Graeme Clark Collection

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    A protocol for the prevention of infection in cochlear implant surgery
    Clark, Graeme M. ; Pyman, Brian C. ; Pavillard, Robin E. (Cambridge University Press, 1980)
    The reduction of infection to an absolute minimum is a very desirable goal in any form of surgery. It is especially important with a cochlear implant operation as infection in the labyrinth can lead to degeneration of the auditory nerve fibres it is hoped to stimulate electrically (Clark et al, 1975). Furthermore, as the implantation of foreign materials increases the risk of infection, as the operation can last 6-7 hours (Altemeier et al., 1976), and as the operators are in very close proximity to the implant site, more stringent measures for the prevention of infection need to be adopted than with other forms of otological surgery. For these reasons a protocol has been developed for preventing infection in our cochlear implant surgery. This is an overall approach to the prevention of infection and involves pre-operative measures, an operating theatre routine, the use of horizontal laminar flow filter units, correct surgical technique and the use of systemic and local antibiotics.
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    The surgery for multiple-electrode cochlear implantations
    Clark, Graeme M. ; Pyman, Brian C. ; Bailey, Quentin R. (Cambridge University Press, 1979)
    The multiple-electrode hearing prosthesis designed in the Departments of Otolaryngology and Electrical Engineering (UMDOLEE) at the University of Melbourne (Clark et al., 1977) has been miniaturized with hybrid circuitry so that, if design changes are necessary as a result of initial patient testing, they can be made at minimal cost. This results, however, in increased package dimensions which makes its placement and the design of the surgery more critical. This problem is increased by the fact that we have considered it important to be able to remove the package and replace it with another without disturbing the implanted electrode array, should the first receiver-stimulator fail or an improved design become available. This has meant the design of a special connector (Patrick, 1977; Clark et al., 1978) which adds to the dimensions of the implanted unit. In addition the placement of the coils for transmitting power and information has to be considered. Not only is it desirable to site the coils at a convenient location behind the ear to facilitate the placement and wearing of the external transmitter, but there should also be no relative movement between the coils and the electronic package. These design considerations have led to the sitting of the coils on top of the hermetically-sealed box, and further increased the height of the package. The dimensions of the package shown in Fig. 1 are length 42 mm, width 32 mm, height of connector 8.5 mm, height of receiver-stimulato unit 13 mm. The surgical considerations discussed are the result of a number of temporal bone and cadaver dissections, and the surgical implantation at The Royal Victorian Eye and Ear Hospital of the UMDOLEE unit in a specially-selected patient.
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    A multiple-electrode cochlear implant
    Clark, Graeme M. ; Tong, Y. C. ; Bailey, Q. R. ; Black, R. C. ; Martin, L. F. ; Millar, J. B. ; O'Loughlin B. J. ; Patrick, J. F. ; Pyman, B. C. ( 1978)
    Interest in artificially stimulating the auditory nerve electrically for sensori-neural deafness was first sparked off by Volta in the 18th century. Count Volta, who was the first to develop the electric battery, connected up a number of his batteries to two metal rods which he inserted into his ears. Having placed the rods in his ears he pressed the switch and received "une secousse dans la tete" and perceived a noise like "the boiling of thick soup".
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    Surgical implications of perimodiolar cochlear implant electrode design: avoiding intracochlear damage and scala vestibuli insertion.
    Briggs, RJ ; Tykocinski, M ; Saunders, E ; Hellier, W ; Dahm, M ; Pyman, B ; Clark, GM (Informa UK Limited, 2001-09)
    OBJECTIVE: To review the mechanisms and nature of intracochlear damage associated with cochlear implant electrode array insertion, in particular, the various perimodiolar electrode designs. Make recommendations regarding surgical techniques for the Nucleus Contour electrode to ensure correct position and minimal insertion trauma. BACKGROUND: The potential advantages of increased modiolar proximity of intracochlear multichannel electrode arrays are a reduction in stimulation thresholds, an increase in dynamic range and more localized neural excitation. This may improve speech perception and reduce power consumption. These advantages may be negated if increased intracochlear damage results from the method used to position the electrodes close to the modiolus. METHOD: A review of the University of Melbourne Department of Otolaryngology experience with temporal bone safety studies using the Nucleus standard straight electrode array and a variety of perimodiolar electrode array designs; comparison with temporal bone insertion studies from other centres and postmortem histopathology studies reported in the literature. Review of our initial clinical experience using the Nucleus Contour electrode array. RESULTS: The nature of intracochlear damage resulting from electrode insertion trauma ranges from minor, localized, spiral ligament tear to diffuse organ of Corti disruption and osseous spiral lamina fracture. The type of damage depends on the mechanical characteristics of the electrode array, the stiffness, curvature and size of the electrode in relation to the scala, and the surgical technique. The narrow, flexible, straight arrays are the least traumatic. Pre-curved or stiffer arrays are associated with an incidence of basilar membrane perforation. The cochleostomy must be correctly sited in relation to the round window to ensure scala tympani insertion. A cochleostomy anterior to the round window rather than inferior may lead to scala media or scala vestibuli insertion. CONCLUSION: Proximity of electrodes to the modiolus can be achieved without intracochlear damage provided the electrode array is a free fit within the scala, of appropriate size and shape, and accurate scala tympani insertion is performed.
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    Comparison of electrode position in the human cochlea using various perimodiolar electrode arrays
    TYKOCINSKI, MICHAEL ; Cohen, Lawrence T. ; Pyman, Brian C. ; Roland (Jr), Thomas ; Treaba, Claudiu ; PALAMARA, JOSEPH ; Dahm, Markus C. ; Shepherd, Robert K. ; XU, JIN ; Cowan, Robert S. ; Cohen, Noel L. ; Clark, Graeme M. ( 2000)
    Objective: This study was conducted to evaluate the insertion properties and intracochlear trajectories of three perimodiolar electrode array designs and to compare these designs with the standard Cochlear /Melbourne array. Background: Advantages to be expected of a perimodiolar electrode array include both a reduction in stimulus thresholds and an increase in dynamic range, resulting in a more localized stimulation pattern of the spiral ganglion cells, reduced power consumption, and, therefore, longer speech processor battery life. Methods: The test arrays were implanted into human temporal bones. Image analysis was performed on a radiograph taken after the insertion. The cochleas were then histologically processed with the electrode array in situ, and the resulting sections were subsequently assessed for position of the electrode array as well as insertion-related intracochlear damage. Results: All perimodiolar electrode arrays were inserted deeper and showed trajectories that were generally closer to the modiolus compared with the standard electrode array. However, although the precurved array designs did not show significant insertion trauma, the method of insertion needed improvement. After insertion of the straight electrode array with positioner, signs of severe insertion trauma in the majority o fimplanted cochleas were found. Conclusions: Although it was possible to position the electrode arrays close to the modiolus, none of the three perimodiolar designs investigated fulfilled satisfactorily all three criteria of being easy, safe, and a traumatic to implant.
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    The development of speech perception in children using cochlear implants: effects of etiologic factors and delayed milestones
    PYMAN, BRIAN ; Blamey, Peter J. ; Lacy, Peter ; Clark, Graeme M. ; DOWELL, RICHARD ( 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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    Contributing factors to improved speech perception in children using the nucleus 22-channel cochlear prosthesis
    Cowan, Robert S. C. ; Galvin, Karyn L. ; KLIEVE, SHARON ; Barker, Elizabeth J. ; Sarant, Julia Z. ; DETTMAN, SHANI ; Hollow, Rod ; RANCE, GARY ; Dowell, Richard C. ; PYMAN, BRIAN ; Clark, Graeme M. ( 1997)
    It has been established that use of multiple-channel intracochlear implants can significantly improve speech perception for postlinguistically deafened adults. In the development of the Nucleus 22-channel cochlear implant, there have been significant developments in speech processing strategies, providing additional benefits to speech perception for users. This has recently culminated in the release of the Speak speech processing strategy, developed from research at the University of Melbourne. The Speak strategy employs 20 programmable bandpass filters which are scanned at an adaptive rate, with the largest outputs of these filters presented to up to ten stimulation channels along the electrode array. Comparative studies of the Speak processing strategy (in the Nucleus Spectra-22 speech processor), with the previously-used Multipeak (Multipeak) speech processing strategy (in the Minisystem-22 speech processor), with profoundly deaf adult cochlear implant users have shown that the Speak processing strategy provides a significant benefit to adult users both in quiet situations and particularly in the presence of background noise. Since the first implantation of the Nucleus device in a profoundly hearing-impaired child in Melbourne in 1985, there has been a rapid growth in the number of children using this device. Studies of cochlear implant benefits for children using the Nucleus 22-channel cochlear implant have also shown that children can obtain significant benefits to speech perception, speech production and language, including open-set understanding of words and sentences using the cochlear implant alone. In evaluating contributing factors to speech perception benefits available for children, four specific factors are important to investigate: (1) earlier implantation -resulting from earlier detection of deafness; (2) improved hardware and surgical techniques -allowing implantation in infants; (3) improved speech processing, and (4) improved habilitation techniques. Results reported previously have been recorded primarily for children using the Multipeak strategy implemented in the MSP speech processor. While it is important to evaluate the factors which might contribute to improvements in speech perception benefits, an important question is the effect of improved speech processing strategy, since this will determine what is perceived through the device. Given that adult patients changing to the Spectra speech processor had also shown improved perception in noisy situations, and the fact that children are in general in noisy environments in the classroom setting for a large proportion of their day, it was of obvious interest to evaluate the potential for benefit in poor signal-to-noise ratios from use of the Speak processing strategy and from specific training in the ability to perceive in background noise. The study was aimed at evaluating whether children who were experienced in use of the Multipeak speech processing strategy would be able to changeover to the new Speak processing strategy, which provides a subjectively different output. Secondly, the study aimed to evaluate the benefits which might accrue to children from use of controlled habilitation in background noise.
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    Speech perception results for children with implants with different levels of preoperative residual hearing
    Cowan, Robert S. C. ; DelDot, J. ; Barker, J. Z. ; Barker, Elizabeth J. ; Sarant, Julia Z. ; Pegg, P. ; Dettman, S. ; Galvin, K. L. ; Rance, G. ; Hollow, R. ; Dowell, R. C. ; Pyman, B. ; Gibson, W. P. R. ; Clark, Graeme, M. ( 1997)
    Objective: Many reports have established that hearing-impaired children using the Nucleus 22 channel cochlear implant may show both significant benefits to lipreading and significant scores on open-set words and sentences using electrical stimulation only. These findings have raised questions about whether severely or severely-to-profoundly deaf children should be candidates for cochlear implants. To study this question, postoperative results for implanted children with different levels of preoperative residual hearing were evaluated in terms of speech perception benefits. Study Design/Setting: A retrospective study of the first 117 children, sequentially, to undergo implantation in the Melbourne and Sydney Cochlear Implant Clinics was undertaken. All children had been assessed by and received their implants in a tertiary referral centre. Main Outcome Measures: To assess aided residual hearing, the children were grouped into four categories of hearing on the basis of their aided residual hearing thresholds measured preoperatively. To assess benefits, the scores of children on standard speech perception tests were reviewed. As different tests were used for children with different ages and language skills, children were grouped into categories according to the level of postoperative speech perception benefit. Results: The results showed that children in the higher categories of aided preoperative residual hearing showed significant scores on open-set word and sentence perception tests using the implant alone. For children in lower categories of aided residual hearing, results were variable within the groups. More than 90% of children with implants with aided residual hearing thresholds in the speech range above I kHz achieved open-set understanding of words and sentences. Conclusion: While the results of this preliminary study confirm previous findings of differential outcomes for children with different levels of preoperative residual hearing, they suggest that children with severe to profound hearing impairments should be considered for cochlear implantation.
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    Surgery
    Clark, Graeme M. ; Pyman, Brian C. ; Webb, Robert L. (Singular Publishing, 1997)
    Cochlear implant surgery should be undertaken only after the cochlear implant team has established that the child is not achieving useful communication with a hearing aid. This can be difficult because of poor language development in deaf children in this age group or because the child is at a preverbal stage and too young for the use of formal assessment tests. The child's unaided and aided thresholds, however, are important for assessment, as are his or her communication skills. These need to be evaluated by an experienced paediatric audiologist.
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    Preoperative medical evaluation
    Clark, Graeme M. ; Pyman, Brian C. (Singular Publishing, 1997)
    The aim of the medical assessment of infants and children is to determine the cause, severity and duration of any hearing loss as well as the presence of any medical conditions that may influence their management with a cochlear implant. There should also be an initial assessment of the child's communication skills and the parental expectations for his or her education.