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The Benefits and Limitations of Cochlear Implants

There are varying levels of skill a child with a cochlear implant may demonstrate ranging from basic awareness of sound to understanding of complex connected language. Where a child falls in the continuum of skills depends on many complex and interactive factors that must be taken into consideration as plans are made for educational placement and listening and speech training. What does it mean when it is said that a child with a cochlear implant can "'hear"?

A cochlear implant CAN:

  • provide access to sound by bypassing the damaged or destroyed hair cells in the cochlea, thereby enabling the user to perceive sound;
  • convert sound into electrical signals and send these signals to the auditory nerve and then the brain;
  • provide more access to speech information than traditional hearing aids (digital or transpositional);
  • provide improved speech perception for many children with intensive training; and
  • allow a significant portion of profoundly deaf children useful hearing and speech.

A cochlear implant DOES NOT:

  • interpret sound,
  • provide full access to spoken language for all, or
  • provide enough benefit to allow a child born profoundly deaf to learn spoken language as easily or as quickly as is typical for a hearing child.
"I'll try to make a visual picture that relates to the way sound is heard by a child with a cochlear implant. Suppose that you have to identify a four-legged animal, and youve not seen that animal before but you have to figure out what it is. Maybe you have to draw it. Maybe you have to learn the name for it. Now, that animal is standing behind a bunch of trees. To see that animal, you have to look through tree trunks that are hiding big parts of that animal. Now, if you were looking through those trees with the equivalent of a hearing aid, you could probably only see the tail end of that animal, because you could only hear the low frequencies with that hearing aid. With a cochlear implant, though, you could see pieces of that animals head, pieces of its neck, its legs, its body, and pieces of its tail end, but you still would be missing pieces in between each of those that you could see. The reason Im bringing this up for you to think about is because its important for us to realize that children who are using cochlear implants still dont see the whole animal. They see more of a range of that animal, but they have to use their brains. They have to use what they already know about the world. They have to use their cognitive abilities to fill in those gaps to be able to put together a picture of that whole animal. Thats the kind of task that a child is facing using a cochlear implant."

Dr. Patricia Spencer. Considerations for the Future: Putting It All Together, Presented at Cochlear Implants and Sign Language conference, April, 2002.

Performance: Things to Keep in Mind

Outcomes will vary for each child. Complete understanding of spoken language, similar to hearing children, may not be the outcome for all children with cochlear implants. Based on the factors discussed below, some children may obtain this outcome while others may not. Unfortunately, it is often not possible to predict how a child will function.

Developing effective listening skills is a process. The process of "making sense" of the sound available through a cochlear implant is individual to each child. It is unrealistic to think that each child will understand what he or she hears immediately or soon after his or her implant is "hooked up." Even children who have listening experience prior to cochlear implantation may encounter an adjustment time learning to listen "electronically" as opposed to "acoustically." In fact, some children with good listening skills through their hearing aids prior to cochlear implantation seem to regress temporarily as this adjustment occurs. Learning to listen is sequential, one skill building upon another. Moving through the sequence happens more readily for some children than for others. In addition, some children move higher in the hierarchy of skills than others.

These hierarchies are examples of the levels of competency a child may obtain with his or her cochlear implant. Progress in moving through these hierarchies requires training by therapists, family, and teachers who understand how to facilitate these skills.

Factors Impacting Performance
These factors impact on each child's progress with his or her cochlear implant:

  • age of implantation,
  • pre-implant duration of deafness,
  • age-appropriate sign or spoken language competence,
  • previous listening experience,
  • status of cochlea,
  • cause of hearing loss,
  • family support and motivation,
  • consistency of usage,
  • cochlear implant technology,
  • appropriate programming of device,
  • additional special needs, and
  • quality and consistency of educational and habilitative environment.

Age of Implantation
Research and observation suggest that spoken language performance results are best for those who are implanted prior to age 3. This is the time when the brain most readily adapts and masters language. For children implanted at the youngest ages (prior to 18 months), spoken language appears to emerge most naturally. Based on the outcomes observed in many young implanted children, it appears that the simulated sense of hearing offered through a cochlear implant can offer an excellent opportunity for a child to progress in language "developmentally" rather than "remedially." It still appears, however, that opportunities for structured auditory and speech-training activities are integral to promoting optimal benefit from the cochlear implant for even very young children.

While early cochlear implantation appears to be most optimal for ease of developing spoken language skills, there are still many benefits to implantation for children who are implanted after the early language learning years. For children who are implanted after the early language learning years, "success" with a cochlear implant may need to be defined in a different way. Observation and research suggest that while there is increased benefit from a cochlear implant in comparison to traditional hearing aids, for later implanted students, existing auditory delays at the time of implantation present a continued educational and rehabilitation challenge. This is not to say that a cochlear implant may not be an appropriate choice for an older child, it is just to say that expectations should be guarded and realistic related to outcomes.

Pre-implant Duration of Deafness

The shorter the period of time from the identification of deafness to the time of cochlear implantation, the easier it tends to be to develop spoken language. It appears that the less time the auditory channels remain dormant and unused, the greater the chance for these pathways to be ready and open to accept the new incoming information available through the cochlear implant.

Language Competence

As discussed in Early Beginnings for Families with Deaf and Hard of Hearing Children: Myths and Facts of Early Intervention and Guidelines for Effective Services by Marilyn Sass-Lehrer, "When parents and children communicate effectively with each other from the very start of a hearing loss identification, a foundation for language acquisition (both spoken and signed language) is established and language delays may be prevented or minimized (Yoshinaga-Itano, 2000)." This also applies to students who obtain cochlear implants. It appears that those children who have a strong language foundation (whether signed or spoken) prior to getting a cochlear implant have an easier time developing spoken language through their implant (Tait, M., Lutman, M., and Robinson, K., 2000). Pre-implant Measures of Preverbal Communicative Behavior as Predictors of Cochlear Implant Outcomes in Children, Ear and Hearing.)

Previous Listening Experience

Children who lose their hearing after language has developed, and those children who have had meaningful auditory experiences with a hearing aid prior to implantation, typically demonstrate quicker initial success with a cochlear implant than children who have been deaf from birth. This appears to relate to past imprinting or memory for this information. Children who have never heard before appear to require more time and structured approaches to facilitating spoken language for sound to become meaningful.

Status of the Cochlea

Sometimes the cochlea is insufficiently formed or may have developed an ossification (bony growth). These conditions may impede adequate insertion of all of the electrodes to make the cochlear implant most effective. In these situations, cochlear implantation may still be an option, but outcomes may be impacted.

Cause of Hearing Loss

Some of the associated secondary conditions arising from varying causes of deafness may influence the degree of benefit a child may actualize from a cochlear implant. For example, some children with hearing loss from cytomeglavirus (known as CMV) have demonstrated additional auditory processing problems. If a child has problems decoding sound that is not specifically related to the listening mechanism, but rather the interpretation of sound in the brain, the implant will not remedy this situation. Also, as mentioned before, meningitis produces ossification, causing inconsistent insertion of the electrodes into the cochlea and hence inconsistent benefit may be actualized from an implant.

Family Support and Motivation

Many doctors and educational professionals observe that the children who are most successful with their cochlear implants (regardless of many of the other discussed factors) have strong family involvement and support. Families who are integrally involved in providing a rich listening and language environment and helping a child to receive all of the necessary supports to promote use of the implant seem to positively impact on a child's potential to maximize implant outcomes.

Consistency of Usage

The cochlear implant must be used consistently if a child is going to demonstrate ongoing progress with the implant. If periods of time pass without implant stimulation (even a few days), there appears to be continued need to adjust to incoming sound which will delay progress.

Cochlear Implant Technology

Implant manufacturers are continuing to refine and improve the technology of the cochlear implants themselves. In recent years, the internal device, surgical techniques, and speech-processing capabilities have greatly improved. Enhanced opportunities for greater numbers of electrodes to reach and stay positioned in the necessary parts of the cochlea have improved outcomes with cochlear implants in relation to earlier devices. Improvements in speech-processing computer software for the external parts of the cochlear implant have also made the implant better able to approximate characteristics of true listening. Children who have been implanted with the more current technology appear to have increased potential with their cochlear implants in comparison to children implanted during the early advent of cochlear implants with few channels and less sophisticated technology.

Appropriate Programming of Device

The external components of each cochlear implant must be programmed specific to each individual. This program is referred to as a "map." Obtaining an appropriate map takes numerous appointments and ongoing modifications. Especially with young children, determining an appropriate map is as much of an art as it is a science.

It is imperative that a child's functioning with a map be closely monitored or a child may not be able to "hear" at his or her potential. As the brain adjusts to sound, what may have at first been comfortable and "loud enough" becomes insufficient and "not enough." This acclimation to sound may be clearly apparent or can sometimes go unnoticed, similar to a light on a dimmer that grows dim so slowly as to almost be imperceptible until it becomes too dark. A child may also inadvertently have electrodes that have been set for too much stimulation causing discomfort. If this occurs and is not remedied, the child will see listening as a negative experience and may resist using the cochlear implant. If a child is functioning with an inadequate map, this will negatively impact on progress with the implant.

Additional Special Needs

Children may have additional learning or behavioral issues that may impact on the rate of progress and outcomes with a cochlear implant. Some children may be implanted taking these issues into consideration. Some children may be so young when they obtain a cochlear implant that it is impossible to know if additional issues will be a factor. When possible, it is important to look at additional special needs and to figure out to what degree they will impact a child's functioning with an implant as plans are made for appropriate educational programming. Families and specialists should always be on the look out for issues secondary to deafness and cochlear implants that may be impacting on a child's development.

Quality of Educational and Habilitative Environment

Children with cochlear implants may be in a variety of educational environments using a variety of communication approaches. Regardless of program type and methodology, success with an implant will be positively impacted by the consistency and quality of spoken language use that is integrated into a child's program. Determining the best strategies to address integration and use of spoken language for each child should be individualized and based on the current language and communication functioning of the child. It is important that the communication environment and support services are designed to challenge, yet not overwhelm, the child.

In Summary

While it is never possible to predict how any one child will do with a cochlear implant, prognosis for the greatest success for spoken language development with an implant appears to be positively impacted by the following factors:

  • short duration of deafness;
  • early identification of hearing loss followed by early amplification, language stimulation (spoken or signed language), and early implantation;
  • good prior listening experience and speech perception skills (for later-implanted students);
  • at least average cognitive skills and good attention skills; and
  • home and school environments that provide extensive exposure to spoken language.

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