Graeme Clark Collection
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ItemMeningitis after cochlear implantation: the risk is low, and preventive measures can reduce this further( 2007)Since the 1980s, more than 80 000 people have received cochlear implants worldwide. These implants are designed to enable people who are severely or profoundly deaf to experience sound and speech. Since 1990, implantation has become standard treatment for people who cannot communicate effectively despite well fitted hearing aids. Children who are deaf when they are born can perceive sound and learn to speak if they receive cochlear implants at a young age (ideally under 18 months). The use of cochlear implants has been thought to be safe. But since 2002 the number of patients with meningitis related to cochlear implantation has increased worldwide. Mortality and neurological complications after meningitis are high. We need to investigate the reasons for this and look at measures to reduce them.
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ItemThreshold shift: effects of cochlear implantation on the risk of pneumococcal meningitis( 2007)Unavailable due to copyright.
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ItemEffects of inner ear trauma on the risk of pneumococcal meningitis( 2007)Objective: To examine the risk of pneumococcal meningitis in healthy rats that received a severe surgical trauma to the modiolus and osseous spiral lamina or the standard insertion technique for acute cochlear implantation. Design: Interventional animal studies. Subjects: Fifty-four otologically normal adult Hooded- Wistar rats. Interventions: Fifty-four rats (18 of which received a cochleostomy alone; 18, a cochleostomy and acute cochlear implantation using standard surgical techniques; and 18, a cochleostomy followed by severe inner ear trauma) were infected 4 weeks after surgery with Streptococcus pneumoniae via 3 different routes (hematogenous, middle ear, and inner ear) to represent all potential routes of bacterial infection from the upper respiratory tract to the meninges in cochlear implant recipients with meningitis. Results: Severe trauma to the osseous spiral lamina and modiolus increased the risk of pneumococcal meningitis when the bacteria were given via the middle or inner ear (Fisher exact test, P<.05). However, the risk of meningitis did not change when the bacteria were given via the hematogenous route. Acute electrode insertion did not alter the risk of subsequent pneumococcal meningitis for any route of infection. Conclusions: Severe inner ear surgical trauma to the osseous spiral lamina and modiolus can increase the risk of pneumococcal meningitis. Therefore, every effort should be made to ensure that cochlear implant design and insertion technique cause minimal trauma to the bony structures of the inner ear to reduce the risk of pneumococcalmeningitis.
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ItemAssessment of the protective effect of pneumococcal vaccination in preventing meningitis after cochlear implantation( 2007)Objectives: To examine if a 23-valent pneumococcal capsular polysaccharide vaccine (PPV23) reduces the risk of meningitis in healthy rats after cochlear implantation. Design: Interventional animal study. Interventions: Thirty-six rats (18 immunized and 18 unimmunized) received cochlear implantations and were then infected with Streptococcus pneumoniae via 3 different routes (hematogenous, middle ear, and inner ear) in numbers sufficient to induce meningitis. Results: The rats with implants that received PPV23 were protected from meningitis when the bacteria were delivered via the hematogenous and middle-ear routes (Fisher exact test P<.05). However, the protective effect of the vaccine in the rats with implants was only moderate when the bacteria were inoculated directly into the inner ear. Conclusions: Our animal model clearly demonstrates that immunization can protect healthy rats with a cochlear implant from meningitis caused by a vaccine-covered serotype. This finding supports the notion that all current and future implant recipients should be vaccinated against S pneumoniae.
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ItemA stochastic model of the electrically stimulated nerve designed for the analysis of large-scale population [Abstract]( 1997)Accurate models of Auditory Nerve (AN) response to electrical stimulation may aid in the development of speech processing strategies for cochlear implants. Most models of AN response to electrical stimulation utilize deterministic (non-random) description in spite of strong evidence for stochastic (random) activity in physiological data. Inclusion of stochastic activity in complex models of neural response such as the Hodgkin-Huxley equations has proven to be computationally expensive. They are therefore unsuitable at this time for the calculation of large-scale population responses which could be required for the investigation of sound coding in ensembles of nerve fibers, for the explanation or prediction of psychophysical results, or for the development of speech processing strategies for cochlear implants. It is therefore necessary to develop a simpler model of single-fiber response to electrical stimulation which includes stochastic activity.
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ItemElectrical stimulation of the auditory nerve: prediction psychophysical by a model including stochastic aspects of neural response [Abstracts]( 1997)Accurate models of Auditory Nerve (AN) response to electrical Stimulation may assist with the development of speech processing strategies for cochlear implants. Until recently most models of AN response to electrical stimulation have utilised deterministic (non random) descriptions, in spite of strong evidence for stochastic (random) components of behaviour in the neurophysiological data models of auditory performance using these deterministic descriptions have been unable to predict many important psychophysical phenomena. Can stochastic models improve these predictions.
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ItemA mathematical model of electrical stimulation of the auditory nerve [Abstract]( 1997)Accurate models of Auditory Nerve (AN) response to electrical Stimulation may assist with the development of speech processing strategies for cochlear implants. Until recently most models of AN response to electrical stimulation have utilised deterministic (non random) descriptions, in spite of strong evidence for stochastic (random) components of behaviour in the neurophysiological data. Models of auditory performance using these deterministic descriptions have been unable to predict many important psychophysical phenomena. Can stochastic models improve these predictions.
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ItemResponses from single units in the dorsal cochlear nucleus to electrical stimulation of the cochlea( 1992)To help improve our understanding of how the brain responds to electrical stimulation of the auditory nerve we have examined the responses of dorsal cochlear nucleus (DCN) units to both acoustic stimulation and electrical stimulation of the cochlea. This work extended our previous studies which have compared the responses to electrical and acoustic stimulation In the auditory nerve (Javel et al 1987, Ann. Otol. Rhinol. laryngeal. Suppl. 128, 96:2630) and the ventral cochlear nucleus (Shepherd et al 1988, NIH Contract NO1-NS-72342, 5th Quarterly Progress Report).