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What is a Cochlear Implant?

A Cochlear implant is a hearing device, which enables restoration of hearing to those who have severe to profound hearing loss, and which enables babies and young children with severe to profound hearing loss to hear and to develop oral language and subsequently to speak.

The cochlear implant consists of two main components. The first is an external sound "receiver" rather like a hearing aid. This "picks up" sound and passes it through a short cable to a small antenna/transmitter.

The second component is surgically implanted under the skin behind the ear. A small circular "antenna" picks up the signal from the transmitter and passes this signal through a series of 22 electrodes into the "cochlea" (the hearing organ) of the inner ear.

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Photo of externally worn part of a cochlear implant

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  Photo of "Nucleus" brand Cochlear implant

 

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  Kanso 2 Processor

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Kanso 2 Processor

Nucleus N8 Processor

Listen to Simon Morton's radio NZ programme on cochlear implants (with an interview with Dr Brown)

http://www.radionz.co.nz/national/programmes/thiswayup/audio/2509612/the-hearing-house

Who is a candidate for a cochlear implant?

Children and babies who have severe to profound bilateral or asymmetric progressive hearing loss, who demonstrate limited ability to benefit from the most powerful hearing aids. In babies, the hearing loss is diagnosed by a combination of "auditory brainstem response" (ABR) testing, Otoacoustic emission testing (which assesses tiny sounds which are actually made by the ear) and also by behavioural testing (looking at the child's response to sound,  without and with wearing hearing aids).

Responses to hearing aid fitting are also assessed typically over several months, and determined by parents, audiologists and hearing therapists.In children who have lost hearing as a result of meningitis, (particularly pneumococcal meningitis), we do not have the luxury of such an assessment period, as the cochlea typically "closes up" with new bone in the first few weeks to months after meningitis, rendering the cochlea extremely difficult or impossible to implant beyond 12 weeks after a meningitis infection.

Public funding is available for bilateral cochlear implants in eligible children.

Adults who have bilateral severe or worse hearing loss, and show limited benefit from the most powerful hearing aids. The reduced ability to understand speech clearly while wearing the hearing aids is an important assessment tool and helps guide candidacy. We compare the abilities of an adult candidate using hearing aids with someone in similar circumstances using a cochlear implant. Those who are able to understand less than 50% of words correctly, whilst wearing the aids, may be candidates, as this ability would be expected to be superior with an implant. Some adults who have a progressive hearing loss, but who perform slightly better than this on speech testing may also be candidates to benefit from a cochlear implant. Studies in adults have shown that adults implanted earlier, have much better hearing, compared with those who delay the decision to have an implant.

Public funding (wait listed) is available for a single implant for eligible adults. If a second implant is desired, this must be self funded. Insurance companies usually cover the cost of the procedure but not the cost of the hardware required. For those insured by Southern Cross, funding may improve further in 2024.

Adults and some children with single sided hearing loss. The typical adult client is someone who has suffered a severe " sudden sensorineural hearing loss" or has had a head injury.  Unfortunately at present there is no public funding for cochlear implants for children's single sided deafness, unless this occurs as a result of meningitis, however ACC does cover the full costs of cochlear implants following a head injury.

When should a cochlear implant be fitted?

The simple answer is "as early as possible." 

In babies who are diagnosed through screening programmes, this may mean the benefits of an implant are obtainable by five to six months of age.

In young children who have never heard before, the brain gradually loses its ability to utilise sound. By the age of 4-5 years in a child with profound hearing loss, this ability has diminished so much that even a cochlear implant fitted after this stage, will be of limited benefit.

Children and adults who have a progressive hearing loss and who have already developed oral language may all potentially benefit from a cochlear implant.

The duration of profound deafness has a significant impact on the potential benefit of a cochlear implant. In an adult or child,an ear which no longer is able to benefit from amplification of a hearing aid would be expected to slowly lose its nerve supply over 2 decades or so. Therefore, adults with a long duration of deafness and no hearing aid use would be expected not to be able to hear as well with an implant, compared to someeone who receives an implant after a shorter duration of deafness. Again, the message is, "as early as possible". We encourage adults with deteriorating abilities to hear on the telephone (with hearing aids on) to come for an assessment.

How is the assessment for a cochlear implant done?

The assessment usually starts with referral from an audiologist or hearing therapist or advisor on deaf children to the public or the private cochlear implant programme. Assessment is performed by myself and cochlear implant specialist audiologists and hearing therapists. Information from those making the referral is utilised, in addition to further testing of the hearing, and MRI (magnetic resonance imaging) and sometimes CT (computerised tomography) scanning of the ears and head.

Children (New Zealand Residents): The assessments are discussed as a group with the implant candidate (or parents),myself, the cochlear implant audiologist and the hearing therapist. A recommendation may then be made for public funding of the implant, to the Northern Cochlear Implant Trust. This decision is made by a committee of cochlear implant experts in surgery, audiology and hearing therapy, and would include those who are directly responsible for the hearing care of the candidate. In New Zealand, public funding is expected to cover most cochlear implant costs for life.At present there are long waiting lists for cochlear implantation for adults, despite recent imporvements in funding.

Private funding of cochlear implants and cochlear implant surgery is also possible. In this situation, there is no requirement for a review by the funding committee, and the decision is made by yourself with advice and recommendations from your cochlear implant audiologist/habilitationist team at Hearing House and myself.

Cochlear Implant surgery

I perform this surgery at Southern Cross Gillies Hospital, 160 Gillies Ave, Epsom. This is where all Cochlear Implant operations take place in Auckland (see the map on my website).This procedure involves the insertion of the receiver with electrode array. It is regarded as a fairly routine operation, typically taking about 2 1/2 hours in the operating room.  It is performed under general anaesthesia (asleep).A small amount of hair is shaved from behind the ear. An incision (cut) is made behind the ear and a pocket created to house the implant. Some air cells in the mastoid bone, which is part of the ear, are removed to enable access to the inner ear. The electrode array (with 22 electrodes along it) is inserted through the mastoid, over the top of the facial nerve and into the "round window" of the inner ear. The device is secured and the incision is then closed using buried dissolving stitches and skin glue. A head bandage is worn overnight. In some cases, it may be possible to return home at the end of the day, and for some, an overnight stay is required.We prescribe paracetamol and an anti inflammatory (such as brufen or celebrex) to manage discomfort for 5-7 days post operatively. Most children seem to have very little pain, and often "run around" normally the next day (depending on their age , of course!).

What are the risks of a cochlear implant?

These include:

  • Device failure. The internal device is guaranteed for 10 years. The failure rate in children is slightly greater than in adults, but less than 1% over this time. If this occurs, the implant can be removed and replaced.
  • Infection: this could necessitate the removal (and replacement) of the device. Very uncommon-I have not had this occur in any of my patients.
  • Facial nerve injury: because this nerve runs through the middle ear, it is at risk in a surgical procedure on the ear. In experienced hands, this risk is minimal. I have not had this occur in any of my patients. 
  • Facial nerve stimulation: In some people who have had meningitis or who have lost hearing as a result of otosclerosis, it is possible that sound may result in facial twitching. It is usually possible to overcome this with programming of the device.
  • Temporary or permanent alteration of the sensation of taste on the side of the tongue. This may occur uncommonly as a result of damage to the "chorda- tympani nerve" which runs also through the ear and the mastoid bone.
  • Meningitis: this is a rare consequence of cochlear implantation, and also deafness itself presents a greater risk of meningitis. For this reason, all children and adults should be fully vaccinated against  the bacteria ,streptococcus pneumoniae. This is something which you should ask your GP to do. This vaccination is currently routine in babies in New Zealand.
  • MRI Scanning- the current implants are compatible with MRI scanning- but if the head is being scanned, there is usually a zone of 10cm around the implant which is not visible. The removeable magnet in the implant may be removed temporarily, with a small procedure, to reduce this invisible zone.

Cochlear Implant Programming

This is done post operatively, between days 1-7. The first appointment is called "switch on", where each individual electrode is adjusted to maximise the ability to hear. in the subsequent weeks and months, the stimulation of each electrode is adjusted. Usually, minimal adjustment is required after a year of use. Programming is performed for children at Hearing House in Auckland and at outreach clinics in Whagarei, Hamilton, Rotorua and Tauranga . For adults this is performed at Hearing House. Future programming is increasingly able to be done remotely.

What may I reasonably expect from a cochlear implant?

Adults may expect significant benefits of improved clarity of speech perception. The hearing is stabilised and usually remains stable. Typically, self confidence improves vastly, as does the ability to function in many day to day tasks, as does the ability to work. Many may hear enough to use a standard telephone.For most adults who have the implant, this is a life changing event.Children who receive the implant very early in life, before the development of speech, can be expected in most cases to hear sufficiently develop normal speech clarity, and to develop sufficient language to enable their attendance at a normal local school. Every child is different however, and specific advice about this would be needed from your "cochlear implant team."

Now, adults and children may swim with their implants, using a special implant cover.

Henry, wearing his cochlear implant (and a headband) swimming with his Dad, Scott  (used with permission) 

 

Watch Danielle test out her new cochlear implant under water:

https://www.facebook.com/video.php?v=1508136739431297&set=vb.1456530507925254&type=2&theater

Two cochlear implants

We recommend bilateral cochlear implantation where possible. There is now good evidence from overseas research and from our own personal experience that two cochlear implants are better than one. Children  perform better with bilateral implants when these are implanted at an early age. Ideally the implants should be inserted simultaneously. Advantages of two implants include better perception in noise, the ability to localise sound direction and a greater feeling of being "connected" with or centred in the sound world. It is also very nice to have a back up if batteries unexpectedly go flat in one of the implants.

Cochlear implant safety

Cochlear MRI safety Guidelines – PDF file containing guidelines on Cochlear Implant Safety

 

 

If you need further information or advice please do not hesitate to contact me for an appointment - This email address is being protected from spambots. You need JavaScript enabled to view it.

Reviewed January 2024


Where to find us?

Address
Gillies Hospital and Clinic,
160 Gillies Ave, Epsom, Auckland
Phone Number
(09) 631 1965
email: office@ear.co.nz