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PubMedDate not supplied

Electrode discrimination by early-deafened cochlear implant patients.

Electrode discrimination was measured in six cochlear-implant patients who became profoundly deaf prior to the full development of auditory and speech skills. The cochlear implant manufactured by Cochlear Limited was used. Comparisons were made between two electric stimulation paradigms and two data collection procedures. The paradigms consisted of electrode trajectories and electrodes with random variation in electric current levels. The data collection methods consisted of an adaptive procedure to obtain difference limens and a method of constant stimuli that gives psychometric functions of discrimination performance. Data were collected for reference electrodes at the apical, mid, and basal positions on the array. The psychometric functions showed that discrimination performance improved with increases in the spatial separation between reference and comparison electrodes. The difference limens were similar to the corresponding spatial separation estimated from the psychometric function in most cases. The discrimination performance of most patients was consistent across the two stimulation paradigms. Difference limens were 1-4 electrodes from the reference electrode for most patients. There were differences in performance across patients and the three positions on the array.

Adolescent↗

PubMed2001

Adult cochlear implantation: the Birmingham and United Kingdom experiences.

Cochlear implantation has been called a modern miracle and has probably exceeded the expectations of even its most ardent early pioneers. The capabilities of the preprogrammed brain permits patients, within minutes of activation, to appreciate common sounds not heard for many years and within days and weeks to comprehend open-set language without lip reading and even to use the telephone. In the last two decades, cochlear implantation has been widely accepted by the medical community, and rapid developments have been made in the technology and reliability of the devices by the manufacturers.

Adult↗

PubMed2000

Enhanced coding in a cochlear-implant model using additive noise: aperiodic stochastic resonance with tuning.

Analog electrical stimulation of the cochlear nerve (the nerve of hearing) by a cochlear implant is an effective method of providing functional hearing to profoundly deaf people. Recent physiological and computational experiments have shown that analog cochlear implants are unlikely to convey certain speech cues by the temporal pattern of evoked nerve discharges. However, these experiments have also shown that the optimal addition of noise to cochlear implant signals can enhance the temporal representation of speech cues [R. P. Morse and E. F. Evans, Nature Medicine 2, 928 (1996)]. We present a simple model to explain this enhancement of temporal representation. Our model derives from a rate equation for the mean threshold-crossing rate of an infinite set of parallel discriminators (level-crossing detectors); a system that well describes the time coding of information by a set of nerve fibers. Our results show that the optimal transfer of information occurs when the threshold level of each discriminator is equal to the root-mean-square noise level. The optimal transfer of information by a cochlear implant is therefore expected to occur when the internal root-mean-square noise level of each stimulated fiber is approximately equal to the nerve threshold. When interpreted within the framework of aperiodic stochastic resonance, our results indicate therefore that for an infinite array of discriminators, a tuning of the noise is still necessary for optimal performance. This is in contrast to previous results [Collins, Chow, and Imhoff, Nature 376, 236 (1995); Chialvo, Longtin, and Müller-Gerking, Phys. Rev. E 55, 1798 (1997)] on arrays of FitzHugh-Nagumo neurons.

Cochlear Implants↗

PubMed1991

Better speech recognition with cochlear implants.

HIGH levels of speech recognition have been achieved with a new sound processing strategy for multielectrode cochlear implants. A cochlear implant system consists of one or more implanted electrodes for direct electrical activation of the auditory nerve, an external speech processor that transforms a microphone input into stimuli for each electrode, and a transcutaneous (rf-link) or percutaneous (direct) connection between the processor and the electrodes. We report here the comparison of the new strategy and a standard clinical processor. The standard compressed analogue (CA) processor presented analogue waveforms simultaneously to all electrodes, whereas the new continuous interleaved sampling (CIS) strategy presented brief pulses to each electrode in a nonoverlapping sequence. Seven experienced implant users, selected for their excellent performance with the CA processor, participated as subjects. The new strategy produced large improvements in the scores of speech reception tests for all subjects. These results have important implications for the treatment of deafness and for minimal representations of speech at the auditory periphery.

Cochlear Implants↗

PubMed2002

The effects of age on auditory speech perception development in cochlear-implanted prelingually deaf children.

One of the most important factors in auditory speech perception of cochlear-implanted children is age. The goal of this study was to compare auditory speech perception among children implanted from 6 different age groups: 0 to 3, 4 to 5, 6 to 7, 8 to 9, 10 to 11, and >12 years. The subjects of this study were matched based on socioeconomic status, residual hearing before cochlear implantation, the kinds of cochlear implant device, speech processing strategy, communication mode after implantation, and primary language in family. All of them have used the device minimally for 2 years. The subjects were tested with a range of closed and open-set auditory speech perception tests, and the levels of auditory speech perception in different age groups were compared. Results showed that the children who received an implant at 0 to 3 years of age had maximum auditory speech perception.

Adolescent↗

PubMed1984

Cochlear implant: our preliminary experience.

We have performed cochlear implants on 16 patients (12 cases with the plug type electrodes and 4 cases with the coil type electrodes) with analogue single channel electroacoustic stimulators. The follow-up period was 8 months to 3 years. The selection of patients, operative approach and the results of these cases are presented. Our present cochlear implant can bring the totally sensory deaf patient back to the world of sound but the sounds heard are distorted so they are unable to discriminate speech, although it improves their lipreading capacity and sense of safety. The results are encouraging but much more is to be desired and further research and investigation are required.

Adolescent↗

PubMed2003

Health-service costs of pediatric cochlear implantation: multi-center analysis.

OBJECTIVE: Pediatric cochlear implantation (CI) entails surgery followed by lifetime maintenance, and hence incurs both initial and ongoing costs. Previous assessments of these costs were either undertaken early in the evolution of services, or were based on single hospitals, or estimated costs largely from hospital charges. The aim was to overcome these limitations by conducting a multi-center evaluation of the costs of providing unilateral CI to children in the United Kingdom (UK). METHODS: Annual numbers of implantations in all UK pediatric CI programs were monitored prospectively from 1991. Resource use was measured in 12 programs in 1998/1999 and retrospectively back to the year of inception of each program. The profile of outpatient and outreach visits was assessed in the 12 programs. Together these variables were used to estimate health-service costs for four phases of management: pre-operative assessment, implantation, tuning, and subsequent maintenance, using economic micro-costing methods. Costs were subsequently estimated for all children implanted in 1998/1999 (N=199) and were aggregated over 1, 15, and 73 years following implantation. To assess the robustness of cost estimates, parameter values were varied over plausible ranges and costs re-estimated. Total UK health-service costs were also estimated. All costs are presented in euros (1=US dollars 0.98= pound 0.65, 1st July 2002), inflated to 2000/2001 financial-year levels, and discounted at 6% per annum. RESULTS: Per-child average costs were 42972 (1-year), 73763 (15-years), and 95034 (73-years). Cost estimates were not overly sensitive to the value of any one cost component nor to the relative cost of outpatient and outreach visits. When these parameters were varied, costs ranged between 30000 and 47000 (1-year), 61000 and 83000 (15-years), and 82000 and 108000 (73-years). The total UK health-service cost of unilateral pediatric CI was estimated to be 14 million in 2000/2001 and is predicted to rise to 23 million in 2015/2016, if the present model of service-delivery continues. The cost of maintaining implanted children was estimated to account for 22% of the total in 2000/2001 and is predicted to rise to 63% by 2015/2016. CONCLUSIONS: Ongoing costs of maintaining implanted children and their implant systems are significant and should be factored into resource-allocation decisions.

Adolescent↗

PubMed2004

Predicting speech perception outcomes following cochlear implantation using Nottingham children's implant profile (NChIP).

BACKGROUND/OBJECTIVE: Nottingham children's implant profile (NChIP) is a systematic framework to assess deaf children before implantation taking into account not only the well-known factors (age, duration of deafness) but also family and support services, expectations, children's cognitive abilities and learning style. The aim of the present paper is to assess the predictive value of the NChIP in the long-term outcomes of implanted children. PATIENTS: This prospective and longitudinal study involved 51 profoundly deaf children, implanted within the same paediatric cochlear implant programme. All children were pre-lingually deaf with age at onset of deafness <2 years and age at implantation <6 years. Three and 4 years following implantation all children were assessed using two measures of speech perception. No child was lost to follow-up and no child was excluded from the study for any reason. RESULTS: The most constant predictor of the outcomes was children's learning style explaining upto 29% of the variance. Other significant predictors of the outcome were shorter duration of deafness, young age at implantation and family structure/support. CONCLUSIONS: Intrinsic factors in children and how well they communicate with their environment are of paramount importance to the outcome following implantation. The predictive value of NChIP has been demonstrated and the most important predictors of the outcome were children's learning style, short duration of deafness, young age at implantation, and family structure/support.

Age Factors↗

PubMed1986

Cochlear implant candidate selection.

In recent years there has been an increased acceptance of the cochlear implant as an appropriate sensory aid for selected hearing-impaired individuals with profound losses. With the Food and Drug Administration's release of the 3M/House single channel cochlear implant on November 29, 1984 and the Nucleus 22-channel cochlear implant on October 31, 1985 it is anticipated that many new groups of otologists and audiologists will have direct involvement in this exciting new approach to the management of patients with profound hearing impairments. This report reviews our cochlear implant selection protocol for the severe to profound adult hearing-impaired population.

Adult↗

PubMed1983

Long-term results of the multichannel cochlear implant.

Clinical results obtained with the multichannel cochlear implant are described in 48 cases of total deafness (27 cases of prelingual and 21 cases of postlingual deafness). The tolerance for implanted material and the survival of the electrode-nerve interface have not yet been altered after more than 5 years. After some months of training the patients, the percentages of phoneme-, word-, and sentence-recognition vary from one patient to another, but depend approximately on the value of the threshold level of the round-window stimulation test, and the degree of socialization of each patient. These results suggest that the multichannel cochlear implant may now be considered as a useful tool in the rehabilitation of totally deaf persons.

Adolescent↗

PubMed1997

Cochlear implants: what can be achieved?

Cochlear implants in children are effective in terms of speech perception and production. Onset of deafness, date of implantation, and duration of deafness are important prognostic factors for long-term results. Sophisticated intraoperative and postoperative device control measurements enable detection of partial or total device failure and calculation of the reliability of the implant. However, the present technological status is far from an optimal device. Future developments will include improvements of both electrode design and speech processing. The number and separation of channels will be increased, and the pattern of stimulation will approach the natural excitation pattern of the auditory nerve. Behind-the-ear implants or totally implantable devices will further increase the acceptance and reliability of this technology. The implant systems will become more versatile and adaptable to the physiological conditions of the individual patient. Apart from these technological improvements, rehabilitation and proper selection of patients will still play a major role in successful implantation in children. Outcome studies are necessary to calculate the cost-benefit ratio and justify a further extension of implantation. We are still on the way toward the artificial ear.

Child↗

PubMed1998

New developments in cochlear implants.

Essential to improve the performance with cochlear implants is a better control of the electrode-nerve interface. The long-term stability of the electrode characteristics has to be guaranteed. Most important herein is to have a low and stable electrical impedance and to prevent fibrosis. Results of electrode coating and fibrosis-inhibiting products are described. To assess the properties of the electrode-nerve interface such as stimulation threshold, spatial selectivity and channel interaction, the electrically evoked compound action potential is measured. The measurement paradigm and the first results are described. Models of auditory nerve response to electrical stimulation can be used as a tool for cochlear implant fitting. A simple model is proposed and its predictions are compared with measured responses.

Cochlear Implantation↗

PubMed1999

[The usefulness of intraoperatively registered, electrically evoked stapedius reflex for the programming of cochlear implants in children].

The programming of a cochlear implant speech processor used by young children is often difficult, especially when the stimulus level associated with maximum auditory loudness (MAL) needs to be determined. Excessively high stimulation should be avoided as this can have a traumatic effect. The aim of this study was to determine if a relationship exists between the intraoperatively determined electrical stapedius reflex threshold (ESRT) and the postoperatively determined MAL and hearing threshold for 27 patients, each having one of three implant types. The question of whether the ESRT provides a practical technique to simplify, improve and accelerate speech processor programming was investigated. For the monopolar stimulation mode used for the Med-El and Clarion implant systems, the average MAL and threshold was expressed as a percentage of the average ESRT across all electrodes. For the "common ground" stimulation mode used for the Nucleus implant system, a parabolic transformation was used to relate MAL and ESRT to one another. These transformations between MAL values calculated from the ESRT and the actual MAL values, determined psychoacoustically, diverged considerably from one another. Therefore, it was not possible to determine the MAL from the ESRT with certainty. The ESRT does, however, provide a means to estimate an approximate upper boundary for the MAL, apart from its use to control implant function. The determination of the exact MAL will still need to be determined using behavioural techniques.

Adolescent↗

PubMed2004

Development of spoken language grammar following cochlear implantation in prelingually deaf children.

OBJECTIVES: To assess the development of grammar comprehension in spoken language in prelingually deaf children following cochlear implantation and compare their grammatical abilities with those of their hearing peers. DESIGN: A prospective study of 82 consecutive prelingually deaf children up to 5 years following implantation. The children were less than 7 years old at the time of implantation (mean age +/- SD, 4.2 +/- 1.3 years). All received the same multichannel cochlear implant system. No child was lost to follow-up and there were no exclusions from the study. SETTING: Tertiary referral cochlear implant center. METHODS: The children were assessed using the Test for Reception of Grammar. This individually administered, multiple-choice test designed to assess the understanding of grammatical contrasts in the English language also allows direct comparison of grammar comprehension between test subjects and their normal-hearing peers. RESULTS: Before implantation, only a small proportion (2%) of prelingually deaf children were above the first percentile of their normal-hearing peers. This percentage increased to 40% and 67%, respectively, 3 and 5 years after implantation; and 5 years after implantation, 20% of the children performed between the 25th and the 75th percentile or better. In the subgroup of children who received their cochlear device before the age of 4 years, this percentage reached 36%. CONCLUSIONS: Spoken language grammar acquisition in prelingually deaf children with a cochlear implant was found to be considerably delayed. However, there was a clear trend toward the development of grammar skills following cochlear implantation, and the greatest advance was made by children who received their implant at a younger age. These findings support the present trend toward early implantation.

Adolescent↗

PubMed1997

[Cochlear implant in patients with residual hearing].

INTRODUCTIONS: Cochlear implants are used for the rehabilitation of bilaterally deaf patients. Due to the improvements in speech processing they might be also useful for patients with residual hearing and some speech understanding. METHODS: Pre- and postoperative speech understanding scores in 26 patients receiving implants were evaluated in a retrospective study. RESULTS: The preoperative pure-tone threshold in the implanted ear was between 80 and 115 dB in the frequency range of 500 to 2000 Hz. On the contralateral side the mean threshold was 10 dB better. The mean score for the number test was 11.3%, for the monosyllables below 5%. Postoperatively speech understanding improved significantly up to 97% for numbers and 48% for monosyllables (tested with the Freiburger Speech Test). Cochlear implantation also benefits patients with residual hearing and some speech understanding with hearing aids under optimum conditions. The speech understanding scores must be below certain limits. General selection criteria cannot yet be specified. The individual decision must be based upon several criteria, especially the speech understanding scores in quiet and noise under optimum conditions. A prospective study is needed to develop generally applicable criteria.

Audiometry, Pure-Tone↗

PubMed2006

Speech recognition at 1-year follow-up in the childhood development after cochlear implantation study: Methods and preliminary findings.

The Childhood Development after Cochlear Implantation (CDaCI) study is a longitudinal multicenter investigation designed to identify factors influencing spoken language in young deaf children with cochlear implants. Normal-hearing peers serve as controls. As part of a comprehensive evaluation battery, a speech recognition hierarchy was designed to assess how well these children recognize speech stimuli across developmental stages. Data were analyzed for the earliest measures in 42 pairs of children reaching 1 year of follow-up. A number of children in the cochlear implant group who met criteria for testing approached levels of performance similar to the normal-hearing controls, and some could identify sentences in competition. These results demonstrate the responsiveness of the speech recognition hierarchy in tracking emergent skills from a sample of the CDaCI cohort.

Case-Control Studies↗

PubMed1989

[Selection of candidates for cochlear implants].

The successful results of cochlear implantation depend on the correct selection of patients. Suitable candidates for operation are healthy adult, postlingually deaf subjects with a positive promontor test and adequate motivation. In the selection participates an otologist, audiologist, phoniatrist and psychologist. The authors describe their own experience with the selection of hitherto implanted patients and the importance of different tests.

Adult↗

PubMed2005

[Comparing the characteristics of psychophysical tests between cochlear implant children with large vestibular aqueduct syndrome and normal inner ear].

OBJECTIVE: The purpose of this study is to compare the characteristics of psychophysical tests between cochlear implant children with large vestibular aqueduct syndrome and normal inner ear and to analyse the characteristics of psychophysical and impedance tests for cochlear implant patients with large vestibular aqueduct syndrome. METHOD: One hundred and thirty-one cochlear implant pre-lingual deafness patients participated in this study. They received cochlear implant surgery at the age of 1.5 to 12 years old from Nov, 1998 to Aug, 2003. The patients were divided into two groups. Group A had 111 patients with normal inner ear. Group B had 20 patients with radiographically proven large vestibular aqueduct syndrome. All of the patients were inserted with Nucleus 24M. The time of the first programming session was approximately 4 weeks after surgery. The psychophysical tests included T and C-Level tests. The programming techniques used in the test were suitable for the age of the patients. The R116 and R126 software were used to test the impedance of the electrodes automatically. RESULT: Using the independent-samples t-test, the impedance and T/C-Level of each electrode did not differ significantly between group A and B ( P > 0.05). The impedance and T/C-Level were not significantly different between group A and B at the time of switch-on, 1 week, 2 weeks, 3 weeks, 2 months, 3 months, 6 months, 9 months and 1 year after switch-on (P > 0.05). CONCLUSION: The parameters of mapping were not significantly different between cochlear implant children with large vestibular aqueduct syndrome and normal inner ear. The management and procedure of mapping used in cochlear implant children with normal inner ear can be used in the children with large vestibular aqueduct syndrome.

Case-Control Studies↗