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PubMed1981

The use of rare-earth magnet couplers in cochlear implants.

The cochlear implant is an electronic auditory prosthesis gaining widespread acceptance as a means of restoring partial hearing to the totally deaf. A number of engineering and biological hurdles remain toward the improvement of existing implantable systems and development of multichannel systems. One hurdle concerns reliable transcutaneous coupling of the external electric signal to the implanted device. To date this has been accomplished by inductive means through coils which were mechanically held in place. The incorporation of small, permanent, rare-earth (SmCo5) magnets with the coil assemblies has eliminated the unreliable mechanical supporting devices. Magnetic attachment was simulated in dogs to examine for biological compatibility. Electron micrographs indicated normal subcellular structures in tissue exposed for 10 weeks. Five patients were implanted with magnet-modified coil assemblies and tested for the proper alignment and support of the external coil assembly, as well as efficiency of inductive coupling. Electromagnetic coupling was not interfered with and mechanical support was adequate. We conclude that rare-earth magnets provide an effective means for supporting and positioning in place medical devices, such as the cochlear implant.

Animals↗
PubMed2000

Determinants of speech perception in children after cochlear implantation.

BACKGROUND: Cochlear implants provide access to the speech signal in those profoundly deaf children who derive no material benefit from acoustic hearing aids. Speech perception after implantation can vary widely--we have analysed the contribution of several factors. METHODS: We examined 40 children with mean age at implantation of 52 months who were either born deaf or became deaf before 3 years. All patients received the same multichannel implant system and were followed up for 5 years. We used connected discourse tracking (CDT) as the measure of speech perception. The effect of five potential predictors (age at implantation, number of inserted electrodes, origin of deafness, mode of communication, and socioeconomic group) on speech perception was analysed. FINDINGS: The mean number of words per minute perceived increased from 0 before implantation to 44.8 (SD 24.3) 5 years after implantation. Repeated-measures ANOVA showed that children significantly progressed over time (p=0.001). Age at implantation was a significant covariate (p=0.01) and mode of communication was a significant between-individuals factor (p=0.04). INTERPRETATION: Young age at intervention and oral communication mode are the most important known determinants of later speech perception in young children after cochlear implantation. Early identification of candidate children necessitates implementation of universal neonatal screening programmes for hearing impairment.

Child, Preschool↗
PubMed1993

Effects of noise and noise reduction processing on the operation of the Nucleus-22 cochlear implant processor.

Cochlear implants, like other types of auditory sensory aids, become increasingly ineffective with increasing ambient noise levels. One method of signal processing to reduce additive random wideband noise, the INTEL method, has been used to good effect as an input preprocessor for the Nucleus-22 cochlear implant. The implant's own signal processor estimates and encodes pitch frequency and the frequencies of Formants 1 and 2. The study reported here shows that additive noise results in substantial deviations in formant frequency estimates from those that would be observed in the absence of noise. When noisy speech is preprocessed by the INTEL method to reduce noise intensity, the deviations in the frequency estimates for Formant 2 are substantially reduced.

Acoustic Stimulation↗
PubMed1996

Accuracy of high-resolution computed tomography in cochlear implantation.

Multichannel cochlear implants are a proven method for the auditory rehabilitation of individuals who have severe-to-profound sensorineural hearing loss. These devices typically require insertion into the scala tympani of the cochlea to provide auditory stimulations. A patent scala provides the best chance for an adequate insertion of the electrode array. Preoperative high-resolution computed tomography imaging has traditionally been used to determine the patency of the scala tympani. Its ability to accurately predict the patency of the cochlea has been questioned in several retrospective studies. A prospective study was undertaken in 28 consecutive individuals undergoing cochlear implant surgery to compare the findings on high-resolution computed tomography with the surgical findings in an attempt to determine high-resolution computed tomography's accuracy. Cochlear obstruction caused by ossification was accurately predicted in six of six individuals but overestimated in the round window region in three individuals. High-resolution computed tomography accurately predicted patent cochleas in 19 individuals. No false-negative results were encountered. In this study sensitivity of high-resolution computed tomography was 100%, and specificity was 86%. High-resolution computed tomography appears to be more helpful than previously reported for determining cochlear patency.

Acoustic Stimulation↗
PubMed2006

Acoustic model investigation of a multiple carrier frequency algorithm for encoding fine frequency structure: implications for cochlear implants.

Current cochlear implants provide frequency resolution through the number of channels. Improving resolution by increasing channels is limited by factors such as the physiological feasibility of increasing the number of electrodes, the inability to increase the number of channels for those already implanted, and the increased possibility of channel interactions reducing channel efficacy. Recent studies have suggested an alternative method: providing a continuum of pitch percepts for each channel based on the frequency content of that channel. This study seeks to determine the frequency resolution necessary for the highest performance gain, which may give some indication of the feasibility for implementation in implants. A discrete set of carrier frequencies, instead of a continuum, are evaluated using an acoustic model to measure speech recognition. Performance increased as the number of available frequencies increased, and substantive improvement was seen with as few as two frequencies per channel. The effect of variable frequency discrimination was also assessed, and the results suggest that frequency modulation can still provide benefits with poor frequency discrimination on some channels. These results suggest that if two or more discriminable frequencies per channel can be generated for cochlear implant subjects then an improvement in speech recognition may be possible.

Acoustics↗
PubMed1997

Comparative results with different cochlear implants.

The cochlear implant program in Budapest began in 1985, since when 60 operations have been performed, 14 of them on children (51 primary procedures and 9 reimplantations). Different devices and also different techniques have been used: extracochlear promontory, extracochlear round window and intracochlear implants. Various speech processors were applied; at first a digital pulsatile sound-encoding system, later on analog processors were used, while processors operating on the basis of the CIS strategy are preferred nowadays. The operations were performed on both pre- and postlingual patients. In several cases contralateral hearing improvement was observed 6 months after the operation. Considerable experience has been gained of unique cases, such as a deaf-blind prelingual child and prelingual twins. Evaluating cochlear implant performance, in addition to the usual audiological tests measuring postoperative speech understanding, warble tone sound field thresholds were also established.

Adolescent↗
PubMed1982

The cochlear implant.

The cochlear implant offers an alternative to selected profoundly deaf patients in whom conventional treatments or prostheses have been unsuccessful. Substantial benefits have been obtained by patients, with apparently minimal risk. There have been no serious surgical complications and only a few postoperative problems, which were remedied satisfactorily. The device has continued to function in patients over a period of years, and in cases of internal coil failure it has been removed and replaced. Replacement devices seem to function as well as the patient's first device. There has been no evidence of any decrement in performance after years of electrical stimulation or any measurable adverse effects. The cochlear implant is now widely available and should be considered an option to be offered to appropriate patients.

Adolescent↗
PubMed2003

Across-site variation in detection thresholds and maximum comfortable loudness levels for cochlear implants.

In cochlear implants, variation across stimulation sites in psychophysical detection thresholds (T levels) and maximum comfortable loudness levels (C levels) can be large when narrow-bipolar (BP) stimulation is used. This across-site variation is typically smaller when monopolar (MP) stimulation is used. At least two models can account for across-site variation and the effects of electrode configuration on the magnitude of the variation. According to one model, across-site variation reflects site-to-site differences in the distances between the stimulating electrodes and the sites of action-potential initiation. Under this model, the lower across-site variation with MP stimulation is due to shallower current versus distance gradients. An alternative model assumes that T and C levels depend on integration of activity across the whole population of neurons and that MP stimulation activates neurons over a larger spatial extent than does BP stimulation. If T and C levels are determined by integration of activity across large overlapping populations of neurons, then their values at adjacent sites should be more similar than if these levels result from integration across smaller, more independent populations. We tested the models by examining the effects on across-site variation of three variables believed to affect the spatial extent of activation: electrode configuration, stimulus level within the dynamic range, and electrode-array design. T levels and C levels were measured in 13 subjects with Nucleus CI24M (straight array) and 9 subjects with Nucleus CI24R(CS) (Contour) cochlear implants using bipolar (BP) and monopolar (MP) electrode configurations. Site-to-site variation in T and C levels for BP stimulation was 2.1-3.3 times larger than that for MP stimulation. Contrary to the across-neuron integration hypothesis, no significant differences were found between across-site variation for T levels and that for C levels for the BP configuration. There was considerable overlap in site-to-site variation values for the two types of implants but mean site-to-site variation in C levels for CI24M implants was significantly lower than that for CI24R(CS) implants. Control studies suggested that these results were not an artifact of the scale, and not due to differences in inherent variability of the psychophysical measures, or to the method of quantifying across-site variation.

Adult↗
PubMed1999

Speech perception results for children implanted with the CLARION cochlear implant at the Medical University of Hannover.

The perception of speech of 167 children implanted with a CLARION Multi-Strategy Cochlear Implant (1.2 device) was evaluated preimplantation and at 3, 6, 12, 18, and 24 months postimplantation. The children were between 15 months and 15 years of age. The test materials consisted of 8 tests involving syllable structure, single- and 2-syllable words, differentiation of word pairs, and sentences. Two difficulty levels were used, depending on developmental age (<7, and 7 to 15 years). There was an improvement in test scores over time for both age groups. The younger children (particularly those under age 4) improved steadily over the first 2 years, while the older children tended to plateau between 12 and 18 months after implantation. These findings demonstrate that deaf children up to 15 years old benefit from cochlear implants. Children under 4 years of age may even have the ability to compensate for delays in speech development before they reach school age.

Adolescent↗
PubMed1995

Cochlear implantation in patients with cochlear malformations.

OBJECTIVE: To report operative findings, postoperative course, and postimplantation performance in patients with cochlear malformations who underwent cochlear implantation. DESIGN: Case study and intervention study (before-after trial). Minimum follow-up of 12 months; average follow-up of 24 months. SETTING: Academic tertiary referral center. PATIENTS: Six patients, including five children who underwent implantation at ages 3.5 to 13 years and one adult who underwent implantation at age 27 years. malformations included common cavity deformity (n = 1), cochlear hypoplasia (n = 2), and incomplete partition (n = 3). All patients with cochlear malformations who underwent implantation at the University of Michigan, Ann Arbor, are included, selected from a group of 196 patients so treated since 1986. INTERVENTION: Implantation with a standard multichannel cochlear implant. MAIN OUTCOME MEASURES: Operative findings described include round window and facial nerve anatomy and cerebrospinal fluid leak. Postoperative roentgenographic findings, electrode activation, and reason for non-use of electrodes were investigated. Standard tests of speech perception were used to compare preoperative and postoperative performance for each subject. RESULTS: Operative findings included round window abnormalities (three patients), anomalous facial nerve (one patient), and cerebrospinal fluid leak (three patients). No surgical complications occurred. A minimum of 10 electrodes were activated for all patients. Electrode thresholds and discomfort levels were variable for several months after implantation. All patients demonstrated improved performance after implantation. Four subjects demonstrated open-set speech perception. Two other subjects, whose poor language skills precluded administration of standard tests, showed increased awareness of environmental sounds and increased vocalization after implantation. CONCLUSIONS: Cochlear implantation can be a successful method of rehabilitation in patients with congenital deafness who have cochlear malformations.

Adolescent↗
PubMed2004

[Examination to possibilities of a physiological fitting of cochlear implants].

BACKGROUND: Cochlear implants (CI) convert acoustic events into electrical pulses. The auditory nerve picks these tiny electrical pulses up and sends them to the brain. The dynamics of the audible sound is compressed considerably. The limits for stimulation are determined with the patient. A map law determines which sound pressure level is assigned to which stimulation level. A sufficient speech understanding requests an allocation of high stimulation levels for weak sound signals. The higher the sound level, the lower the increase. Unfortunately, with such kind of map law unwanted background noise is also presented as well audible stimulation. These stimuli are often annoying to CI users in everyday situations. PATIENTS AND METHOD: The possibility to give an s-shaped course to these map laws was examined in 9 patients. After the fitting procedure their speech understanding were tested. The results were compared with the results of former tests. RESULTS: 8 patients reported definite improvement of their hearing situation. Such map laws seem, therefore, suitable to optimise speech processor programming.

Adult↗
PubMed1994

Facial nerve stimulation produced by cochlear implants in patients with cochlear otosclerosis.

Thirty-eight adult cochlear implants have been performed at the University of Minnesota. Facial nerve stimulation by the implant in response to sound has been noted in four of these cases. Three of the four were patients whose sensorineural hearing loss was caused by cochlear otosclerosis. In each case it was possible to place the electrodes, however multiple leads had to be deprogrammed in order to avoid facial nerve stimulation. In each case characteristic radiographic findings of cochlear otosclerosis could be identified on preoperative temporal bone computed tomography scans. Although facial nerve stimulation has been described as a complication of cochlear implantation, it has not been reported to be associated with cochlear otosclerosis. Postoperative programming of the implant may be limited by facial nerve stimulation. In some cases these limits may reduce the efficacy of the device. This possibility should be taken into account during preoperative counseling of patients with cochlear otosclerosis considering cochlear implantation.

Aged↗
PubMed1999

Cochlear implantation in children under the age of two: the MHH experience with the CLARION cochlear implant. Medizinische Hochschule Hannover.

This paper examines reports on the selection criteria, the surgical procedure, and the postoperative performance for children under the age of 2 implanted with the CLARION Multi-Strategy Cochlear Implant (1.2 device). Eighteen children have been implanted since 1996 with a mean age at implantation of 18 months (range 11 to 23 months). All children were selected by means of a standardized preoperative diagnostic protocol. The surgical procedure used in older children was modified depending on the head and mastoid size, skull thickness, and recurrent otitis media. Auditory perception was tested prior to as well as 3, 6, 12, and 18 months following implantation by means of a standardized age-adapted test protocol. The electrode array was inserted without difficulty in all cases, with no complications to date. On average, auditory performance improved over time up to 18 months after implantation. Closed-set test scores increased by 25% to 55% in 18 months. Open-set test scores began to show improvement between 6 and 12 months postoperatively. Overall, our experience indicates that cochlear implantation in children under the age of 2 is relatively safe and reliable. The Clarion 1.2 device surgery can be performed without complications. Auditory performance results support the effectiveness of early implantation.

Cochlear Implantation↗
PubMed2002

Impact of dental devices on cochlear implants.

A cochlear implant (CI) converts mechanical sound energy into electrical signals that can be delivered to the cochlear nerve of profoundly deaf patients. The purpose of this study was to investigate whether electromagnetic interference with the CI occurs during the operation of the electric pulp tester, apex locator, electrocautery unit, electrosurgery unit, or panoramic radiograph machine. A mastoidectomy and cochleostomy were performed on a cadaver, and a CI was implanted. The dental devices were used intraorally, and the implant's circuitry was tested after each trial. A second CI was implanted in a human skull, which was then exposed to 50 panoramic radiographs, testing the implant's circuitry after each exposure. The probability of damage to the CI by any of the devices was negligible, except for the electrosurgery unit operated at level 7, which destroyed the CI's circuitry. Therefore, although the other devices seem safe, it is recommended that the electrosurgery unit not be used on a CI patient.

Cadaver↗
PubMed1994

Cochlear implants in children.

Cochlear implants are no longer considered new or experimental technology. Difficulty in evaluating the degree of hearing loss and response to traditional forms of amplification in young children makes pediatric cochlear implant candidacy a complex issue. Cochlear implantation and, in particular, pediatric cochlear implantation, requires a team commitment with contributions from surgeons, audiologists, speech pathologists, psychologists, and special educators. Elements discussed include assessment and candidacy issues, surgical technique, elements of a cochlear implant team, outcome assessment, and potential complications. The decision to perform pediatric cochlear implantation should not be undertaken without serious consideration to the enormous commitment required in both financial and personnel terms.

Child↗
PubMed2005

Speech perception with the ACE and the SPEAK speech coding strategies for children implanted with the Nucleus cochlear implant.

OBJECTIVE: The aim of this study is to determine whether implanted children using the ACE speech coding strategy demonstrate superior performances compared to implanted children using the SPEAK speech coding strategy over time. METHODS: Cochlear implanted children with prelinguistic sensorineural bilateral deafness of profound degree, using either the ACE or SPEAK coding strategy, were evaluated and compared. Both groups of children used one of the speech coding strategies continuously from the initial programming session and for a period of 2 years post-switch-on. One group comprised children who were retrospectively implanted and had received the SPEAK speech coding strategy (n=32) and the second group consisted of prospectively implanted children who received the ACE speech coding strategy (n=26). Both populations were homogenous as far as age of implantation, degree of hearing loss, anatomy of the cochlea, depth of electrode insertion, and educational and rehabilitative support provided. Children were assessed at 6, 12 and 24 months post switch-on via pure-tone audiometry and for speech perception tests. Children using the ACE speech coding strategy were additionally evaluated using the MAIS and MUSS language scales. RESULTS: Satisfactory benefits in speech perception were demonstrated by both groups of implanted children. No significant difference between the mean pure tone thresholds was observed postoperatively between the groups. Two years post switch-on the group using the ACE speech coding strategy demonstrated superior results for vowel discrimination in comparison to children using the SPEAK coding strategy. No significant difference was observed between the groups for performance on discrimination of syllable patterns (ESP) or for disyllablic word recognition tests. Additionally, the group of ACE users demonstrated maximum performance on MAIS and MUSS scales, 2 years post switch-on. CONCLUSIONS: The results clearly demonstrate significant benefit of cochlear implantation in prelinguistically deafened children for speech perception ability when using either the SPEAK or ACE speech coding strategies. Children using the ACE speech coding strategy demonstrate more rapid progress in improved speech perception ability initially, however 2 years post switch-on, no significant difference in performance on open-set speech recognition tests can be noted irrespective of the strategy in use.

Audiometry, Pure-Tone↗