Understanding Cochlear Implants

This booklet is designed...
to supplement the information pack which MED-EL has supplied to your Cochlear Implant Team. You may already have worked through all or part of that pack with someone from your Implant Team, in which case this booklet will act as a reminder of what you have covered/ or you may be reading this in advance of such discussions with your Implant Team.

In this booklet we will look at the ear and how we hear/ the causes and treatments of hearing loss; then we focus on the cochlear implant system, how it works/ who can benefit from it and the general steps involved in obtaining an implant if, indeed, it is the appropriate treatment for you or your family member. If you need any further information or explanation, please ask your Cochlear Implant Team.

The Ear?
...

There are three main parts to the ear...

1. Outer Ear

The ear or pinna which helps us to tell where sound is coming from. The ear canal (the part where ear wax can collect) which acts as a channel for sound.

2. Middle Ear

The ear drum or tympanic membrane is taut, like the skin of a real drum, turns sound into vibrations. A chain of 3 small bones: the hammer, anvil and stirrup,

Or malleus, incus and stapes. These bones pass vibrations on to the inner ear.

3. Inner Ear

Snail-shaped and filled with fluid. It contains very sensitive cells, called hair cells, which have a tiny hair-like structure on the top of each cell. These hair cells play a very important part in enabling us to hear. The vestibule contains. The delicate cells which enable us to have a sense of balance. And auditor leading from the cochlea to the brain.

How we
hear?

Sound travels down the ear canal...
and hits  The ear drum is taut, like the skin of a real drum and it vibrates when sound hits it. This vibration is passed down the chain of bones to the cochlea (the inner ear). The vibrations make the fluid in the cochlea move. This movement in turn makes the hair cells move. When this happens the hair cells make tiny electrical signals which are picked up by the auditory nerve. Hair cells at one end of the cochlea send low pitch sound information in these signals and those at the other end send high pitch sound information. These electrical signals pass up the nerve to the brain. The brain interprets the electrical signals as sounds.

Why people have hearing difficulties?

Conductive Hearing Loss Any problem in the outer or middle ear...

can block sound to the ear and cause a conductive hearing loss (so called as it stops the ear from conducting sound properly). Conductive losses are usually mild or moderate in nature i.e. causing hearing loss of up to about 60 or 70 decibels. Conductive hearing losses can be temporary in some cases. In many cases medication or surgery can help, depending on the cause of the problem. This type of hearing loss can usually be helped very well with hearing aids.

Conductive hearing loss is due to  a problem in the outer or middle ear.

Sensorineural Hearing Loss

A problem in the inner ear can cause a sensorineural hearing loss. This can be mild, moderate, severe/ profound or even total hearing loss. Sensorineural losses are usually permanent. There is no surgical procedure to cure problems in this part of the ear; depending on the cause, medication may be helpful in some cases. Conventional hearing aids can usually help in mild to severe hearing loss. Cochlear implants can be a very effective option for those with severe/ profound or total hearing loss/ meaning those people who are not able to gain sufficient speech information even with the most powerful hearing aids.

Sensorineural hearing loss is due to a problem in the inner ear or cochlea.

Neural Hearing Loss

In very rare cases hearing loss may be caused by the absence of or damage to the auditory nerve, resulting in a neural hearing loss. Conventional hearing aids will give little benefit because the nerve is not able to pass on enough information to the brain. A cochlear implant will not help unless there is some auditory nerve function. An auditory brainstem implant will help in some cases.

Neural hearing loss is due to a problem in the nerve pathway.

How a Cochlear Implant works?

Cochlear implants are only appropriate for hearing losses...
primarily caused by a problem in the inner ear (the cochlea). They are intended for people who are unable to gain sufficient speech information through conventional hearing aids. Both children and adults can use cochlear implants effectively, whether they are born deaf or whether hearing loss occurs later in life. It is not possible to predict how much benefit any individual will get from a cochlear implant, but the following points are widely recognized: the longer the period of profound deafness, the more limited the benefits are likely to be. Born deaf children will have the greatest benefit if they have an implant before the age of 5 and preferably by the age of 3. If a person has memory of speech and language they may have more benefit from a cochlear implant.

How we hear?
...

Sounds are picked up by a microphone and turned into an electrical signal...
  1. This signal goes to the speech processor where it is “coded” (turned into a special pattern of electrical pulses)
  2. These pulses are sent to the coil and are then transmitted across the intact skin (by radio waves) to the implant
  3. The implant sends a pattern of electrical pulses to the electrodes in the cochlea
  4. The auditory nerve picks up these tiny electrical pulses and sends them to the brain
  5. The brain recognizes these signals as sound.

Why might a Cochlear Implant not be suitable?

A range of common reasons include...

1. Your hearing is “too good”

The most common reason for not needing a cochlear implant is that the hearing is too “good.” If a person can hear enough of the sounds of speech through well-fitting hearing aids, even if they need lip-reading to aid their understanding, this will normally be the best option for them.

2. You have been profoundly deaf for a very long time

If the auditory nerve has never been stimulated or has not been stimulated for a very long time, it may not pass sound information to the brain very well even with a cochlear implant. The brain also needs experience of understanding sounds from childhood on in order to optimally utilize any information a cochlear implant can provide.

3. The cochlea is not the main cause of the hearing loss

A cochlear implant is designed to make up for poor inner ear function. A cochlear implant cannot help if the main problem lies elsewhere.

4. Surgery is not likely to be successful

The cochlea may be in too poor a condition to receive the electrode. For example, the auditory nerve may be damaged or absent, in which case a standard cochlear implant will not help.

5. Medically Unfit

A patient needs to be well enough to undergo surgery, to tolerate and recover from the anesthetic and the surgery. In some cases, the operation can be carried out under powerful local anesthetic for adults. He or she must also be well enough to, and capable of undergoing the follow-up program necessary to use the implant well, including wearing the external parts of the device, having the speech processor programmed and being involved in the rehabilitation program.

It is essential that realistic expectations of the likely benefits are held by the patient and family. What to expect and what not to expect should be discussed thoroughly with the implant team.

Lack of support from family or caregivers

Support from family and caregivers is important and indeed vital in the case of children with cochlear implants. Having a cochlear implant is a commitment for the lifetime of the individual concerned. Patients will only achieve optimum results if their device is well programmed, fully functioning and if they go through a rehabilitation program designed for them by the implant team specialists.

The benefits of Cochlear Implants

Hearing everyday sounds...

Virtually all users benefit by being able to hear environmental sounds. This helps people to keep in touch with their environment. It is also an important safety consideration as it enables people to hear traffic, sirens, alarms and so on.

Hearing and understanding speech

Virtually all users will hear speech sounds through the cochlear implant. It usually takes some time before they begin to understand these sounds, especially for children. Being able to hear speech can be of great help to those who lip-read, and it makes everyday communication much easier for the vast majority of users. Furthermore, users may go on to understand speech without lip-reading. Many, although not all, cochlear implant users do achieve this with time.

Improving the user’s own speech

Hearing their own speech and the speech of others often helps cochlear implant users to fine-tune their speech. Hearing their own speech and the speech of others often helps cochlear implant users to fine-tune their speech.

Listening in background noise

When there is background noise/ it is more difficult for all of us to hear speech, but especially so for hearing aid and cochlear implant users. The Maestro Cochlear Implant System cochlear implant has special features to help in this, including its fast stimulation rate and advanced speech processing strategy, providing outstanding speech understanding in background noise.

Using the phone can become a reality

Many users are eventually able to understand speech without lip-reading. Some users also go on to be able to have interactive conversations over the telephone.

The limitations of Cochlear Implants?

There is a wide range of benefits...

obtained from cochlear implants. Benefits range from an aid in lip-reading to understanding speech without lip-reading.

Prediction of benefit

There is no test yet available which accurately predicts how much benefit any particular person will receive. Many factors affect the likely benefits to be derived. They are discussed in the section ,”who can benefit from a cochlear implant.”

Risk of device failure

As with any technical device there is a small risk that the implant could break down. This rarely occurs, but when it has done, re-implantation with a new implant has been highly successful.

Everyday considerations and precautions

The system is easy to use but certain precautions should be taken:

  • Keep the external parts of the device dry (as with hearing aids)
  • Avoid activities and sports which could cause a severe blow to the head
  •  Keep exposure to static electricity as low as possible
  • Sources of radio frequencies (e.g. mobile phones) can cause some temporary interference with the sound through the implant for some users
    Cochlear implant users can continue to participate in most everyday activities; sports such as boxing, however, are not advised.

The MED-EL MAESTRO Cochlear Implant System

 The Next Generation Cochlear Implant System...

Components:

The Maestro Cochlear Implant System electrode array

Available in 3 types

1. Standard Array

The longest electrode array on the market, reaches deep into the cochlea to stimulate as many of the auditory nerve endings as possible.

2. Short Array

Specially designed for ossified or malformed cochleae.

3. Split Electrode Array

For highly ossified cochleae.

The Role of the Cochlear Implant Team

Cochlear implantation is undertaken within specialist centers, to which patients are commonly referred by their local doctor or Ear, Nose and Throat Specialist.

Assessments Involved
...
...

Audiological Hearing levels with and without...

hearing aids, for tonnes and, or noise, for speech. Test of an auditory nerves function. Establishing existence of any significant additional conditions or needs. Establishing appropriate expectations.

Medical

Evaluation of cause of hearing loss, general health, condition of the ears, establishing the existence of any significant additional conditions or needs, establishing appropriate expectations.

Radiological

CT and, or MRI scan of the ears.

Psychological

Ability to cope with operation tries to cope with the follow-up program. Establishing existence of any significant additional conditions or needs. Establishing appropriate expectations.

Speech & Language

Assessing stage of speech & language: establishing existence of any significant additional conditions or needs. Establishing appropriate expectations.

Educational

Assessing stage of development of child, establishing existence of any significant additional conditions or needs, establishing appropriate expectations.

The operation

The operation usually takes between 2 and 4 hours. The risks involved in cochlear implant surgery are small and compare well involved in cochlear implant surgery are small and compare well

  1. The skin is shaved around where the incision is to be made
  2. The incision is made and the skirl and tissue are lifted back to expose the skull
  3. A bed is drilled out in the bone behind the ear for the implant
  4. A hole is drilled into the cochlea
  5. The electrode array is inserted into the cochlea
  6. The electrode array and the implant itself are secured in place
  7. The skin and tissue are reattached, and the wound is stitched up
  8. There is usually little discomfort when the patient wakes up. Pain medication can normally be given if required
  9. Patients are usually up and about the next day. The length of stay in the hospital depends upon local practice and can be as short as 3 days.

Fine Hearing: The Fine Details of Sound Come Alive

A strategy is a plan with a clear destination...

With cochlear implants “getting from here to there,” means creating the most effective blueprint for the conversion of sound into electrical signals that the brain can understand.

For years, coding strategies have only been able to represent one part of the sound, known as the “envelope,” while improvements to the “fine structure” of sound have been limited by technological advancement. Fine Hearing™ from MED EL overcomes these limitations.

The “envelope approach” to implant development allows most users to achieve good levels of speech understanding in a quiet environment.

  1. Unfortunately, focusing on the envelope portion of sound alone cannot provide the best results for more complex hearing tasks. Without the fine structure information, which gives each sound its own unique quality (e.g., musical pitch), cochlear implant users often report difficulty enjoying music and focusing on speech in noisy environments.
  2. Special settings for certain situations, such as focused listening, music, or soft sounds have not been an effective or convenient solution. In addition, languages that rely largely on changes in tone, or tonal languages such as Mandarin Chinese, have also been particularly challenging for cochlear implant users.

Elements of Sound
...

Envelope The envelope is the loudness contour...

of the sound signal and is essential for speech understanding.

Fine Structure

The fine structure contains the subtle details of a sound signal and enhances pitch and sound quality.

Studies demonstrate that fine structure is the main information carrier for music and sound localisation. With Fine Hearing technology and Complete Cochlear Coverage, users can benefit from enhanced sound coding that represents both parts of the sound, the envelope and the fine structure. Unlike traditional sound processing, Maestro uses a highly advanced algorithm, known as the Hilbert Transform, to provide high-definition digital signal processing that closely extracts the overall shape, or envelope, of an incoming sound with a high degree of accuracy. In addition, special patented electrical pulses are presented to the apex of the cochlea, using a unique pulse shape that carries the tone and quality information. In this way, the fine structure of the sound is also presented with great accuracy to provide unprecedented sound quality.

Fine Structure Processing, an implementation of Fine Hearing technology from MED EL, offers users a new level of sound quality, especially when listening to music, by offering both the envelope and the fine structure sound information.

  1. Helms J. Comparison of the TEMPO+ ear-level speech processor and the CIS PRO+ body-worn processor in adult MED-EL cochlear implant users. ORL Head Neck Surg 2001; 63: 31-40.
  2. Nopp P, Polak M. From electric acoustic stimulation to improved sound coding in cochlear implants. Accepted for publication in: van de Heyning P (ed), Cochlear Implant and Hearing Preservation, Karger.

First Sounds Through the Cochlear Implant

The speech processor is fitted 3 to 6 weeks after surgery...

The speech processor is set up individually for each user. To program the processor for the user:

  • The user wears the processor
  • The processor is also attached to the clinic computer
  • The clinic computer generates signals at carefully controlled levels

The user indicates:

  1. The quietest signal heard (his threshold level)
  2. The loudest comfortable signal heard (his most comfortable level)
  • These two levels are measured for all the electrodes in the cochlea
  • using this information a speech processor program is created which allocates sounds between these two levels, i.e. loud enough to hear but not so loud as to be uncomfortable. The program is fine-tuned during following clinic sessions.

The Follow-up Program
...

The cochlear implant user needs to...
be fully committed to the follow-up program designed by the Cochlear Implant team in order to benefit most from the implant system. The follow-up program will depend on local practices but may include:

Availability of help, advice and support

Assistance should be available not only for technical matters which may arise, but also for general questions. The team can also give you information on support groups for cochlear implant users and their families.

Regular medical check-ups

The implant site should be checked regularly by a physician.

Regular reprogramming of the speech processor

Cochlear implant users should visit their clinic regularly for reprogramming of the speech processor. This allows the audiologist to check that the implant is continuing to function well. He can also make any small modifications or improvements to the program so that the user will continue to have the greatest benefit from the implant system.

Speech and language therapy and advice

Regular speech and language therapy is usually available, especially for children.

Educational advice and support (for children)

Children using cochlear implants usually have regular contact with an educational specialist qualified to work with the hearing impaired. He or she can offer advice and support and monitor the child’s progress with the cochlear implant system.

Cochlear Implant Team members may include:

Specialist Ear, Nose & Throat Surgeons...
  • Audiological Scientists Clinical Audiologists
  • Clinical Audiologists
  • Speech & Language Therapists
  • Educators/ Teachers of the Deaf
  • Medical Physicists
  • Educational Psychologist
  • Administrative Staff
  • Implant Team Coordinator

Their Role
...

Medical evaluation Surgery...
  • Evaluation of hearing abilities
  • Processor fitting, programming and follow-up
  • Evaluation of speech and language status
  • Rehabilitation and Support
  • Evaluation of educational, support needs,
  • Rehabilitation and Support
  • Technical support
  • Evaluation of psychological
  • Status, Support
  • Administration
  • Coordination of activities