![[Layout Image: No Content]](Images/Clerc/v2_header_LCC.jpg)
![[Layout Image: No Content]](Images/Templates/gu_nav_sectional_bottom.gif)
Factors Influencing Performance
 Performance |
|||
By Debra Nussbaum, M.A., CCC-A/March 2003
Cochlear Implants: Navigating a Forest of Information...One Tree at a Time in PDF (113 pages, 1.35 mb)
Factors Influencing Performance in PDF (11 pages, 355 kb)
Factors Influencing Performance
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); and
- provide improved speech perception for many children with intensive training.
A cochlear implant DOES NOT:
- interpret sound or
- provide guaranteed potential to understand complex connected spoken language.
The process and ultimate outcome of "making sense" of the sound available through a cochlear implant is individual to each child. Learning to listen and speak 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 skill development than others.
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.
The process and ultimate outcome of "making sense" of the sound available through a cochlear implant is individual to each child. Learning to listen and speak 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 skill development 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 (see Training the Ear to Listen).
Factors Impacting Performance
Performance outcomes related to listening and speaking depend on many complex and interactive factors. Each of the factors listed below should be taken into consideration as decisions are made for a child related to language and communication planning, educational placement, and listening and speech training. (See Choosing a Communication Methodology, Choosing an Educational Setting, and Considerations for the Use of Sign Language.)
Research and observation suggest that spoken language performance outcomes are best for those who are implanted very young when language is typically developing. This is the time when the brain most readily masters language. For children implanted at the youngest ages (prior to 18 months), spoken language appears to emerge most naturally. As children are implanted at progressively later ages, outcomes and rate of development are varied. (McConkey Robbins, A., Burton Koch, D., Osberger, M.J., Zimmerman-Phillips, S., & Kishon-Rabin, L. (2004). Effect of age at cochlear implantation on auditory skill development in infants and toddlers. Journal of Otolaryngology-Head & Neck Surgery, 130, 570-574.)
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." Younger children with implants tend to acquire spoken language readily in natural listening environments. Even with early implantation and natural exposure to spoken language, opportunities for structured auditory and speech-training may also be beneficial to promote optimal benefit from the cochlear implant.
For further discussion regarding implantation of young children, see:
Cochlear Implantation Below 12 Months Of Age: Challenges And Considerations and Cochlear Implantation in Children Younger Than 12 Months.
For children who are implanted after the early language learning years, "success" may need a broader definition. For later implanted children, observation and research suggest that while there is increased benefit from a cochlear implant in comparison to traditional hearing aids, existing auditory delays at the time of implantation present a continued educational and rehabilitation challenge. Pre-lingually deaf children implanted beyond the language learning years may enjoy their implant, however, they may not progress to the highest levels in the hierarchy of auditory and speech development. This is not to say that a cochlear implant may not be an appropriate choice for an older pre-lingually 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.
Research suggests the importance of keeping the auditory neural pathways stimulated prior to implantation or these pathways will be utilized by other senses and then become unavailable to benefit listening if implantation is chosen at a later time. For further information on the auditory plasticity of the brain, see the research being completed at the Auditory Cortical Function Laboratory at the University of Texas at Dallas.
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.)
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 excellent outcomes with a cochlear implant. This appears to relate to past imprinting or memory for this information. Older children who have had limited listening experiences require more time and structured approaches to facilitating spoken language for sound to become meaningful.
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 vary.
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 may 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.
Increasing numbers of children with the diagnosis of auditory neuropathy or auditory dys-synchrony are obtaining cochlear implants. These conditions involve a type of hearing loss beyond the outer hair cells of the cochlea, either in the inner hair cells (responsible for converting sound vibrations into electrical signals), or at a higher neural level in the hearing system. Depending on where the dysfunction occurs in the auditory system, there appears to be differing degrees of benefit from implantation. It is important that a complete battery of diagnositic evaluations be completed prior to proceeding with a cochlear implant for individuals with this condition. For further information about the importance of including an Electrical Brainstem Response Evaluation (EABR) as part of a test battery to predicting cochlear implant success with this diagnosis, see: Gardner-Berry, K. , Gibson, W., & Sanli, H. (Nov. 2005). Pre-operative testing of patients with neuropathy or dys-synchrony. Emerging trends in cochlear implants. The Hearing Journal, No. 11.
For more information about auditory neuropathy, see:
National Information Center on Deafness and Other Communication Disorders
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.
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 a repeated need to adjust to incoming sound which will delay progress.
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. Improvements in speech-processing computer software for the external parts of the cochlear implant have made the implant better able to approximate characteristics of true listening. Children who are 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 when the devices had fewer channels and less sophisticated speech processing capabilities.
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." (See Fitting the Speech Processor.) 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.
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 language and communication functioning of the child. (See: Choosing a Communication Methodology and Choosing an Educational Setting.)
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.
