Aural Rehab: Chapter 3 Cochlear Implants Part 3

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The Deaf community defines Deafness with a capital “D” as a

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as a culture rather than a disability

It is characterized by having its own language, American Sign Language (ASL)

Some individuals within the deaf community have voiced that they resent anyone trying to “fix a Deaf child.”

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Over the past 15 years, the National Association of the Deaf (NAD) has

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has softened its criticisms of cochlear implants.
However, despite all the evidence that demonstrate that children implanted at a young age received significant speech perception benefits, many still oppose implantation.

It is important that the implant team members be able to help parents make informed decisions taking into consideration Deaf culture issues.

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Once the evaluation and patient counseling have been completed and the decision has been made to proceed with the cochlear implant, the implant team may suggest that the patient go through

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the patient go through some pretraining

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With adults and older children the pre-training may include

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may include speechreading therapy and training in the use of communication strategies for communication breakdowns

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The cochlear implant surgery is completed under

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is completed under general anesthesia. Typically, the surgeon makes an incision behind the ear and drills a small area in the mastoid bone for the placement of the receiver stimulator and the insertion of the electrode array

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The electrode array (in cochlear implant surgery) is then threaded through the mastoid and the middle ear cavity and then

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and then inserted in the scala tympani of the cochlea through the round window

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Insertion depths (in cochlear implant surgery) can range up to

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can range up to 30 mm depending on the implant system being used. The operation normally ranges from one to three hours and often is done on an outpatient basis

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After surgical placement of the internal receiver/stimulator and the electrode array, the patient must wait approximately

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must wait approximately two to three weeks before the external head-set and speech processor can be fitted

This waiting period allows for healing of the incision area prior to placing the magnet on the sensitive surface where the external transmitter is placed.

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The initial fitting and programming of the cochlear implant, commonly called the

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commonly called the hook-up, usually takes 1½ to 2 hours

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During the hook-up, or fitting of the headset and speech processor, the audiologist must

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audiologist must program the speech processor using a specific manufacturer-designed diagnostic program

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telemetry

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Current implants have the capability of testing the integrity of the internal device

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Neural response telemetry (NRT)

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Allows the implant system to function as a miniature evoked potential system by sampling and recording action potentials generated by electrical stimulation

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Electrode voltages and impedances can be measured when

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when current is supplied through the system. In this manner the audiologist can check the internal device prior to programming the system

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In order to create the program, or MAP, for the speech processor, the audiologist must

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the audiologist must determine the electrical dynamic range for each electrode used

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The programming system delivers an electrical current through the cochlear implant system to each electrode in order to obtain the

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in order to obtain the electrical threshold and maximal level of current that is comfortably loud measures

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T-level or minimum stimulation level is

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is the softest electrical current that produces an auditory sensation by the patient 100 percent of the time

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C- level is the loudest level that can be

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that can be listened to comfortably for a long period of time

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Treatment Plans for Cochlear Implant Recipients

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The speech processor is then programmed or “mapped” using one of the several encoding strategies so that the electrical current delivered to the implant will be within this measured dynamic range between T- and C-levels.

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T- and C-levels are much easier to obtain on adults and older children with postlingual hearing loss.

Techniques for testing the T-levels in young children are similar to

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are similar to testing pure tone hearing thresholds, ranging from observational testing to conditioned play audiometry

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Using a team approach with two audiologists is very helpful when programming or mapping the cochlear implants of young children.
 
Obtaining the C-levels in children is

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is a challenging task, with the audiologist often relying totally on behavioral observation

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Neural Response Telemetry (NRT), Neural Response Imaging (NRI), or Auditory Response Telemetry (ART) are

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are objective techniques that can be used to estimate the dynamic ranges in young children or difficult-to-test patients

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NRT, NRI, and ART offer a means of

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offer a means of testing the compound action potential of the nerve using two of the electrodes in the array as recording electrodes and two as stimulating electrodes. No additional equipment is necessary. From these measures, T- and C-levels can be estimated

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With children, audiologists will often evaluate only a limited number of

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only a limited number of electrodes spaced throughout the electrode array during the initial hook-up and either estimate the levels for the other electrodes or only include the tested electrodes in the initial program

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After T- and C-levels are established and the MAP is created, the microphone is then

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the microphone is then activated so that the patient is able to hear speech and sounds in the environment

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The initial reaction to speech varies among patients. Most adults describe speech as sounding mechanical and cartoonlike.

Children often react with

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often react with tears. This is understandable, considering that they may have no concept of what sound and hearing are and may find the stimulation frightening

Often they are hearing their own voice, including their crying, for the first time. As they are calmed down, they often realize that when they stopped crying, the stimulation stopped. This can be the first step to auditory awareness.

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Acclimatization to sound

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Adaptation to sound stimulation that changes the measured T- and C-levels allowing the individual to tolerate higher levels

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The patient and family should also be instructed on the daily care and maintenance of the system. They must know how to

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They must know how to place the processor and coil on the head, change batteries, manipulate the controls, and troubleshoot the unit.

Parents need to be shown how to check the system prior to putting it on the child. Spare cords or cables should be supplied.
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Suggestions on wearing the units using

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using clips, belts, or harnesses should be given. Accessories should be explained and demonstrated.

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Warnings on the dangers of electrostatic discharge (ESD) should be given, as well as any other safety factors. Static electricity can

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can corrupt stored programs or, in rare cases, cause damage to the internal unit when the external device is being worn.

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Parents are told to remove the device when their child

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when their child plays on plastic slides or on other static-generating materials. Warranty and loss and damage insurance information should be covered.

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second programming session is usually performed within one week of the initial hook-up. Review of the patient diary and experiences with the implant are helpful in determining if

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are helpful in determining if the programs provided sufficient power for sound awareness and detection or if any sounds were uncomfortably loud, indicating that the C-levels were set too high.

During this visit, the T- and C-values are reevaluated, and new MAPs are placed in the processor.

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Auditory training methods such as speech tracking are extremely helpful in

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are extremely helpful in both treatment and monitoring progress with the device. Various therapy materials are available to the clinician through each of the implant manufacturers.

Software programs, such as Sound and WAY Beyond® and Earobics®, are available for both children and adults and can be used both in the clinic and at home.

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The amount and length of therapy with the cochlear implant depend on the patient, but all cochlear implant patients regardless of age will

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will benefit from an audiologic therapy plan based on their needs

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In many cases, the implant user will receive device programming and monitoring at the cochlear implant center and other audiologic re/habilitation and speech–language therapy through

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through their schools or local audiologists and therapists

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A coordinated effort on the part of all professionals and parents is very important in developing and implementing the treatment plans.

Programming follow-ups for adult patients with postlingual hearing loss usually consist of

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usually consist of approximately six visits in the first two months of use, then at three months, six months, and annually thereafter

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For young children, the programming schedule suggested is weekly visits for two months, then at six months, nine months, and every six months thereafter.

These schedules can be modified to include

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can be modified to include more or fewer visits depending on the person’s adaptation to the implant, auditory responsiveness, and ease of programming.

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Variables Affecting Performance

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As stated previously, patient performance varies greatly among cochlear implant users. Many users are able to achieve open-set speech recognition even in the presence of background noise, whereas some patients receive only improvement in their speechreading abilities and awareness of environmental sounds.

Age of onset, length of deafness, age of implantation, length of implant use, etiology of the hearing loss, nerve survival, mode of communication, cochlear implant technology, surgical issues, audiologic re/habilitation methods, and motivation are examples of variables that affect success with the implant.

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Some of these are known factors, such as age of onset and length of deafness. Studies have shown that the shorter the length of

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that the shorter the length of severe-to-profound hearing loss and better the pre-implant discrimination score, the better the prognosis for benefit from the cochlear implant

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Others are unknown quantities for Variables Affecting Performance

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such as the amount of nerve survival, both prior to and following surgical insertion of the electrode array. Patients, parents, and significant others need to be made aware of the many variables that can affect performance

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Bilateral Hearing with Cochlear Implants

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Recent studies have shown that some of the benefits of binaural hearing such as localization and improved hearing in noise can be accomplished using bimodal hearing when the patient wears a hearing aid in the ear opposite the cochlear implant .

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Research has indicated that the hearing aid, even in cases with profound hearing loss, can provide

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can provide the patients with prosody information that cannot be provided by current generation implants.

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Prosody

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or suprasegmental information includes rhythm, stress, and intonation that can help in understanding in noise, music appreciation, and hearing emotion in speech

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Even patients with a corner audiogram can receive some benefit from

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some benefit from a hearing aid in the opposite ear to supplement what they are receiving from the cochlear implant

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hearing aid trial in the opposite ear is recommended for all patients receiving unilateral cochlear implants.
Bilateral cochlear implantation is becoming

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is becoming more common worldwide and has also shown significant improvement in localization and hearing in noise in adults

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binaural benefits in children have also demonstrated

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have also demonstrated improved localization abilities and improved speech understanding in noise. The possible benefits of bilateral cochlear implantation must be weighed against the possible disadvantages

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The cost of bilateral implantation will be

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will be $60,000 to $80,000 greater than with a unilateral cochlear implant

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Studies on the cost effectiveness of bilateral cochlear implantation in the pediatric population have found

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population have found mixed results in that there was an improvement in quality of life with the second implant, but its cost effectiveness was questionable. Monetary costs are not the only consideration.

Surgical risks are also increased. In addition, one must consider the possibility that some future device may be developed that could only be used in an ear that had never had an implant.

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With the rapid changes in technology, if the child only has the implant in one ear, the other ear would be

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would be available so the new procedure could be performed.

When reviewing the options for a young child whose expected lifespan is 70 to 75 years, the importance of keeping one ear open for future options needs to be considered.

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The decision between bimodal stimulation or bilateral implantation must be made on

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must be made on an individual basis

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In children, Litovsky (2006) found children with bilateral implants could

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localize better than unilateral users, but some of the bimodal (using hearing aid) children could perform localization tasks at the same level that the average bilateral user functioned

More research is needed to determine the best way to afford bilateral listening to the cochlear implant user.

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Currently, many clinics recommend unilateral cochlear implant surgery with the use of a hearing aid in the opposite ear. If, after a trial period, the patient does not receive any benefit from the bimodal condition compared to the cochlear implant alone condition,

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, a second implant should be considered.

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Some clinics are recommending simultaneous bilateral implantation

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(both ears during the same surgery) for infants and young children with bilateral profound hearing loss so the child has the best possible hearing for the development of speech and language.

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Others are recommending a trial with bimodal stimulation to allow the child the ability to hear

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to allow the child the ability to hear prosody information from the hearing aid during the early development of speech and language before receiving a second cochlear implant (Nittrourer & Chapman, 2009).

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Bilateral implantation would then be considered if

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would then be considered if testing shows no benefit from the hearing aid in the opposite ear.

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auditory brainstem implant (ABI) has been developed for individuals with

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has been developed for individuals with neurofibromatosis who are deafened from bilateral VIII nerve tumors.
 
The implant is placed on the cochlear nucleus of the brainstem during the surgery to remove the tumor.

To date, over 600 patients have received the ABI, and in early November 2000, the Nucleus 24 ABI was approved by the U.S. FDA for use in cases of neurofibromatosis for patients over the age of 12 years

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Results with this implant are similar to early generation multi-electrode implants and show promise to those

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show promise to those who have not been able to benefit from cochlear implants because they lack functioning VIII nerves.

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Advances in cochlear implants are

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are occurring rapidly in design, programming techniques, coding strategies, and determining candidacy

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Both internal and external devices are becoming smaller. The introduction of behind-the-ear speech processors has provided

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has provided cosmetic advantages that are particularly attractive to adolescent and young adult users.

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Electric-acoustic stimulation is

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is currently being investigated. Many individuals have usable hearing in the low to mid frequency range but have no hearing in higher frequencies. These people with “dead regions” of the cochlea receive little to no high-frequency information from hearing aids.

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With electric-acoustic stimulation, the cochlear implant electrode array is placed only in the

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is placed only in the basal portion of the cochlea and programmed for high-frequency sounds

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At the same time, the low to mid frequencies are amplified using

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frequencies are amplified using standard hearing aid technology. This cochlear implant/hearing aid combination could help many individuals who currently do not qualify for cochlear implants but are dissatisfied with their hearing aids because the higher pitches cannot be amplified.

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Both MED-EL and Cochlear Corporation have active clinical trials investigating the benefits of electro-acoustic stimulation. The term Hybrid© cochlear implant refers to the

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refers to the Cochlear Corporation system, whereas MED-EL simply refers to it as electrico-acoustic stimulation.

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Patients have significantly better speech recognition in both quiet and noise with electric-acoustic stimulation, but in a carefully controlled multicenter study with eighty-seven patients, eight patients have

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lost all of their residual acoustic hearing and seventeen had significant loss of their residual acoustic hearing due to the surgery

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Improved surgical techniques designed to preserve acoustic hearing are being developed so that

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so that this technology can be made available to patients in clinical settings.