Modiolar proximity of three perimodiolar cochlear implant electrodes

A new generation of cochlear implant electrodes has been designed to position the stimulating contacts close to the modiolus in order to reduce power consumption and increase stimulation selectivity. The purpose of this study was to assess electrode position in the cochlea for three recently designed electrodes. Fifteen cadaveric temporal bones were implanted with one of three perimodiolar electrode arrays: Nucleus Contour; Med-El Combi40+ PM (developmental version); and Clarion HiFocus II. Image-enhanced videofluoroscopy and computer morphometrics were used to assess stimulating contact position relative to the modiolus. The mean distance (+/- 1 standard deviation) to the modiolus for all electrode contacts was 0.33 (+/-0.24), 0.30 (+/-0.27) and 0.16 mm (+/-0.19) for the Contour, Combi40+ PM and HiFocus II arrays, respectively. In addition, dynamic videofluoroscopy was used to correlate device-specific insertion characteristics with contact-to-modiolus distance. All three devices were successful in terms of locating electrode contacts very close to the modiolar wall.

Results from a European clinical investigation of the Nucleus multichannel auditory brainstem implant

OBJECTIVE

This study was designed to investigate the perceptual benefits and potential risks of implanting the Nucleus(R) multichannel auditory brainstem implant.

DESIGN

Between September 1992 and October 1997 a total of 27 subjects received a Nucleus 20- or 21-channel Auditory Brainstem Implant (ABI). All subjects involved in the trial had bilateral acoustic tumour as a result of neurofibromatosis type 2 (NF2) resulting in complete dysfunction of the VIIIth nerve. The study used each subject as their own control without a preoperative baseline because residual hearing, if existing, was destroyed at surgery by tumour removal. A battery of speech tests was conducted to evaluate each patient's performance and communication abilities. Tests were conducted, where possible, in the auditory-only, visual-only, and auditory-visual conditions at 3 days postoperatively (baseline), at 3-mo intervals for the first year and every 12 mo thereafter. A subjective performance questionnaire was administered together with an extensive neurological examination at each test interval.

RESULTS

27 subjects involved in this trial were successfully implanted with a Nucleus ABI. One subject died 2 days postoperatively due to a lung embolism unrelated to the device. Twenty-six subjects underwent device activation and all but one patient received auditory sensation at initial stimulation (96.2%). On average 8.6 (+/-4.2) of the available 21 electrodes were used in the patients' MAPs. Performance evaluation measures showed that the majority of users had access to auditory information such as environmental sound awareness together with stress and rhythm cues in speech that assist with lipreading. Although most subjects did not achieve any functional auditory-alone, open-set speech understanding, two subjects from this series (7.4%) did receive sufficient benefit to be able to use the ABI in conversation without lipreading.

CONCLUSIONS

Although the medical risks and surgical complexity associated with ABI device implantation are far greater than those for a cochlear implant, the clinical results from this trial show that the Nucleus multichannel ABI is capable of providing a significant patient benefit over risk ratio for subjects suffering loss of hearing due to bilateral retrocochlear lesions.

Multichannel auditory brainstem implant: update on performance in 61 patients

OBJECT

Neurofibromatosis Type 2 (NF2) has typically resulted in deafness after surgical removal of bilateral vestibular schwannomas (VSs). Cochlear implants are generally ineffective for this kind of deafness because of the loss of continuity in the auditory nerve after tumor removal. The first auditory brainstem implant (ABI) in such a patient was performed in 1979 at the House Ear Institute, and this individual continues to benefit from electrical stimulation of the cochlear nucleus complex. In 1992, an advanced multichannel ABI was developed and a series of patients with NF2 received this implant to study the safety and efficacy of the device.

METHODS

At the time of first- or second-side VS removal, patients received an eight-electrode array applied to the surface of the cochlear nucleus within the confines of the lateral recess of the fourth ventricle. The device was activated approximately 6 weeks after implantation. and patients were tested every 3 months for the 1st year after the initial stimulation, and annually thereafter. The protocol included a comprehensive battery of psychophysical and speech perception tests.

CONCLUSIONS

The multichannel ABI proved to be effective and safe in providing useful auditory sensations in most patients with NF2. The ABI improved patients' ability to communicate compared with the lipreading-only condition, it allowed the detection and recognition of many environmental sounds, and in some cases it provided significant ability to understand speech by using just the sound from the ABI (with no lipreading cues). Its performance in most patients has continued to improve for up to 8 years after implantation.

Speech understanding in quiet and noise in bilateral users of the MED-EL COMBI 40/40+ cochlear implant system

OBJECTIVE

The purpose of the study was to investigate speech understanding in quiet and noise in subjects bilaterally implanted with multi-channel cochlear implants.

DESIGN

Nine adults bilaterally implanted with MED-EL implants were included in the study. The subjects were tested in three conditions: with both implants, with the right implant only, and with the left implant only. Speech tests included monosyllables in quiet and sentences in noise (10 dB signal to noise ratio). Speech was presented from the front, and noise was presented from either 90 degrees or 270 degrees azimuth.

RESULTS

All subjects reported benefit from bilateral stimulation. Speech scores for all subjects were higher with bilateral than with unilateral stimulation. The average score across subjects for sentence understanding was 31.1 percentage points higher with both cochlear implants compared with the cochlear implant ipsilateral to the noise, and 10.7 percentage points higher with both cochlear implants compared with the cochlear implant contralateral to the noise. The average score for recognition of monosyllabic words was 18.7 percentage points higher with both cochlear implants than with one cochlear implant. All of these differences in average scores were significant at the 5% level.

CONCLUSIONS

Bilateral cochlear implantation provides a significant benefit in speech understanding in both quiet and noise.

Cochlear implants in children--a review

Over the past two decades, cochlear implantation has become a widely accepted treatment of deafness in children. Over 20,000 children have received cochlear implants worldwide. Hearing, language and social development outcomes have been positive. We review current issues in cochlear implantation, candidacy, evaluation, surgery, habilitation, ethics and outcomes.

Initial evaluation of the Clarion CII cochlear implant: speech perception and neural response imaging

OBJECTIVE

To evaluate the new Clarion CII cochlear implant with the perimodiolar HiFocus electrode array, including both speech perception outcomes and the device's capabilities of measuring the electrically evoked compound action potential (eCAP) of the auditory nerve (Neural Response Imaging, NRI).

DESIGN

The speech perception scores on CVC words without lip reading were monitored prospectively for the 10 postlingually deaf patients implanted with the Clarion CII device in the period July 2000 until May 2001 in the Leiden University Medical Center. Preoperative and postoperative NRI recordings were made, applying various combinations of monopolar stimulating and recording electrodes with the alternating polarity paradigm available in the test bench software.

RESULTS

Nine patients preferred the CIS, one the PPS strategy, none the SAS strategy. With their favorite strategy they acquired significant open set speech understanding within a few weeks, resulting in an average CVC phoneme score of 84% (word score 66%) at the end of the study (follow-up 3 to 11 mo). In speech-shaped noise, the average phoneme recognition threshold (PRT) was reached at a signal to noise ratio just below 0 dB. The NRI recordings had clear N1 and P1 peaks if there was at least one contact between the stimulating and recording electrodes, necessitating just 15 sweeps for a reliable recording. We observed considerable inter-patient and inter-electrode variability, but for a given situation NRI input/output curves were stable over time. More apical contacts generally elicited larger eCAPs. Response amplitudes tended to peak at recording sites around apical and basal stimulating electrodes, suggesting a limited spread of excitation. Preliminary recordings with the forward masking paradigm were consistent with the ones with the alternating polarity scheme.

CONCLUSIONS

The Clarion CII is a promising cochlear implant with which our first 10 patients have obtained excellent speech perception results. The NRI system yields high quality signals with a limited number of sweeps at a high sampling rate.

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.

Delayed implantation in congenitally deaf children and adults

OBJECTIVE

To determine the efficacy of cochlear implants with current processing strategies in children and adults with long-term congenital deafness, and to determine whether the growth of auditory perceptual skills in these patients is similar to the data reported for patients who have undergone implantation with earlier devices and coding strategies.

STUDY DESIGN

A prospective study of children and adults fulfilling the study inclusion criteria.

SETTING

University medical center.

PATIENTS

Thirty-five congenitally deaf children who received implants after the age of 8 years and 14 congenitally deaf adults who received implants as adults participated in this study. Length of device use ranged from 6 months to 3 years.

MAIN OUTCOME MEASURES

Open set phoneme, word recognition tests, and sentence recognition tests were administered in quiet and noise auditory only conditions preoperatively and postoperatively. Changes in test scores were examined by paired t tests, and differences between groups were compared by Student's t tests. Spearman correlation coefficients were calculated to identify associations between scores and subject characteristics. A two-sided alpha of less than 0.05 was considered statistically significant.

RESULTS

The results indicated significant improvement in open set speech perception skills in the children after implantation; the adults demonstrated improved mean scores on both word and sentence recognition. A shorter length of deafness correlated with better postoperative performance, but all subjects continued to improve over time. The improvement in test scores was similar between the devices, and no significant differences were detected between the different processing strategies.

CONCLUSION

Children and adults with long-term congenital deafness can obtain considerable open set speech understanding after implantation. Length of deafness (age at implantation), length of device use, and mode of communication contribute to outcome.

Long-term effects of cochlear implants in children

OBJECTIVE

Since 1987, when the use of multichannel cochlear implants was initiated in children, candidacy has expanded; many thousands of children have received these devices, and results have revealed a wide range of performance. However, few long-term studies exist on a large population of these children. There have been concerns expressed that cochlear implant function might degrade over time, that devices and electrodes might migrate and extrude in the growing child, or that there might even be a deleterious effect of long-term stimulation of the cochlear nerve. The purpose of this study was to explore the long-term effects of implantation as a function of performance over time, reimplantation, and educational factors.

STUDY DESIGN AND SETTING

We studied 81 children who received implants at a major academic medical center and were followed for 5 to 13 years.

RESULTS

Results revealed significant gains in speech perception, use of oral language, and ability to function in a mainstream environment. There was no decrease in performance over time and no significant incidence of device or electrode migration or extrusion, and device failure did not cause a deterioration in long-term outcome.

CONCLUSIONS

Multichannel cochlear implants in children provide perception, linguistic, and educational advantages, which are not adversely affected by long-term electrical stimulation.

The perception of Cantonese lexical tones by early-deafened cochlear implantees

This study investigated whether cochlear implant users can identify Cantonese lexical tones, which differ primarily in their F0 pattern. Seventeen early-deafened deaf children (age= 4 years, 6 months to 8 years, 11 months; postoperative period= 11-41 months) took part in the study. Sixteen children were fitted with the Nucleus 24 cochlear implant system; one child was fitted with a Nucleus 22 implant. Participants completed a 2AFC picture identification task in which they identified one of the six contrastive Cantonese tones produced on the monosyllabic target word /ji/. Each target stimulus represented a concrete object and was presented within a carrier phrase in sentence-medial position. Group performance was significantly above chance for three contrasts. However, the cochlear implant listeners performed much worse than a 6 1/2-year-old, moderately hearing impaired control listener who was tested on the same task. These findings suggest that this group of cochlear implant users had great difficulty in extracting the pitch information needed to accurately identify Cantonese lexical tones.

An animal model of auditory cortex prostheses

Experiments aimed at rehabilitating deaf and blind patients with cortical prostheses were first conducted decades ago, but epicortical electrodes allowed only crude information transfer. Here we report that in Mongolian gerbils with electrodes implanted in input layers of the primary auditory cortex, spatial, temporal and spatiotemporal variations in intracortical stimulation all lead to perceptual differences as evidenced by discrimination training. For some stimulus regimes discrimination learning was as fast as with intracochlear stimulation in this animal. Intracortical stimulation induced field potentials and 2-deoxyglucose labeling patterns in primary auditory cortex similar to those induced by auditory click or tone stimuli, respectively. Given the common organization principles of neocortical areas, these results are presumably also of significance to prostheses interfacing with visual cortex.

Sound-direction identification, interaural time delay discrimination, and speech intelligibility advantages in noise for a bilateral cochlear implant user

OBJECTIVES

To characterize some of the benefits available from using two cochlear implants compared with just one, sound-direction identification (ID) abilities, sensitivity to interaural time delays (ITDs) and speech intelligibility in noise were measured for a bilateral multi-channel cochlear implant user.

METHODS

Sound-direction ID in the horizontal plane was tested with a bilateral cochlear implant user. The subject was tested both unilaterally and bilaterally using two independent behind-the-ear ESPRIT (Cochlear Ltd.) processors, as well as bilaterally using custom research processors. Pink noise bursts were presented using an 11-loudspeaker array spanning the subject's frontal 180 degrees arc in an anechoic room. After each burst, the subject was asked to identify which loudspeaker had produced the sound. No explicit training, and no feedback were given. Presentation levels were nominally at 70 dB SPL, except for a repeat experiment using the clinical devices where the presentation levels were reduced to 60 dB SPL to avoid activation of the devices' automatic gain control (AGC) circuits. Overall presentation levels were randomly varied by +/- 3 dB. For the research processor, a "low-update-rate" and a "high-update-rate" strategy were tested. Direct measurements of ITD just noticeable differences (JNDs) were made using a 3 AFC paradigm targeting 70% correct performance on the psychometric function. Stimuli included simple, low-rate electrical pulse trains as well as high-rate pulse trains modulated at 100 Hz. Speech data comparing monaural and binaural performance in noise were also collected with both low, and high update-rate strategies on the research processors. Open-set sentences were presented from directly in front of the subject and competing multi-talker babble noise was presented from the same loudspeaker, or from a loudspeaker placed 90 degrees to the left or right of the subject.

RESULTS

For the sound-direction ID task, monaural performance using the clinical devices showed large mean absolute errors of 81 degrees and 73 degrees, with standard deviations (averaged across all 11 loud-speakers) of 10 degrees and 17 degrees, for left and right ears, respectively. Fore bilateral device use at a presentation level of 70 dB SPL, the mean error improved to about 16 degrees with an average standard deviation of 18 degrees. When the presentation level was decreased to 60 dB SPL to avoid activation of the automatic gain control (AGC) circuits in the clinical processors, the mean response error improved further to 8 degrees with a standard deviation of 13 degrees. Further tests with the custom research processors, which had a higher stimulation rate and did not include AGCs, showed comparable response errors: around 8 or 9 degrees and a standard deviation of about 11 degrees for both update rates. The best ITD JNDs measured for this subject were between 350 to 400 microsec for simple low-rate pulse trains. Speech results showed a substantial headshadow advantage for bilateral device use when speech and noise were spatially separated, but little evidence of binaural unmasking. For spatially coincident speech and noise, listening with both ears showed similar results to listening with either side alone when loudness summation was compensated for. No significant differences were observed between binaural results for high and low update-rates in any test configuration. Only for monaural listening in one test configuration did the high rate show a small significant improvement over the low rate.

CONCLUSION

Results show that even if interaural time delay cues are not well coded or perceived, bilateral implants can offer important advantages, both for speech in noise as well as for sound-direction identification.

Does cochlear reimplantation affect speech recognition?

Although cochlear implantation has been proven to be a very effective method of rehabilitation for post-lingually deaf adults and pre-lingually deaf children, as electronic devices, cochlear implants are occasionally subject to damage or breakdowns. In these cases, reimplantation would be necessary. The aim of this study was to find out whether or not there are any negative effects on speech abilities after reimplantation with the same type of multichannel digital implant in the same ear. Seven patients were provided with a digital multi-channel cochlear implant. One subject suffered manipulative damage to the implant, and in six subjects an implant failure was observed. All reimplantations were performed on the same ear as the initial implantation. with the same implant type. Parameters such as insertion depth and number of active channels were the same in all subjects before and after reimplantation. Immediately following the revision surgery, three patients attained the same level of hearing that they had with their original implants. Three months following reimplantation, five subjects achieved almost the same scores that they had before reimplantation. The results showed that cochlear implant patients undergoing re-implantation can anticipate achieving nearly the same level of speech recognition as they had with their original implant. Nevertheless, patients need to be aware of potential problems before undergoing reimplantation so that expectations are not too high.

The educational settings of profoundly deaf children with cochlear implants compared with age-matched peers with hearing aids: implications for management

The educational settings of 42 implanted profoundly deaf children 3 years after implantation were compared with the respective settings of 635 age-matched severely deaf and 511 profoundly deaf children with hearing aids. All implanted children received their implants before beginning school. The results revealed that 3 years after implantation. 38% (16 children) of the implanted profoundly deaf children attended mainstream schools, whereas 57% (24 children) were in a unit, or special class, in a mainstream school, and 5% (two children) were in schools for the deaf. With regard to the age-matched profoundly deaf children with hearing aids, 12% (63 children) attended mainstream schools, whereas 55% (281 children) were in a unit of a mainstream school, and 33% (167 children) were in schools for the deaf. In the group of age-matched severely deaf children, 38% (239 children) attended mainstream schools, whereas 51% (326 children) were in a unit of a mainstream school, and 11% (70 children) were in schools for the deaf. Statistical analysis revealed a highly significant difference between the educational placement of implanted children and hearing-aided profoundly deaf children (p<0.00001), whereas there was no statistically significant difference between implanted children and hearing-aided severely deaf children. In conclusion, implanted profoundly deaf children who have received their implants before beginning school have the same profile of educational placement as aided severely deaf children rather than aided profoundly deaf children of the same age in the UK. This is likely to have significant implications for the future management of profoundly deaf children and to influence future planning of educational support services.

[Cochleography and cochlear view as the way of assessment of successful surgical inner ear implantation]

115 cochlear implantation were performed in ENT Department Karol Marcinkowski University of Medical Sciences in Poznań in 1994-2001. Nucleus Mini System 22 and Nucleus 24 of Cochlear Ltd were used in these operations. Two approaches were performed: middle fossa approach in one case and traditional one. The aim of this study was evaluation of cochleogram and cochlear view as the ways of assessment of successful inner ear implantation. One of X-ray projection were performed in implanted patients 24 hours after implantation. In cochleograms the degree of electrodes rotation in cochlea was calculated. The number of inserted electrodes in cochlea was calculated in cochler view projection. Described X-ray projection were performed in 70 patients. On X-ray projection (cochleograms) rotation degree of electrodes in majority were equal or higher than 250 grades (according to literature it is sufficient for successful speech rehabilitation). X-ray projection--cochlear view confirmed full insertion of electrode.

Speech recognition in background noise of cochlear implant patients

OBJECTIVES

The performances of adult patients using Spectral peak (Nucleus 22 or Nucleus 24 patients) or Continuous Interleaved Sampling or Advanced Combination Encoder (Clarion patients) were evaluated in their ability to perform in quiet and in 2 levels of background noise.

PATIENTS AND METHODS

Ninety-six patients were tested with the City University of New York Sentences presented at 70 dB in quiet and at signal-to-noise ratios (SNR) of +10 and +5 dB. Patients were scored on the number of words perceived correctly.

RESULTS

Scores were different at each condition (P < 0.05): 88% words correct in quiet, 73% correct at an SNR of +10 dB, and 47% correct at an SNR of +5 dB. Linear regression analysis found no significant correlation between test score and age at implantation or time using the implant. A weak negative correlation was found between years of hearing loss and score.

CONCLUSION

Competing noise interferes with comprehension of connected speech for most cochlear implant patients.

Comparison of methods in speech acquisition research

The paper examines the effect of choices involved in speech acquisition research among children with impaired hearing. Choices involving transcription method, sampling procedures, subject selection and statistical approaches affect the outcome of any research. Two recent papers used different methodological approaches to examine the conversational speech samples of children with impaired hearing and arrived at differing conclusions about their rates of improvement. To compare these results, a further data set was examined using both methodologies. The analyses indicated a closer alignment of results than was immediately obvious from the two previous studies, suggesting that the different results were primarily due to differences in methodology.

Binaural cochlear implants placed during the same operation

OBJECTIVE

To evaluate the binaural listening advantages for speech in quiet and in noise and to localize sound when independently programmed binaural cochlear implants are used, and to determine whether ears with different hearing ability and duration of profound deafness perform differently with cochlear implants as well as to what extent preimplant psychophysical and physiologic assessment could be predictive of performance.

STUDY DESIGN

Prospective study in which patients were prospectively selected to undergo bilateral implantation during a single surgical procedure at a tertiary referral center. All testing was performed with patients using their right, left, or both cochlear implants. Preimplant and intraoperative measures used electrical stimulation at the round window and stimulation through the cochlear implant.

RESULTS

Bilateral implantation during the same operation did not cause any postoperative problems such as severe vertigo or ataxia. At 1 year, results of speech testing in quiet demonstrated a binaural advantage for 2 of 10 subjects. Speech-in-noise testing demonstrated that two implants were beneficial for two individuals. All subjects benefited from a head shadow effect when an ear with a better signal-to-noise ratio was available. The ability to localize sound was improved with binaural implants in all subjects. Preimplant psychophysical or physiologic measures were not predictive of eventual speech perception performance.

CONCLUSION

Binaural cochlear implants can assist in the localization of sounds and have the potential in some individuals to improve speech understanding in quiet and in noise.

Speech perception and language criteria for paediatric cochlear implant candidature

Existing criteria for cochlear implantation of children with impaired hearing aim to select children who will eventually achieve better speech perception scores with an implant than with a hearing aid. It is difficult to predict the eventual outcomes with hearing aid and implant because speech perception scores typically increase with age, and because the distribution of scores for implant and hearing aid users overlap considerably at all ages. This paper shows how speech perception scores can be combined with spoken language measures to arrive at an objective criterion for implant selection. The method also allows estimation of the likely increase in speech perception score within a few months of implantation and estimation of the probability that the child will perform better with the implant than the hearing aid. The criteria were based on data from 135 evaluations of 50 children using cochlear implants with monosyllabic words, open-set sentences, the Clinical Evaluation of Language Fundamentals, and the Peabody Picture Vocabulary Test. Data from 114 evaluations of 43 children using hearing aids were used to illustrate the sensitivity of the criteria.

A multidimensional scaling analysis of tone discrimination ability in Cantonese-speaking children using a cochlear implant

Tone discrimination testing with two groups of profoundly hearing-impaired children using a cochlear implant and one group of normally hearing children suggests that pitch level is perceptually more salient than pitch contour. In this paper, the discrimination results from these children are submitted to a multidimensional scaling analysis to determine what differences if any exist between the children in the information they use to discriminate between tone types. Through the multidimensional scaling analysis it is shown that, 'average pitch height' and 'pitch direction' are the most salient acoustic features in tone with pitch height being perceptually more important than pitch level. Furthermore, these acoustic features are similarly salient for all three groups of children despite differences in the source of auditory information and linguistic experience. Finally, the two groups of cochlear implant users who employ different speech processing strategies with their implant are shown to be distinguishable by differences in the relative salience of pitch direction.