Hearing Aids, Implants and Other Devices

Cochlear Implants

What is a cochlear implant?

A cochlear implant is an electronic device that is designed to provide hearing to those with profound deafness. Part of the device is surgically implanted into the inner ear and part is worn externally. As a prosthetic device, the cochlear implant stimulates the auditory or hearing nerve directly, bypassing the damaged part of the inner ear or cochlea. Many viable nerve fi bres remain in the auditory nerve even in cases of profound deafness, and the cochlear implant can restore activity to this nerve and the hearing pathway.

Many individuals who have lost their hearing after acquiring speech and language (post-lingual deafness) are capable of excellent speech understanding with their implant. When children who are deaf are provided with cochlear implants they can perceive speech and environmental sounds previously unavailable to them. As they learn to attach meaning to the sounds they are hearing, they build the foundations for spoken language.

How does a cochlear implant work?

The implant has two components, an externally worn microphone and processor and the internal electrode array. The microphone picks up sounds near the ear level and sends it to the speech processor. The speech processor takes the acoustic signal and codes it for speech electrically. The signal is sent to the transmitter worn on the head where it is then sent through the skin to the implanted device. Under the skin, the receiver decodes the signal and sends it to the electrode array. The electrode array distributes the signal and stimulates the nerve endings in the cochlea, producing nerve impulses. The impulses are sent to the brain where they are interpreted as sound.

Who is a candidate for a cochlear implant?

Cochlear implants are available to children and adults in Canada who meet the following criteria:

Adults

  • Must demonstrate a moderate to severe/profound sensorineural hearing loss
  • Have limited benefit from optimally fitted amplification
  • Hearing loss can be acquired before (pre-linguistic) or after (post-linguistic) learning speech and language
  • No medical contraindications
  • Realistic expectations and a desire to be a part of the hearing world

Children

  • Age 0-18 years
  • Severe-to-Profound sensorineural hearing loss bilaterally
  • Receive little or no benefit from appropriate hearing aids
  • No medical contraindications
  • An educational placement where the development of listening and speaking skills is emphasized
  • Family support that includes the commitment to the rehabilitative process
What is the process of getting a cochlear implant?

Before receiving a cochlear implant, an extensive evaluation is performed that includes a hearing aid evaluation, an audiological evaluation, an otological evaluation, CT scan, a speech-language evaluation, and possibly a psychological evaluation. These tests are performed to ensure that candidacy requirements have been met and that certain benefits may be provided by the implant. Counseling will also be provided by the cochlear implant team regarding the benefits and risks of cochlear implantation.

This will include the medical and surgical risks, the possible benefits to be expected, and the follow-up necessary to ensure an appropriate fitting of the speech processor and rehabilitation.

 

When does surgery take place?

Once patients have completed the necessary testing to determine candidacy, surgery can be scheduled. Surgery is performed under general anaesthesia, and typically takes two to three hours to complete. The electrode array is fed into the cochlea, and the receiver is placed behind the. Most hospitals require a one to two day hospital stay before going home.

 

What happens after surgery?

Four to six weeks following surgery the speech processor will be programmed. Threshold and comfort levels are obtained for each electrode on the internal array, which creates a “map”that is stored on a computer chip inside your processor. This process is usually done in two to three hours.

During the first three months of wearing the device, some fine-tuning needs to take place. Numerous “mapping” sessions may need to be performed to obtain the best possible sound for each patient. Typically once a stable map is established, the map is checked and speech perception testing is performed every six months following activation.

Will I need rehabilitation after surgery?

Rehabilitation following cochlear implantation offers a structured approach by which patients learn to identify and associate meaning to the new sounds they are hearing. For children, rehabilitation is vital to develop an understanding of what is being heard through a cochlear implant. Therapy allows children to take the restored level of sensitive hearing and learn to understand spoken language and produce intelligible speech. Unlike adults who have lost their hearing after the development of speech and language, deaf children have no auditory memories to draw upon to understand spoken communication. Rehabilitation is a lifelong process that takes the child through language acquisition learning to attach meaning first to syllables, then to words, phrases, and sentences and ultimately to conversation. For adults, rehabilitation can provide the structure necessary to fine-tune their listening skills. Some adults feel that they are receiving enough stimulation in their everyday life that therapy is not needed.

Hearing Aids and Assistive Devices

Should I get a hearing aid?

Have your friends or family been suggesting that this would be a good idea? Do you feel that people are mumbling? Before you purchase any hearing aid, see a qualified audiologist. Your audiologist will test your hearing and make the appropriate recommendations. If you are a hearing aid candidate, your audiologist will guide you through the selection process.

Do I need two hearing aids?

People hear better with two ears than with one. Binaural hearing improves your ability to understand speech in noise and helps you to locate the sounds around you.

Can I get hearing aids that filter out background noise?

Understanding of speech, especially in noisy environments, will vary depending upon your degree of hearing loss, how well the hearing aids have been fitted, how frequently the hearing aids are used, and the signal-to-noise ratio present in the environment. Many recent developments in hearing aid design help you to cope with adverse listening situations.

Will hearing aids restore my hearing to normal?

Hearing aids are designed to aid hearing but they cannot restore hearing. They are only a part of the hearing rehabilitation process. Your audiologist will help you with all aspects of your journey towards better hearing.

 

What Kinds of Hearing Aids Are There?

If you have a hearing loss, you have may have several options to help improve your ability to hear. When we are looking at traditional hearing aids there are two main things to consider: 1) the style (the way the hearing aids look) and 2) the technology (the electronics inside). It is your job to choose the style with guidance from your audiologist and it is your audiologist’s job to choose the technology with input from you. Speak to your audiologist to discuss which options are best for you, your hearing loss and your hearing needs.

Styles of Hearing Aids

In-the-Ear (ITE) Hearing Aid

This type of hearing aid fits in the ear canal and the concha (outer portion of the ear). This is a very popular style for adult hearing aid users but there are drawbacks for use with children who are still growing. They cannot be used with many assistive listening devices including direct audio input FM systems. This style of hearing aid cannot provide adequate amplification for individuals with severe to profound hearing losses.

Behind-the-Ear (BTE) Hearing Aid

With this style of hearing aid the electronics sit behind the ear and the amplified sound is then routed to the ear through the tubing and ear mould. This style of hearing aid can provide the amplification necessary for all degrees of hearing loss from mild to profound. BTE hearing aids can be used with a variety of other assistive devices including FM systems, telephone adaptors, television amplifiers and many others. Because the electronics are behind the ear, BTEs are particularly useful for those with chronic ear infections, excess cerumen (ear wax) and those with small ear canals. Behind-the-ear hearing aids and ear moulds come in a variety of colours and designs.

Open Fit Hearing Aid

Open fit hearing aids are similar to the behind-the-ear (BTE) style because the amplifier and electronics sit behind the ear. However, these hearing aids typically utilize a slim tube and small tip that sit inside the ear canal. The small tip in the ear results in an open fit without plugging the ear resulting in a more comfortable fit, and can eliminate problems with your own voice. However, the open fit hearing aids are not appropriate for severe hearing losses and are best for persons with mild to moderate high frequency hearing loss.

CROS (Contralateral Routing of Signal)

This hearing aid system is designed for people with one ear that is unaidable (i.e. insufficient hearing to benefit from traditional hearing amplification). The better ear can have normal hearing (CROS Aid) or have some hearing loss as well (Bi-CROS). A microphone is placed on the poorer ear and the sound from that microphone is routed to a hearing aid on the better ear. This provides sound from the “dead” or unusable side of the head. While this does not restore full ability to localize sounds in space, it does provide useful sound information that is not otherwise available to the individual.

Are hearing aids expensive?

Your hearing aids could be the best investment you make for yourself. Good communication is fundamental to all our personal relationships. The variety of hearing instruments available makes it very likely that you will be able to find good amplification in a comfortable price range.

Do I have to wear hearing aids all the time?

You haven’t heard well for a long time and you have adapted to imperfect hearing. You have to relearn what “normal hearing” is and one of the best ways to achieve this is to wear the hearing aids as much as possible, as consistently as possible during waking hours. You may have to increase wearing time gradually in the beginning but full time use is the ultimate goal. Your audiologist will help you to accomplish this.

How can I use the telephone?

Often, as a hearing aid wearer, when you place a telephone receiver to your ear your hearing aid makes an unpleasant whistling noise. A telecoil option, added to your hearing aid, uses the electromagnetic energy produced by the telephone and eliminates the annoying feedback. The hearing aid will have a switch allowing you to choose between the standard microphone mode and telephone compatible mode. Ask your audiologist to explain the features of your hearing aid to you.

How do I care for my hearing aids?

Very little care is required. You must keep the hearing aids clean and dry. Every 10 to 14 day fresh batteries must be inserted. Your audiologist will show you how to do these things when you get the hearing aids for the first time and you will be given a booklet of instructions to take home with you.

 

What other devices could help me?

FM Systems

These are assistive listening devices used to improve the signal-to-noise ratio for the listener and to reduce the effects of poor acoustics. This system is made up of two parts: 1) the transmitter which is used by the speaker or placed near the device to be amplified (eg.TV, computer, stereo) and 2) the receiver which is used by the individual trying to hear. This system helps to bring the speaker’s voice directly to the listener’s ears either through hearing aids or headphones. The listener is able to hear the speaker above the background noise at considerable distances. There are no wires connecting the listener to the speaker which gives mobility to both. These units are often of benefit for classes, lectures, conferences, meetings, in restaurants, and in large groups.

Cochlear Implant

A device surgically implanted into the cochlea to bypass the sensory organ to activate the hearing nerve directly. It is designed for individuals with severe-profound sensorineural hearing loss (in both ears) who do not receive benefit from traditional hearing aid amplification. The system consists of a processor that looks like a behind the ear hearing aid, an external magnet that attaches to an internal magnet implanted in the mastoid bone and the actual electrode that is surgically implanted in the cochlea (inner ear). Once implanted, the device is programmed for the individual over several months.

Bone Conduction Amplification Device (BCAD)

This device combines a sound processor with a small titanium fixture implanted behind the ear. The system allows sound to be conducted through the bone rather than via the middle ear – a process known as direct bone conduction. The surgery is minor, and many patients report a wide range of advantages over other hearing devices. BCAD is used for people with chronic ear infections, congenital conductive hearing loss, and/or single-sided deafness.