Graeme Clark Collection
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ItemPost-implant habilitation for children using cochlear implants: effects on long-term outcome( 2002)Most clinicians working in the cochlear implant field advocate a regular habilitation program for young children receiving implants. The development of auditory skills and the incorporation of these skills into language development are thought to be key areas for such programs. Studies of speech perception and language outcomes demonstrate that an educational approach that emphasises spoken language development appears to enhance the results for implanted children. It remains difficult, however, to demonstrate clearly the effect of habilitation objectively and to determine how much individual attention is desirable for each child. This pilot study considered the long term speech perception and language outcomes for two groups of children who received Nucleus cochlear implants in Melbourne. One group (n=17) was identified as receiving regular habilitation from the Melbourne Cochlear Implant Clinic over a four year post-operative period. Another group (n=l1) was identified as receiving very little regular habilitation over the post-operative period. The language and speech perception results for these two groups showed a significant difference in performance on a wide range of measures with the group receiving regular formal habilitation demonstrating better performance on all measures. These groups included only congenitally, profoundly hearing-impaired children and did not differ significantly on mean age at implant or experience at the time of assessment. Further studies are needed to clarify these results on a larger group of children, and to control for additional confounding variables. Nonetheless, these preliminary results provide support for the incorporation of regular long-term habilitation into cochlear implant programs for children.
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ItemAuditory processing abilities in children using cochlear implants: their relevance to speech perception [Abstract]( 1999)This study aimed to investigate the relationships between some basic auditory processing skills, subject variables and speech perception ability in young children using cochlear implants. A modification of the play audiometry procedure was used to measure electrode discrimination and "rate-of-processing" ability in seventeen 4-10 year old children. In the electrode discrimination task, children responded with a game-like motor response when a repeating stimulation on a reference electrode "changed" to a different electrode. In the "rate-of processing" task, children had to respond to the "change" to a different electrode, when the duration of the stimuli and the time interval between the stimuli were decreased. Normally hearing children were assessed on this task with acoustic stimulation. Nonverbal intelligence, speech feature discrimination and closed-set word recognition were also measured in the children using implants.
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ItemThe use of click-ABR and steady state evoked potentials for hearing assessment in young cochlear implant candidates [Abstract]( 1997)The accurate assessment of hearing thresholds in prospective cochlear implant candidates is essential. As the minimum age of implantation has reduced, audiologists have been faced with the complicated task of obtaining precise audiometric information in children whose immaturity may severely restrict the assessment process. Clearly for these young candidates, there is a place for a reliable, objective measure of residual hearing in the pre-operative test battery. This paper examines the degree of accuracy with which the click-ABR and the steady-state evoked potential (SSEP) techniques can provide estimates of hearing level in subjects with several profound hearing loss.
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ItemTowards a SSEP hearing screening test for neonates [Abstracts]( 1997)Newborn hearing screening tests utilizing evoked otoacoustic emissions (EOAEs) and/or the auditory brainstem response (ABR) recording have been recommended by the NIH(1993). The University of Melbourne experience with steady-state evoked potentials (SSEPs) in newborns suggests that they too, have potential as a screening tool (Rickards et al, 1984). In the present study, SSEPs were recorded from neonates in a pilot study of how the technology may be applied to newborn hearing screening. Eighty-eight neonates were tested using transient-and distortion product EOAEs, ABRs and SSEPs. Only those infants who had TEOAEs, DPOAEs, and ABRs that met a rigid and objective "pass" criteria were included in the study. SSEPs were evoked by amplitude modulated tones using carrier frequencies at 500, 1000, 2000, and 4000 HZ, and modulation frequencies between 75 and 95 Hz presented at levels between 40 and 80 dB SPL. Out of 324 individual SSEP tests, 12% were no-stimulus control trials. Phase-coherence statistics were used to determine when a significant or "passing" result had been obtained. Preliminary results show that a 94% pass rate is achieved for a CF of 2 KHZ, presented at 60 dB SPL, but that pass rates are lower (79% to 89%) for 500, 1KHz and 4KHZ CF's at the same stimulus levels. For lower stimulus levels, pass rates do not exceed 80% for any carrier frequency. Phase-coherence estimates were made for 32, 64, ahd 96 samples at each carrier and modulation frequency combination. We will report the phase coherence estimates for each CF, MF and level combination as a function of sample size, in order to suggest a protocol that may be efficient in newborn hearing screening applications.
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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.
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ItemFactors associated with open-set speech perception in children using the Cochlear multiple-channel prosthesis [Abstract]( 1993)Since 1985, nearly 100 children have received the 22-channel cochlear prosthesis from the Melbourne and Sydney cochlear implant clinics. These two clinics account for the bulk of casesin Australia, and have similar management philosophies and selection criteria. The patient population represents a variety of etiologies, and ranges in age from 2 - 18 years of age. Bothcongenital and postlinguistic hearing losses are included. In order to assess benefit to speech perception in such a diverse group, the children's results have been tabulated according to a six level hierarchical scale of speech perception achievement. The scale ranges from category I,detection of sound only, to category 6, which includes significant perception scores for open-setwords and sentences. Analysis of the results shows that the majority of the children are achieving open-set speech perception benefits, and that results continue to improve with additional experience with their devices. There are a number of contributing factors to these open-set speech� perception results which have impact both on selection issues and on habilitation with different age ranges �of patients.
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ItemThe postnatal growth of the temporal bone and its implications for cochlear implantation in children( 1993)The growth of the human temporal bone is of practical concern if young children are implanted. It is feared that the normal development of the temporal bone after implantation may displace the electrode array and jeopardize the success of the device. To evaluate the extent of growth 60 cadaver specimens of all ages were examined by direct anatomical measurements. The bones were dissected by imitating the cochlear implantation surgical procedure in the temporal bone laboratory. 19 anatomical/surgical landmarks with implications for cochlear implant surgery were identified and the distance between them measured. The inner ear and middle ear are adult size at birth. The external auditory canal and most parts of the temporal bone are subject to significant lateral growth. The size of the pneumatised mastoid was found to increase in all directions. In the facial recess however, no postnatal growth could be noted. Between birth and adulthood a considerable amount of growth is to be expected between the sino-dural angle and the round window, the landmarks representing the implantation site for the receiver/stimulator and the electrode entry site respectively. From an anatomical and surgical point of view, cochlear implantation in very young children proved to be feasible, provided the electrode array is secured close to the cochlea and the design accommodates for controlled leadwire lengthening.
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ItemThe postnatal growth of the temporal bone and its implications for cochlear implants in children( 1993)An understanding of the postnatal growth of the temporal bone is an important prerequisite for the development of cochlear implantation in very young children. Such information will have an important bearing on both the design of the implant and the surgical procedure. We have measured the postnatal growth of the temporal bone by direct anatomical measurements on 60 cadaver specimens with ages ranging from 2 months to 84 years. Nineteen anatomical landmarks with implications for cochlear implant surgery were identified on each bone and the distance between these points measured. The inner and middle ears were adult size at birth. The external auditory canal and most parts of the temporal bone were subject to significant lateral growth. The size of the pneumatized mastoid increased with age in all directions. Significantly, no postnatal growth was observed in the facial recess. The fossa incudis showed no growth relative to the round window and was found to be a convenient fixation site for the electrode array close to the cochlea. However, with the electrode leadwire fixed at a cortical site such as the osterosuperior point of McEwan's triangle, the leadwire would be subject to approximately 20 mm of growth between this point and the cochlea. These anatomical results indicate that a paediatric cochlear implant would require an expandable leadwire to accommodate these growth changes.
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ItemMultichannel cochlear implants in children: an overview of experimental and clinical results at the University of Melbourne [Opening Lecture]( 1992)During the last decade there has been great progress in the clinical management of profound, postlinguistically deafened adults through the use of multichannel cochlear implants. The device developed by The University of Melbourne in association with Cochlear Pty Ltd, electrically stimulates selective regions of the auditory nerve using an array of 22 platinum (Pt) electrodes located in the scala tympani. Its development followed basic experimental studies and the development and evaluation of a prototype device in the 1970's. Following safety studies and a successful clinical trial, the Melbourne/Cochlear multichannel implant was approved for use in adults by the United States Food and Drug Administration (FDA) in 1985. More than 3000 patients throughout the world have since been implanted with this device, many being able to understand a significant amount of unfamiliar, connected speech without lipreading Following miniaturization of the implant, it became suitable for use with children. In 1990, after additional biological safety and clinical investigations, the FDA approved the use of the Melbourne/Cochlear multichannel implant for profoundly deaf children above the age of two years. And in 1991, the device received the medical device implantation approval certificate from the Japanese Government. The present paper presents an overview of our recent biological safety studies and clinical experience in children, and discusses the likely future development of these devices.
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ItemAn antibacterial seal and fixation device for cochlear implants in young children [Abstract]( 1992)Concerns associated with cochlear implantation in young children include intracochlear spread of infection along the electrode array during otitis media, and electrode extraction caused by skull growth post-implantation. New biomaterials were used to seal and secure the electrode at its entry point into the cochlea. Hydroxyapatite was deposited around the outside of an electrode cuff and it bonded well to the surrounding bone of the otic capsule. The electrode cuff accommodated variable insertion depths with the help of a new, silicone based hydroscopic polymer. Preliminary results, including experimental testing of the device in an animal model of pneumococcal otitis media, indicate protection of the implanted cochlea against the spread of infection. Electrode leadwire displacement is prevented by fixation of the array at its entry point This concept may play an important role in the development of a safe cochlear implant design for children under two years of age, who are expected to benefit most from early auditory rehabilitation.