimulate hearing nerve, bypassing damaged hair cells, and the brain perceives signals; you hear sound.
The visible parts of a cochlear implant are called the speech processor and transmitting coil. These consist of a microphone, batteries and a mini-computer that analyses incoming sounds and converts them into digital signals. These signals are then transmitted by radio waves through the skin via the coil to the internal implant.
Are you eligible?
You may be eligible if:
A severe to profound hearing loss has been diagnosed.
Hearing aids are unable to help your level of hearing loss.
You are becoming socially isolated.
Your hearing loss means you are unable to work or your job is under threat.
You are unable to communicate effectively.
What you can hear?
An audiogram, as seen below, is a graph of your hearing. It provides information on the softest sounds that a person can hear. The banana shape indicates all the speech sounds when they’re spoken at normal conversational volume. When your hearing thresholds are plotted, the speech and environmental sounds that fall below the line are audible while sounds above the line cannot be heard. If your hearing falls into the severe to profound loss area at the bottom of the graph, then you may not be able to hear all conversational sounds even with strong hearing aids. A cochlear implant may then be a viable alternative.
The implant operation lasts for two to three hours and carries the normal risks of any surgery requiring general anaesthetic. The surgical process will be explained in detail during assessment.
What do you do next?
If you have not been referred to the NCIP and you would like to be assessed for a cochlear implant:
The first step is to ask your GP for a referral to a local audiologist, ear nose and throat (ENT) specialist, or hearing therapist. If they believe you could benefit from a cochlear implant, they will then refer you to The Hearing House for a Cochlear Implant Assessment.
Suspecting a hearing problem
Most people with hearing loss dont realise how bad their hearing has become until someone else tells them. Often it is a family member who realises that you are unable to hear them properly.
Assessing a hearing problem
A hearing test is pain-free and can reveal if an adult needs to be referred to the adult cochlear implant assessment programme, which is run at the University of Auckland’s Tamaki campus. The hearing test can measure an adult’s hearing levels on an audiogram, which is basically a graph plotting how well someone can hear. If an audiologist diagnoses that an adult has a severe to profound hearing loss, they are referred to Auckland University’s audiology clinics for further tests.
You may be eligible for a publicly-funded cochlear implant if you have a severe to profound hearing loss and hearing aids are unable to help.
There is no maximum age for referral to the Adult Cochlear Implant Programme, where The Hearing House will carry out a Cochlear Implant Assessment.
Currently the Government caps the number of adults eligible for a publicly-funded operation. Patients with additional needs are not excluded.
You will be referred to the NCIP Adult Cochlear Implant Assessment Programme if you:
- Have a bilateral moderate to profound sensorineural hearing loss, one that is above 90 decibels for their better ear.
- Have developed spoken language; (however, a cochlear implant may be considered on a case by case basis for adults with little spoken language if there is a significant need for hearing of environmental sounds).
- Receive no or limited benefit from hearing aids.
The Northern Cochlear Implant Programme (NCIP) assessment process for adults is a multi-stage process which involves hearing tests, a medical evaluation, and an assessment to check that you would benefit from a cochlear implant.
A Computerised Tomography scan (CT) to check that the surgery is possible may also be required.
Involves review by the NCIP Adult Programme Team Leader, and then referral to a Hearing Therapist who undertakes a communication needs evaluation and also screens them for speech perception.
If the referral to the NCIP Programme is accepted, you will receive a referral to a local Ear, Nose, and Throat Specialist for a medical evaluation and CT scan.
You will then be invited to a two-day assessment in Auckland. This involves various sessions that may include the following:
- An audiology appointment where you are tested with and without hearing aids to verify the level of hearing loss.
- Rehabilitation appointments to test your speech perception
- Appointments with a cochlear implant user
- Demonstrations of cochlear implant equipment and how it works
- Discussions about an implant’s limitations
- Discussion regarding your expectations about having an implant
- A 45-minute meeting with an Ear Nose and Throat Specialist where medical issues, the surgical procedure, an ear check, and results of the CT scan are discussed.
A decision is then made by the assessment team, in consultation with you, on whether to go on the waiting list for cochlear implant surgery.
Discussions about the surgery itself take place in a pre-operative consultation where details about what to expect before and after the operation are explained by your ENT Surgeon.
Admission to Gillies Hospital, where the operation will take place, is usually on the actual day of surgery.
After admission by nursing staff, there is a consultation with the anaesthetist who explains what happens with the anaesthetic (cochlear implant surgery is done under a general anaesthetic).
Before surgery, both ears are examined to ensure they are free from infection and ready for the implant.
The surgery itself, can take several hours to perform and the hair just behind the ear is shaved. There are stitches in this area and you will receives antibiotics and mild pain relief during and after surgery.
Usually you can go home the day after surgery. It is common for your ear to stick out a little after surgery, but this eventually settles down.
The area where the implant package has been placed is slightly prominent, but it is unusual to have any significant swelling in the area.
You usually have a follow-up with the implant Surgeon or an Ear, Nose and Throat Specialist between 10 days and four weeks after surgery.
Living with a Cochlear Implant
The cochlear implant is switched on shortly following surgery and involves MAPping of the device, and rehabilitation to ensure you receive as much benefit from the implant as possible.
The switch-on is the first time an adult has access to sound.
Some adults find the first few hours quite disconcerting because the noises heard can resemble beeps and whistles, however over time the brain starts to convert those sounds into language.
The time it takes for the brain to perceive the electrical stimulation as meaningful sound differs between individuals.
Some people adapt to the new sound very quickly while others can take a few months to make sense of what they hear.
As they do with children, an Audiologist works with you to ensure your device is appropriately MAPped – (sound is heard at an appropriate level and tone).
Because it takes time for the brain to make sense of what it is hearing, this process does require a number of visits after switch-on to ensure the implant device is MAPped at the correct level.
The Audiologists and Rehabilitationists carefully monitor your speech perception and provide rehabilitation to ensure you are speaking and hearing at an appropriate level.
Advantages of a Cochlear Implant
Most recipients can follow a normal conversation and participate more easily in the hearing community.
May enable use of the telephone.
Avoids problems with acoustic feedback and ear moulds.
Can detect soft environmental sounds across the frequency range 250Hz-8KHz.
Enables greater ease with high frequency consonant perception and production; e.g. /s/ /sh/ /f/ /t/ /k/ /p/ /h/ /th/.
Disadvantages of a Cochlear Implant
Requires significant time commitment to rehabilitation following surgery.
Residual hearing in the implanted ear may be lost as a result of the surgery.
The speech processor must be removed during water activities (such as swimming or showering), and the cochlear implant recipient will not be able to hear during this time.