Technology

Cochlear Implants

Many children are being implanted with cochlear implants – at as early an age as 1 year old.  There is a rigorous procedure that must be followed in order to qualify. The child must have a severe to profound or profound sensorineural bilateral hearing loss and there can be no compromising medical conditions (a damaged cochlea or auditory nerve) that would compromise the child or the use of the implant. A strong commitment and realistic expectations on the behalf of the family is also very important.  After the implant has healed, there is then an intense “mapping” of the speech processor and auditory training period (weekly for about a year) so that the child can adjust and learn to translate the sounds heard into meaningful language.  It is necessary for the parents to realize that the expectation of them is to provide a rich auditory and listening environment so that their child has every opportunity to develop speech and understand and communicate using spoken language.  For many, but certainly not all, children, the cochlear implant has been most successful but it is not a guarantee that this will happen, or that the child will function as a “hearing” child. It has, however, allowed many, many children to have greater access to the hearing world by bringing a greater awareness to a broader range of sounds in contrast to the traditional hearing aid. However, with the numbers of children being implanted, it is imperative that the educational and communicational needs be closely studied. The cochlear implant is controversial procedure seen by many of the Deaf community as a effort to “fix” the deaf child’s who doesn’t need fixing. 

In British Columbia there are two hospitals, BC Children’s and St. Paul’s both in Vancouver which perform cochlear implants.   St. Paul’s is the province-wide resource for severe to profoundly deaf adults who no longer benefit from their hearing aids.  BC Children’s perform the cochlear implants on children, between the ages of 1 year to 16 years.  The implant team is made of up audiologists, speech-language pathologists, auditory-verbal therapists and the surgeon.  Cochlear implants don’t cure hearing. But they do provide an opportunity to hear sound to which the child then must learn to give meaning.  Although implants give greater access to sound, if the child is born profoundly deaf, the new process of learning speech and language through the use of hearing will be more difficult and slower than for the typical hearing child.  Predicting how any individual child will function when implanted, though, is not possible.  If any part of the cochlear implant is not worn, the child reverts to being profoundly deaf.

Which Ear?

Arguments can be made for the choice of either the better or the worse ear or automatically implanting the right ear, assuming there is a difference in the hearing levels between the 2 ears.  The reasoning behind implanting the ear with the more hearing suggests that that ear has been aided in the past and is more accustomed to receiving stimulation and therefore will adapt more readily and successfully to the new sounds.  On the other hand, if the ear with less hearing is implanted, then the better ear can still process sound through the use of the hearing aid.  If by implanting the electrodes, the hair cells in the cochlear are essentially  destroyed, then the implant will be a bonus while little has been lost.  However, if the 2 ears have basically the same amount of hearing or lack of hearing, some centres advise that the right ear be implanted.  The reasoning for this suggestion is that speech is processed on the left side of the brain.  When sound enters the right ear, it crosses over to the left side of the brain to be processed.  When sound enters the left side of the brain, it crosses over to the right side of the brain and then crosses back to the left side for processing.  The time delay between speech and language processing between the 2 ears is measured in nano-seconds.  However, it is thought that by implanting the right ear, the crossover time is shortened and thus the processing of speech and language information may very slightly be enhanced.

The next issue will be implanting both ears.  The use of 2 hearing aids is a benefit for sound localization, listening in a less than optimal environment, and generally making listening and understanding less stressful and tiring.  This practice is under study but would add a significant cost to the procedure. 

 

The Parts of the Cochlear Implant
Three companies, Cochlear Inc., Med-El Corp. and Advanced Bionics Corp. are making cochlear implants.  Although there are slight variations, essentially the components are the same. There are 2 main parts to a cochlear implant: the internal component that is comprised of the decoder and magnet in a protective casing with a flexible wire with electrodes along its length which is threaded through the curved passage of the cochlear. 

                                  

                                   

 

www.lhsc.on.ca/cochlear/device.htm

www.cochlearamericas.com/products17.asp

www.cochlearamericas.com/products23.asp

The external component, or part worn outside the body, is made up of the microphone, transmitting coil, speech processor and the cords that connect these pieces.  The internal device imbedded in the bone behind the ear and covered with skin so that when the wound is healed it is barely noticeable. 

 

www.lhsc.on.ca/cochlear/device.htm

How do Cochlear Implants Differ From Hearing Aids 

The cochlear implant performs quite differently than the hearing aid. The hearing aid relies on what hearing a person has, by increasing the volume.  The very nature of a hearing loss means that some sounds can be heard, some a little and others, not at all.  The hearing aid is a valuable tool for some hearing losses but for others, the pattern of what can and cannot be heard is so compromised that the acoustic signal is severely distorted. This distortion greatly compromises listening, speech and hence language learning.Hearing aids also increase all sounds even background sounds.  Lights or computers humming, paper being shuffled, a pencil being sharpened, a student dropping a book on the floor, greatly compromises listening abilities. For the student in a crowded and noisy school hall or at dinner where conversation moves quickly and laughter abounds, the deaf child’s ability to hear virtually disappears.  The child with a hearing loss is unable to selectively choose wants he wants to hear as easily as the hearing child.  The cochlear implant on the other hand, completely bypasses the damaged or missing hair cells in the cochlear sending the acoustical message through to the auditory nerve to be transmitted to the brain. The cochlear implant usually, destroys any functioning hearing the cochlear might have had, which is why the hearing loss must be in the severe to profound range with hearing aids able to provide little to no benefit. 

The Process

The process involves medical staff, audiologists, speech and language pathologists, teachers of the Deaf and hard of hearing and support professionals.  Although each medical centre may differ slightly, the process is basically the same.  This process includes:

 

Surgery and Mapping

The surgery lasts between 2 and 3 hours, during which time the child is given a general anesthetic.  The greatest risk of performing a cochlear implant is that which is related to general anesthetics.  The doctor makes a “bed” for the decoder in the bone behind the ear.  He must cut out a piece of the bone, approximately the size of a quarter.  He then makes a small hole behind the eardrum going through the round window and threads the flexible wire containing twenty-two electrodes along the curved passages of the cochlear.  Once the decoder is in place, the doctor stitches the wound closed. Within a week, the child will have recovered sufficiently to return to his activities – with care. The wound is allowed to heal for 4 weeks before the external parts are introduced to the child.  The young child is usually given a body processor but older children usually will be given an ear level speech processor.  Residual hearing in the implanted ear will most likely be lost although with recent technological and surgical improvements this side effect is no longer a certainty.   Because of the proximity of the surgery to the semi-circular canals, the individual’s sense of balance may be disrupted causing some dizziness. 

After the microphone and speech processor are activated, then the audiologist with work with the child to establish his individual “Map”.  Often, at first, the child, unaccustomed to sound, may become upset when the implant is turned on.  Mapping is the term that the audiologists have use to describe how the speech processor is programmed.  It is necessary to find the sound levels for each of the 22 electrodes, both the softest or threshold (T) level and the upper or comfort (C) level.  This process will take place over several months to refine the child’s Map.  At the same time the child is beginning to learn to identify and associate meaning to the new sounds that they are hearing.  They are beginning to build a foundation for speech and learning spoken language.  Therapy will help the child to interpret what he is hearing.  If the child was deafened so had a history of understanding sound and speech, however limited, this initial process is less complicated. 

How the Cochlear Implant Works

During the normal process of sound entering the ear, the outer ear takes the   acoustic energy, directs it towards the eardrum which vibrates, turning the acoustic energy into mechanical energy.  Sound in the form of mechanical energy moves through the middle ear to the cochlear where it is transformed into electrical energy.  It is electrical energy that is sent up the auditory nerve to the brain to be interpreted back to sound.  In the cochlea implant the electrodes take over the function of the hair cells in the cochlea.  High frequency sounds are decoded at the base of the cochlea that is the closest to the middle ear; low frequency sounds are decoded at the apex, further away. Because the electrodes lie along the length of the cochlea, it is possible to have a full range of sound.

The microphone, (1) worn at ear level, picks up the sounds in the environment and transmits it down a long cord (2) to the speech processor (3) a tiny computer approximately the size of a deck of cards which contains the child’s map of T and C levels.  The speech processor analzes and digitizes the speech/sound signals into coded electrical signals and transmits it back up the long cord to the transmitting coil (4) which has a magnet at its center.  This holds the coil directly over the internal receiver/stimulator (5) which lies under the skin, .  The information is then sent across the skin via FM radio frequencies.  This internal receiver/stimulator takes the information and determines which electrodes should be activated and with what power.  This process takes place at 1000 times a second and the child hears sound. 


   Movement of Sound via a Cochlear Implant on Its Way to the Brain

Sound picked up by microphone

Sound sent to speech processor

Speech processor filter, analyzes and digitizes sound into coded electrical signals

Coded signals sent from speech processor to transmitting coil via cable

Transmitting coil sends signals across skin to internal implanted receiver/stimulator via FM radio signals

Receiver/stimulator delivers stimulation to appropriate implanted electrodes

Electrodes stimulated, and sound carried to brain via auditory nerve

http://clerccenter2.gallaudet.edu/KidsWorldDeafNet/e-docs/CI/ModuleA.html

 

The Debate

Many professionals advise against the using of sign language when a child has been given a cochlear implant.  The reasoning behind this philosophy suggests that the child is then forced to be totally reliant on the auditory signal and learning to interpret and use the new information will occur more readily.  On the other hand, if the child was using sign language to communicate prior to the implant, to stop using sign language could cause unnecessary frustration added to any trauma the implant caused.  The educational environment should be able to be designed to facilitate the use of both sign language and auditory/oral stimulation that will help the child to maximize learning potential.  The use of one method need not preclude the use and benefits available from the other.  The obvious goal behind giving a child a cochlear implant is to give the opportunity to hear sound and actively integrate spoken language into his life.  How this is achieved needs to fit the individual child.

 

Hearing Aids

Hearing aids make sound (all sounds louder); they don’t restore normal hearing nor are they quite as efficient as glasses are for the individual who needs them.  Hearing aids come in a variety of sizes.  The audiologist will help determine which hearing aids would be the most beneficial for individual hearing losses. 

Parts of a Hearing Aid

     

www.bchealthguide.org

There are 3 major hearing aid types:

Analog Adjustable: amplify both speech and other sounds in equal volume.  They are the least expensive and although it is possible to control the loudness to some degree, there is little flexibility in adapting these hearing specifically to a very complicated hearing loss. 

Analog Programmable: contain a computer chip that allow the hearing aid to be more successfully programmed to individual hearing losses.  They can be programmed to adapted to several different environments: individual conversations, table conversation in a restaurant, telephone conversations, larger group meetings.  A remote control can be used to change the programmes.

Digital Programmable: are the most advanced of hearing aids.  They can analyze the environment and make adjustments to the sound.  They allow a greater flexibility in programming than do analog hearing aids.  They are also the most expensive.  Digital hearing aids do tend however provide a cleaner and clearer sound, especially which the presence of background noise.  However some Deaf and hard of hearing individuals continue to prefer their analog over the digital hearing aids.  It largely depends on the type of hearing loss and individual preferences.  Other people wear one analog in one ear and one digital in the other. 

Technology has progressed to such an extent that the large body hearing aids that once were worn are now a thing of the past.  There are essentially 3 styles of hearing aids available:  behind the ear, in the ear, and in the canal.  Below are a couple of diagrams of the parts of the ear, followed by the different styles of hearing aids.  

Behind-the-ear (BTE): are used for all types of losses, but especially the severe and profound hearing loss.  All the parts of the hearing aid are housed in the case which fits behind the ear.  A connecting tube channels the sound into the earmold and into the middle ear.

       

Hearing Aids at B.C. Children's Hospital

In-the-Ear (ITE): are generally used by those with mild to severe hearing losses.  The parts of this hearing are found in the case that sits at the entrance of the ear canal.  They are small which can make them more difficult to manage and because they would need to be changed regularly as a child grew, children rarely wear them.            *   

Hearing Aids at B.C. Children's Hospital

In-the-Canal (ITC): can be used by individuals with mild to moderate hearing losses.  The parts are housed in the case which fits entirely in the ear canal.  They are fitted to the shape and size of each ear canal. They also are not recommended for children because of the expense needed to continually change them as the child grew. 

         

 

CROS hearing aids (Contralateral Routing of signals):  When one ear has a profound hearing loss and will not benefit from the usual hearing aid, a CROS hearing aid can be worn and linked with either the behind-the-ear or in-the-ear hearing aids so that the sound signal from the one side can be transferred to the opposite hearing aid/ear.  The BTE or ITE hearing aid will then receive the sound signal from both sides of the head.  This gives the child/student/individual greater access to “surround” sound which in classrooms during discussions or in large meetings where many different people will be taking turns talking, can be a great benefit.  Localizing from where the sound originates, is a major problem for individuals with a hearing loss.  By the time they figure out from which direction the sound is coming from, they have missed much of what has been said, and then the speaker changes.  

 

Hearing Aids at B.C. Children's Hospital

B.C. Health Guide

Hearing Center Online

 

Communication Aids

There are many assistive devices that are available for the use of Deaf and hard of hearing persons to given greater and easier access to their environment whether for within the home or out in the community. 

www.chs.ca

www.widhh.ca

 

Hearing Ear Dogs Of Canada

Hearing Ear Dogs alert people who are hard of hearing to important sounds and bring a certain independence and confidence to their lives.  All programs are offered at no charge but future care and maintenance is the responsibility of the recipient. 

Basic Skills:

Typical Breeds

The program usually trains small to meduim sized dogs which, at the age of one year, demonstrate that they are friendly, active and willing to work.  The pup is either born at the Breslau Centre, or is donated to the Foundation.  They are placed in foster homes to live, in ordr to be socialized in different environments for their first year.

Training Program

When the dog is about one year of age, he is returned for an assessment and a medical examination.  Dogs which qualify, begin a six-month training program in a simulated home environment at the training centre.  Successful applicants undertake a two-week program to learn how to work and to bond with their new Dog Guide partner.  The dog can also be trained to respond to hand signals if the new owner signs.

Entering the Community

Certified Hearing Ear Dogs are distinguished by the internationally recognized bright orange harness which is stencilled with "Hearing Dogs of Canada".

www.dogguides.com  (on The Lions Foundation of Canada website)

www.dogsforthedeaf.org