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PubMed2004

An in vitro model for investigating impedance changes with cell growth and electrical stimulation: implications for cochlear implants.

The impedance of stimulating electrodes used in cochlear implants and other neural prostheses often increases post-implantation, and is thought to be due to fibrous tissue encapsulation of the electrode array. Increased impedance results in higher power requirements to stimulate target neurons at set charge densities. We developed an in vitro model to investigate the electrode-tissue interface in a highly controlled environment. This model was tested using three cell types, with and without charge-balanced biphasic electrical stimulation. Under standard tissue culture conditions, a monolayer of cells was grown over the electrode surface. Electrode impedance increased in proportion to the extent of cell coverage of the electrode. Cell type was a significant factor in the amount of impedance increase, with kidney epithelial cells (MDCK) creating the greatest impedance, followed by dissociated rat skin fibroblasts and then macrophages (J774). The application of electrical stimulation to cell-covered electrodes caused impedance fluctuations similar to that seen in vivo, with a lowering of impedance immediately following stimulation, and a recovery to pre-stimulation levels during inactive periods. Examination of these electrodes suggests that the stimulation-induced impedance changes were due to the amount of cell cover over the electrodes. This in vitro technique accurately models the changes in impedance observed with neural prostheses in vivo, and shows the close relationship between impedance and tissue coverage adjacent to the electrode surface. We believe that this in vitro approach holds great promise to further our knowledge of the mechanisms contributing to electrode impedance.

Animals↗

PubMed1990

Computer-aided 3-D temporal bone anatomy for cochlear implant surgery.

To define anatomical relationships important in cochlear implantation, computer-aided three-dimensional reconstruction and measurement of middle and inner ear structures in six normal temporal bones were performed. Our findings were as follows: 1. When viewed from the posterior hypotympanotomy (facial recess) approach, the inferior 10% to 30% of the round window (RW) membrane was visible in only half the cases. 2. The most inferior portion of the basal turn of the scala tympani was not only inferior but also slightly anteriorly behind the RW membrane in more than half the cases. 3. The shortest distances from the aperture of the RW niche and from the margin of the RW to the stapes head were 2.38 +/- 0.33 and 2.15 +/- 0.22 mm, respectively. 4. The distance between the RW and the most inferior portion of the basal turn scala tympani was 5.15 +/- 0.34 mm. 5. The direction of the electrode advancement lay at a sharp angle to the inferior part of the RW (mean 31.9 +/- 3.6 degrees). 6. The direction from the RW to the most inferior portion of the basal turn scala tympani lay 16.0 +/- 5.3 degrees anteroinferior to the direction of the advancement of the electrode to the RW. 7. The distance between the margin of the RW and the basilar membrane of the cochlea was 0.58 +/- 0.10 mm at the superior aspect of the RW, and was 1.23 +/- 0.12 mm at the lateral aspect of the RW. 8. Dissecting away less than 1 mm (mean 0.7 +/- 0.27 mm) of the RW margin inferiorly or inferolaterally was enough to permit straight insertion of the electrode in most cases.

Adolescent↗

PubMed1982

Interim assessment of candidates for cochlear implants.

The Minimal Auditory Capabilities battery was administered to patients with profound postlingual sensorineural hearing loss to obtain interim audiometric indices on the relative benefits of cochlear implants and hearing aids. One group used a cochlear implant comprising a multielectrode array and a single-channel stimulator, another group wore hearing aids, with only borderline satisfaction, and the third group wore hearing aids to good advantage. Scores for the latter group were consistently higher than the borderline group on two prosodic tests, but the borderline group scored better on closed-set spondee and vowel recognition tests. Scores were essentially the same for the two groups on the remaining tests. Tentative criteria induces were applied to members of the borderline group in terms of the hearing improvement that might be anticipated from an implant.

Adult↗

PubMed2000

Cochlear implantation of Danish prelingually deaf children.

The aim of the study was to review the indications, techniques and results of cochlear implant (CI) treatment with the Nucleus CI multi-channel electrode for the first children operated on in Denmark. The study material comprised 16 children (5 girls, 11 boys). Their median age at the time of CI operation was 27 months. Anacusis was caused by pneumococcal meningitis in 31% of the children in this relatively young prelingual material. Obliteration of the cochlea was found in two children, indicating the need for surgery as soon as possible after the verification of post-meningitis, total deafness. There were no technical difficulties with operating on the youngest children in the congenital group and the age of 2 years is optimal for implantation. These preliminary results have contributed definitively to an increase in the number of cochlear implantations being carried out in young prelingually deaf Danish children.

Child↗

PubMed2005

Cochlear implantation in a patient with profound hearing loss with the A1555G mitochondrial DNA mutation and no history of aminoglycoside exposure.

The A1555G mitochondrial deoxyribonucleic acid (mtDNA) point mutation has classically been associated with sensorineural hearing loss in patients following aminoglycoside exposure. More recently, the mutation has been implicated in sensorineural hearing loss in patients without previous aminoglycoside use. In addition, cochlear implantation has been shown to be effective in the group of patients with prior aminoglycoside exposure but, to date, no case of cochlear implantation in a patient with the A1555G mutation and no prior exposure to aminoglycosides has been explicitly described in the literature. We report the case of an 80-year-old woman with the A1555G mtDNA mutation, a 35-year history of bilateral progressive hearing loss and no history of aminoglycoside exposure who underwent successful implantation of a Nucleus 24 Contour device at our institution. Post-operatively, the patient exhibited marked improvement in tests of auditory performance. We conclude that cochlear implantation can be an effective method to restore some sense of hearing in patients with the A1555G mtDNA mutation and sensorineural hearing loss.

Aged, 80 and over↗

PubMed2003

Long-term evaluation of the effect of intracochlear steroid deposition on electrode impedance in cochlear implant patients.

OBJECTIVE: To evaluate the long-term effect of intracochlear steroid deposition on electrode impedance in patients with cochlear implants. STUDY DESIGN: A retrospective study was carried out comparing the impedances of cochlear implant electrodes with and without a single application of steroids in the cochlea. PATIENTS: Ninety two implanted children with an average age of 5 years (range, 0.7 to 16 years) were divided in four groups according to the type of electrode and the use of steroids or not. In addition, the impedances of five children who required a reimplantation are reported. MAIN OUTCOME MEASURE: The impedances of Nucleus electrodes, either straight or Contour, were measured at regular intervals up to 12 months after surgery. RESULTS: Two months after surgery, the impedances in the steroid groups were significantly lower than in the nonsteroid groups (straight electrodes, 3.9 versus 4.7 kOhm, respectively; Contour electrodes, 5.4 versus 6.5 kOhm, respectively). This reduction remained stable over time for the straight electrodes, but for the Contour electrodes, it seemed to disappear after 6 months. The impedances after a second implantation were significantly higher than after a first implantation (median value, 8.8 kOhm after 2 months). CONCLUSIONS: The application of a single dose of a steroid solution reduces the electrode impedances significantly, and, for the straight electrodes, this effect seems to last. It seems justified to reimplant with caution, because this seems to increase the impedances substantially.

Administration, Topical↗

PubMed1989

Temporal bone computed tomography in the preoperative evaluation for cochlear implantation.

High resolution computed tomography of the temporal bone is performed routinely in the preoperative evaluation for cochlear implantation. A retrospective review was performed to determine the effect of these studies. The clinical significance was determined through consultation with the referring otolaryngologist and review of the operative reports. Twelve examinations were reviewed. Abnormalities were identified in 12 of the 24 ears examined (eight of 12 patients studied). In two patients the CT examination strongly influenced the selection of the ear to be implanted. In four additional cases information felt to be useful in preoperative planning was provided. Useful information related to potential complications with the mechanical insertion of the electrode apparatus. We conclude that temporal bone abnormalities are common in the population undergoing cochlear implantation and that high resolution temporal bone CT is essential in preoperative evaluation. The CT scan should be interpreted with adequate knowledge of the operative procedure to evaluate any possible barriers to the mechanical insertion of the internal components of the system.

Cochlear Implants↗

PubMed2000

Language and reading acquisition in children with and without cochlear implants.

These data provide a coherent view of the spoken language and reading skills of children receiving cochlear implants. The data reveal both spoken language gains and clear benefit to these children with regard to reading. Improvement in reading is consistent with predictions based on prior research demonstrating a strong association between spoken language and reading. An intervention such as a cochlear implant has a direct effect on spoken language, and this can subsequently affect reading performance. This provides some of the first experimental evidence supporting the causal relationship between spoken language and reading.

Adolescent↗

PubMedDate not supplied

[Computed tomography in the evaluation of cochlear structural features in cochlear implantation].

Temporal bone computed tomographic scans were studied in 136 deaf patients of different age and sex, including 56 patients (39 children and 17 adults) rehabilitated with cochlear implantation (CI). The mean values of the cochlear parameters that are important for the results of a surgical CI stage, namely: the diameter of the cochlear base (DCB), the diameter of the basal helix, the height of the cochlea, the angle between the cochlear base and the promontorial wall, were calculated. These parameters were compared in different age groups. A correlation was determined for each of the studied parameters and for the depth of intracochlear insertion of electrodes. There was a significant correlation between DCB and the depth of insertion of the electrodes of CI22M and CI24M cochlear implants. DBC at which the active part of the electrode chain of an implant could be significantly more frequently placed in the tympanic scala of the cochlea was estimated.

Adolescent↗

PubMed2003

Patterns of phoneme perception errors by listeners with cochlear implants as a function of overall speech perception ability.

Many studies have noted great variability in speech perception ability among postlingually deafened adults with cochlear implants. This study examined phoneme misperceptions for 30 cochlear implant listeners using either the Nucleus-22 or Clarion version 1.2 device to examine whether listeners with better overall speech perception differed qualitatively from poorer listeners in their perception of vowel and consonant features. In the first analysis, simple regressions were used to predict the mean percent-correct scores for consonants and vowels for the better group of listeners from those of the poorer group. A strong relationship between the two groups was found for consonant identification, and a weak, nonsignificant relationship was found for vowel identification. In the second analysis, it was found that less information was transmitted for consonant and vowel features to the poorer listeners than to the better listeners; however, the pattern of information transmission was similar across groups. Taken together, results suggest that the performance difference between the two groups is primarily quantitative. The results underscore the importance of examining individuals' perception of individual phoneme features when attempting to relate speech perception to other predictor variables.

Adolescent↗

PubMed1999

Complications in pediatric cochlear implant surgery.

In a retrospective analysis we evaluated the intra and postoperative complications in children who underwent cochlear implantation between 1984 and 1993 at the Medizinische Hochschule Hannover. The data and records of 366 children were collected and analyzed. Relevant parameters were major complications such as significant infection, intraoperative bleeding, facial nerve injury, implant loss and device failure, as well as lesser complications, including delayed wound healing, chronic pain and vertigo. Late complications such as cholesteatoma or electrode dislocations were also registered. Cases of acute otitis media were managed with conservative treatment. Data presented indicate that cochlear implant surgery in children is a reliable and safe procedure with a low percentage of severe complications. Problems related to ear surgery can occur and should be manageable with standard procedures. Careful operative techniques and sufficient personal experience can help avoid severe post-operative problems.

Adolescent↗

PubMed2006

Surgical and medical complications following cochlear implantation: comparison of two surgical approaches.

Our study was designed to evaluate the complication rate of cochlear implantation (CI) and to compare two different surgical approaches that are currently being used for implantations in our department. This retrospective study was conducted on the patients who underwent CI in our center between 1989 and 2003 and who were followed-up for at least 18 months. The patients were divided into two groups according to the surgical technique that had been used for the implantation: the mastoidectomy with posterior tympanotomy approach and the suprameatal approach (without mastoidectomy). The incidence of complications following CI was compared between the two groups and between children and adults. Facial nerve paralysis, electrode misplacement, injury to the chorda tympani nerve and mastoiditis occurred only in the mastoidectomy with posterior tympanotomy approach group. Acute middle ear infection with or without mastoiditis emerged as the most common complication in both groups, followed by vestibular and wound problems. Disequilibrium was significantly more common among the adults than among the children (p < 0.0001). The suprameatal approach was demonstrated as being a good alternative technique to the classical surgery for CI.

Adolescent↗

PubMed2003

The perceptual effects of interphase gap duration in cochlear implant stimulation.

The most common current pulse shape used for cochlear implants is a biphasic rectangular pulse. The interphase gap (IPG) is the duration of the zero-current portion which lies between the two phases. It is known from single-nerve studies in animals that, as the IPG decreases, the biphasic pulse becomes less efficient in activating the nerve cell. Thus, it can be predicted that stimulation using smaller IPGs will necessitate the use of higher currents to maintain the loudness required by the cochlear implantee. The development of contemporary processing schemes commonly involves the maximization of the rate parameter, and to achieve this in sequential pulsatile stimulation, the IPG as well as the pulse phase duration must be minimized. This experiment investigated the effect of IPG on loudness in eight cochlear implantees who use the CI24 implant manufactured by Cochlear Ltd. An exponential increase in current level was required to maintain equal loudness when IPG is reduced from 100 to 45 and 8.4 micros. The effect of IPG was greater at lower levels, was greater for shorter pulse durations (26 micros compared to 52 micros), and was not significantly different for the rates (1 kHz or 4 kHz) tested.

Cochlear Implants↗

PubMed2003

[How is tinnitus influenced by cochlear implantation?].

INTRODUCTION: Tinnitus is one of the most common symptoms in patients with profound sensorineural hearing loss (SNHL). Cochlear implantation (CI), which has become a standard method to rehabilitate profound SNHL, has been also observed to effect tinnitus in many cases. In the Salzburg Cochlear Implant Center,more than 230 profoundly deaf patients, mainly children,have been provided with CI between 1992 and 2000. PATIENTS AND METHOD: In a retrospective study, 39 adult patients were assessed by questionnaire for the frequency of tinnitus, subjective loudness sensitivity, and tinnitus-specific impairment before and after the CI. RESULTS: Before implantation 26 patients had tinnitus, while 24 patients had the same symptoms after the CI. In 13 patients (50%) tinnitus remained unaffected by the operation. Intensity of tinnitus decreased in seven patients (26.7%), and in four patients (15.4%) it completely disappeared after the implantation.However, intensity increased in two patients (7.7%), and in another two patients, who had not experienced tinnitus before, it began first after the implantation. No correlation has been found between the daily using time of CI and the tinnitus impairment.Also no effect of tinnitus was seen on postoperative hearing assessed by Freiburg numbers, monosyllables, and Innsbruck sentence test scores. CONCLUSION: CI significantly reduces the subjectively perceived impairment, although the reduction in the subjectively perceived loudness of the tinnitus is not significant.

Adult↗

PubMed2004

[The psychophysical tests in different age of patients with cochlear implants].

OBJECTIVE: The aim of this research is to analyse and compare the psychophysical tests in different age of patients with a cochlear implant. METHOD: One hundred and seventy patients with Nucleus CI24M cochlear implant system participated in this study. The patients were divided into four groups according to their age. They were group A (<3 year), B(3-<6 year) C(6-12 year) and D(>12 year). The psychophysical tests included T and C-Level evaluation. RESULT: C-Levels of each electrode (except electrode No. 20) were significantly different between group A and D at the time of one month after switch-on (P<0.01, P<0.05 for the No. 2, 18, 19, 21, 22 electrode). The normalized differences between used C-Levels and C-Levels for group D were significantly higher than the other three groups at the switch-on session (P<0.01, P<0.05 between group D and C). The normalized differences between used C-Levels and C-Levels were significantly different for the group A and D at one week after first programming session (P<0.05). CONCLUSION: T and C-Level for different age groups were different. The normalized differences between used C-Levels and C-Levels were significantly different among the four groups in the few weeks after switch-on.

Adolescent↗

PubMed2003

Technical report: modification of a cochlear implant electrode for drug delivery to the inner ear.

OBJECTIVE: To investigate the possibility of modifying a cochlear implant electrode for the purpose of drug delivery to the cochlea. BACKGROUND: Animal experiments suggest that local therapy of the inner ear could be a promising new approach to the interventional treatment of inner ear disease, and that pharmacologic intervention could possibly enhance cochlear implant performance. One of the key aspects is the deployment of a means of drug delivery to the human inner ear. METHODS: The tip of the Contour electrode array was cut to open the lumen of the array, and a connecting piece was developed to connect the electrode to a pump. The feasibility of using the array for drug delivery was tested using both an Alzet mini-osmotic pump and a mechanical pump. The connection was tested for its stability in terms of leakage and resistance to tractive forces. The system was also applied to temporal bones to evaluate its applicability to the human cochlea. RESULTS: The modified Contour electrode is easy to handle in temporal bones and can be used to simulate drug delivery to the inner ear. The connection to the pump was sealed for all tested pump rates and resisted tractive forces up to 50 N. CONCLUSIONS: The described modified electrode could provide a safe and easy-to-handle means of combining electrical stimulation with the beneficial effects of a local drug therapy applied to the inner ear.

Cochlear Implantation↗

PubMed2002

Histopathologic changes in the vestibule after cochlear implantation.

OBJECTIVE: The study goal was to determine the histopathologic changes of the vestibular end organs after cochlear implantation and to relate them to clinical performance. STUDY DESIGN: To differentiate the effect of implantation from the disease process that originally destroyed the hearing, 11 pairs of temporal bones from unilateral implantees were studied with light microscopy to compare the vestibular damage in the implanted ears with that in the nonimplanted ears. RESULTS: Significant histopathologic damage of the vestibular end organs was noted in 6 patients (54.5%). The major histopathologic findings were fibrosis in the vestibule, saccule membrane distortion, new bone formation, and reactive neuromas. The scala vestibuli involvement, as a result of damage to the osseous spiral lamina or basilar membrane in cochlear basal turn, was highly correlated with vestibular damage (75%). CONCLUSIONS: Although the clinical incidence of balance disturbance after cochlear implantation is low, damage of the vestibular end organs may occur and be asymptomatic. Keeping the electrode array in the scala tympani will minimize vestibular damage.

Adult↗

PubMed1997

Speech intelligibility of children with multichannel cochlear implants.

The purpose of this longitudinal study is to document improvements in speech intelligibility in children who have received multichannel cochlear implants, to compare their performance to that of a matched group of children with different levels of hearing loss who use conventional hearing aids. Speech intelligibility was measured by panels of listeners who analyzed recorded speech samples preimplant and at 6-month intervals following implantation. The results of this study demonstrate that prelingually deafened children with the Nucleus multichannel cochlear implant achieved significant improvements in speech intelligibility. By the 4.5- to 7.5-year intervals, the speech intelligibility exceeded 40%.

Child↗