T H E J O U R N A L OF
PEDIATRICS JANUARY
1991
Volume 118
Number 1
MEDICAL PROGRESS Status of cochlear implantation in children American Academy of Otolaryngology-Head and Neck Surgery Subcommittee on Cochlear Implants,* with John Kveton, MD, Principal Author, and Thomas J. Balkany, ME),Chairman The cochlear implanl is a medical device, part of which is placed surgically, that uses electrical stimulation to provide hearing. For almost a d e c a d e , investigational studies have been ongoing to define its safety and efficacy in profoundly deaf children. During this period, more than 500 children a g e d 2 through 17 years have been implanted with either a single-electrode or multielectrode device. Extensive auditory, speech, educational, and psychologic testing has been performed before and after implantation. Results show that the cochlear implant provides auditory detection over much of the speech signal. C o m p a r e d with the preimplant period, there is significant improvement in auditory discrimination and speech production skills. Limited open-set word and sentence recognition is possible for at least some children. Complications with the device have been minimal. The cochlear implant can provide sound to deaf children unable to benefit from hearing aids. The complex assessment, rehabilitation, and parent counseling should be performed by centers with the multidisciplinary staffs necessary to provide effective care for patients with this specialized auditory prosthesis. (J PEDIATR1991;118:1-7) A cochlear implant is a prosthetic device used to produce the sensation of sound by electrically stimulating the auditory system. It is for those hearing-impaired persons who cannot benefit significantly from conventional hearing aids. The recent U.S. Food and Drug Administration (FDA) apprOval for the general use of implants in children refocuses our concern on the profoundly hearing-impaired child. The first 5 years of childhood involve speech and language acquisition, as well as development of emotional, social, and
academic skills. Adequate hearing is critical in this stage of development, and the implications of deafness are serious. In contrast to a normal-hearing 5-year-old child, who will have a vocabulary of 5000 to 26,000 words, a profoundly hearing-impaired child of the same age typically has a vocabulary of 200 words. 1 Fifty percent of children with hearing loss greater than 85 decibels hearing level have no reading comprehension, and the average reading achievedB HL dB SPL
Reprint requests: John F. Kveton, MD, Associate Professor of Surgery, Yale University School of Medicine, Section of Otolaryngology, 333 Cedar St., New Haven, CT 06510. *Karen 1. Berliner, PhD, Bruce Gantz, MD, Noel L. Cohen, MD, Robert Jackter, MD, William Luxford, MD, Richard Miyamoto, MD, Edwin M. Monsell, MD, PhD, Joseph Nadol, Jr., MD, Michael Novak, MD, and James Parkin, MD. 9/18/24667
Decibelshearing level Decibelssound pressure level
]
I
ment for hearing-impaired 16-year-old adolescents is at the third- or fourth-grade level. 2 Speech development can be related to the degree of hearing loss; deficits occur in duration, intensity, and pitch of speech as well as in articulation of specific sounds) Serious delays occur in language development, including vocabulary, syntax, and word structure,
1
2
Kveton and Balkany
The Journal of Pediatrics January 1991
External Cod
/
Inlernal Coil
Speech Processor
ernal Electrode
,/
4
71ear Nerve
Fig. t. Typical cochlear implant system, showing surgically implanted internal receiver and electrodes and externally worn microphone, signal processor, and transmitter. simply because the child cannot experience the parents' language. This is particularly so for those who are deaf before the age of 2 or 3 years (prelingual deafness). Pragmatic skills such as requesting information or clarification, making commands, and social interaction are also delayed. Even children who have acquired some speech and language skills before they become deaf (postlingual deafness) may lose many of those skills, especially if deafened before 5 years of age. Children with mild to severe hearing losses are treatable with conventional hearing aids. However, until the past decade, the profoundly hearing-impaired child was left with little potential for sound stimulation. The development of the cochlear implant has changed this situation. Although use of the device is rapidly becoming accepted by hearing health care professionals, some concerns remain regarding implantation in children. 4 These include the difficulty of evaluating the young child's hearing loss and assessing performance of children with profound hearing loss, the effect of implantation on the child's development in comparison with the results of traditional types of training, the risks of implantation (both intraoperatively and for the long term), the effects of implantation on the auditory system, and the challenges of effective programming of sophisticated devices in young children. The purpose of this article is to review the current "state of the art" regarding cochlear implantation in children and to report the results obtained in clinical trials. Some of the data available address the concerns regarding pediatric implantation; long-term issues will be answered only slowly. DEVELOPMENT
OF COCHLEAR
IMPLANT
Although interest in electrical stimulation of the cochlea to produce auditory sensation began in the 1950s, develop-
merit and production of an implantable cochlear prosthesis did not occur until the 1960s through independent investigations by House, Simmons, and Michelson. Several histories, edited works, and review articles are available to describe both the early work and subsequent results. 57 Two patients received implants of single gold-wire electrodes and one of a multiple-electrode system as early as 1961 by House. In 1964, Simmons reported implanting a six-electrode array into the cochlea of a volunteer subject and made early discoveries in electrode-specific, or "place pitch", stimulation. Michelson developed a suitable animal model to evaluate electrical stimulation and placed implants in several deaf adults in the late 1960s. In 1973 a clinical trials program began at the House Ear Institute under the direction of Dr. William House. From 1974 to 1979 a total of 31 patients received a singleelectrode implant. In December 1980, pursuant to new medical device regulations, the FDA approved an Investigational Device Exemption application. Clinical trials were extended to a multicenter, coinvestigator program. The 3M Company modified the House single-electrode cochlear implant in 1982, and by 1984 data on 369 prelingually and postlingually deaf adults from 36 coinvestigators were evaluated by the FDA. Marketing approval for the first cochlear implant was granted in November 1984. During this period, several other implantable cochlear prostheses were in various stages of development, including multielectrode, multichannel devices. One of these, the Nucleus 22 Channel Cochlear Prosthesis (Cochlear Corp., Englewood, Colo.), received marketing approval from the FDA in 1985 for postlingually deaf adults. Other devices have been available on an investigational basis, and one, the Ineraid multichannel implant (Richards, Memphis, Tenn.), is approaching marketing approval for use in adults.
Volume 118 Number t
On the basis of experience with adults, the House Ear Institute began placing implants in children in 1980, later adding seven coinvestigator teams across the country. These clinical trials include medical, audiologic, speech, language, and psychologic evaluations both before implantation and at regular postimplantation intervals. As of April 1988, a total of 289 children ranging in age from 2 through 17 years had undergone implantation with the 3M/House singlechannel implant.8 A premarketing application was submitted to the FDA and received a recommendation for approval from the FDA ENT Advisory Panel. Final steps for approval have not been taken. The 22-electrode Nucleus .device has been used in clinical trials with children since 1985, and 263 children aged 2 to 17 years have received implants.9 This device has also recei,~ed an FDA advisory panel recommendation for approval and received formal approval for marketing in June 1990. DEVICE DESCRIPTION All cochlear implants have two major components, the internal, or implanted, component and the external component, which is worn on the body (Fig. 1). The internal component consists of one or more electrodes implanted into or on the cochlea and an internal receiver embedded into the temporal bone above and behind the auricle. The distance of insertion of intracochlear electrodes depends on the type of device used but can be up to 25 ram. The external components consist of a microphone, external transmitter, and signal processor. The signal processor is responsible for transforming the sound stimulus received from the microphone and preparing it for transmission to the external transmitter and then to the internal receiver. In the 3M/House device, the incoming sound from the microphone amplitude modulates a 16 kHz carrier wave in the signal processor, and this amplitude-modulated signal is sent to the external transmitter, l~ It is transferred to the internal receiver by electromagnetic induction. In the more complex Nucleus 22-channel device, the incoming sound is analyzed by the signal processor into fundamental acoustic information representing key elements in human speech. 11 The analysis results in coding for the appropriate electrode, current amplitude, and stimulus rate. This information is sent to the external transmitter. The processed signal is sent transdermally via radio frequency transmission to the internal receiver. In the multielectrode system, the message is decoded so that separate bipolar pairs of the 22 electrodes can be activated to stimulate segments of the auditory nerve. Other cochlear implants use different types of signal processing or different forms of transmission, or both, across or through the skin. In each case, some form of a simplified or coded representation of speech and environmental sounds
Status o f cochlear implantation in children
3
Frequency (Hz) 125
250
500
1000
2000
Im lant
(Mean)
4000
8000
-10 0
01 (O (3} y-
10
s Z
50
_J 01 r-,
60
70 80
"lOO "10
Nil
90
100 110
( )
_
NR
NR
9
~i~cl;Mean)
120
I
[
NR
NR
Fig. 2. Audiogram for typical cochlear implant candidates, showing unaided and hearing-aid warble tone thresholds in relation to average speech spectrum. Also shown are average thresholds with cochlear implant. NR, No response; ANSI, American National Standards Institute. (From House WF, Berliner KI, Luxford WM. Curt Probl Pediatr 1987;17:345-88.)
is provided for the deaf patient through an electrical stimulus. CANDIDATE SELECTION Although more complex than in adults, candidate selection can be achieved in children. Through a combination of behavioral audiometric testing and the more objective auditory brain-stem response testing, good estimation of the child's hearing loss can be obtained. Once identified, the hearing-impaired child is fitted with appropriate hearing aids and assessed according to well-defined frequency and intensity levels for communication performance (Fig. 2). If the child's auditory detection is not comfortably within the speech range, a full evaluation for applicability of an implant is performed. A graded series of tests evaluates progressively more complex speech skills and includes speech awareness thresholds, uncomfortable loudness levels, warble-tone thresholds at frequencies ranging from 250 to 4000 Hz, simple speech discrimination testing, and auditory comprehension of environmental sounds and speech. A history of use of appropriately fit hearing aids is required. A trial with hearing aids or a vibrotactile device may be initiated if this requirement has not already been met, and testing is repeated after a period of training. If little or no significant benefit is demonstrated with hearing aids or a vibrotactile device, particularly in an auditory-only test mode, the cochlear implant is
4
Kveton and Balkany
an appropriate alternative. Performance on discrimination tests, in particular, is compared with results in persons with successful implants. 12' 13 Candidate selection for a cochlear implant, whether the candidate is an adult or a child, rests not merely on the results of auditory testing but on medical and psychosocial factors. The routine history taking, physical examination, and laboratory evaluation that precede standard middle ear surgery are performed. Radiographic studies using computed tomography are performed to determine the patency of the cochlea, identify congenital malformations of the ears, and assess surgical anatomy. Magnetic resonance imaging is not practical for examining implant candidates; it shows little bony detail and an insufficient portion of the membranous inner ear. (With improvements and the use of surface coils, magnetic resonance imaging may become more useful in examining the membranous inner ear and detecting cochlear fibrosis.) Bone formation in the round window or scala tympani does not necessarily preclude surgery. Congenital malformations (such as the Mondini deformity) that alter the usual tonotopic organization of the cochlea may limit the benefits of implantation. Extreme congenital anomalies (i.e., absence of cochlea or auditory nerve) would exclude a child from implantation. The psychosocial considerations for a successful candidate include (1) no evidence of severe organic brain damage, (2) no evidence of psychosis, (3) no evidence of mental retardation, (4) no behavioral-personality traits that would make completion of the program unlikely, (5) no unremitting, unrealistic expectations about the implant on the part of the family, and (6) a pattern of parent-child interaction that indicates that the family will be able to follow the postimplant rehabilitation program effectively. Parents must be willing to spend extra time with the child, carrying implant-oriented exercises into their daily interaction with the child. The child's educational setting not only must be open to accepting a child with a cochlear implant but should be willing and able to adapt educational methods to enhance implant performance. Both parental and educational support are considered in the decision for implantation. SURGICAL
PROCEDURE
The cochlear implant is placed according to conventional surgical techniques developed to treat chronic middle ear disease. The cochlea is adult sized at birth, and, in general, the middle ear, eardrum, and ossicles are also adult sized. The surgical approach through the mastoid, facial recess, and round window leaves the ear canal wall intact and provides direct access to the scala tympani. The surgery is performed with the child under general anesthesia. A large postauricular incision is made; a seat is
The Journal of Pediatrics January 1991
made in the temporal squama for the internal receiver; a mastoidectomy is performed; the facial recess is opened and the lip of the round window niche is removed; the internal receiver is placed in the bony seat and sutured into place; the electrode array is inserted through the opening of the round window into the scala tympani; fascia is packed around the electrode at the round window and at the facial recess; and the postauricular flap is closed in layers. Surgery lasts about 1I/2 hours, and the patient is usually discharged from the hospital the day after surgery. A period of 1 to 2 months is allowed for healing and resolution of swelling over the receiver before the initiation of electrical stimulation. REHABILITATION After the healing period, the child must return to the implant center frequently for fitting and adjusting of the device, orientation on caring for and using the implant, and initiation of the auditory training process. Decisions regarding internal settings of the signal processor must be made on the basis of electrical threshold and comfort level measurements. Every child is unique with respect to device settings. The complex nature of the multichannel devices has brought concern that complete programming of these devices in this young age group may not be possible. Experience now shows that although such programming does take longer, complete setting of the signal processor is still an obtainable goal. Awareness of sound, discrimination of sounds, and sound identification activities are introduced. The parents' active participation during the lessons helps them to realize the benefits and limitations of the implant and gives them practice in working with the child. Depending on the device, the particular implant center, and the child's age and needs, the rehabilitation program may require daily trips to the center for 1 or 2 weeks, and monthly visits for an additional period. The time commitment on the part of the parents must be understood before the child receives the implant. RESULTS Assessing the performance of children is understandably different from assessing the adult population's performance, and the effect of implantation on the child's development is a unique consideration. Performance before implantation and at regular intervals thereafter is assessed in the areas of auditory detection, auditory discriminationidentification, auditory recognition, and speech production. Auditory thresholds are assessed through behavioral audiometric techniques. The child's ability to make simple auditory discriminations--from stress and pattern discriminations to identification of words--is assessed with a variety of tests. The ability to understand speech without speech
Volume 118 Number 1
reading ("open set" speech recognition) can be measured in children who have sufficient cognitive and language abilities to take the test and respond intelligibly by either speech or signs. Threshold, discrimination, and recognition performance with the implant can be compared with preimplant performance with hearing aids. Speech production skills can also be measured to monitor the effect of the implant on the child, and the results can be compared with those in age-matched patients without implants. For speech, a skill that develops gradually, comparison with age-matched, deaf children without an implant is important in determining the effects of the implant itself as opposed to the effects of continuing education and maturation. Single-channel implant. Detailed results, including statistical analysis of the clinical trials data, have been reported elsewhere 8 and are only briefly summarized here. As of April 1988, a total of 289 children had received the 3M/House device. Demographic characteristics for 265 children included in data analysis indicated an age range of 2 years 2 months to 18 years, with a mean age at the time of implantation of 7.8 years. The mean age at onset of deafness was 1.6 years, with a median of 1 year. The vast majority of patients were prelingually deaf; only 13% were deafened after 3 years. The average duration of deafness was 6.1 years and ranged from 6 months to almost 18 years. Fifty-nine percent of these children were deafened by meningitis; other causes included cytomegalovirus infection, congenital ear malformations, trauma, maternal toxemia, maternal infection, maternal rubella, ototoxicity, and unknown hereditary and congenital causes. Median preimplantation auditory thresholds with hearing aids were 67 dB HL at 250 Hz and 86.5 dB H L at 500 Hz. Measurable responses with hearing aids were obtained in 28.7% of patients at 1000 Hz, 15% at 2000 Hz, 5% at 3000 Hz, and 1.6% at 4000 Hz. After implantation the median thresholds across the frequency range of 250 to 4000 Hz ranged from 46.5 to 59.5 dB HL, with a median speech detection threshold of 39.5 dB HL. The children were stratified by age at time of surgery (2 to 5 years, 5 to 11 years, >11 years), age at onset of deafness, (congenital, birth to 3 years, >3 years), and length of auditory deprivation (5 years), Scores were significantly higher after implantation for all age groups and were higher at the second year than at year 1 for the two younger age groups. The youngest children showed the most rapid improvement. All age-at-onset groups showed significant improvement after implantation, and children with a shorter duration of deafness improved at a faster rate. Higher overall levels of performance were obtained by children deafened later, but even congenitally deaf children had significant improvement. A longitudinal study of children with cochlear implants
Status o f cochlear implantation in children
5
who continued regular use of a hearing aid in the opposite ear provided evidence that such improvements in auditory performance after implantation are not a maturational effect. No significant improvement in performance occurred with the use of the hearing aid for a 2-year period, whereas performance of the ear with a cochlear implant was significantly better than that obtained before implantation. The ability to recognize speech without the aid of speech reading was examined in a group of children with the implanted 3M/House device who had sufficient cognitive and language abilities to take open-set word and sentence tests.14 The word-recognition task, consisting of 12 words of varying syllable and stress patterns, was administered to 50 children. Some level of open-set word recognition (8.3% to 75%) was attained by 52% of the children. Forty-one children were given the sentence comprehension task, consisting of 10 questions, and 41.5 % achieved some open-set sentence comprehension, ranging from 10% to 100%. The chance level for both of these tasks is zero. In a comparison of the group of children with open-set performance and of those without, those who had open-set speech recognition were older at the onset of deafness and were deaf for a shorter time before implantation. Significant improvement in speech production skills was evident when preimplantation performance with a hearing aid was compared with performance 1 and 2 years after implantation in children who underwent a standard speech evaluation. Significant improvements on the nonsegmental aspects (rhythm, pitch, intensity) of speech were identified in the two younger groups (2 to 5 years, >5 to 11 years). These groups also showed significant improvement, in comparison with preimplantation tests results, 1 year after implantation in the segmental aspects (e.g., vowels, consonants) of imitative speech production, and hearing improved in all three age groups from the first to the second year after implantation. In general, greater rates of improvement in speech production occurred in children who received implants at a younger age and who were deaf for a shorter period before implantation. However, significant improvements were also seen in the congenitally deaf children. Overall, at the second postimplantation visit, 61% of children demonstrated usable or very good imitative segmental speech skills, in comparison with 26% before implantation. The speech of children with implants was better than the speech of agematched control subjects for the age groups studied (4-, 5-, 6-, and 7-year-old children). The children with implants were also stratified by length of use of the implant (>2 or --2000 Hz. After implantation, the median thresholds across the frequency range of 250 to 4000 Hz ranged from 48 to 58 dB SPL. All patients detected sound at normal conversational levels. As with the 3M device, assessing the ability of children to recognize or understand speech was difficult because of the ages and cognitive levels of the children in the clinical trials. Evaluation of 62 children 12 months after implantation demonstrated improved ability to recognize timeintensity information and some limited spectral cues. Recorded word recognition tests were given to 24 children15; 71% recognized one or more words. In a related sentence comprehension task consisting of 10 questions, 60% of children with the Nucleus device recognized one or more sentences. Speech production skills were analyzed before implantation and 12 months after implantation in 45 children by separating speech elements into two categorized nonsegm e n t a l and seven segmental categories. 16 The hearing of 31% of the children improved by at least one nonsegmental category, and 67% showed improvement by at least one segmental category before to after implantation. A measure of speech intelligibility was also carried out in 27 patients and indicated that 63% were significantly more intelligible 12 months after the implantation. Complications. During clinical trials with the two cochlear implant devices, safety-related data have been gathered on almost 500 children. The rate of significant complications has been low (2.4% in the 3M series and 3.5% in the Nucleus series) but has included infection and extrusion, pain and inflammation, delayed wound healing and extrusion, skin flap complications, transient drainage, electrode displacement or misplacement, and facial nerve damage. All these complications have been successfully resolved, except that one patient has an unresolved but improved facial palsy. In addition, patients have had transient loud sound sensations after implantation, all of which resolved after
The Journal of Pediatrics January 1991
software reprogramming or external hardware replacement. There have been no reported cases of meningitis, anesthetic complications, or increased incidence of otitis media. DISCUSSION
Efficacy. Current experience with pediatric implantation indicates that the communication ability of the profoundly hearing-impaired child can be improved by electrical stimulation via a cochlear implant. Postimplantation auditory thresholds are routinely improved over preimplantation thresholds, resulting in the ability to detect most mediumand high-intensity environmental sounds and the acoustic speech signal. Auditory discrimination and identification are more difficult skills to assess. Even within age groups, cognitive and language abilities vary from one patient to another and may influence "auditory" performance. Despite assessment difficulties, the use of a standardized battery of tests in a large number of children, with appropriate statistical analyses, reveals that the ability to make simple auditory pattern and stress discriminations improves after implantation in all age groups. This cannot be explained as a maturational effect, because matched control ears assisted by hearing aids do not show such improvement. The ability to understand speech without speech reading is the ultimate benefit of the cochlear implant. This ability is more difficult to demonstrate in children than in adults, but it is present in some of those children with sufficient cognitive and language abilities to take the tests. Comparisons of speech production skills before and after implantation, as well as data from a cross-sectional, age-matched study, indicate that speech production improves with implant use. Several factors appear to be predictive of more rapid or greater improvement in speech perception and production with the cochlear implant. These include postlingual onset of deafness, implantation during preschool years, a short period of auditory deprivation, and participation in an oral communication therapy program. Safety. Implantation of such devices has resulted in few medical complications. As noted, the rate of complications from surgery has been low. In addition, the presence of a cochlear implant has not increased the frequency of otitis media, nor has it increased the severity of disease in children with implants who have acquired otitis media.t7 Because the devices are expansible, skull growth has not been reported to cause implant malfunction. Conversely, implantation has not affected skull growth rates. 18 Concerns about effects of long-term auditory system stimulation and the development of osteoneogenesis after implantation have been addressed both in animal studies 19, 20 and by clinical data, and there is no evidence of significant problems. Earlier concern about
Volume 118 Number 1
the size of the multichannel internal receiver has been alleviated by progressive miniaturization. Comments, A t the time of this writing, only two devices-the 3 M / H o u s e single-channel cochlear implant and the Nucleus multichannel cochlear i m p l a n t - - h a v e undergone clinical trials in children in the United States. Both have received F D A Advisory Panel recommendations for approval. However, the 3 M / H o u s e device is no longer owned by 3M Company and is not currently available for use in new patients. Clinical trials for several additional devices may begin in children in the future. At present, there are approximately 30 experienced clinical cochlear implant centers in the United States. The training of a child with a cochlear implant cannot stop after the brief rehabilitation received in the implant center; on the contrary, the primary rehabilitation received after implantation is merely an introduction to a continuous learning process. The most important factors, well recognized by centers that have managed such children, cannot be readily included in statistical analyses of performance data. TO deal appropriately with these psychosocial factors, pediatric implant centers must maintain large staffs dedicated to assessing family cooperation and expectations, to interacting with parents and family after implantation, and to serving as intermediaries and consultants in the child's educational activities, in addition to the expected tasks of audiol0gic screening, treatment, and postimplantation rehabilitation of the patient. CONCLUSION Cochlear implantation is a viable means to provide sound stimulation to the profoundly deaf child. Because of the complex nature of assessment and rehabilitation of deaf children, cochlear implantation should be considered only in centers that can provide t h e necessary medical, auditory, educationall and psychosocial care of the patient. In May 1988 the National Institutes of Health held a Consensus Development Conference on cochlear implants. The resulting statement from the panel of nationally recognized scientists states: It is recommended that hearing loss in children be corroborated with both behavioral and electrophysiological techniques, indications in favor of an implant are profound sensorineural hearing loss bilaterally and aided thresholds greater than 60 dB HL with confirmation of test/retest reliability . . . . Children with implants still must be regarded as hearing impaired, even with improved detection thresholds in the range of conversational speech. These children will continue to require educational, audiological, and speech and language support services for long periods of time. 21
Status o f cochlear implantation in children
7
REFERENCES
1. Schwab WA. Effects of hearing loss on education. In: Jaffee BF, ed. Hearing loss in children. Baltimore: University Park Press, 1977:650-4. 2. Conrad R. The deaf school child: language and cognitive function. New York: Harper & Row, 1979. 3. Boothroyd A. Residual hearing and the problem of carry-over in the speech of the deaf. ASHA 1985;15:8-14. 4. House WF, Berliner KI, Luxford WM. Cochlear implants in deaf children. Curr Probl Pediatr 1987;17:345-88. 5. Berliner KI, House WF. Cochlear implants: an overview and bibliography. Am J Otol 1981;2:277-82. 6. Schindler RA, Merzenich MM, eds. Cochlear implants. New York: Raven Press, 1985. 7. Luxford WM, Brackmann DE. The history of cochlear implants. In: Gray RF, ed. Cochlear implants. London: Croom Helm, 1985:1-26. 8. Berliner KI, Tonokawa LL, Brown C J, Dye LM. Cochlear implants in children: benefits and concerns: Am J Otol 1988;9:1-8. 9. Staller S J, Beiter AL, Brimacombe JA, Mecklenburg D J, Arndt P. Pediatric performance with the Nucleus 22 Channel Cochlear Implant System. Am J Otol (in press). 10. Fretz RJ, Fravel RP. Design and function: a physical and electrical description of the 3M/House cochlear implant system. Ear Hear 1985;6(suppl):145-95. 11. Clark GM, Dewhurst D J, Black RC, Foster IC, Patrick JF, Tong YG. A multiple electrode hearing prosthesis for cochlear implantation in deaf patients. Med Progr Technol 1977;5: 127-40. 12. Children's protocol for Nucleus 22 Channel Cochlear Implant. Englewood. Colo.: Cochlear Corp., 1988. 13. Thielemeir MA. Discrimination after training test. Los Angeles. Calif.: House Ear Institute. 1982. 14. Berliner KI. Tonokawa LL, Dye LM. House WF. Open-sel speech recognition in children with a single-channel cochlear implant. Ear Hear 1989:10:237-42. 15. Staller S J, Beiter AL, Tobey EA, Brimacombe JA. Mecklenburg DJ. Koch DB. Speech perception and production abilities of children with multichannel cochlear implants. Otolaryngol Head Neck Surg (in press). 16. Tobey EA, Angelette S. Murchison C. et al. Speech production performance in children with a multichannel cochlear implant. Am J Otology (in press). 17. House WF. Luxford WM, Courtney B. Otitis media in children following the cochlear implant. Ear Hear 1985: 6(suppl):245-65. 18. O'Donoghue GM, Jackler RK. Jenkins WM. et al. Cochlear implantation in children: the problem of head growth. Otolaryngol Head Neck Surg 1986:94:78-8l. 19. Shepherd RK, Clark GM. Black RC. Chronic electrical stim-. ulation of the auditory nerve in cats: physiological and histopathological results. Acta Otolaryngol Suppl (Stockh) 1983: 399:19-31. 20. Walsh SM. Leake-Jones PA. Chronic electrical stimulation of the auditory nerve in cats: physiological and histological results. Hear Res 1982:7:281-304. 21. National Institutes of Health. Cochlear implants. Consensus Development Conference Statement, 1988;7(2):1-25.
PEDIATRICS JANUARY
1991
Volume 118
Number 1
MEDICAL PROGRESS Status of cochlear implantation in children American Academy of Otolaryngology-Head and Neck Surgery Subcommittee on Cochlear Implants,* with John Kveton, MD, Principal Author, and Thomas J. Balkany, ME),Chairman The cochlear implanl is a medical device, part of which is placed surgically, that uses electrical stimulation to provide hearing. For almost a d e c a d e , investigational studies have been ongoing to define its safety and efficacy in profoundly deaf children. During this period, more than 500 children a g e d 2 through 17 years have been implanted with either a single-electrode or multielectrode device. Extensive auditory, speech, educational, and psychologic testing has been performed before and after implantation. Results show that the cochlear implant provides auditory detection over much of the speech signal. C o m p a r e d with the preimplant period, there is significant improvement in auditory discrimination and speech production skills. Limited open-set word and sentence recognition is possible for at least some children. Complications with the device have been minimal. The cochlear implant can provide sound to deaf children unable to benefit from hearing aids. The complex assessment, rehabilitation, and parent counseling should be performed by centers with the multidisciplinary staffs necessary to provide effective care for patients with this specialized auditory prosthesis. (J PEDIATR1991;118:1-7) A cochlear implant is a prosthetic device used to produce the sensation of sound by electrically stimulating the auditory system. It is for those hearing-impaired persons who cannot benefit significantly from conventional hearing aids. The recent U.S. Food and Drug Administration (FDA) apprOval for the general use of implants in children refocuses our concern on the profoundly hearing-impaired child. The first 5 years of childhood involve speech and language acquisition, as well as development of emotional, social, and
academic skills. Adequate hearing is critical in this stage of development, and the implications of deafness are serious. In contrast to a normal-hearing 5-year-old child, who will have a vocabulary of 5000 to 26,000 words, a profoundly hearing-impaired child of the same age typically has a vocabulary of 200 words. 1 Fifty percent of children with hearing loss greater than 85 decibels hearing level have no reading comprehension, and the average reading achievedB HL dB SPL
Reprint requests: John F. Kveton, MD, Associate Professor of Surgery, Yale University School of Medicine, Section of Otolaryngology, 333 Cedar St., New Haven, CT 06510. *Karen 1. Berliner, PhD, Bruce Gantz, MD, Noel L. Cohen, MD, Robert Jackter, MD, William Luxford, MD, Richard Miyamoto, MD, Edwin M. Monsell, MD, PhD, Joseph Nadol, Jr., MD, Michael Novak, MD, and James Parkin, MD. 9/18/24667
Decibelshearing level Decibelssound pressure level
]
I
ment for hearing-impaired 16-year-old adolescents is at the third- or fourth-grade level. 2 Speech development can be related to the degree of hearing loss; deficits occur in duration, intensity, and pitch of speech as well as in articulation of specific sounds) Serious delays occur in language development, including vocabulary, syntax, and word structure,
1
2
Kveton and Balkany
The Journal of Pediatrics January 1991
External Cod
/
Inlernal Coil
Speech Processor
ernal Electrode
,/
4
71ear Nerve
Fig. t. Typical cochlear implant system, showing surgically implanted internal receiver and electrodes and externally worn microphone, signal processor, and transmitter. simply because the child cannot experience the parents' language. This is particularly so for those who are deaf before the age of 2 or 3 years (prelingual deafness). Pragmatic skills such as requesting information or clarification, making commands, and social interaction are also delayed. Even children who have acquired some speech and language skills before they become deaf (postlingual deafness) may lose many of those skills, especially if deafened before 5 years of age. Children with mild to severe hearing losses are treatable with conventional hearing aids. However, until the past decade, the profoundly hearing-impaired child was left with little potential for sound stimulation. The development of the cochlear implant has changed this situation. Although use of the device is rapidly becoming accepted by hearing health care professionals, some concerns remain regarding implantation in children. 4 These include the difficulty of evaluating the young child's hearing loss and assessing performance of children with profound hearing loss, the effect of implantation on the child's development in comparison with the results of traditional types of training, the risks of implantation (both intraoperatively and for the long term), the effects of implantation on the auditory system, and the challenges of effective programming of sophisticated devices in young children. The purpose of this article is to review the current "state of the art" regarding cochlear implantation in children and to report the results obtained in clinical trials. Some of the data available address the concerns regarding pediatric implantation; long-term issues will be answered only slowly. DEVELOPMENT
OF COCHLEAR
IMPLANT
Although interest in electrical stimulation of the cochlea to produce auditory sensation began in the 1950s, develop-
merit and production of an implantable cochlear prosthesis did not occur until the 1960s through independent investigations by House, Simmons, and Michelson. Several histories, edited works, and review articles are available to describe both the early work and subsequent results. 57 Two patients received implants of single gold-wire electrodes and one of a multiple-electrode system as early as 1961 by House. In 1964, Simmons reported implanting a six-electrode array into the cochlea of a volunteer subject and made early discoveries in electrode-specific, or "place pitch", stimulation. Michelson developed a suitable animal model to evaluate electrical stimulation and placed implants in several deaf adults in the late 1960s. In 1973 a clinical trials program began at the House Ear Institute under the direction of Dr. William House. From 1974 to 1979 a total of 31 patients received a singleelectrode implant. In December 1980, pursuant to new medical device regulations, the FDA approved an Investigational Device Exemption application. Clinical trials were extended to a multicenter, coinvestigator program. The 3M Company modified the House single-electrode cochlear implant in 1982, and by 1984 data on 369 prelingually and postlingually deaf adults from 36 coinvestigators were evaluated by the FDA. Marketing approval for the first cochlear implant was granted in November 1984. During this period, several other implantable cochlear prostheses were in various stages of development, including multielectrode, multichannel devices. One of these, the Nucleus 22 Channel Cochlear Prosthesis (Cochlear Corp., Englewood, Colo.), received marketing approval from the FDA in 1985 for postlingually deaf adults. Other devices have been available on an investigational basis, and one, the Ineraid multichannel implant (Richards, Memphis, Tenn.), is approaching marketing approval for use in adults.
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On the basis of experience with adults, the House Ear Institute began placing implants in children in 1980, later adding seven coinvestigator teams across the country. These clinical trials include medical, audiologic, speech, language, and psychologic evaluations both before implantation and at regular postimplantation intervals. As of April 1988, a total of 289 children ranging in age from 2 through 17 years had undergone implantation with the 3M/House singlechannel implant.8 A premarketing application was submitted to the FDA and received a recommendation for approval from the FDA ENT Advisory Panel. Final steps for approval have not been taken. The 22-electrode Nucleus .device has been used in clinical trials with children since 1985, and 263 children aged 2 to 17 years have received implants.9 This device has also recei,~ed an FDA advisory panel recommendation for approval and received formal approval for marketing in June 1990. DEVICE DESCRIPTION All cochlear implants have two major components, the internal, or implanted, component and the external component, which is worn on the body (Fig. 1). The internal component consists of one or more electrodes implanted into or on the cochlea and an internal receiver embedded into the temporal bone above and behind the auricle. The distance of insertion of intracochlear electrodes depends on the type of device used but can be up to 25 ram. The external components consist of a microphone, external transmitter, and signal processor. The signal processor is responsible for transforming the sound stimulus received from the microphone and preparing it for transmission to the external transmitter and then to the internal receiver. In the 3M/House device, the incoming sound from the microphone amplitude modulates a 16 kHz carrier wave in the signal processor, and this amplitude-modulated signal is sent to the external transmitter, l~ It is transferred to the internal receiver by electromagnetic induction. In the more complex Nucleus 22-channel device, the incoming sound is analyzed by the signal processor into fundamental acoustic information representing key elements in human speech. 11 The analysis results in coding for the appropriate electrode, current amplitude, and stimulus rate. This information is sent to the external transmitter. The processed signal is sent transdermally via radio frequency transmission to the internal receiver. In the multielectrode system, the message is decoded so that separate bipolar pairs of the 22 electrodes can be activated to stimulate segments of the auditory nerve. Other cochlear implants use different types of signal processing or different forms of transmission, or both, across or through the skin. In each case, some form of a simplified or coded representation of speech and environmental sounds
Status o f cochlear implantation in children
3
Frequency (Hz) 125
250
500
1000
2000
Im lant
(Mean)
4000
8000
-10 0
01 (O (3} y-
10
s Z
50
_J 01 r-,
60
70 80
"lOO "10
Nil
90
100 110
( )
_
NR
NR
9
~i~cl;Mean)
120
I
[
NR
NR
Fig. 2. Audiogram for typical cochlear implant candidates, showing unaided and hearing-aid warble tone thresholds in relation to average speech spectrum. Also shown are average thresholds with cochlear implant. NR, No response; ANSI, American National Standards Institute. (From House WF, Berliner KI, Luxford WM. Curt Probl Pediatr 1987;17:345-88.)
is provided for the deaf patient through an electrical stimulus. CANDIDATE SELECTION Although more complex than in adults, candidate selection can be achieved in children. Through a combination of behavioral audiometric testing and the more objective auditory brain-stem response testing, good estimation of the child's hearing loss can be obtained. Once identified, the hearing-impaired child is fitted with appropriate hearing aids and assessed according to well-defined frequency and intensity levels for communication performance (Fig. 2). If the child's auditory detection is not comfortably within the speech range, a full evaluation for applicability of an implant is performed. A graded series of tests evaluates progressively more complex speech skills and includes speech awareness thresholds, uncomfortable loudness levels, warble-tone thresholds at frequencies ranging from 250 to 4000 Hz, simple speech discrimination testing, and auditory comprehension of environmental sounds and speech. A history of use of appropriately fit hearing aids is required. A trial with hearing aids or a vibrotactile device may be initiated if this requirement has not already been met, and testing is repeated after a period of training. If little or no significant benefit is demonstrated with hearing aids or a vibrotactile device, particularly in an auditory-only test mode, the cochlear implant is
4
Kveton and Balkany
an appropriate alternative. Performance on discrimination tests, in particular, is compared with results in persons with successful implants. 12' 13 Candidate selection for a cochlear implant, whether the candidate is an adult or a child, rests not merely on the results of auditory testing but on medical and psychosocial factors. The routine history taking, physical examination, and laboratory evaluation that precede standard middle ear surgery are performed. Radiographic studies using computed tomography are performed to determine the patency of the cochlea, identify congenital malformations of the ears, and assess surgical anatomy. Magnetic resonance imaging is not practical for examining implant candidates; it shows little bony detail and an insufficient portion of the membranous inner ear. (With improvements and the use of surface coils, magnetic resonance imaging may become more useful in examining the membranous inner ear and detecting cochlear fibrosis.) Bone formation in the round window or scala tympani does not necessarily preclude surgery. Congenital malformations (such as the Mondini deformity) that alter the usual tonotopic organization of the cochlea may limit the benefits of implantation. Extreme congenital anomalies (i.e., absence of cochlea or auditory nerve) would exclude a child from implantation. The psychosocial considerations for a successful candidate include (1) no evidence of severe organic brain damage, (2) no evidence of psychosis, (3) no evidence of mental retardation, (4) no behavioral-personality traits that would make completion of the program unlikely, (5) no unremitting, unrealistic expectations about the implant on the part of the family, and (6) a pattern of parent-child interaction that indicates that the family will be able to follow the postimplant rehabilitation program effectively. Parents must be willing to spend extra time with the child, carrying implant-oriented exercises into their daily interaction with the child. The child's educational setting not only must be open to accepting a child with a cochlear implant but should be willing and able to adapt educational methods to enhance implant performance. Both parental and educational support are considered in the decision for implantation. SURGICAL
PROCEDURE
The cochlear implant is placed according to conventional surgical techniques developed to treat chronic middle ear disease. The cochlea is adult sized at birth, and, in general, the middle ear, eardrum, and ossicles are also adult sized. The surgical approach through the mastoid, facial recess, and round window leaves the ear canal wall intact and provides direct access to the scala tympani. The surgery is performed with the child under general anesthesia. A large postauricular incision is made; a seat is
The Journal of Pediatrics January 1991
made in the temporal squama for the internal receiver; a mastoidectomy is performed; the facial recess is opened and the lip of the round window niche is removed; the internal receiver is placed in the bony seat and sutured into place; the electrode array is inserted through the opening of the round window into the scala tympani; fascia is packed around the electrode at the round window and at the facial recess; and the postauricular flap is closed in layers. Surgery lasts about 1I/2 hours, and the patient is usually discharged from the hospital the day after surgery. A period of 1 to 2 months is allowed for healing and resolution of swelling over the receiver before the initiation of electrical stimulation. REHABILITATION After the healing period, the child must return to the implant center frequently for fitting and adjusting of the device, orientation on caring for and using the implant, and initiation of the auditory training process. Decisions regarding internal settings of the signal processor must be made on the basis of electrical threshold and comfort level measurements. Every child is unique with respect to device settings. The complex nature of the multichannel devices has brought concern that complete programming of these devices in this young age group may not be possible. Experience now shows that although such programming does take longer, complete setting of the signal processor is still an obtainable goal. Awareness of sound, discrimination of sounds, and sound identification activities are introduced. The parents' active participation during the lessons helps them to realize the benefits and limitations of the implant and gives them practice in working with the child. Depending on the device, the particular implant center, and the child's age and needs, the rehabilitation program may require daily trips to the center for 1 or 2 weeks, and monthly visits for an additional period. The time commitment on the part of the parents must be understood before the child receives the implant. RESULTS Assessing the performance of children is understandably different from assessing the adult population's performance, and the effect of implantation on the child's development is a unique consideration. Performance before implantation and at regular intervals thereafter is assessed in the areas of auditory detection, auditory discriminationidentification, auditory recognition, and speech production. Auditory thresholds are assessed through behavioral audiometric techniques. The child's ability to make simple auditory discriminations--from stress and pattern discriminations to identification of words--is assessed with a variety of tests. The ability to understand speech without speech
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reading ("open set" speech recognition) can be measured in children who have sufficient cognitive and language abilities to take the test and respond intelligibly by either speech or signs. Threshold, discrimination, and recognition performance with the implant can be compared with preimplant performance with hearing aids. Speech production skills can also be measured to monitor the effect of the implant on the child, and the results can be compared with those in age-matched patients without implants. For speech, a skill that develops gradually, comparison with age-matched, deaf children without an implant is important in determining the effects of the implant itself as opposed to the effects of continuing education and maturation. Single-channel implant. Detailed results, including statistical analysis of the clinical trials data, have been reported elsewhere 8 and are only briefly summarized here. As of April 1988, a total of 289 children had received the 3M/House device. Demographic characteristics for 265 children included in data analysis indicated an age range of 2 years 2 months to 18 years, with a mean age at the time of implantation of 7.8 years. The mean age at onset of deafness was 1.6 years, with a median of 1 year. The vast majority of patients were prelingually deaf; only 13% were deafened after 3 years. The average duration of deafness was 6.1 years and ranged from 6 months to almost 18 years. Fifty-nine percent of these children were deafened by meningitis; other causes included cytomegalovirus infection, congenital ear malformations, trauma, maternal toxemia, maternal infection, maternal rubella, ototoxicity, and unknown hereditary and congenital causes. Median preimplantation auditory thresholds with hearing aids were 67 dB HL at 250 Hz and 86.5 dB H L at 500 Hz. Measurable responses with hearing aids were obtained in 28.7% of patients at 1000 Hz, 15% at 2000 Hz, 5% at 3000 Hz, and 1.6% at 4000 Hz. After implantation the median thresholds across the frequency range of 250 to 4000 Hz ranged from 46.5 to 59.5 dB HL, with a median speech detection threshold of 39.5 dB HL. The children were stratified by age at time of surgery (2 to 5 years, 5 to 11 years, >11 years), age at onset of deafness, (congenital, birth to 3 years, >3 years), and length of auditory deprivation (5 years), Scores were significantly higher after implantation for all age groups and were higher at the second year than at year 1 for the two younger age groups. The youngest children showed the most rapid improvement. All age-at-onset groups showed significant improvement after implantation, and children with a shorter duration of deafness improved at a faster rate. Higher overall levels of performance were obtained by children deafened later, but even congenitally deaf children had significant improvement. A longitudinal study of children with cochlear implants
Status o f cochlear implantation in children
5
who continued regular use of a hearing aid in the opposite ear provided evidence that such improvements in auditory performance after implantation are not a maturational effect. No significant improvement in performance occurred with the use of the hearing aid for a 2-year period, whereas performance of the ear with a cochlear implant was significantly better than that obtained before implantation. The ability to recognize speech without the aid of speech reading was examined in a group of children with the implanted 3M/House device who had sufficient cognitive and language abilities to take open-set word and sentence tests.14 The word-recognition task, consisting of 12 words of varying syllable and stress patterns, was administered to 50 children. Some level of open-set word recognition (8.3% to 75%) was attained by 52% of the children. Forty-one children were given the sentence comprehension task, consisting of 10 questions, and 41.5 % achieved some open-set sentence comprehension, ranging from 10% to 100%. The chance level for both of these tasks is zero. In a comparison of the group of children with open-set performance and of those without, those who had open-set speech recognition were older at the onset of deafness and were deaf for a shorter time before implantation. Significant improvement in speech production skills was evident when preimplantation performance with a hearing aid was compared with performance 1 and 2 years after implantation in children who underwent a standard speech evaluation. Significant improvements on the nonsegmental aspects (rhythm, pitch, intensity) of speech were identified in the two younger groups (2 to 5 years, >5 to 11 years). These groups also showed significant improvement, in comparison with preimplantation tests results, 1 year after implantation in the segmental aspects (e.g., vowels, consonants) of imitative speech production, and hearing improved in all three age groups from the first to the second year after implantation. In general, greater rates of improvement in speech production occurred in children who received implants at a younger age and who were deaf for a shorter period before implantation. However, significant improvements were also seen in the congenitally deaf children. Overall, at the second postimplantation visit, 61% of children demonstrated usable or very good imitative segmental speech skills, in comparison with 26% before implantation. The speech of children with implants was better than the speech of agematched control subjects for the age groups studied (4-, 5-, 6-, and 7-year-old children). The children with implants were also stratified by length of use of the implant (>2 or --2000 Hz. After implantation, the median thresholds across the frequency range of 250 to 4000 Hz ranged from 48 to 58 dB SPL. All patients detected sound at normal conversational levels. As with the 3M device, assessing the ability of children to recognize or understand speech was difficult because of the ages and cognitive levels of the children in the clinical trials. Evaluation of 62 children 12 months after implantation demonstrated improved ability to recognize timeintensity information and some limited spectral cues. Recorded word recognition tests were given to 24 children15; 71% recognized one or more words. In a related sentence comprehension task consisting of 10 questions, 60% of children with the Nucleus device recognized one or more sentences. Speech production skills were analyzed before implantation and 12 months after implantation in 45 children by separating speech elements into two categorized nonsegm e n t a l and seven segmental categories. 16 The hearing of 31% of the children improved by at least one nonsegmental category, and 67% showed improvement by at least one segmental category before to after implantation. A measure of speech intelligibility was also carried out in 27 patients and indicated that 63% were significantly more intelligible 12 months after the implantation. Complications. During clinical trials with the two cochlear implant devices, safety-related data have been gathered on almost 500 children. The rate of significant complications has been low (2.4% in the 3M series and 3.5% in the Nucleus series) but has included infection and extrusion, pain and inflammation, delayed wound healing and extrusion, skin flap complications, transient drainage, electrode displacement or misplacement, and facial nerve damage. All these complications have been successfully resolved, except that one patient has an unresolved but improved facial palsy. In addition, patients have had transient loud sound sensations after implantation, all of which resolved after
The Journal of Pediatrics January 1991
software reprogramming or external hardware replacement. There have been no reported cases of meningitis, anesthetic complications, or increased incidence of otitis media. DISCUSSION
Efficacy. Current experience with pediatric implantation indicates that the communication ability of the profoundly hearing-impaired child can be improved by electrical stimulation via a cochlear implant. Postimplantation auditory thresholds are routinely improved over preimplantation thresholds, resulting in the ability to detect most mediumand high-intensity environmental sounds and the acoustic speech signal. Auditory discrimination and identification are more difficult skills to assess. Even within age groups, cognitive and language abilities vary from one patient to another and may influence "auditory" performance. Despite assessment difficulties, the use of a standardized battery of tests in a large number of children, with appropriate statistical analyses, reveals that the ability to make simple auditory pattern and stress discriminations improves after implantation in all age groups. This cannot be explained as a maturational effect, because matched control ears assisted by hearing aids do not show such improvement. The ability to understand speech without speech reading is the ultimate benefit of the cochlear implant. This ability is more difficult to demonstrate in children than in adults, but it is present in some of those children with sufficient cognitive and language abilities to take the tests. Comparisons of speech production skills before and after implantation, as well as data from a cross-sectional, age-matched study, indicate that speech production improves with implant use. Several factors appear to be predictive of more rapid or greater improvement in speech perception and production with the cochlear implant. These include postlingual onset of deafness, implantation during preschool years, a short period of auditory deprivation, and participation in an oral communication therapy program. Safety. Implantation of such devices has resulted in few medical complications. As noted, the rate of complications from surgery has been low. In addition, the presence of a cochlear implant has not increased the frequency of otitis media, nor has it increased the severity of disease in children with implants who have acquired otitis media.t7 Because the devices are expansible, skull growth has not been reported to cause implant malfunction. Conversely, implantation has not affected skull growth rates. 18 Concerns about effects of long-term auditory system stimulation and the development of osteoneogenesis after implantation have been addressed both in animal studies 19, 20 and by clinical data, and there is no evidence of significant problems. Earlier concern about
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the size of the multichannel internal receiver has been alleviated by progressive miniaturization. Comments, A t the time of this writing, only two devices-the 3 M / H o u s e single-channel cochlear implant and the Nucleus multichannel cochlear i m p l a n t - - h a v e undergone clinical trials in children in the United States. Both have received F D A Advisory Panel recommendations for approval. However, the 3 M / H o u s e device is no longer owned by 3M Company and is not currently available for use in new patients. Clinical trials for several additional devices may begin in children in the future. At present, there are approximately 30 experienced clinical cochlear implant centers in the United States. The training of a child with a cochlear implant cannot stop after the brief rehabilitation received in the implant center; on the contrary, the primary rehabilitation received after implantation is merely an introduction to a continuous learning process. The most important factors, well recognized by centers that have managed such children, cannot be readily included in statistical analyses of performance data. TO deal appropriately with these psychosocial factors, pediatric implant centers must maintain large staffs dedicated to assessing family cooperation and expectations, to interacting with parents and family after implantation, and to serving as intermediaries and consultants in the child's educational activities, in addition to the expected tasks of audiol0gic screening, treatment, and postimplantation rehabilitation of the patient. CONCLUSION Cochlear implantation is a viable means to provide sound stimulation to the profoundly deaf child. Because of the complex nature of assessment and rehabilitation of deaf children, cochlear implantation should be considered only in centers that can provide t h e necessary medical, auditory, educationall and psychosocial care of the patient. In May 1988 the National Institutes of Health held a Consensus Development Conference on cochlear implants. The resulting statement from the panel of nationally recognized scientists states: It is recommended that hearing loss in children be corroborated with both behavioral and electrophysiological techniques, indications in favor of an implant are profound sensorineural hearing loss bilaterally and aided thresholds greater than 60 dB HL with confirmation of test/retest reliability . . . . Children with implants still must be regarded as hearing impaired, even with improved detection thresholds in the range of conversational speech. These children will continue to require educational, audiological, and speech and language support services for long periods of time. 21
Status o f cochlear implantation in children
7
REFERENCES
1. Schwab WA. Effects of hearing loss on education. In: Jaffee BF, ed. Hearing loss in children. Baltimore: University Park Press, 1977:650-4. 2. Conrad R. The deaf school child: language and cognitive function. New York: Harper & Row, 1979. 3. Boothroyd A. Residual hearing and the problem of carry-over in the speech of the deaf. ASHA 1985;15:8-14. 4. House WF, Berliner KI, Luxford WM. Cochlear implants in deaf children. Curr Probl Pediatr 1987;17:345-88. 5. Berliner KI, House WF. Cochlear implants: an overview and bibliography. Am J Otol 1981;2:277-82. 6. Schindler RA, Merzenich MM, eds. Cochlear implants. New York: Raven Press, 1985. 7. Luxford WM, Brackmann DE. The history of cochlear implants. In: Gray RF, ed. Cochlear implants. London: Croom Helm, 1985:1-26. 8. Berliner KI, Tonokawa LL, Brown C J, Dye LM. Cochlear implants in children: benefits and concerns: Am J Otol 1988;9:1-8. 9. Staller S J, Beiter AL, Brimacombe JA, Mecklenburg D J, Arndt P. Pediatric performance with the Nucleus 22 Channel Cochlear Implant System. Am J Otol (in press). 10. Fretz RJ, Fravel RP. Design and function: a physical and electrical description of the 3M/House cochlear implant system. Ear Hear 1985;6(suppl):145-95. 11. Clark GM, Dewhurst D J, Black RC, Foster IC, Patrick JF, Tong YG. A multiple electrode hearing prosthesis for cochlear implantation in deaf patients. Med Progr Technol 1977;5: 127-40. 12. Children's protocol for Nucleus 22 Channel Cochlear Implant. Englewood. Colo.: Cochlear Corp., 1988. 13. Thielemeir MA. Discrimination after training test. Los Angeles. Calif.: House Ear Institute. 1982. 14. Berliner KI. Tonokawa LL, Dye LM. House WF. Open-sel speech recognition in children with a single-channel cochlear implant. Ear Hear 1989:10:237-42. 15. Staller S J, Beiter AL, Tobey EA, Brimacombe JA. Mecklenburg DJ. Koch DB. Speech perception and production abilities of children with multichannel cochlear implants. Otolaryngol Head Neck Surg (in press). 16. Tobey EA, Angelette S. Murchison C. et al. Speech production performance in children with a multichannel cochlear implant. Am J Otology (in press). 17. House WF. Luxford WM, Courtney B. Otitis media in children following the cochlear implant. Ear Hear 1985: 6(suppl):245-65. 18. O'Donoghue GM, Jackler RK. Jenkins WM. et al. Cochlear implantation in children: the problem of head growth. Otolaryngol Head Neck Surg 1986:94:78-8l. 19. Shepherd RK, Clark GM. Black RC. Chronic electrical stim-. ulation of the auditory nerve in cats: physiological and histopathological results. Acta Otolaryngol Suppl (Stockh) 1983: 399:19-31. 20. Walsh SM. Leake-Jones PA. Chronic electrical stimulation of the auditory nerve in cats: physiological and histological results. Hear Res 1982:7:281-304. 21. National Institutes of Health. Cochlear implants. Consensus Development Conference Statement, 1988;7(2):1-25.
