Modeling of Auditory Neuron Response Thresholds with Cochlear Implants.

The quality of the prosthetic-neural interface is a critical point for cochlear implant efficiency. It depends not only on technical and anatomical factors such as electrode position into the cochlea (depth and scalar placement), electrode impedance, and distance between the electrode and the stimulated auditory neurons, but also on the number of functional auditory neurons. The efficiency of electrical stimulation can be assessed by the measurement of e-CAP in cochlear implant users. In the present study, we modeled the activation of auditory neurons in cochlear implant recipients (nucleus device). The electrical response, measured using auto-NRT (neural responses telemetry) algorithm, has been analyzed using multivariate regression with cubic splines in order to take into account the variations of insertion depth of electrodes amongst subjects as well as the other technical and anatomical factors listed above. NRT thresholds depend on the electrode squared impedance (ß = -0.11 ± 0.02, P < 0.01), the scalar placement of the electrodes (ß = -8.50 ± 1.97, P < 0.01), and the depth of insertion calculated as the characteristic frequency of auditory neurons (CNF). Distribution of NRT residues according to CNF could provide a proxy of auditory neurons functioning in implanted cochleas.

Improvement of cognitive function after cochlear implantation in elderly patients.

IMPORTANCE: The association between hearing impairment and cognitive decline has been established; however, the effect of cochlear implantation on cognition in profoundly deaf elderly patients is not known. OBJECTIVE: To analyze the relationship between cognitive function and hearing restoration with a cochlear implant in elderly patients. DESIGN, SETTING, AND PARTICIPANTS: Prospective longitudinal study performed in 10 tertiary referral centers between September 1, 2006, and June 30, 2009. The participants included 94 patients aged 65 to 85 years with profound, postlingual hearing loss who were evaluated before, 6 months after, and 12 months after cochlear implantation. INTERVENTIONS: Cochlear implantation and aural rehabilitation program. MAIN OUTCOMES AND MEASURES: Speech perception was measured using disyllabic word recognition tests in quiet and in noise settings. Cognitive function was assessed using a battery of 6 tests evaluating attention, memory, orientation, executive function, mental flexibility, and fluency (Mini-Mental State Examination, 5-word test, clock-drawing test, verbal fluency test, d2 test of attention, and Trail Making test parts A and B). Quality of life and depression were evaluated using the Nijmegen Cochlear Implant Questionnaire and the Geriatric Depression Scale-4. RESULTS: Cochlear implantation led to improvements in speech perception in quiet and in noise (at 6 months: in quiet, 42% score increase [95% CI, 35%-49%; P < .001]; in noise, at signal to noise ratio [SNR] +15 dB, 44% [95% CI, 36%-52%, P < .001], at SNR +10 dB, 37% [95% CI 30%-44%; P < .001], and at SNR +5 dB, 27% [95% CI, 20%-33%; P < .001]), quality of life, and Geriatric Depression Scale-4 scores (76% of patients gave responses indicating no depression at 12 months after implantation vs 59% before implantation; P = .02). Before cochlear implantation, 44% of the patients (40 of 91) had abnormal scores on 2 or 3 of 6 cognition tests. One year after implant, 81% of the subgroup (30 of 37) showed improved global cognitive function (no or 1 abnormal test score). Improved mean scores in all cognitive domains were observed as early as 6 months after cochlear implantation. Cognitive performance remained stable in the remaining 19% of the participants (7 of 37). Among patients with the best cognitive performance before implantation (ie, no or 1 abnormal cognitive test score), 24% (12 of 50) displayed a slight decline in cognitive performance. Multivariate analysis to examine the association between cognitive abilities before implantation and the variability in cochlear implant outcomes demonstrated a significant effect only between long-term memory and speech perception in noise at 12 months (SNR +15 dB, P = .01; SNR +10 dB, P < .001; and SNR +5 dB, P = .02). CONCLUSIONS AND RELEVANCE: Rehabilitation of hearing communication through cochlear implantation in elderly patients results in improvements in speech perception and cognitive abilities and positively influences their social activity and quality of life. Further research is needed to assess the long-term effect of cochlear implantation on cognitive decline.

A Retrospective Multicenter Study Comparing Speech Perception Outcomes for Bilateral Implantation and Bimodal Rehabilitation.

OBJECTIVES: To compare speech perception outcomes between bilateral implantation (cochlear implants [CIs]) and bimodal rehabilitation (one CI on one side plus one hearing aid [HA] on the other side) and to explore the clinical factors that may cause asymmetric performances in speech intelligibility between the two ears in case of bilateral implantation. DESIGN: Retrospective data from 2247 patients implanted since 2003 in 15 international centers were collected. Intelligibility scores, measured in quiet and in noise, were converted into percentile ranks to remove differences between centers. The influence of the listening mode among three independent groups, one CI alone (n = 1572), bimodal listening (CI/HA, n = 589), and bilateral CIs (CI/CI, n = 86), was compared in an analysis taking into account the influence of other factors such as duration of profound hearing loss, age, etiology, and duration of CI experience. No within-subject comparison (i.e., monitoring outcome modifications in CI/HA subjects becoming CI/CI) was possible from this dataset. Further analyses were conducted on the CI/CI subgroup to investigate a number of factors, such as implantation side, duration of hearing loss, amount of residual hearing, and use of HAs that may explain asymmetric performances of this subgroup. RESULTS: Intelligibility ranked scores in quiet and in noise were significantly greater with both CI/CI and CI/HA than with a CI-alone group, and improvement with CI/CI (+11% and +16% in quiet and in noise, respectively) was significantly better than with CI/HA (+6% and +9% in quiet and in noise, respectively). From the CI/HA group, only subjects with ranked preoperative aided speech scores >60% performed as well as CI/CI participants. Furthermore, CI/CI subjects displayed significantly lower preoperative aided speech scores on average compared with that displayed by CI/HA subjects. Routine clinical data available from the present database did not explain the asymmetrical results of bilateral implantation. CONCLUSIONS: This retrospective study, based on basic speech audiometry (no lateralization cues), indicates that, on average, a second CI is likely to provide slightly better postoperative speech outcome than an additional HA for people with very low preoperative performance. These results may be taken into consideration to refine surgical indications for CIs.

Effects of electrode array length on frequency-place mismatch and speech perception with cochlear implants.

Frequency-place mismatch often occurs after cochlear implantation, yet its effect on speech perception outcome remains unclear. In this article, we propose a method, based on cochlea imaging, to determine the cochlear place-frequency map. We evaluated the effect of frequency-place mismatch on speech perception outcome in subjects implanted with 3 different lengths of electrode arrays. A deeper insertion was responsible for a larger frequency-place mismatch and a decreased and delayed speech perception improvement by comparison with a shallower insertion, for which a similar but slighter effect was noticed. Our results support the notion that selecting an electrode array length adapted to each individual's cochlear anatomy may reduce frequency-place mismatch and thus improve speech perception outcome.

Predictive factors of cochlear implant outcomes in the elderly.

OBJECTIVE: To analyze predictive factors of cochlear implant outcomes and postoperative complications in the elderly. STUDY DESIGN: Prospective, longitudinal study performed in 10 tertiary referral centers. METHODS: Ninety-four patients aged 65-85 years with a profound, postlingual hearing loss were evaluated before implantation, at time of activation, and 6 and 12 months after cochlear implantation. Speech perception and lipreading were measured using disyllabic word recognition in quiet and noise, and lipreading using disyllabic words and sentences. The influence of preoperative factors on speech perception in quiet and noise at 12 months was tested in a multivariate analysis. Complications, presence of tinnitus and of vestibular symptoms were collected at each evaluation. RESULTS: The effect of age was observed only in difficult noisy conditions at SNR 0 dB. Lipreading ability for words and sentences was negatively correlated with speech perception in quiet and noise. Better speech perception scores were observed in patients with shorter duration of hearing deprivation, persistence of residual hearing for the low frequencies, the use of a hearing aid before implantation, the absence of cardiovascular risk factors, and in those with implantation in the right ear. General and surgical complications were very rare, and the percentage of vestibular symptoms remained stable over time. CONCLUSION: This study demonstrates that cochlear implantation in the elderly is a well-tolerated procedure and an effective method to improve communication ability. Advanced age has a low effect on cochlear implant outcome. Analyses of predictive factors in this population provide a convincing argument to recommend treatment with cochlear implantation as early as possible in elderly patients with confirmed diagnosis of a severe-to-profound hearing loss and with only limited benefit from hearing aid use in one ear.

Factors affecting auditory performance of postlinguistically deaf adults using cochlear implants: an update with 2251 patients.

OBJECTIVE: To update a 15-year-old study of 800 postlinguistically deaf adult patients showing how duration of severe to profound hearing loss, age at cochlear implantation (CI), age at onset of severe to profound hearing loss, etiology and CI experience affected CI outcome. STUDY DESIGN: Retrospective multicenter study. METHODS: Data from 2251 adult patients implanted since 2003 in 15 international centers were collected and speech scores in quiet were converted to percentile ranks to remove differences between centers. RESULTS: The negative effect of long duration of severe to profound hearing loss was less important in the new data than in 1996; the effects of age at CI and age at onset of severe to profound hearing loss were delayed until older ages; etiology had a smaller effect, and the effect of CI experience was greater with a steeper learning curve. Patients with longer durations of severe to profound hearing loss were less likely to improve with CI experience than patients with shorter duration of severe to profound hearing loss. CONCLUSIONS: The factors that were relevant in 1996 were still relevant in 2011, although their relative importance had changed. Relaxed patient selection criteria, improved clinical management of hearing loss, modifications of surgical practice, and improved devices may explain the differences.

Pre-, per- and postoperative factors affecting performance of postlinguistically deaf adults using cochlear implants: a new conceptual model over time.

OBJECTIVE: To test the influence of multiple factors on cochlear implant (CI) speech performance in quiet and in noise for postlinguistically deaf adults, and to design a model of predicted auditory performance with a CI as a function of the significant factors. STUDY DESIGN: Retrospective multi-centre study. METHODS: Data from 2251 patients implanted since 2003 in 15 international centres were collected. Speech scores in quiet and in noise were converted into percentile ranks to remove differences between centres. The influence of 15 pre-, per- and postoperative factors, such as the duration of moderate hearing loss (mHL), the surgical approach (cochleostomy or round window approach), the angle of insertion, the percentage of active electrodes, and the brand of device were tested. The usual factors, duration of profound HL (pHL), age, etiology, duration of CI experience, that are already known to have an influence, were included in the statistical analyses. RESULTS: The significant factors were: the pure tone average threshold of the better ear, the brand of device, the percentage of active electrodes, the use of hearing aids (HAs) during the period of pHL, and the duration of mHL. CONCLUSIONS: A new model was designed showing a decrease of performance that started during the period of mHL, and became faster during the period of pHL. The use of bilateral HAs slowed down the related central reorganization that is the likely cause of the decreased performance.

Effect of surgical technique on electrode impedance after cochlear implantation.

OBJECTIVES: We compare the evolution of electrode impedance values (IVs) following either conventional cochlear implantation or implantation by the soft surgery (SS) technique. METHODS: We performed a retrospective chart review of 20 consecutive adult patients who underwent implantation with the Nucleus CA 24 device between 2004 and 2007. Five patients with preoperative residual hearing at the frequencies 256, 512, and 1,024 Hz underwent implantation by an SS cochlear implantation technique (SS group), and the 15 other patients underwent a conventional implantation technique (conventional cochleostomy [CC] group). The active electrodes were classified as distal (17 to 22), middle (10 to 16), or proximal (3 to 9) according to their position in relation to the tip of the electrode array. Their IVs were collected at 1, 3, 12, 24, and 36 months after implantation. Changes in auditory thresholds at 3 and 24 months were reported for patients in the SS group. RESULTS: The postoperative IVs of both the CC and SS groups decreased significantly between 1 and 3 months after implantation (p < 0.05) and then remained stable. The IVs after 12 months were significantly lower (p < 0.05) in the SS group than in the CC group. CONCLUSIONS: Patients who underwent the SS technique displayed lower long-term electrode IVs than did their counterparts in the CC group. If electrode IVs are indeed an indirect representation of cochlear fibrosis, the use of the SS technique in lieu of the CC technique could reduce fibrotic development.

Educational and employment achievements in prelingually deaf children who receive cochlear implants.

OBJECTIVE: To investigate the educational and employment achievements of prelingually deaf children who undergo cochlear implantation. DESIGN: Prospective study. Data were examined within groups defined by current age and additional disabilities. Multivariate analyses were used to identify variables influencing grade failure and communication mode. SETTING: Tertiary referral center. PARTICIPANTS: One hundred prelingually deaf children who received cochlear implants before 6 years of age and who also had at least 4 years of follow-up. INTERVENTION: Interview of parents using a standardized questionnaire. MAIN OUTCOME MEASURES: The type of schooling, form of communication, employment status, age at which the child learned to read and write, number of grade failures, and educational support required. RESULTS: Mainstream schooling, regardless of educational level, was the standard experience for children without additional disabilities (16 of 24 [67%] in the 12- to 15-year age group to 20 of 24 [83%] in the 8- to 11-year age group). Four of 8 participants older than 18 years (50%) had a university-level education; the remainder had vocational training. Delayed reading and writing skills were experienced by 19 of 74 participants (26%) and, depending on the age group, 42% to 61% of participants (10 of 24 in the 8- to 11-year age group to 11 of 18 in the 16- to 18-year age group) had failed a grade. The number of grade failures was associated with communication mode at the time of the survey. Age at implantation, preoperative communication mode, and educational support influenced the final communication mode. In children with additional disabilities, the level of academic achievement and employment status varied. CONCLUSIONS: Despite significant differences in the grade failure rate between the children with cochlear implants and the general population, the participants in the present study ultimately achieved educational and employment levels similar to those of their normal-hearing peers. To minimize these delays and improve academic success in mainstream education, early oral education and early cochlear implantation are important.

Impact of early cochlear implantation on the linguistic development of the deaf child.

OBJECTIVE: The purpose of this study was to examine prognostic factors of cochlear implantation and to evaluate the impact of early implantation on linguistic development in deaf children. STUDY DESIGN: Retrospective study. SETTING: Tertiary referral center. PATIENTS: Seventy-four prelingually deafened children implanted before the age of 5 years. INTERVENTION: Annual follow-up after cochlear implantation. MAIN OUTCOME MEASURES: Speech perception, intelligibility, and expressive and receptive language scores from age 3 to 8 years were globally compared between 4 subgroups of children. Significant differences were further explored by intergroup comparisons. Stepwise logistic linear regression was performed using the following variables: age at implantation, duration of cochlear implant (CI) use, preoperative hearing levels, age of hearing aid (HA) fitting, and age at time of the evaluation. Preoperative data were not available. RESULTS: Between group comparisons displayed significant differences according to age at implantation. Multivariate analysis demonstrated the positive impact of early implantation on receptive language. Moreover, duration of CI use and preoperative hearing levels were statistically correlated with performance on speech perception, intelligibility, and expressive and receptive language. Age of HA fitting was associated with speech intelligibility. CONCLUSION: Age at implantation, duration of CI, preoperative hearing levels, and age of HA fitting may each be useful in predicting linguistic success after cochlear implantation. Other factors such as preoperative linguistic development may also influence postoperative outcomes, but the lack of tests suitable for use with very young children makes such a hypothesis difficult to confirm.

Reliability and complications of 500 consecutive cochlear implantations.

OBJECTIVES: To assess device failures as well as early postoperative, late postoperative, and medical complications occurring after cochlear implantation and to discuss their causes and treatments. STUDY DESIGN: Retrospective study of 500 consecutive cochlear implantations. SETTING: Tertiary referral center. PATIENTS: All patients receiving cochlear implants at our institution between 1989 and 2006. MAIN OUTCOME MEASURES: All complications and treatments were systematically reviewed with a maximum follow-up of 18 years. The number of reimplantations was calculated according to follow-up duration to determine the cochlear implant survival rate. Specific risks of reimplantation were calculated for groups with differing durations of implantation. RESULTS: The overall rate of complications was 16.0% (79 of 500), with minor complications accounting for 5.6%; major complications, 3.2%; and reimplantations, 7.2%. Reasons for revision surgery were device failure, infection, trauma, and "soft device failure" (failure despite normal results from integrity testing). Revision surgery was performed in 51 of the 500 cases (10.2%), and other complications were managed medically (28 of 500; 5.6%). The rate of hard and soft device failures was 6% (30 of 500). Seventy-two percent of reimplantations occurred within 5 years. The risk of severe infection (eventually requiring explantation) was 1.4% (7 of 500). There was 1 case of transient facial palsy following surgery (0.2%), and the incidence of postsurgical meningitis was 0. CONCLUSIONS: Cochlear implantation is a safe technique with a relatively low complication rate; however, certain complications may require specific attention to prevent or correct them.

Ten-year follow-up of a consecutive series of children with multichannel cochlear implants.

OBJECTIVES: To assess a group of children who consecutively received implants more than 10 years after implantation with regard to speech perception, speech intelligibility, receptive language level, and academic/occupational status. STUDY DESIGN: A prospective longitudinal study. SETTING: Pediatric referral center for cochlear implantation. PATIENTS: Eighty-two prelingually deafened children received the Nucleus multichannel cochlear implant. INTERVENTIONS: Cochlear implantation with Cochlear Nucleus CI22 implant. MAIN OUTCOME MEASURES: The main outcome measures were open-set Phonetically Balanced Kindergarten word test, discrimination of sentences in noise, connective discourse tracking (CDT) using voice and telephone, speech intelligibility rating (SIR), vocabulary knowledge measured using the Peabody Picture Vocabulary Test (Revised), academic performance on French language, foreign language, and mathematics, and academic/occupational status. RESULTS: After 10 years of implant experience, 79 children (96%) reported that they always wear the device; 79% (65 of 82 children) could use the telephone. The mean scores were 72% for the Phonetically Balanced Kindergarten word test, 44% for word recognition in noise, 55.3 words per minute for the CDT, and 33 words per minute for the CDT via telephone. Thirty-three children (40%) developed speech intelligible to the average listener (SIR 5), and 22 (27%) developed speech intelligible to a listener with little experience of deaf person's speech (SIR 4). The measures of vocabulary showed that most (76%) of children who received implants scored below the median value of their normally hearing peers. The age at implantation was the most important factor that may influence the postimplant outcomes. Regarding educational/vocational status, 6 subjects attend universities, 3 already have a professional activity, 14 are currently at high school level, 32 are at junior high school level, 6 additional children are enrolled in a special unit for children with disability, and 3 children are still attending elementary schools. Seventeen are in further noncompulsory education studying a range of subjects at vocational level. CONCLUSION: This long-term report shows that many profoundly hearing-impaired children using cochlear implants can develop functional levels of speech perception and production, attain age-appropriate oral language, develop competency level in a language other than their primary language, and achieve satisfactory academic performance.

Molecular epidemiology of DFNB1 deafness in France.

BACKGROUND: Mutations in the GJB2 gene have been established as a major cause of inherited non syndromic deafness in different populations. A high number of sequence variations have been described in the GJB2 gene and the associated pathogenic effects are not always clearly established. The prevalence of a number of mutations is known to be population specific, and therefore population specific testing should be a prerequisite step when molecular diagnosis is offered. Moreover, population studies are needed to determine the contribution of GJB2 variants to deafness. We present our findings from the molecular diagnostic screening of the GJB2 and GJB6 genes over a three year period, together with a population-based study of GJB2 variants. METHODS AND RESULTS: Molecular studies were performed using denaturing High Performance Liquid Chromatograghy (DHPLC) and sequencing of the GJB2 gene. Over the last 3 years we have studied 159 families presenting sensorineural hearing loss, including 84 with non syndromic, stable, bilateral deafness. Thirty families were genotyped with causative mutations. In parallel, we have performed a molecular epidemiology study on more than 3000 dried blood spots and established the frequency of the GJB2 variants in our population. Finally, we have compared the prevalence of the variants in the hearing impaired population with the general population. CONCLUSION: Although a high heterogeneity of sequence variation was observed in patients and controls, the 35delG mutation remains the most common pathogenic mutation in our population. Genetic counseling is dependent on the knowledge of the pathogenicity of the mutations and remains difficult in a number of cases. By comparing the sequence variations observed in hearing impaired patients with those sequence variants observed in general population, from the same ethnic background, we show that the M34T, V37I and R127H variants can not be responsible for profound or severe deafness.

Cochlear implantation in prelingually deafened children with residual hearing.

OBJECTIVE: The purpose of this study was to examine the speech perception skills of prelingually deafened French children with preoperative residual hearing who received multichannel cochlear implants. DESIGN: The design of the study incorporated a within-subject, repeated measures design for assessing speech perception skills. SETTING: Montpellier, Toulouse and Lyon Pediatric Cochlear Implant Centers. SUBJECTS: Seven prelingually deafened children demonstrating marginal benefit from conventional amplification prior to implantation with a Nucleus multichannel cochlear implant, served as subjects for the speech perception assessment (a speech recognition score less than 30% defines marginal benefit from acoustic amplification on open set materials). The mean age at implantation was 7 years, 9 months. OUTCOME MEASURES: Speech perception skills were assessed using open set materials and the MUSS and MAIS questionnaires. RESULTS: Open-set speech recognition averaged 21.4% before implantation, and 83.6% after 1 year's cochlear implant experience. All children demonstrated an open-set score over 60% after 12 months of CI use. MAIS test scores averaged 18.1/40 before implantation and 35.1/40 after 9 months of CI use. MUSS test scores averaged 24.4/40 before implantation and 34.1/40 after 9 months of CI use. CONCLUSIONS: Cochlear implantation should be considered for prelingually hearing impaired children demonstrating marginal benefit from hearing aids, with a speech recognition score less than 30% on open set materials, in order to improve their speech discrimination skills.