Graeme Clark Collection
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ItemThe development of speech perception in children using cochlear implants: effects of etiologic factors and delayed milestones( 2000)Hypothesis: Speech perception outcomes for cochlear implantation of children vary over a wide range, and it is hypothesized that central pathologic states associated with certain causes of hearing impairment account for a substantial part of the variance. Study Design: A retrospective analysis was carried out to ascertain the relationships between speech perception, etiologic factors, and central pathologic states as indicated by preoperative delayed motor milestones and/or cognitive delays. Setting: Data were obtained from the pre-and postoperative records of patients attending a hospital cochlear implant clinic. Patients: Results for 75 consecutive patients up to age 5 years who underwent implantation were included in the study. Intervention: Patients received a 22-electrode cochlear prosthesis and were seen by the clinic for regular tune-up and assessments. Home-and school-based habilitation was recommended by the clinic. Main Outcome Measures: Speech perception measures were classified on a five-point scale to allow for different evaluation procedures at different ages and developmental stages. Results: The incidence of motor and cognitive delays were fairly evenly spread across etiologic factors, except for cytomegalovirus, which had a much higher than average incidence. Children with motor and/or cognitive delays were significantly slower than other children in the development of speech perception skills after implantation. Etiologic factors did not have a statistically significant effect on speech perception outcome. Conclusions: It is likely that central pathologic states account for a substantial part of the variance among children using cochlear implants. Specific indicators of central pathologic states should be used to assess a child's prognosis in preference to less specific information based on etiologic factors alone.
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ItemThe progress of children using the multichannel cochlear implant in Melbourne( 1995)Multi-channel cochlear implantation in children began in Australia in 1985 and there are now close to 4000 profoundly deaf children and adolescents using the Australian implant system around the world. The aim of the implant procedure is to provide adequate hearing for speech and language development through auditory input. This contrasts with the situation for adults with acquired deafness where the cochlear implant aims to restore hearing for someone with well-developed auditory processing and language skills. As with adults, results vary over a wide range for children using the Multi-channel implant. Many factors have been suggested that may contribute to differences in speech perception for implanted children. In an attempt to better understand these factors, the speech perception results for children implanted in Melbourne were reviewed and subjected to statistical analysis. This has indicated that the amount of experience with the implant and the length of sensory deprivation are strongly correlated with perceptual results. This means that younger children are likely to perform better with an implant and that a number of years of experience are required for children to reach their full potential. The results have also indicated that educational placement and management play a crucial role in children reaching their potential. Overall, 60% of the children and adolescents in the study have reached a level of open-set speech understanding using the cochlear implant without lipreading.
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ItemAnatomic and surgical considerations in the design of a new receiver-stimulator suitable for implantation in young children( 1995)The anatomy of the temporal bone was studied to determine the optimal shape and dimensions of a new receiver-stimulator for use in young children even less than 12 months of age. There was a need to make the receiver-stimulator electronic package smaller so that it could be placed within the mastoid cavity, and the antenna wider, for more efficient power and data transmission. The antenna needed to conform to the smaller radius of a young child's skull. Anatomic dissections were carried out on skulls of children from 3 to 11 months of age to establish the variations in dimensions relevant for implantation. Prototype implant designs were evaluated in these skulls and it was found that the maximum thickness the anterior section of the receiver-stimulator should be was 5.5 mm, and its maximum width, 18 mm. It was found that a prototype electronics package with these dimensions could be fitted comfortably into the average skull of an 8-month-old child. A particular constraint was the depth of the bone over the sigmoid sinus and middle fossa. The radius of curvature of the skull of young children also required the package to be bent in its center at an angle of 160°.
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ItemHabilitation issues in the management of children using the cochlear multiple-channel cochlear prosthesis(Wien, 1994)Since 1985, a significant proportion of patients seen in the Melbourne cochlear implant clinic have been children. The children represent a diverse population, with both congenital and acquired hearing-impairments, a wide-range of hearing levels pre-implant, and an age range from 2 years to 18 years. The habilitation programme developed for the overall group must be flexible enough to be tailored to the individual needs of each child, and to adapt to the changing needs of children as they progress. Long-term data shows that children are continuing to show improvements after 5-7 years of device use, particularly in their perception of open-set words and sentences. Habilitation programs must therefore be geared to the long-term needs of children and their families. Both speech perception and speech production need to be addressed in the specific content of the habilitation program for any individual child. In addition, for young children, the benefits of improved speech perception should have an impact on development of speech and language, and the focus of the programme for this age child will reflect this difference in emphasis. Specific materials and approaches will vary for very young children, school-age and teenage children. In addition, educational setting will have a bearing on the integration of listening and device use into the classroom environment.
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ItemSpeech perception benefits for implanted children with preoperative residual hearing [Abstract]( 1995)Since the implantation of the first children with the Nucleus 22-channel cochlear prosthesis in Melbourne in 1985, there has been rapid expansion in the number of implanted children world-wide. Improved surgical technique and experience in paediatric assessment and management have contributed to a trend to implant very young children. At the same time there has also been continuing development of improved speech processing strategies resulting in greater speech perception benefits. In the Melbourne program, over 60% of children obtain significant scores on open-set word and sentence tests using their cochlear implant alone without the aid of lipreading. As parents and professionals have become aware of these improved benefits to speech perception benefits in profoundly deaf children, there have been requests to consider implanting severely-to-profoundly deaf children. In these children with higher levels of residual hearing, only those children with poorer-than-expected performance on speech perception tests using hearing aids have been considered for surgery. A number of such cases have now been implanted in the Melbourne program. The speech perception benefits for this group are reported and are being compared with benefits for the profoundly deaf group of children.
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ItemSpeech perception benefits for children using the 22-channel Melbourne/cochlear hearing prosthesis [Abstract]( 1993)In 1985; the first child was implanted with the Cochlear 22-channel cochlear prosthesis at the University of Melbourne Royal Victorian Eye & Ear Hospital Cochlear Implant Clinic. There are now 42 children who have received the device in Melbourne. Analysis of patient details for these children show a very heterogeneous group, with a wide range in age, hearing thresholds, duration of deafness and aetiology. The major aetiologies found were either a congenital profound deafness.; or a hearing loss due to meningitis. In all but 3 cases, the children are using 15 or more electrodes in the array. Speech perception benefits have been analyzed according to a six-level hierarchical classification scheme. All of-the children achieved a minimum benefit of discrimination of suprasegmental information (Category 2), and 59% of the children achieved open-set understanding of unfamiliar speech material without the aid of lip-reading (Categories 5 & 6). Detailed analysis suggests that the majority of children achieving open-set speech perception benefits had more than one year of experience with their implant. and less than seven years of profound deafness prior to implantation.