Deaf Cochlear Implant Research Articles

Bilateral cochlear implants in young children.

Cochlear implants (CIs) are provided to a growing number of people who are deaf. Single CIs offer opportunity for language acquisition, but there exist remaining challenges. In normal‐hearing individuals binaural hearing provides cues that are important for sound localization and speech understanding in noisy environments. Provision of bilateral CIs to many children occurs with the expectation that they will develop spatial hearing abilities. Outcomes in these children are mixed; while some are able to localize sound significantly better with bilateral CIs than with a single CI, other children demonstrate poor spatial hearing skills. Factors that seem to contribute to performance include amount of auditory deprivation prior to implantation and auditory experience following bilateral activation. Hardware/software limitations in implanted devices result in binaural cues being distorted or discarded. Studies using research processors show that these cues can be transmitted with fidelity to the patients, but that perceptual sensitivity to these cues may depend on the period of auditory deprivation that listeners have experienced. This talk will focus on progress and outcomes in children who are deaf and use bilateral CIs, with suggestions for future development that will depend on improved audio signal processing and signal delivery to the implantable devices.

Artificial hearing, natural speech: Cochlear implants, speech production, and the expectations of a high-tech society (review)

Reviewed by: Artificial hearing, natural speech: Cochlear implants, speech production, and the expectations of a high-tech society Mario A. Svirsky Artificial hearing, natural speech: Cochlear implants, speech production, and the expectations of a high-tech society. By Joanna Hart Lowenstein. (Outstanding dissertations in linguistics.) New York: Routledge, 2007. Pp. 160. ISBN 9780415976046. $153 (Hb). Cochlear implants (CIs) represent the first successful attempt to replace a human sense with electronic means. These devices are primarily indicated for patients whose inner hair cells (the neurons that convert sound into neural information) do not function. In these cases, amplifying sound with a conventional hearing aid does not work because the crucial step of converting sound to neural activity fails, no matter what the intensity of the sound. CIs bypass the normal hearing mechanism by stimulating auditory neurons electrically, via electrodes implanted in the inner ear. An external part includes a microphone, a speech processor that encodes sound information into electrical stimulation patterns, and a transmitter antenna. This antenna sends the stimulation information [End Page 215] to an implanted receiver that decodes the information and sends stimulation pulses to electrodes placed in the inner ear, in the snail-shaped organ named cochlea. The first CIs were built and tested in humans by a French team in the late 1950s. Since then, after a process that included many breakthroughs as well as some setbacks, CIs have become the standard of care for treating many kinds of deafness. As of this writing, more than 67,000 patients in the United States and close to 200,000 worldwide have received CIs. Most of these patients can understand at least some speech without the aid of lipreading, and even congenitally deaf children can develop speech perception, speech production, and oral language skills that are sufficient to allow them to attend mainstream schools. Despite the fact that results are very good on average, a major hallmark of CI outcomes is their individual variability. Each group of patients, no matter how uniform their demographics might be, tends to include ‘stars’ as well as more mediocre performers. There are important differences between groups as well, and it is useful to think about three different groups when discussing the scientific interest and the clinical impact of CIs. The first group includes congenitally or prelingually deaf children. When they are implanted in the first few years of life, the CI not only helps these children’s speech perception, but it also facilitates their development of intelligible speech production and that of language skills in an oral language such as English. Most of these children obtain significant benefit from their CIs, can understand at least some speech without lipreading, and can participate in mainstream classrooms. A second group is composed of congenitally or prelingually deaf individuals who are implanted in their adolescence or adulthood. Communicative benefit is much more limited than in the first group. Patients are able to detect sounds and obtain some lipreading enhancement, but speech perception is generally limited. Speech production and oral language skills are also much more limited than in the first group. The third group—and the one that is the focus of Lowenstein’s book—is that of postlingually deafened adults, people who developed oral language and speech production prior to becoming deaf. Despite years or even decades of profound deafness, changes in speech production are subtle. By and large, patients in this group have no major difficulty producing intelligible speech. The main benefit these patients obtain is improved speech perception. Using their CIs, the vast majority of them are able to have fluent face-to-face conversations, and most of them can communicate on the telephone. Beyond the clinical benefit they provide, patients with CIs are also interesting because they may help answer basic questions about human communication, such as those concerning the role of hearing on speech production. Postlingually deaf CI users undergo several years of sound deprivation and then start receiving auditory input again (albeit a degraded version) once they receive CIs. The subtle changes in speech production before and after implantation in this population have been studied before, and much of the literature is reviewed in L’s book, focusing on a...

Cross-Modal Plasticity and Speech Perception in Pre- and Postlingually Deaf Cochlear Implant Users

A great amount of variability is observed in speech perception outcomes with cochlear implants. The mechanisms behind the observed variability need to be elucidated. One possible mechanism contributing to the observed variability is the development of cross-modal plasticity. This study examines the association between visual/auditory cross-modal plasticity and speech perception with a cochlear implant in individuals with pre- and postlingual onset of severe to profound hearing loss. The N1 visual evoked potential (VEP) in response to peripheral visual motion stimuli was recorded in individuals with pre- (N = 10) and postlingual (N = 12) onset of severe to profound hearing loss who use a cochlear implant. The association between the amplitude of the N1 VEP response over the right temporal lobe and sentence and word perception scores obtained with the cochlear implant was examined through linear regression analyses. In addition, the association between the duration of auditory deprivation and the amplitude of the N1 VEP response was examined. As the amplitude of the N1 VEP recorded over the right temporal lobe increased, speech perception scores in individuals with prelingual onset of severe to profound hearing loss decreased. However, a clear association between the amplitude of the N1 VEP over the right temporal lobe and speech perception scores was not observed for individuals with postlingual onset of severe to profound hearing loss. Neither group demonstrated an association between the amplitude of the VEP over the right temporal lobe and the duration of auditory deprivation before cochlear implantation. The results suggest that cross-modal plasticity accounts for a significant amount of the variability observed in speech perception performance with a cochlear implant in individuals with prelingual onset of severe to profound hearing loss but not in individuals who acquire severe to profound hearing loss later in life. Furthermore, the results suggest that the influence of cross-modal plasticity on speech perception ability is more greatly influenced by when (pre- or postlingually) a person acquires a severe to profound hearing impairment rather than the duration of auditory deprivation before receipt of a cochlear implant.

Combined Electric and Acoustic Stimulation: Successful Treatment Option for Partial Deafness

Combined Electric and Acoustic Stimulation: Successful Treatment Option for Partial Deafness

A Comparison of Vowel Productions in Prelingually Deaf Children Using Cochlear Implants, Severe Hearing-Impaired Children Using Conventional Hearing Aids and Normal-Hearing Children

Objective: The purpose of this study was to compare vowel productions by deaf cochlear implant (CI) children, hearing-impaired hearing aid (HA) children and normal-hearing (NH) children. Patients and Methods: 73 children [mean age: 9;14 years (years;months)] participated: 40 deaf CI children, 34 moderately to profoundly hearing-impaired HA children and 42 NH children. For the 3 corner vowels [a], [i] and [u], F₁, F₂ and the intrasubject SD were measured using the Praat software. Spectral separation between these vowel formants and vowel space were calculated. Results: The significant effects in the CI group all pertain to a higher intrasubject variability in formant values, whereas the significant effects in the HA group all pertain to lower formant values. Both hearing-impaired subgroups showed a tendency toward greater intervowel distances and vowel space. Conclusion: Several subtle deviations in the vowel production of deaf CI children and hearing-impaired HA children could be established, using a well-defined acoustic analysis. CI children as well as HA children in this study tended to overarticulate, which hypothetically can be explained by a lack of auditory feedback and an attempt to compensate it by proprioceptive feedback during articulatory maneuvers.

A new software tool to optimize frequency table selection for cochlear implants.

When cochlear implant (CI) users are allowed to self-select the "most intelligible" frequency-to-electrode table, some of them choose one that differs from the default frequency table that is normally used in clinical practice. CIs reproduce the tonotopicity of normal cochleas using frequency-to-electrode tables that assign stimulation of more basal electrodes to higher frequencies and more apical electrodes to lower frequency sounds. Current audiologic practice uses a default frequency-to-electrode table for most patients. However, individual differences in cochlear size, neural survival, and electrode positioning may result in different tables sounding most intelligible to different patients. No clinical tools currently exist to facilitate this fitting. A software tool was designed that enables CI users to self-select a most intelligible frequency table. Users explore a 2-dimensional space that represents a range of different frequency tables. Unlike existing tools, this software enables users to interactively audition speech processed by different frequency tables and quickly identify a preferred one. Pilot testing was performed in 11 long-term, postlingually deaf CI users. The software tool was designed, developed, tested, and debugged. Patients successfully used the tool to sample frequency tables and to self-select tables deemed most intelligible, which for approximately half of the users differed from the clinical default. A software tool allowing CI users to self-select frequency-to-electrode tables may help in fitting postlingually deaf users. This novel approach may transform current methods of CI fitting.

Intelligibility of hearing impaired children as judged by their parents: A comparison between children using cochlear implants and children using hearing aids

Objectives The aim of this study was to determine the intelligibility of prelingually deaf children with cochlear implants (CI) as judged by their own parents, and to compare these results with prelingually hearing impaired children using hearing aids (HA) and normally hearing (NH) children. The authors hypothesised that subjects using conventional hearing aids would have poorer intelligibility judgements compared to NH and CI children. Methodology This is a comparative study of 24 prelingually deaf CI children (m.a. 8.3 years), 24 prelingually hearing impaired HA children (m.a. 9.0 years) and 25 NH children. Recorded speech samples at word-, sentence- and story-level were perceptually judged by two speech pathologists and the child's main caregiver (the mother in most cases) using a five-point hierarchical scale. In addition, the sample of each child was transcribed by the child's main caregiver. The investigators counted and determined a percentage of words correctly understood. Results The judgements of the speech pathologists and the transcriptions of the mothers were not different between the CI and NH children, although the mothers tended to judge their CI child to be less intelligible. The HA children on the other hand, showed a mean intelligibility inferior to NH and CI children, as demonstrated by the judgements of the mothers and speech pathologists as well as by the percentages of correctly identified words by the mothers. Conclusion The intelligibility of the prelingually deaf CI children is very close to the intelligibility of NH children, while the HA children still show a decreased mean intelligibility.

Subjective Benefit after Partial Deafness Cochlear Implantation

Benefits after cochlear implantation are not limited to auditory gains, but also extend to improvement in physical, psychological, and social function. Cochlear implant (CI) eligibility criteria have broadened to now include a variety of patient groups. To clearly understand the complex change experienced by patients and their families, it is necessary to use subjective questionnaires for the individual patient groups. One distinct group of CI patients includes individuals with Partial Deafness (PD) who frequently have normal hearing in the low frequencies. Individuals with PD often do not wear a hearing aid. In 2002, our centre pioneered partial deafness cochlear implantation (PDCI). Since 2004, children with PD have been implanted at the Institute of Physiology and Pathology of Hearing. The benefits of PDCI for both adults and children have been well documented (Skarzynski et al., 2009; 2007; 2006; 2003; Lorens et al., 2008). The benefits of PDCI have primarily been evaluated with objective measures of sound detection and speech discrimination. Although subjective benefit after conventional cochlear implantation for profound hearing loss has been assessed with a wide range of methodologies (Archbold et al., 2002), these techniques have not been extended to individuals undergoing PDCI. As the paediatric PDCI group is particularly unique, we were especially motivated to gather evidence of subjective benefit from multiple sources. We believe that parents are likely the primary source of information about PDCI children. We created an open-ended questionnaire to assess parent’s perception of the process and outcomes of PDCI. Open-ended questions were seen as the most appropriate format to permit parents to freely describe their perceptions of the experience of PD children undergoing cochlear implantation.

Partial Deafness Cochlear Implantation at the University of Kansas: Techniques and Outcomes

One of the most significant recent advances in cochlear implantation is the implantation of patients with residual hearing. These patients have a downsloping sensorineural hearing loss with poor speech discrimination and perform poorly with standard amplification. Studies using a variety of different electrode designs have demonstrated that it is possible to implant an inner ear and preserve residual hearing. Initial studies have demonstrated that a combination of residual acoustic hearing in the low frequencies with electrical stimulation in the mid- to high frequencies resulted in superior hearing performance in background noise. The objective of this study was to determine the effect of electrode insertion depth on hearing preservation. Eighteen patients with mild to severe hearing loss in the low frequencies combined with poor word recognition were recruited for the study. Cochlear implantation. Pre- and postoperative hearing test, Hearing in Noise Test, and consonant-nucleus-consonant testing. Data analysis was performed with Kruskal Wallis and Mann-Whitney testing. In our study of 18 patients implanted with a Med-El PulsarCI100 we demonstrated the ability to preserve residual hearing with implant insertion depths ranging from 20 to 28 mm, giving us the possibility of near complete cochlear frequency coverage with an implant array while preserving residual hearing. These patients performed well both in quiet and in 10 dB signal-to-noise ratio conditions. Hearing preservation was achievable even with deep implant insertion. Patients performed well in combined acoustic and electric conditions.

Cochlear implants and spoken language processing abilities: review and assessment of the literature.

Cochlear implants (CIs) process sounds electronically and then transmit electric stimulation to the cochlea of individuals with sensorineural deafness, restoring some sensation of auditory perception. Many congenitally deaf CI recipients achieve a high degree of accuracy in speech perception and develop near-normal language skills. Post-lingually deafened implant recipients often regain the ability to understand and use spoken language with or without the aid of visual input (i.e. lip reading). However, there is wide variation in individual outcomes following cochlear implantation, and some CI recipients never develop useable speech and oral language skills. The causes of this enormous variation in outcomes are only partly understood at the present time. The variables most strongly associated with language outcomes are age at implantation and mode of communication in rehabilitation. Thus, some of the more important factors determining success of cochlear implantation are broadly related to neural plasticity that appears to be transiently present in deaf individuals. In this article we review the expected outcomes of cochlear implantation, potential predictors of those outcomes, the basic science regarding critical and sensitive periods, and several new research directions in the field of cochlear implantation.

Results of Partial Deafness Cochlear Implantation Using Various Electrode Designs

Nineteen adults and 9 children who received a unilateral cochlear implant between 2002 and 2007 were included in the study. All subjects were preoperatively diagnosed with significant residual hearing in low frequencies, termed as ‘partial deafness’, and were implanted according to a 6-step round window surgical technique for partial deafness cochlear implantation. Hearing was preserved to a great extent in the partial deafness cochlear implantation (PDCI) group. After a short period following activation of the cochlear implant, highly significant improvement in the recognition of monosyllabic words was observed. With a developed round window surgical procedure and limited electrode insertion, hearing can be preserved in the majority of patients with partial deafness. PDCI is a feasible means of treating individuals who have good low-frequency hearing but severe to profound hearing loss in the mid to high frequencies.

Verbesserung der Sprachverständlichkeit durch neuen Cochlear-Implant-Sprachprozessor

The aim of this multicenter clinical field study was to assess the benefits of the new Freedom 24 sound processor for cochlear implant (CI) users implanted with the Nucleus 24 cochlear implant system. The study included 48 postlingually profoundly deaf experienced CI users who demonstrated speech comprehension performance with their current speech processor on the Oldenburg sentence test (OLSA) in quiet conditions of at least 80% correct scores and who were able to perform adaptive speech threshold testing using the OLSA in noisy conditions. Following baseline measures of speech comprehension performance with their current speech processor, subjects were upgraded to the Freedom 24 speech processor. After a take-home trial period of at least 2 weeks, subject performance was evaluated by measuring the speech reception threshold with the Freiburg multisyllabic word test and speech intelligibility with the Freiburg monosyllabic word test at 50 dB and 70 dB in the sound field. The results demonstrated highly significant benefits for speech comprehension with the new speech processor. Significant benefits for speech comprehension were also demonstrated with the new speech processor when tested in competing background noise.In contrast, use of the Abbreviated Profile of Hearing Aid Benefit (APHAB) did not prove to be a suitably sensitive assessment tool for comparative subjective self-assessment of hearing benefits with each processor. Use of the preprocessing algorithm known as adaptive dynamic range optimization (ADRO) in the Freedom 24 led to additional improvements over the standard upgrade map for speech comprehension in quiet and showed equivalent performance in noise. Through use of the preprocessing beam-forming algorithm BEAM, subjects demonstrated a highly significant improved signal-to-noise ratio for speech comprehension thresholds (i.e., signal-to-noise ratio for 50% speech comprehension scores) when tested with an adaptive procedure using the Oldenburg sentences in the clinical setting S(0)N(CI), with speech signal at 0 degrees and noise lateral to the CI at 90 degrees . With the convincing findings from our evaluations of this multicenter study cohort, a trial with the Freedom 24 sound processor for all suitable CI users is recommended. For evaluating the benefits of a new processor, the comparative assessment paradigm used in our study design would be considered ideal for use with individual patients.

Perception of speech and environmental sounds in cochlear implant patients

Limited research has investigated cochlear implant (CI) patients' ability to perceive environmental sounds. In this study, environmental sound perception was assessed with a large‐item test composed of 40 sound sources, each represented by four different tokens. The relationship between speech and environmental sound perception and the role of working memory and basic auditory abilities was examined based on patient performance on a battery of speech tests (HINT, CNC, and individual consonant and vowel tests), tests of basic auditory abilities (audiometric thresholds, gap detection, temporal pattern and temporal order tests), and a backward digit recall test. Twelve postlingually deaf adult CI patients, having 1‐5 years of implant experience participated. The results indicate substantially reduced ability to identify common environmental sounds in CI patients. Speech test scores correlated strongly with the scores on the environmental sound test. Both speech and environmental sound tests moderately correlated with gap detection, temporal order test and backward digit recall test. However, the correlation between speech and environmental sounds changed little after partialling out the variance due to other variables. These results suggest that speech and environmental sounds may overlap considerably in their perceptual processing, being largely independent of peripheral limitations that may affect both sound classes.

Outcomes of Treatment of Partial Deafness With Cochlear Implantation: A DUET Study

To compare speech test performance of adults with partial deafness cochlear implantation (PDCI) with that of adults with cochlear implant (CI). Based on the results, our objective is to determine the efficacy of the two applications of cochlear implantation, the first characterized by a shallow electrode insertion and preservation of low-frequency natural hearing for partial deafness, and the second characterized by a very deep electrode insertion used in subjects with severe to profound deafness. All the PDCI participants in this study were fitted with a recently upgraded DUET Hearing System from Med-El Corporation, Innsbruck, Austria. This is a two-group comparison study. Eleven experienced PDCI adults and 22 postlingually deafened CI adults participated in this study. Subjects were implanted with either COMBI 40+ or PULSAR cochlear implant. Subjects were tested with monosyllable and sentence tests in Polish in quiet and under various signal-to-noise ratio (SNR) in the conditions of DUET only, CI only, DUET hearing aid (HA) only, and best aided (DUET plus contralateral hearing). CI subjects were tested with their CI. PDCI subjects performed significantly better than CI subjects did. Speech tests demonstrated the best results in the conditions of best aided and DUET only. The poorest results were obtained in the condition DUET HA only. Results show a greater benefit for the PDCI group of subjects fitted with the DUET, compared to the CI alone group. The shallow electrode array insertion with preserved low-frequency hearing is a highly effective method for the treatment of partial deafness. The combination of HA and CI processor, i.e., the DUET, is beneficial in noise and in quiet.

Hearing Preservation in Patients With a Cochlear Implant

Hearing Preservation in Patients With a Cochlear Implant

Partial deafness cochlear implantation in children

Partial deafness cochlear implantation and electric-acoustic stimulation have proven to be a useful method of treating adults with a ski-slope type hearing loss. Good hearing preservation and speech perception outcomes have been reported. This study aims to assess partial deafness cochlear implantation in children. Nine children, ranging in age from 4.2 to 12 years, received a cochlear implant following the round window surgical technique for partial deafness cochlear implantation. Hearing preservation was assessed by pure-tone audiometry and speech perception outcomes were measured using monosyllable word tests in quiet and noise. Data are available for most children up to a period of 1 year. Hearing could be preserved partially in all cases, however, one child does not have sufficient preservation to make use of electric-acoustic stimulation. The eight children with sufficiently preserved hearing either use the natural low frequency hearing in combination with a cochlear implant to hear or use the DUET combined hearing system. Speech perception tests showed improvement in quiet and noise over time. Results suggest that partial deafness cochlear implantation is a viable treatment method in children. However, surgery should only be conducted by an experienced surgeon and parents need to be carefully counselled about the risks and benefits of partial deafness cochlear implantation.

Preservation of low frequency hearing in partial deafness cochlear implantation (PDCI) using the round window surgical approach

Conclusion. Successful hearing preservation is possible in individuals with excellent low frequency hearing. This is possible due to the partial insertion of an atraumatic electrode using an atraumatic round window surgical technique. Objectives. This paper describes the round window surgical technique used to preserve excellent low frequency hearing in patients receiving partially inserted MED-EL cochlear implant electrodes. Results of preserved low frequency hearing in partial deafness cochlear implantation (PDCI) are reported. Patients and methods. The surgical approach is described in detail. Ten subjects received a partial insertion of a standard electrode, using the round window approach. Pure tone audiometry was conducted in the implanted and non-implanted ear preoperatively, at implant fitting and then at 1, 3, 6 and 12 months after initial device fitting. Results. Results show hearing preservation in 9 of the 10 subjects. One subject lost all hearing 2 weeks after cochlear implantation. Hearing has remained essentially stable up to the 1 year postoperative period. Eight of the nine subjects use the cochlear implant together with their natural low frequency hearing; one subject uses a hearing aid in the implanted ear to amplify the low frequencies.

Does music perception have an impact on quality of life following cochlear implantation?

Conclusion. Despite the decrease in listening habits, about half of the patients still enjoy music post implantation. Better quality of sound through the implant improves music enjoyment and contributes to achievement of better postoperative quality of life (QOL). Objectives. To evaluate music perception and enjoyment in cochlear implant (CI) users, and to assess their influence on QOL. Materials and methods. Sixty-five post-lingually deaf CI recipients were enrolled in this study. A musical questionnaire evaluated musical background, listening habits, and quality of musical sound through the CI. The validated Glasgow Benefit Inventory (GBI) was used to quantify changes in QOL. Results. Fifty-two patients answered the questionnaires. Listening habits (music enjoyment and hours spent listening to music per week) significantly decreased following implantation when compared with the same parameters before deafness. Nevertheless, 52% of the patients enjoyed music post implantation. The quality of musical sound was rated >50 (0–100 scale) for the adjective pairs ‘like-dislike’, ‘sounds like music-doesn't sound like music’ and ‘natural-mechanical’ by most users. Med-el device users obtained better scores in the adjective pair ‘sounds like music-doesn't sound like music’ than Cochlear device users. Recipients rating higher scores for quality of sound enjoyed music post implantation and had higher total GBI scores than those rating lower scores.

Partial deafness cochlear implantation provides benefit to a new population of individuals with hearing loss

Conclusion. Partial deafness cochlear implantation (PDCI) is a feasible means of treating individuals who have good low frequency hearing, but a severe to profound hearing loss in the mid to high frequencies. The individuals have benefit in noise and show significant benefit in a number of difficult listening conditions, when compared with their acoustic-only hearing prior to implantation. This benefit is maintained over time. Objectives. PDCI using the round window surgical technique is one means of treating individuals with a ‘ski-slope’ hearing loss, who gain minimal benefit from amplification with conventional hearing instruments. This paper aims to demonstrate the benefit that PDCI provides these individuals. Patients and methods. Ten subjects received a partial insertion of a standard MED-EL electrode, using the round window approach. Pure tone audiometry and monosyllable testing in quiet and noise were conducted preoperatively, at implant fitting and then at 1, 3, 6 and 12 months after initial device fitting. The APHAB questionnaire was completed by subjects preoperatively and then at 6 and 12 months after receiving their cochlear implant. Results. Hearing was preserved in 9 of 10 cases. One subject uses a hearing aid to amplify low frequency hearing, the remainder use natural low frequency hearing. Improvements in monosyllabic scores over time in both quiet and noise were significant, particularly within the first 3 months of PDCI use.

Preservation of low-frequency hearing in partial deafness cochlear implantation

Partial deafness is characterised by normal or slightly elevated thresholds in the low-frequency band with nearly total deafness in higher frequencies. The aim of the study was to investigate whether the low-frequency hearing of partially deafened patients could be preserved after cochlear implant surgery applying Med-El Combi 40+ with partially inserted electrode. Cochlear implantation was performed in six partially deafened patients. Changes in auditory thresholds using pure tone audiometry recordings were measured to determine the extent of preservation of low-frequency hearing. Low-frequency hearing was preserved to the large extent in all patients. Preservation of low-frequency hearing creates the opportunity for application of electric and acoustic stimulation in the partially deafened. It could provide speech comprehension better than with either modality alone. Obtained results can be considered as the first step towards the application of cochlear implant in the treatment of partial deafness.