Protective effects of local administration of ciprofloxacin on the risk of pneumococcal meningitis after cochlear implantation. (49/432)

OBJECTIVES: To determine whether ciprofloxacin retains its antimicrobial activity after storage with Healon at ambient temperature and at 37 degrees C over 5 weeks and then to establish whether the application of ciprofloxacin/Healon onto scala tympani electrode arrays reduces the risk of meningitis in implanted rats inoculated with S. pneumoniae. STUDY DESIGN: In vitro laboratory and in vivo animal studies METHODS: The antibacterial activity of three concentrations of ciprofloxacin/Healon (7.5, 75, and 750 microg/mL) was examined over 5 weeks at both ambient temperature (23 degrees C) and body temperature (37 degrees C). Thirty-six rats (18 implanted with ciprofloxacin [750 mg/mL]/Healon-coated electrode array and 18 without the coating) were infected with S. pneumoniae 4 weeks after implantation by way of three different routes of infection (hematogenous, middle ear, and inner ear) and observed for the development of meningitis. RESULTS: The antibacterial activity of ciprofloxacin/Healon was maintained over 5 weeks at both 23 degrees C and 37 degrees C. The implanted rats with the ciprofloxacin/Healon-coated electrode array were protected from meningitis when the bacteria were given by way of the hematogenous route (Fisher's exact test, P = .008) but not when the bacteria were inoculated directly into the middle or inner ear. However, the time to develop meningitis was significantly longer in rats implanted with a coated array, irrespective of the route of inoculation (P < .05, log rank test). CONCLUSION: Our animal model demonstrated that a ciprofloxacin-coated electrode array can protect healthy implanted rats from meningitis when the route of infection is hematogenous and can delay the onset of meningitis when bacteria are inoculated directly into the middle or inner ear.  (+info)

Educational responses to varying objectives of parents of deaf children: a Dutch perspective. (50/432)

In 1999, Mary Brennan wrote "By recognising the child as, in effect, a 'little linguist' we are also recognising the power and effectiveness of the child's linguistic capacity" (Brennan, 1999). The recognition of the power and effectiveness of deaf children's linguistic capacity needs to be taken a step further. Focus should be on the conditions in the children's environments necessary to develop their linguistic capacity to its fullest potential and to enhance the use of this capacity in academic and social learning. This leads to the issue of the identification of the right language and instructional mix for deaf children, the topic that is addressed in this article. Essential in this process of identification are the educational objectives parents of deaf children have and the choices they make. This is related to a second issue, that of professional advice. Both issues are characterized by several dilemmas. These dilemmas are illustrated and directions are put forward that will enable educators to negotiate these dilemmas.  (+info)

Implications of deep electrode insertion on cochlear implant fitting. (51/432)

Using long Med-El Combi40+ electrode arrays, it is now possible to cover the whole range of the cochlea, up to about two turns. Such insertion depths have received little attention. To evaluate the contribution of deeply inserted electrodes, five Med-El cochlear implant users were tested on vowel and consonant identification tests with fittings with first one, two, and up to five apical electrodes being deactivated. In addition, subjects performed pitch-ranking experiments, using loudness-balanced stimuli, to identify electrodes creating pitch confusions. Radiographs were taken to measure each electrode insertion depth. All subjects used each modified fitting for two periods of about 3 weeks. During the experiment, the same stimulation rate and frequency range were maintained across all the fittings used for each individual subject. After each trial period the subject had to perform three consonant and three vowel identification tests. All subjects showed deep electrode insertions ranging from 605 degrees to 720 degrees. The two subjects with the deepest electrode insertions showed significantly increased vowel- and consonant-identification performances with fittings with the two or three most apical electrodes deactivated compared to their standard fitting with all available electrodes activated. The other three subjects did not show significant improvements in performance when one or two of their most apical electrodes were deactivated. Four out of five subjects preferred to continue use of a fitting with one or more apical electrodes deactivated. The two subjects with the deepest insertions also showed pitch confusions between their most apical electrodes. Two possible reasons for these results are discussed. One is to reduce neural interactions related to electrodes producing pitch confusions. Another is to improve the alignment of the frequency components of sounds coded by the electrical signals delivered to each electrode to the overall pitch of the auditory perception produced by the electrical stimulation of auditory nerve fibers.  (+info)

Using evoked potentials to match interaural electrode pairs with bilateral cochlear implants. (52/432)

Bilateral cochlear implantation seeks to restore the advantages of binaural hearing to the profoundly deaf by providing binaural cues normally important for accurate sound localization and speech reception in noise. Psychophysical observations suggest that a key issue for the implementation of a successful binaural prosthesis is the ability to match the cochlear positions of stimulation channels in each ear. We used a cat model of bilateral cochlear implants with eight-electrode arrays implanted in each cochlea to develop and test a noninvasive method based on evoked potentials for matching interaural electrodes. The arrays allowed the cochlear location of stimulation to be independently varied in each ear. The binaural interaction component (BIC) of the electrically evoked auditory brainstem response (EABR) was used as an assay of binaural processing. BIC amplitude peaked for interaural electrode pairs at the same relative cochlear position and dropped with increasing cochlear separation in either direction. To test the hypothesis that BIC amplitude peaks when electrodes from the two sides activate maximally overlapping neural populations, we measured multiunit neural activity along the tonotopic gradient of the inferior colliculus (IC) with 16-channel recording probes and determined the spatial pattern of IC activation for each stimulating electrode. We found that the interaural electrode pairings that produced the best aligned IC activation patterns were also those that yielded maximum BIC amplitude. These results suggest that EABR measurements may provide a method for assigning frequency-channel mappings in bilateral implant recipients, such as pediatric patients, for which psychophysical measures of pitch ranking or binaural fusion are unavailable.  (+info)

Effects of inner ear trauma on the risk of pneumococcal meningitis. (53/432)

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 pneumococcal meningitis.  (+info)

Tone production of Mandarin Chinese speaking children with cochlear implants. (54/432)

OBJECTIVE: The purpose of the present study was to investigate tone production performance of native Mandarin Chinese speaking children with cochlear implants and to evaluate the effects of age at implantation and duration of implant use on tone production in those children. METHODS: Fourteen prelingually deaf children who had received cochlear implantation and 14 age-matched normal-hearing children participated in the study. Both groups were of native Mandarin Chinese speaking children. One hundred and sixty tone tokens were recorded from each of the children. The total of 4480 tokens (160x28) were then used in the tone perception tests in which seven normal-hearing native Mandarin Chinese speaking adults participated. RESULTS: The tone production of the cochlear implant children showed tremendous individual variability. The group mean performance was 48.4% correct, statistically significantly lower than the group mean performance of 78.0% correct in the normal-hearing controls. The tone confusion matrix analysis revealed that the production of Mandarin tone 2 (the rising tone) was most severely impaired in the cochlear implant children, followed by tone 3 (the low and dipping tone) and tone 4 (the falling tone). The most frequently perceived tone irrespective of the target tone was tone 1 (the high level tone). The tone production performance was negatively correlated with the age at implantation and positively correlated with the duration of implant use. CONCLUSIONS: There is a remarkable deficit in tone production in a majority of native tone language speaking, prelingually deaf children who have received cochlear implants. While an increased duration of implant use might facilitate tone production, the age at implantation appears to have a negative effect on tone production in cochlear implant children. Therefore, early implantation might be beneficial to tone production in prelingually deaf children whose native language is a tone language.  (+info)

Cochlear implants and ex vivo BDNF gene therapy protect spiral ganglion neurons. (55/432)

Spiral ganglion neurons often degenerate in the deaf ear, compromising the function of cochlear implants. Cochlear implant function can be improved by good preservation of the spiral ganglion neurons, which are the target of electrical stimulation by the implant. Brain derived neurotrophic factor (BDNF) has previously been shown to enhance spiral ganglion survival in experimentally deafened ears. Providing enhanced levels of BDNF in human ears may be accomplished by one of several different methods. The goal of these experiments was to test a modified design of the cochlear implant electrode that includes a coating of fibroblast cells transduced by a viral vector with a BDNF gene insert. To accomplish this type of ex vivo gene transfer, we transduced guinea pig fibroblasts with an adenovirus with a BDNF gene cassette insert, and determined that these cells secreted BDNF. We then attached BDNF-secreting cells to the cochlear implant electrode via an agarose gel, and implanted the electrode in the scala tympani. We determined that the BDNF expressing electrodes were able to preserve significantly more spiral ganglion neurons in the basal turns of the cochlea after 48 days of implantation when compared to control electrodes. This protective effect decreased in the higher cochlear turns. The data demonstrate the feasibility of combining cochlear implant therapy with ex vivo gene transfer for enhancing spiral ganglion neuron survival.  (+info)

Threshold shift: effects of cochlear implantation on the risk of pneumococcal meningitis. (56/432)

OBJECTIVES: The study goals were to examine whether cochlear implantation increases the risk of meningitis in the absence of other risk factors and to understand the pathogenesis of pneumococcal meningitis post cochlear implantation. STUDY DESIGN AND SETTING: Four weeks following surgery, 54 rats (18 of which received a cochleostomy alone, 18 of which received a cochleostomy and acute cochlear implantation using standard surgical techniques, and 18 of which received a cochlear implant) were infected with Streptococcus pneumoniae via three different routes of bacterial inoculation (middle ear, inner ear, and intraperitoneal) to represent all potential routes of bacterial infection from the upper respiratory tract to the meninges. RESULTS: The presence of a cochlear implant reduced the threshold of bacteria required to cause pneumococcal meningitis from all routes of infection in healthy animals. CONCLUSION: The presence of a cochlear implant increases the risk of pneumococcal meningitis regardless of the route of bacterial infection. SIGNIFICANCE: Early detection and treatment of pneumococcal infection such as otitis media may be required, as cochlear implantation may lead to a reduction of infectious threshold for meningitis.  (+info)