Graeme Clark Collection
Permanent URI for this collection
Search Results
1 - 10 of 124
-
ItemA multiple-channel cochlear implant: an evaluation using open-set CID sentences( 1981)A multiple-channel cochlear implant and speech processor have been used in two postlingually deaf adult patients with a total hearing loss, to enable them to perceive varying degrees of running speech. The results have been confirmed with open-set CID everyday sentence tests. Using the implant alone, the patients obtained 8% and 14% scores with pre-recorded material, and 34% and 36% scores for "live" presentations. This was equivalent to the perception of 35% of connected discourse. When the implant was used in conjunction with lipreading, improvements of 188% and 386% were obtained over lipreading alone, and the scores were 68% and 98% which were equivalent to the perception of 60% and 95% of connected discourse.
-
ItemA protocol for the prevention of infection in cochlear implant surgery(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.
-
ItemA preliminary report on a multiple-channel cochlear implant operation(Cambridge University Press, 1979)Intra-cochlear single-channel electrical stimulation has recently been attempted by Michelson (1971) and by House and Urban (1973). Douek et at. (1977) have described experiments with a single-channel promontory electrode system. It is generally accepted that a single-channel system is useful in conveying crude auditory information such as the presence of sounds and some prosodic features of speech (Bilger et al., 1977; Douek et al., 1977). (From Introduction)
-
ItemThe surgery for multiple-electrode cochlear implantations(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.
-
ItemA cochlear implant round window electrode array(Cambridge University Press, 1979)One important aspect of cochlear implantation is the placement of a multiple-electrode array close to residual auditory nerve fibres so that discrete groups of fibres can be stimulated electrically according to the place basis of frequency coding. Furthermore, in patients who are postlingually deaf these electrodes should lie in relation to the nerve fibres which are responsible for transmitting the frequencies which are important in speech comprehension, viz. 300-3,000 Hz. The method of electrode insertion should also ensure that there is no significant damage to auditory nerve fibres.
-
ItemA multiple-electrode cochlear implant( 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".
-
ItemDesign criteria of a multiple-electrode cochlear implant hearing prosthesis( 1978)Abstract not available due to copyright.
-
ItemHearing restoration with the multichannel auditory brainstem implant( 1997)Restoration of useful hearing is now possible in patients with bilateral acoustic neuromas by direct electrical stimulation of the cochlear nucleus. Our first experience with the Multichannel Auditory Brainstem Implant is reported. A forty four year old female with bilateral acoustic neuromas and a strong family history of Neurofibromatosis Type II presented with profound bilateral hearing impairment. Translabyrinthine removal of the right tumour was performed with placement of the Nucleus eight electrode Auditory Brainstem Implant. Intraoperative electrically evoked auditory brainstem response monitoring successfully confirmed placement over the cochlear nucleus. Postoperatively, auditory responses were obtained on stimulation of all electrodes with minimal non-auditory sensations. The patient now receives useful auditory sensations using the "SPEAK" speech processing strategy. Auditory brainstem Implantation should be considered for patients with Neurofibromatosis Type II in whom hearing preservation tumour removal is not possible.
-
ItemCochlear view: postoperative radiography for cochlear implantation( 2000)Objective: This study aimed to define a spatial position of the cochlea in the skull based on anatomical studies and to design an appropriate method of skull radiography for demonstration of the multichannel intracochlear electrode array and the structures of the inner ear, for use in evaluating the electrode position and its related pitch perception. Background: The conventional skull radiograph (plain radiograph)can offer a complete and direct image of an intracochlear electrode array, if the x-ray is directed to the cochlea and parallel to the axis of the cochlea. Methods: Measurement from computed tomography imaging and three-dimensional reconstruction were performed to define the spatial position of the cochlea in the skull. Results: A radiographic projection, the cochlear view, was designed. A detailed radiographic method and radiologic interpretation of the cochlear view is described. An improved clinical method for measuring the longitudinal and angular position of the electrodes from the cochlear view is recommended. Conclusions: The application of the cochlear view has proved that it is beneficial postoperatively in documenting the results of cochlear implantation, and in evaluating the depth of insertion and position of individual electrodes. It serves as a valuable reference for managing frequency mapping, optimizing speech processing strategies, and further research purposes. The method can be widely used in cochlear implant clinics because of its simplicity, low radiation, speed, and minimal cost.
-
ItemSpeech perception as a function of electrical stimulation rate: using the nucleus 24 cochlear implant system( 2000)Objective: To investigate the effect of varying electrical stimulation rate on speech comprehension by cochlear implant users, while keeping the number of stimulated channels constant. Design: Three average rates of electrical stimulation,250, 807, and 1615 pulses per second per channel (pps/ch), were compared using a speech processing strategy that employed an electrode selection technique similar to that used in the Spectral Maxima Sound Processor strategy (McDermott, McKay,& Vandali, 1992; McDermott & Vandali, Reference Note 1; McKay, McDermott, Vandali, & Clark, 1991)and the Spectral Peak strategy (Skinner et al., 1994;Whitford et al., 1995). Speech perception tests with five users of the Nucleus 24 cochlear implant system were conducted over a 21-wk period. Subjects were given take-home experience with each rate condition. A repeated ABC evaluation protocol with alternating order was employed so as to account for learning effects and to minimize order effects. Perception of open-set monosyllabic words in quiet and open-set sentences at signal to noise ratios ranging from +20 to 0 dB, depending on the subject’s ability, were tested. A comparative performance questionnaire was also administered. Results: No statistical differences in group performance between the 250 and 807 pps/ch rates were observed in any of the speech perception tests. However, significantly poorer group performance was observed for the 1615 pps/ch rate for some tests due predominantly to the results of one subject. Analysis of individual scores showed considerable variation across subjects. For some subjects, one or more of the three rate conditions evaluated provided benefits on some speech perception tasks. The results of the comparative performance questionnaire indicated a preference for the 250 and 807pps/ch rates over the 1615 pps/ch rate for most listening situations. Conclusions: For the speech processing strategy, implant system, and subjects evaluated in this study, the group results indicated that the use of electrical stimulation rates higher than 250 pps/ch (up to 1615 pps/ch) generally provided no significant improvement to speech comprehension. However, individual results indicated that perceptual.