Speech perception in children using cochlear implants: prediction of long-term outcomes

Two are better than one: Differences in cortical EEG patterns during auditory and visual verbal working memory processing between Unilateral and Bilateral Cochlear Implanted children

Despite the proven effectiveness of cochlear implant (CI) in the hearing restoration of deaf or hard-of-hearing (DHH) children, to date, extreme variability in verbal working memory (VWM) abilities is observed in both unilateral and bilateral CI user children (CIs). Although clinical experience has long observed deficits in this fundamental executive function in CIs, the cause to date is still unknown. Here, we have set out to investigate differences in brain functioning regarding the impact of monaural and binaural listening in CIs compared with normal hearing (NH) peers during a three-level difficulty n-back task undertaken in two sensory modalities (auditory and visual). The objective of this pioneering study was to identify electroencephalographic (EEG) marker pattern differences in visual and auditory VWM performances in CIs compared to NH peers and possible differences between unilateral cochlear implant (UCI) and bilateral cochlear implant (BCI) users. The main results revealed differences in theta and gamma EEG bands. Compared with hearing controls and BCIs, UCIs showed hypoactivation of theta in the frontal area during the most complex condition of the auditory task and a correlation of the same activation with VWM performance. Hypoactivation in theta was also observed, again for UCIs, in the left hemisphere when compared to BCIs and in the gamma band in UCIs compared to both BCIs and NHs. For the latter two, a correlation was found between left hemispheric gamma oscillation and performance in the audio task. These findings, discussed in the light of recent research, suggest that unilateral CI is deficient in supporting auditory VWM in DHH. At the same time, bilateral CI would allow the DHH child to approach the VWM benchmark for NH children. The present study suggests the possible effectiveness of EEG in supporting, through a targeted approach, the diagnosis and rehabilitation of VWM in DHH children.

Effects of training length on adaptation to noise-vocoded speech

Listeners show rapid perceptual learning of acoustically degraded speech, though the amount of exposure required to maximize speech adaptation is unspecified. The current work used a single-session design to examine the length of auditory training on perceptual learning for normal hearing listeners exposed to eight-channel noise-vocoded speech. Participants completed short, medium, or long training using a two-alternative forced choice sentence identification task with feedback. To assess learning and generalization, a 40-trial pre-test and post-test transcription task was administered using trained and novel sentences. Training results showed all groups performed near ceiling with no reliable differences. For test data, we evaluated changes in transcription accuracy using separate linear mixed models for trained or novel sentences. In both models, we observed a significant improvement in transcription at post-test relative to pre-test. Critically, the three training groups did not differ in the magnitude of improvement following training. Subsequent Bayes factors analysis evaluating the test by group interaction provided strong evidence in support of the null hypothesis. For these stimuli and procedure, results suggest increased training does not necessarily maximize learning outcomes; both passive and trained experience likely supported adaptation. Findings may contribute to rehabilitation recommendations for listeners adapting to degraded speech signals.

Ceiling effects for speech perception tests in pediatric cochlear implant users

OBJECTIVES

The purpose of this study was to determine the prevalence of ceiling effects for commonly used speech perception tests in a large population of children who received a cochlear implant (CI) before the age of four. A secondary goal was to determine the demographic factors that were relevant for predicting which children were more likely to reach ceiling level performance. We hypothesize that ceiling effects are highly prevalent for most tests.

DESIGN

Retrospective chart review of children receiving a CI between 2002 and 2014.

RESULTS

165 children were included. Median scores were above ceiling levels (≥90% correct) for the majority of speech perception tests and all distributions of scores were highly skewed. Children who were implanted earlier, received two implants, and were oral communicators were more likely to reach ceiling-level performance. Age and years of CI listening experience at time of test were negatively correlated with performance, suggesting a non-random assignment of tests. Many children were re-tested on tests for which they had already scored at ceiling.

CONCLUSIONS

Commonly used speech perception tests for children with CIs are prone to ceiling effects and may not accurately reflect how a child performs in everyday listening situations.

Auditory, Speech and Language Development in Cochlear Implant Children: A One Year Longitudinal Study

The advent of Cochlear Implants (CI) has bought with it, the goal of spoken language performance for severe-profound sensori-neural hearing loss (SNHL) as par with the normal hearing listeners. The aim of this study was to evaluate the outcome of paediatric cochlear implantation in auditory and speech skills below the age of 5 years. The present study consisted of 50 childrens. Auditory skills were assessed in terms of audiometric thresholds and localization abilities. Speech - Language skills were measured using; Categories of Auditory Performance -CAP; Meaningful Use of Speech Scale - MUSS; Meaningful Auditory Integration Scale - MAIS and Speech intelligibility Rating - SIR. Hearing thresholds obtained from all the subjects for pre implant and post implant conditions of 3rd, 6th, 9th, 12th month conditions, evidenced a high significant (p < 0.001) improvement across all test frequencies 500, 1000, 2000 and 4000 Hz. There was also a statistically significant difference across successive measurements of auditory and speech skills, as determined by ANOVA (F (4, 245) = 151.33, p < 0.001 for CAP; F (4, 245) = 89.636, p < 0.001 for SIR; F (4, 245) = 812.282 p < 0.001 for MAIS and F(4, 245) = 435.677 p < 0.001 for MUSS). Auditory localization abilities were also improved considerably over a period of one year. The present study added the evidence to the literature that cochlear implants significantly improved the hearing ability of children with severe-to-profound hearing loss. This study also demonstrated that, children were better able to make use of the auditory information perceived through the implant.

Effects of Segmental and Suprasegmental Speech Perception on Reading in Pediatric Cochlear Implant Recipients

PURPOSE

The aim of this study was to determine whether suprasegmental speech perception contributes unique variance in predictions of reading decoding and comprehension for prelingually deaf children using two devices, at least one of which is a cochlear implant (CI).

METHOD

A total of 104, 5- to 9-year-old CI recipients completed tests of segmental perception (e.g., word recognition in quiet and noise, recognition of vowels and consonants in quiet), suprasegmental perception (e.g., talker and stress discrimination, nonword stress repetition, and emotion identification), and nonverbal intelligence. Two years later, participants completed standardized tests of reading decoding and comprehension. Using regression analyses, the unique contribution of suprasegmental perception to reading skills was determined after controlling for demographic characteristics and segmental perception performance.

RESULTS

Standardized reading scores of the CI recipients increased with nonverbal intelligence for both decoding and comprehension. Female gender was associated with higher comprehension scores. After controlling for gender and nonverbal intelligence, segmental perception accounted for approximately 4% and 2% of the variance in decoding and comprehension, respectively. After controlling for nonverbal intelligence, gender, and segmental perception, suprasegmental perception accounted for an extra 4% and 7% unique variance in reading decoding and reading comprehension, respectively.

CONCLUSIONS

Suprasegmental perception operates independently from segmental perception to facilitate good reading outcomes for these children with CIs. Clinicians and educators should be mindful that early perceptual skills may have long-term benefits for literacy. Research on how to optimize suprasegmental perception, perhaps through hearing-device programming and/or training strategies, is needed.

A Modified Pediatric Ranked Order Speech Perception Score to Assess Speech Recognition Development in Children With Cochlear Implants

PURPOSE

Characterizing and comparing speech recognition development in children with cochlear implants (CIs) is challenging because of variations in test type. This retrospective cohort study modified the Pediatric Ranked Order Speech Perception (PROSPER) scoring system to (a) longitudinally analyze the speech perception of children with CIs and (b) examine the role of age at CI activation, listening mode (i.e., unilateral or bilateral implantation), and interimplant interval.

METHOD

Postimplantation speech recognition scores from 31 children with prelingual, severe-to-profound hearing loss who received CIs were analyzed (12 with unilateral CI [UniCI], 13 with sequential bilateral CIs [SEQ BiCIs], and six with simultaneous BiCIs). Data were extracted from the Massachusetts Eye and Ear Audiology database. A version of the PROSPER score was modified to integrate the varying test types by mapping raw scores from different tests into a single score. The PROSPER scores were used to construct speech recognition growth curves of the implanted ears, which were characterized by the slope of the growth phase, the time from activation to the plateau onset, and the score at the plateau.

RESULTS

While speech recognition improved considerably for children following implantation, the growth rates and scores at the plateau were highly variable. In first implanted ears, later implantation was associated with poorer scores at the plateau (β = -0.15, p = .01), but not growth rate. The first implanted ears of children with BiCIs had better scores at the plateau than those with UniCI (β = 0.59, p = .02). Shorter interimplant intervals in children with SEQ BiCIs promoted faster speech recognition growth of the first implanted ears.

CONCLUSION

The modified PROSPER score could be used clinically to track speech recognition development in children with CIs, to assess influencing factors, and to assist in developing and evaluating patient-specific intervention strategies.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.20113538.

American Cochlear Implant Alliance Task Force Guidelines for Determining Cochlear Implant Candidacy in Children

This article summarizes the available evidence on pediatric cochlear implantation to provide current guidelines for clinical protocols and candidacy recommendations in the United States. Candidacy determination involves specification of audiologic and medical criteria per guidelines of the Food and Drug Administration. However, recommendations for a cochlear implant evaluation also should maintain flexibility and consider a child’s skill progression (i.e., month-for-month progress in speech, language, and auditory development) and quality of life with appropriately fit hearing aids. Moreover, evidence supports medical and clinical decisions based on other factors, including (a) ear-specific performance, which affords inclusion of children with asymmetric hearing loss and single-sided deafness as implant candidates; (b) ear-specific residual hearing, which influences surgical technique and device selection to optimize hearing; and (c) early intervention to minimize negative long-term effects on communication and quality of life related to delayed identification of implant candidacy, later age at implantation, and/or limited commitment to an audiologic rehabilitation program. These evidence-based guidelines for current clinical protocols in determining pediatric cochlear implant candidacy encourage a team-based approach focused on the whole child and the family system.

The Effects of GJB2 or SLC26A4 Gene Mutations on Neural Response of the Electrically Stimulated Auditory Nerve in Children

OBJECTIVES

This study aimed to (1) investigate the effect of GJB2 and SLC26A4 gene mutations on auditory nerve function in pediatric cochlear implant users and (2) compare their results with those measured in implanted children with idiopathic hearing loss.

DESIGN

Participants included 20 children with biallelic GJB2 mutations, 16 children with biallelic SLC26A4 mutations, and 19 children with idiopathic hearing loss. All subjects except for two in the SLC26A4 group had concurrent Mondini malformation and enlarged vestibular aqueduct. All subjects used Cochlear Nucleus devices in their test ears. For each subject, electrophysiological measures of the electrically evoked compound action potential (eCAP) were recorded using both anodic- and cathodic-leading biphasic pulses. Dependent variables (DVs) of interest included slope of eCAP input/output (I/O) function, the eCAP threshold, and eCAP amplitude measured at the maximum comfortable level (C level) of the anodic-leading stimulus (i.e., the anodic C level). Slopes of eCAP I/O functions were estimated using statistical modeling with a linear regression function. These DVs were measured at three electrode locations across the electrode array. Generalized linear mixed effect models were used to evaluate the effects of study group, stimulus polarity, and electrode location on each DV.

RESULTS

Steeper slopes of eCAP I/O function, lower eCAP thresholds, and larger eCAP amplitude at the anodic C level were measured for the anodic-leading stimulus compared with the cathodic-leading stimulus in all subject groups. Children with GJB2 mutations showed steeper slopes of eCAP I/O function and larger eCAP amplitudes at the anodic C level than children with SLC26A4 mutations and children with idiopathic hearing loss for both the anodic- and cathodic-leading stimuli. In addition, children with GJB2 mutations showed a smaller increase in eCAP amplitude when the stimulus changed from the cathodic-leading pulse to the anodic-leading pulse (i.e., smaller polarity effect) than children with idiopathic hearing loss. There was no statistically significant difference in slope of eCAP I/O function, eCAP amplitude at the anodic C level, or the size of polarity effect on all three DVs between children with SLC26A4 mutations and children with idiopathic hearing loss. These results suggested that better auditory nerve function was associated with GJB2 but not with SLC26A4 mutations when compared with idiopathic hearing loss. In addition, significant effects of electrode location were observed for slope of eCAP I/O function and the eCAP threshold.

CONCLUSIONS

GJB2 and SLC26A4 gene mutations did not alter polarity sensitivity of auditory nerve fibers to electrical stimulation. The anodic-leading stimulus was generally more effective in activating auditory nerve fibers than the cathodic-leading stimulus, despite the presence of GJB2 or SLC26A4 mutations. Patients with GJB2 mutations appeared to have better functional status of the auditory nerve than patients with SLC26A4 mutations who had concurrent Mondini malformation and enlarged vestibular aqueduct and patients with idiopathic hearing loss.

Neurodevelopmental Aspects and Cortical Auditory Maturation in Children with Cochlear Implants

Background and objectives: The cochlear implant is not only meant to restore auditory function, but it also has a series of benefits on the psychomotor development and on the maturation of central auditory pathways. In this study, with the help of neuropsychological tests and cortical auditory potentials (CAEPs), we intend to identify a series of instruments that allow us to monitor children with a cochlear implant, and later on, to admit them into an individualized rehabilitation program. Materials and methods: This is a longitudinal study containing 17 subjects (6 boys and 11 girls) diagnosed with congenital sensorineural hearing loss. The average age for cochlear implantation in our cohort is 22 months old. Each child was tested before the cochlear implantation, tested again 3 months after the implant, and then 6 months after the implant. To test the general development, we used the Denver Developmental Screening Test (DDST II). CAEPs were recorded to assess the maturation of central auditory pathways. Results: The results showed there was progress in both general development and language development, with a significant statistical difference between the overall DQ (developmental quotient) and language DQ before the cochlear implantation and three and six months later, respectively. Similarly, CAEP measurements revealed a decrease of positive-going component (P1) latency after cochlear implantation. Conclusion: CAEPs and neuropsychological tests prove to be useful instruments for monitoring the progress in patients with cochlear implants during the rehabilitation process.

In Vivo Real-time Remote Cochlear Implant Capacitive Impedance Measurements: A Glimpse Into the Implanted Inner Ear

OBJECTIVES

To propose a remote, real-time, safe, and easy systematic method to determine electrode electric impedance components: access resistance, polarization capacitance, and polarization resistance.

PATIENTS

Patients who received a cochlear implant and had normal cochlear anatomy and complete array insertion were recruited. A total of four adult patients were included and separated in two groups according to implantation time.

INTERVENTION

Cochlear implant electrical impedance and its components were measured in all patients by using a novel diagnostic tool: a custom made software running in the patient's computer. Data is transmitted in real time to the investigator. Various stimulation and measuring strategies were used to obtain specific information in each cochlear region.

MAIN OUTCOME MEASURES

Access resistance, polarization capacitance, and resistance of each patient were measured. Measurement success rate and required time for the patient were recorded.

RESULTS

Access resistance, polarization capacitance, and resistance were obtained in different modes, thus in every specific region of the cochlea. All measurements were successful. Each measurement took approximately 7 minutes and was transmitted in real time to the investigators.

CONCLUSION

Routine use of this tool may allow constant assessment of cochlear health and could be eventually used to monitor the effect of drugs in the inner ear. This methodology provides an in vivo "electrical view" of the inside of the implanted cochlea.

Residual Cochlear Function in Adults and Children Receiving Cochlear Implants: Correlations With Speech Perception Outcomes

OBJECTIVES

Variability in speech perception outcomes with cochlear implants remains largely unexplained. Recently, electrocochleography, or measurements of cochlear potentials in response to sound, has been used to assess residual cochlear function at the time of implantation. Our objective was to characterize the potentials recorded preimplantation in subjects of all ages, and evaluate the relationship between the responses, including a subjective estimate of neural activity, and speech perception outcomes.

DESIGN

Electrocochleography was recorded in a prospective cohort of 284 candidates for cochlear implant at University of North Carolina (10 months to 88 years of ages). Measurement of residual cochlear function called the "total response" (TR), which is the sum of magnitudes of spectral components in response to tones of different stimulus frequencies, was obtained for each subject. The TR was then related to results on age-appropriate monosyllabic word score tests presented in quiet. In addition to the TR, the electrocochleography results were also assessed for neural activity in the forms of the compound action potential and auditory nerve neurophonic.

RESULTS

The TR magnitude ranged from a barely detectable response of about 0.02 µV to more than 100 µV. In adults (18 to 79 years old), the TR accounted for 46% of variability in speech perception outcome by linear regression (r = 0.46; p < 0.001). In children between 6 and 17 years old, the variability accounted for was 36% (p < 0.001). In younger children, the TR accounted for less of the variability, 15% (p = 0.012). Subjects over 80 years old tended to perform worse for a given TR than younger adults at the 6-month testing interval. The subjectively assessed neural activity did not increase the information compared with the TR alone, which is primarily composed of the cochlear microphonic produced by hair cells.

CONCLUSIONS

The status of the auditory periphery, particularly of hair cells rather than neural activity, accounts for a large fraction of variability in speech perception outcomes in adults and older children. In younger children, the relationship is weaker, and the elderly differ from other adults. This simple measurement can be applied with high throughput so that peripheral status can be assessed to help manage patient expectations, create individually-tailored treatment plans, and identify subjects performing below expectations based on residual cochlear function.

Effectiveness of Rehabilitation Approaches Proposed to Children With Severe-to-Profound Prelinguistic Deafness on the Development of Auditory, Speech, and Language Skills: A Systematic Review

Purpose The purpose of this systematic review is to identify and evaluate the available scientific evidence on the effectiveness of rehabilitation approaches proposed to children with severe-to-profound prelinguistic deafness on the hearing, speech, and language skills development. Method Databases (PubMed, CINHAL, PsycInfo, Cochrane, ERIC, and EMBASE) were searched with relevant key words (children, deafness, rehabilitation approach, auditory, speech, and language). Studies published between 2000 and 2017 were included. The methodological quality of the studies was evaluated with the Quality Assessment Tool for Quantitative Studies, and the level of evidence was evaluated with the Oxford Centre for Evidence-Based Medicine Levels of Evidence. Every step of the selection and analysis was made by 2 independent judges. Results Of 1,739 articles listed in different databases, 38 met the inclusion criteria and were selected for analysis. The majority of included articles present a relatively low level of evidence. Rehabilitation approaches that do not include signs appear more frequently associated with a better auditory, speech, and language development, except for receptive language, than approaches that included any form of signs. Conclusion More robust studies are needed to decide on the approach to prioritize with severe-to-profound deaf children.

Effects of Early Acoustic Hearing on Speech Perception and Language for Pediatric Cochlear Implant Recipients

Purpose The overall goal of the current study was to identify an optimal level and duration of acoustic experience that facilitates language development for pediatric cochlear implant (CI) recipients-specifically, to determine whether there is an optimal duration of hearing aid (HA) use and unaided threshold levels that should be considered before proceeding to bilateral CIs. Method A total of 117 pediatric CI recipients (ages 5-9 years) were given speech perception and standardized tests of receptive vocabulary and language. The speech perception battery included tests of segmental perception (e.g., word recognition in quiet and noise, and vowels and consonants in quiet) and of suprasegmental perception (e.g., talker and stress discrimination, and emotion identification). Hierarchical regression analyses were used to determine the effects of speech perception on language scores, and the effects of residual hearing level (unaided pure-tone average [PTA]) and duration of HA use on speech perception. Results A continuum of residual hearing levels and the length of HA use were represented by calculating the unaided PTA of the ear with the longest duration of HA use for each child. All children wore 2 devices: Some wore bimodal devices, while others received their 2nd CI either simultaneously or sequentially, representing a wide range of HA use (0.03-9.05 years). Regression analyses indicate that suprasegmental perception contributes unique variance to receptive language scores and that both segmental and suprasegmental skills each contribute independently to receptive vocabulary scores. Also, analyses revealed an optimal duration of HA use for each of 3 ranges of hearing loss severity (with mean PTAs of 73, 92, and 111 dB HL) that maximizes suprasegmental perception. Conclusions For children with the most profound losses, early bilateral CIs provide the greatest opportunity for developing good spoken language skills. For those with moderate-to-severe losses, however, a prescribed period of bimodal use may be more advantageous for developing good spoken language skills.

Preimplant Hearing Aid Fittings and Aided Audibility for Pediatric Cochlear Implant Recipients

BACKGROUND

Audibility of speech for children with hearing loss (HL) depends on the degree of HL and the fitting of the hearing aids (HAs) themselves. Many studies on cochlear implant (CI) users have demonstrated that preimplant hearing is associated with postimplant outcomes, but there have been very few reports on the fitting of HAs before surgery.

PURPOSE

The aims of this study were to characterize HA fittings and aided audibility of speech for pediatric HA users with severe to profound HL and to examine the relation between preimplant aided audibility and postimplant speech perception.

RESEARCH DESIGN

A descriptive/observational and correlational study. Audiologic records of pediatric CI participants involved in a larger study examining the effects of early acoustic hearing were analyzed retrospectively; when available, these records included HA verification and speech recognition performance.

STUDY SAMPLE

The CI participants were enrolled in audiology centers and oral schools for the deaf across the United States.

DATA COLLECTION AND ANALYSIS

To determine whether deviations from prescribed DSL target were significantly greater than zero, 95% confidence intervals of the mean deviation were calculated for each frequency (250, 500, 1000, 2000, and 4000 Hz). Correlational analyses were used to examine the relationship between preimplant aided Speech Intelligibility Indices (SIIs) and postimplant speech perception in noise. Correlational analyses were also used to explore the relationship between preimplant aided SIIs and demographic data. T-tests were used to compare preimplant-aided SIIs of HAs of listeners who later became users of either sequential CIs, simultaneous CIs, or bimodal devices.

RESULTS

Preimplant fittings of HAs were generally very close to prescriptive targets, except at 4000 Hz for those HAs with active frequency-lowering processing, and preimplant SIIs, albeit low, were correlated with postimplant speech recognition performance in noise. These results suggest that aided audibility should be maximized throughout the HA trial for later speech recognition purposes.

CONCLUSIONS

It is recommended that HA fittings be optimized to support speech audibility even when considering implantation. In addition to the age at which HA use begins, the aided audibility itself is important in determining CI candidacy and decisions regarding bimodal HA use.

Direct cellular reprogramming and inner ear regeneration

INTRODUCTION

Sound is integral to communication and connects us to the world through speech and music. Cochlear hair cells are essential for converting sounds into neural impulses. However, these cells are highly susceptible to damage from an array of factors, resulting in degeneration and ultimately irreversible hearing loss in humans. Since the discovery of hair cell regeneration in birds, there have been tremendous efforts to identify therapies that could promote hair cell regeneration in mammals.

AREAS COVERED

Here, we will review recent studies describing spontaneous hair cell regeneration and direct cellular reprograming as well as other factors that mediate mammalian hair cell regeneration.

EXPERT OPINION

Numerous combinatorial approaches have successfully reprogrammed non-sensory supporting cells to form hair cells, albeit with limited efficacy and maturation. Studies on epigenetic regulation and transcriptional network of hair cell progenitors may accelerate discovery of more promising reprogramming regimens.

Cochlear Implantation for Children and Adults with Severe-to-Profound Hearing Loss

Cochlear implants (CIs) have proven to be a useful treatment option for individuals with severe-to-profound hearing loss by providing improved access to one's surrounding auditory environment. CIs differ from traditional acoustic amplification by providing information to the auditory system via electrical stimulation. Both postlingually deafened adults and prelingually deafened children can benefit from a CI; however, outcomes with a CI can vary. Numerous factors can impact performance outcomes with a CI. It is important for the audiologist to understand what factors might play a role and impact performance outcomes with a CI so that they can effectively counsel the recipient and their family, as well as establish appropriate and realistic expectations with a CI. This review article will discuss the CI candidacy process, CI programming and postoperative follow-up care, as well as considerations across the lifespan that may affect performance outcomes with a CI.

Factors influencing speech perception in noise for 5-year-old children using hearing aids or cochlear implants

OBJECTIVE

We investigated the factors influencing speech perception in babble for 5-year-old children with hearing loss who were using hearing aids (HAs) or cochlear implants (CIs).

DESIGN

Speech reception thresholds (SRTs) for 50% correct identification were measured in two conditions - speech collocated with babble, and speech with spatially separated babble. The difference in SRTs between the two conditions give a measure of binaural unmasking, commonly known as spatial release from masking (SRM). Multiple linear regression analyses were conducted to examine the influence of a range of demographic factors on outcomes.

STUDY SAMPLE

Participants were 252 children enrolled in the Longitudinal Outcomes of Children with Hearing Impairment (LOCHI) study.

RESULTS

Children using HAs or CIs required a better signal-to-noise ratio to achieve the same level of performance as their normal-hearing peers but demonstrated SRM of a similar magnitude. For children using HAs, speech perception was significantly influenced by cognitive and language abilities. For children using CIs, age at CI activation and language ability were significant predictors of speech perception outcomes.

CONCLUSIONS

Speech perception in children with hearing loss can be enhanced by improving their language abilities. Early age at cochlear implantation was also associated with better outcomes.

Consonant and Vowel Identification in Cochlear Implant Users Measured by Nonsense Words: A Systematic Review and Meta-Analysis

PURPOSE

The purpose of this systematic review and meta-analysis was to establish a baseline of the vowel and consonant identification scores in prelingually and postlingually deaf users of multichannel cochlear implants (CIs) tested with consonant-vowel-consonant and vowel-consonant-vowel nonsense syllables.

METHOD

Six electronic databases were searched for peer-reviewed articles reporting consonant and vowel identification scores in CI users measured by nonsense words. Relevant studies were independently assessed and screened by 2 reviewers. Consonant and vowel identification scores were presented in forest plots and compared between studies in a meta-analysis.

RESULTS

Forty-seven articles with 50 studies, including 647 participants, thereof 581 postlingually deaf and 66 prelingually deaf, met the inclusion criteria of this study. The mean performance on vowel identification tasks for the postlingually deaf CI users was 76.8% (N = 5), which was higher than the mean performance for the prelingually deaf CI users (67.7%; N = 1). The mean performance on consonant identification tasks for the postlingually deaf CI users was higher (58.4%; N = 44) than for the prelingually deaf CI users (46.7%; N = 6). The most common consonant confusions were found between those with same manner of articulation (/k/ as /t/, /m/ as /n/, and /p/ as /t/).

CONCLUSIONS

The mean performance on consonant identification tasks for the prelingually and postlingually deaf CI users was found. There were no statistically significant differences between the scores for prelingually and postlingually deaf CI users. The consonants that were incorrectly identified were typically confused with other consonants with the same acoustic properties, namely, voicing, duration, nasality, and silent gaps. A univariate metaregression model, although not statistically significant, indicated that duration of implant use in postlingually deaf adults predict a substantial portion of their consonant identification ability. As there is no ceiling effect, a nonsense syllable identification test may be a useful addition to the standard test battery in audiology clinics when assessing the speech perception of CI users.

Clinical outcomes following cochlear implantation in children with inner ear anomalies

OBJECTIVE

A significant proportion of children with congenital hearing loss who are candidates for cochlear implants (CIs) may have inner ear malformations (IEMs). Surgical and speech outcomes following CI in these children have not been widely reported.

METHODS

The charts of children who were evaluated for a CI between 1/1/1986 and 12/31/2014 at a university-based tertiary level pediatric cochlear implant center were reviewed. Principal inclusion criteria included (i) age 1-18 years, (ii) history of bilateral severe to profound sensorineural hearing loss, and (iii) limited benefit from binaural amplification. Exclusion criteria included (i) underlying diagnosis of neurodevelopmental disorder and (ii) lack of follow up for speech assessment if a CI was performed. The following outcome measures were reviewed: (i) imaging findings with magnetic resonance imaging or high resolution computed tomography, (ii) intraoperative complications, and (iii) speech perception categorized as the ability to perceive closed set, open set, or none.

RESULTS

The prevalence of IEMs was 27% (102 of 381), of which 79% were bilateral. Cochlear dysplasia accounted for 30% (40 of 136) of the anomalies. Seventy-eight of the 102 patients received a CI (78%). Surgery was noted to be challenging in 24% (19 of 78), with a perilymphatic gusher being the most common intraoperative finding. Cochlear dysplasia, vestibular dysplasia and cochlear nerve hypoplasia were associated with poor speech perception (open OR closed set speech recognition scores, 0-23%), although the outcomes in children with enlarged vestibular aqueduct were similar to those of children with normal inner ear anatomy (65%).

CONCLUSIONS

Cochlear implantation is safe in children with IEMs. However, the speech perception outcomes are notably below those of patients with normal anatomy, with the exception of when an enlarged vestibular aqueduct is present.

Receptive language as a predictor of cochlear implant outcome for prelingually deaf adults

OBJECTIVE

This study investigated outcomes and predictive factors, specifically language skills, for a group of prelingually hearing-impaired adults who received a cochlear implant.

DESIGN

Speech perception data, demographic information, and other related variables such as communication mode, residual hearing, and receptive language abilities were explored. Pre- and post-implant speech perception scores were compared and multiple regression analysis was used to identify significant predictive relationships.

STUDY SAMPLE

The study included 43 adults with a prelingual onset of hearing loss, who proceeded with cochlear implantation at the Royal Victorian Eye and Ear Hospital in Melbourne, Australia.

RESULTS

The majority of patients experienced benefit from their cochlear implants, with 88% demonstrating significant improvement in speech perception performance. Volunteers achieved better post-operative speech perception scores if they had a shorter duration of severe-to-profound hearing loss, better language skills, and used an exclusively oral communication mode.

CONCLUSIONS

Although post-operative speech perception performance is significantly poorer for prelingually hearing-impaired adults compared to postlingually hearing-impaired patients, the study group demonstrated significant benefit from their cochlear implants. The variability in post-operative outcomes can be predicted to some extent from the hearing history and language abilities of the individual patient.

Barriers to early cochlear implantation

OBJECTIVE

Identify variables associated with paediatric access to cochlear implants (CIs).

DESIGN

Part 1. Trends over time for age at CI surgery (N = 802) and age at hearing aid (HA) fitting (n = 487) were examined with regard to periods before, during, and after newborn hearing screening (NHS). Part 2. Demographic factors were explored for 417 children implanted under 3 years of age. Part 3. Pre-implant steps for the first 20 children to receive CIs under 12 months were examined.

RESULTS

Part 1. Age at HA fitting and CI surgery reduced over time, and were associated with NHS implementation. Part 2. For children implanted under 3 years, earlier age at HA fitting and higher family socio-economic status were associated with earlier CI. Progressive hearing loss was associated with later CIs. Children with a Connexin 26 diagnosis received CIs earlier than children with a premature / low birth weight history. Part 3. The longest pre-CI steps were Step 1: Birth to diagnosis/identification of hearing loss (mean 16.43 weeks), and Step 11: MRI scans to implant surgery (mean 15.05 weeks) for the first 20 infants with CIs under 12 months.

CONCLUSION

NHS implementation was associated with reductions in age at device intervention in this cohort.

The Relationship Between EABR and Auditory Performance and Speech Intelligibility Outcomes in Pediatric Cochlear Implant Recipients

PURPOSE

The primary purpose of the present study was to investigate the relationship between postimplant electrically evoked auditory brainstem response (EABR) measures (wave V threshold, wave V latency, input-output functions) and auditory performance and speech intelligibility outcomes measured using parental rating scales, such as Categories of Auditory Performance (CAP; Archbold, Lutman, & Marshall, 1995) and the Speech Intelligibility Rating scale (SIR; Allen, Nikolopoulos, Dyar, & O'Donoghue, 2001), respectively. The secondary purpose was to evaluate the relationship between age at implantation and ratings on the CAP and SIR.

METHOD

Forty children with congenital sensorineural hearing loss participated. Preimplant parental ratings on the CAP and SIR were obtained, and all the children underwent cochlear implantation. Intracochlear EABRs were recorded postimplantation. Postimplant parental ratings on the CAP and SIR were obtained. The relationships between EABR parameters and auditory performance and speech intelligibility outcomes were studied. The effect of age at implantation on auditory performance and speech intelligibility outcomes was also investigated.

RESULTS

A significant negative correlation was found between EABR wave V thresholds and SIR growth (r = -.415, p = .016). Children with better CAP growths tended to have lower wave V thresholds than those with poorer CAP growths. Age at implantation had an effect on the auditory performance as measured using the CAP.

CONCLUSIONS

The present study provides evidence for the relationship between wave V thresholds of the intracochlear EABR and auditory performance and speech intelligibility outcomes measured using parental rating scales in pediatric cochlear implant recipients. Data also indicate that early intervention has a positive impact on auditory performance outcomes.

Acoustic temporal modulation detection in normal-hearing and cochlear implanted listeners: effects of hearing mechanism and development

Temporal modulation detection ability matures over many years after birth and may be particularly sensitive to experience during this period. Profound hearing loss during early childhood might result in greater perceptual deficits than a similar loss beginning in adulthood. We tested this idea by measuring performance in temporal modulation detection in profoundly deaf children and adults fitted with cochlear implants (CIs). At least two independent variables could constrain temporal modulation detection performance in children with CIs: altered encoding of modulation information due to the CI-auditory nerve interface, and atypical development of central processing of sound information provided by CIs. The effect of altered encoding was investigated by testing subjects with one of two different hearing mechanisms (normal hearing vs. CI) and the effect of atypical development was studied by testing two different age groups. All subjects were tested for their ability to detect acoustic temporal modulations of sound amplitude. A comparison of the slope, or cutoff frequency, of the temporal modulation transfer functions (TMTFs) among the four subject groups revealed that temporal resolution was mainly constrained by hearing mechanism: normal-hearing listeners could detect smaller amplitude modulations at high modulation frequencies than CI users. In contrast, a comparison of the height of the TMTFs revealed a significant interaction between hearing mechanism and age group on overall sensitivity to temporal modulation: sensitivity was significantly poorer in children with CIs, relative to the other three groups. Results suggest that there is an age-specific vulnerability of intensity discrimination or non-sensory factors, which subsequently affects sensitivity to temporal modulation in prelingually deaf children who use CIs.

Longitudinal speech perception and language performance in pediatric cochlear implant users: the effect of age at implantation

OBJECTIVES

Few studies have examined the long-term effect of age at implantation on outcomes using multiple data points in children with cochlear implants. The goal of this study was to determine whether age at implantation has a significant, lasting impact on speech perception, language, and reading performance for children with prelingual hearing loss.

DESIGN

A linear mixed-model framework was used to determine the effect of age at implantation on speech perception, language, and reading abilities in 83 children with prelingual hearing loss who received cochlear implants by the age of 4 years. The children were divided into two groups based on their age at implantation: (1) under 2 years of age and (2) between 2 and 3.9 years of age. Differences in model-specified mean scores between groups were compared at annual intervals from 5 to 13 years of age for speech perception, and 7 to 11 years of age for language and reading.

RESULTS

After controlling for communication mode, device configuration, and preoperative pure-tone average, there was no significant effect of age at implantation for receptive language by 8 years of age, expressive language by 10 years of age, reading by 7 years of age. In terms of speech-perception outcomes, significance varied between 7 and 13 years of age, with no significant difference in speech-perception scores between groups at ages 7, 11, and 13 years. Children who used oral communication (OC) demonstrated significantly higher speech-perception scores than children who used total communication (TC). OC users tended to have higher expressive language scores than TC users, although this did not reach significance. There was no significant difference between OC and TC users for receptive language or reading scores.

CONCLUSIONS

Speech perception, language, and reading performance continue to improve over time for children implanted before 4 years of age. The present results indicate that the effect of age at implantation diminishes with time, particularly for higher-order skills such as language and reading. Some children who receive cochlear implants after the age of 2 years have the capacity to approximate the language and reading skills of their earlier-implanted peers, suggesting that additional factors may moderate the influence of age at implantation on outcomes over time.

Communication development in children who receive a cochlear implant by 12 months of age

OBJECTIVE

Describe the long-term benefits of early cochlear implantation. Provide a comprehensive description of outcomes, including: language, speech production, and speech perception. Compare the communication outcomes for the early implanted children to those of normally hearing children and children who received a cochlear implant at a comparatively older age.

METHOD

Retrospective review of the communication development of 35 children implanted between 6 and 12 months of age and 85 children implanted between 13 and 24 months of age. Audiologic assessments included unaided and aided audiograms, auditory brainstem response (ABR), auditory steady state response (ASSR), and otoacoustic emissons (OAEs). Formal language, speech production, and speech perception measures were administered, preimplant and at 1, 2, 3, and 5 years postimplant.

RESULTS

The children who received their cochlear implant by 12 months of age demonstrated language growth rates equivalent to their normally hearing peers and achieved age appropriate receptive language scores 3 years postimplant. The children who received their cochlear implant between 13 and 24 months demonstrated a significant language delay at 3 years postimplant. Speech production development followed a similar pattern to that of normal-hearing children, although was delayed, for both groups of children. Mean open-set speech perception scores were comparable with previous reports for children and adults who use cochlear implants.

CONCLUSION

Children implanted by 12 months of age demonstrate better language development compared with children who receive their cochlear implant between 13 and 24 months. This supports the provision of a cochlear implant within the first year of life to enhance the likelihood that a child with severe-to-profound hearing impairment will commence elementary school with age-appropriate language skills.

Effectiveness of cochlear implants in children: long term results

OBJECTIVES

This study aimed to evaluate the effectiveness, according to the hearing threshold and language performance, of cochlear implants through a period of 10 or more years of follow-up.

METHODS

A retrospective chart review was conducted. 132 patients were selected from the children's population that underwent cochlear implantation at the Department of Otorhinolaryngology, Centro Hospitalar e Universitário de Coimbra, from 1992 to 2001, with a minimum follow-up period of 10 years. A comparison of the pure-tone and speech audiometric thresholds between two periods (T0 and T1) was performed. T0 refers to the initial evaluation, immediately after the rehabilitation programme, within the first year after cochlear implantation. T1 refers to the most recent annual assessment, carried out in 2010 and 2011. Speech understanding was also evaluated through word and sentence recognition tests.

RESULTS

No statistically significant differences were found between early and late assessments, in paediatric cochlear implants users, after a 10 years period of cochlear implantation. Both speech and pure-tone audiometry seem to stabilize except for 2000 Hz where the results were even better after 10 years. Factors such as age at time of implantation, duration of deafness, aetiology and exchange of the speech processor do not seem to have a role in auditory performance after a long rehabilitation period. In tests of verbal discrimination rates of words and phrases recognition were of 84.6% and 65.1%, respectively.

CONCLUSIONS

Cochlear implant is an effective treatment for severe to profound hearing loss in children, contributing to a hearing performance and an appropriate language acquisition, currently comparable to normal hearing children. These benefits appear to keep stable over the years. No deterioration was identified.

Friction force measurement during cochlear implant insertion: application to a force-controlled insertion tool design

HYPOTHESIS

The aim of the study was to evaluate force profiles during array insertion in human cochlea specimens and to evaluate a mechatronic inserter using a 1-axis force sensor.

BACKGROUND

Today, the surgical challenge in cochlear implantation is the preservation of the anatomic structures and the residual hearing. In routine practice, the electrode array is inserted manually with a limited sensitive feedback.

MATERIALS AND METHODS

Hifocus 1J electrode arrays were studied. The bench test comprised a mechatronic inserter combined to a 1-axis force sensor between the inserter and the base of the array and a 6-axis force sensor beneath the cochlea model. Influence of insertion tube material, speed (0.15, 0.5, and 1.5 mm/s) and lubricant on frictions forces were studied (no-load). Different models were subsequently evaluated: epoxy scala tympani model and temporal bones.

RESULTS

Frictions forces were lower in the plastic tube compared with those in the metal tube (0.09 ± 0.028 versus 0.14 ± 0.034 at 0.5 mm/s, p < 0.001) and with the use of hyaluronic acid gel. Speed did not influence frictions forces in our study. Insertion force profiles provided by the 1- and 6-axis force sensors were similar when friction forces inside the insertion tool (no-load measurements) were subtracted from the 1-axis sensor data in the epoxy and temporal bone models (mean error, 0.01 ± 0.001 N).

CONCLUSION

Using a sensor included in the inserter, we were able to measure array insertion forces. This tool can be potentially used to provide real-time information to the surgeon during the procedure.

Factors contributing to speech perception scores in long-term pediatric cochlear implant users

OBJECTIVES

The objectives of this report are to (1) describe the speech perception abilities of long-term pediatric cochlear implant (CI) recipients by comparing scores obtained at elementary school (CI-E, 8 to 9 yrs) with scores obtained at high school (CI-HS, 15 to 18 yrs); (2) evaluate speech perception abilities in demanding listening conditions (i.e., noise and lower intensity levels) at adolescence; and (3) examine the relation of speech perception scores to speech and language development over this longitudinal timeframe.

DESIGN

All 112 teenagers were part of a previous nationwide study of 8- and 9-yr-olds (N = 181) who received a CI between 2 and 5 yrs of age. The test battery included (1) the Lexical Neighborhood Test (LNT; hard and easy word lists); (2) the Bamford Kowal Bench sentence test; (3) the Children's Auditory-Visual Enhancement Test; (4) the Test of Auditory Comprehension of Language at CI-E; (5) the Peabody Picture Vocabulary Test at CI-HS; and (6) the McGarr sentences (consonants correct) at CI-E and CI-HS. CI-HS speech perception was measured in both optimal and demanding listening conditions (i.e., background noise and low-intensity level). Speech perception scores were compared based on age at test, lexical difficulty of stimuli, listening environment (optimal and demanding), input mode (visual and auditory-visual), and language age.

RESULTS

All group mean scores significantly increased with age across the two test sessions. Scores of adolescents significantly decreased in demanding listening conditions. The effect of lexical difficulty on the LNT scores, as evidenced by the difference in performance between easy versus hard lists, increased with age and decreased for adolescents in challenging listening conditions. Calculated curves for percent correct speech perception scores (LNT and Bamford Kowal Bench) and consonants correct on the McGarr sentences plotted against age-equivalent language scores on the Test of Auditory Comprehension of Language and Peabody Picture Vocabulary Test achieved asymptote at similar ages, around 10 to 11 yrs.

CONCLUSIONS

On average, children receiving CIs between 2 and 5 yrs of age exhibited significant improvement on tests of speech perception, lipreading, speech production, and language skills measured between primary grades and adolescence. Evidence suggests that improvement in speech perception scores with age reflects increased spoken language level up to a language age of about 10 yrs. Speech perception performance significantly decreased with softer stimulus intensity level and with introduction of background noise. Upgrades to newer speech processing strategies and greater use of frequency-modulated systems may be beneficial for ameliorating performance under these demanding listening conditions.

Behavioral training restores temporal processing in auditory cortex of long-deaf cats

Temporal auditory processing is poor in prelingually hearing-impaired patients fitted with cochlear prostheses as adults. In an animal model of prelingual long-term deafness, we investigated the effects of behavioral training on temporal processing in the adult primary auditory cortex (AI). Neuronal responses to pulse trains of increasing frequencies were recorded in three groups of neonatally deafened cats that received a cochlear prosthesis after >3 yr of deafness: 1) acutely implanted animals that received no electric stimulation before study, 2) animals that received chronic-passive stimulation for several weeks to months before study, and 3) animals that received chronic-passive stimulation and additional behavioral training (signal detection). A fourth group of normal adult cats that was deafened acutely and implanted served as controls. The neuronal temporal response parameters of interest included the stimulus rate that evoked the maximum number of phase-locked spikes [best repetition rate (BRR)], the stimulus rate that produced 50% of the spike count at BRR (cutoff rate), the peak-response latency, and the first spike latency and timing-jitter. All long-deaf animals demonstrated a severe reduction in spiral ganglion cell density (mean, <6% of normal). Long-term deafness resulted in a significantly reduced temporal following capacity and spike-timing precision of cortical neurons in all parameters tested. Neurons in deaf animals that received only chronic-passive stimulation showed a gain in BRR but otherwise were similar to deaf cats that received no stimulation. In contrast, training with behaviorally relevant stimulation significantly enhanced all temporal processing parameters to normal levels with the exception of minimum latencies. These results demonstrate the high efficacy of learning-based remodeling of fundamental timing properties in cortical processing even in the adult, long-deaf auditory system, suggesting rehabilitative strategies for patients with long-term hearing loss.

Adapting to bilateral cochlear implants: early post-operative device use by children receiving sequential or simultaneous implants at or before 3.5 years

OBJECTIVE

To classify adaptation difficulties, or lack thereof, experienced by a clinical population of young bilateral cochlear implant recipients.

METHOD

Forty-six of the first 48 children sequentially or simultaneously implanted at ≤3.5 years at the Melbourne Clinic participated. Classification into categories was based on daily use of both implants at 2 months post-switch-on, with follow-up information obtained at 12 months.

RESULTS

The 37 Category 1 children wore both implants full time at 2 months, and 35 still did so at 12 months. The two Category 2 children used both implants 4 hours daily at 2 months, but achieved full-time use within 12 months. The five Category 3 children used both implants for ≤1 hour, with only three achieving full-time use within 12 months. The two Category 4 children did not use two implants at 2 months, and one still did not wear both implants at 12 months. There were weak/modest but significant relationships between category and each of time between implants and age at bilateral implantation.

DISCUSSION

Ninety-five percent of simultaneously and 70% of sequentially implanted children demonstrated full-time use within 2 months, and nearly all continued to do so at 12 months. Full-time use maximizes opportunities to develop listening skills. Monitoring device use is necessary for all children, especially when significant change occurs. For those experiencing difficulty in adapting, bilateral implant use usually increased over 12 months. Pre-operative counselling must include discussion of possible adaptation difficulties and raise the potential negative influence of age at bilateral implantation and time between implants.

Neural prostheses and brain plasticity

The success of modern neural prostheses is dependent on a complex interplay between the devices' hardware and software and the dynamic environment in which the devices operate: the patient's body or 'wetware'. Over 120 000 severe/profoundly deaf individuals presently receive information enabling auditory awareness and speech perception from cochlear implants. The cochlear implant therefore provides a useful case study for a review of the complex interactions between hardware, software and wetware, and of the important role of the dynamic nature of wetware. In the case of neural prostheses, the most critical component of that wetware is the central nervous system. This paper will examine the evidence of changes in the central auditory system that contribute to changes in performance with a cochlear implant, and discuss how these changes relate to electrophysiological and functional imaging studies in humans. The relationship between the human data and evidence from animals of the remarkable capacity for plastic change of the central auditory system, even into adulthood, will then be examined. Finally, we will discuss the role of brain plasticity in neural prostheses in general.

The effect of auditory experience on speech perception, localization, and functional performance of children who use a cochlear implant and a hearing aid in opposite ears

This study was aimed at determining the effect of auditory experience on binaural benefits from using a cochlear implant and a hearing aid in opposite ears. Eighteen children were evaluated using tests of speech perception, horizontal localization, and functional performance when they used either a cochlear implant alone (CI) or a cochlear implant with a hearing aid (CIHA). Eight were experienced CIHA users, whereas ten had not worn a hearing aid in the non-implanted ear for up to eight years prior to participation. All children were fitted with a hearing aid in the non-implanted ear using the NAL-RP prescription, and the hearing aids were fine-tuned individually using a paired-comparisons procedure and a loudness balancing test. Evaluation results indicated that performance for all measures was significantly better with CIHA than with CI for both groups of children. We conclude that children who receive a unilateral cochlear implant should be encouraged to wear a hearing aid in the opposite ear where there is usable residual hearing.

Cochlear implant use following neonatal deafness influences the cochleotopic organization of the primary auditory cortex in cats

Electrical stimulation of spiral ganglion neurons in a deafened cochlea, via a cochlear implant, provides a means of investigating the effects of the removal and subsequent restoration of afferent input on the functional organization of the primary auditory cortex (AI). We neonatally deafened 17 cats before the onset of hearing, thereby abolishing virtually all afferent input from the auditory periphery. In seven animals the auditory pathway was chronically reactivated with environmentally derived electrical stimuli presented via a multichannel intracochlear electrode array implanted at 8 weeks of age. Electrical stimulation was provided by a clinical cochlear implant that was used continuously for periods of up to 7 months. In 10 long-term deafened cats and three age-matched normal-hearing controls, an intracochlear electrode array was implanted immediately prior to cortical recording. We recorded from a total of 812 single unit and multiunit clusters in AI of all cats as adults using a combination of single tungsten and multichannel silicon electrode arrays. The absence of afferent activity in the long-term deafened animals had little effect on the basic response properties of AI neurons but resulted in complete loss of the normal cochleotopic organization of AI. This effect was almost completely reversed by chronic reactivation of the auditory pathway via the cochlear implant. We hypothesize that maintenance or reestablishment of a cochleotopically organized AI by activation of a restricted sector of the cochlea, as demonstrated in the present study, contributes to the remarkable clinical performance observed among human patients implanted at a young age.

Cochlear implants and brain plasticity

Cochlear implants have been implanted in over 110,000 deaf adults and children worldwide and provide these patients with important auditory cues necessary for auditory awareness and speech perception via electrical stimulation of the auditory nerve (AN). In 1942, Woolsey and Walzl presented the first report of cortical responses to localised electrical stimulation of different sectors of the AN in normal hearing cats, and established the cochleotopic organization of the projections to primary auditory cortex. Subsequently, individual cortical neurons in normal hearing animals have been shown to have well characterized input-output functions for electrical stimulation and decreasing response latencies with increasing stimulus strength. However, the central auditory system is not immutable, and has a remarkable capacity for plastic change, even into adulthood, as a result of changes in afferent input. This capacity for change is likely to contribute to the ongoing clinical improvements observed in speech perception for cochlear implant users. This review examines the evidence for changes of the response properties of neurons in, and consequently the functional organization of, the central auditory system produced by chronic, behaviourally relevant, electrical stimulation of the AN in profoundly deaf humans and animals.

Effects of steroids and lubricants on electrical impedance and tissue response following cochlear implantation

The present study examined the effects of steroids and lubricants on electrical impedance and tissue response following cochlear implantation in animal models. Guinea pigs were implanted following either no treatment, or intrascalar injection with dexamethasone, triamcinolone, sodium hyaluronate or saline. Cats were implanted following either no treatment, or intrascalar injection with dexamethasone, triamcinolone or a mixture of triamcinolone with sodium hyaluronate. In guinea pigs, impedance changes and intracochlear tissue response were less for the hyaluronate and saline groups. In cats, impedance in the dexamethasone group increased similar to non-treated cats. Impedance of triamcinolone treated cats remained low for about two months after implantation, before increasing to levels similar to the other groups. Significant fibrous tissue growth was observed histologically. The results of the present study indicate that a single intracochlear application of hyaluronate or triamcinolone may postpone, but will ultimately not prevent the rise in impedance following cochlear implantation.

Communication development in children who receive the cochlear implant younger than 12 months: risks versus benefits

BACKGROUND

The advent of universal neonatal hearing screening in some countries and the availability of screening programs for at-risk infants in other countries has facilitated earlier referral, diagnosis, and intervention for infants with hearing loss. Improvements in device technology, two decades of pediatric clinical experience, a growing recognition of the efficacy of cochlear implants for young children, and the recent change in the U.S. Food and Drug Administration's age criteria to include children as young as 12 mo has led to increasing numbers of young children receiving cochlear implants. Evidence to support provision for infants younger than 12 mo is extrapolated from physiological studies, studies of children using hearing aids, and studies of children older than 12 mo of age with implants. To date, however, there are few published research findings regarding communication development in children between 6 and 12 mo of age who receive implants. The current study hypothesized that earlier implantation would lead to increased rates of language acquisition as the children were still in the critical period for their development.

METHOD

A retrospective review was completed for 19 infants (mean age at implantation, 0.88 yr; range, 0.61-1.07, SD 0.15) and 87 toddlers (mean age at implantation, 1.60 yr; range, 1.13-2.00, SD 0.24) who received the multichannel implant in Melbourne, Australia. Preimplantation audiological assessments for these children included aided and unaided audiograms, auditory brain stem response, auditory steady state response (ASSR), and otoacoustic emission and indicated profound to total bilateral hearing loss in all cases. Communication assessment included completion of the Rossetti Infant-Toddler Language Scale and educational psychologists' cognitive and motor assessment. Computed tomography scan, magnetic resonance imaging, and surgical records for all cases were reviewed. Postimplantation language assessments were reported in terms of the rate of growth over time on the language comprehension and language expression subscales of the Rossetti Infant-Toddler Language Scale.

RESULTS

Results demonstrated that cochlear implantation may be performed safely in very young children with excellent language outcomes. The mean rates of receptive (1.12) and expressive (1.01) language growth for children receiving implants before the age of 12 mo were significantly greater than the rates achieved by children receiving implants between 12 and 24 mo, and matched growth rates achieved by normally hearing peers. These preliminary results support the provision of cochlear implants for children younger than 12 mo of age within experienced pediatric implantation centers.

Auditory neuropathy/dys-synchrony and its perceptual consequences

Auditory neuropathy/dys-synchrony is a form of hearing impairment in which cochlear outer hair cell function is spared but neural transmission in the auditory pathway is disordered. This condition, or group of conditions with a common physiologic profile, accounts for approximately 7% of permanent childhood hearing loss and a significant (but as yet undetermined) proportion of adult impairment. This paper presents an overview of the mechanisms underlying auditory neuropathy/dys-synchrony-type hearing loss and the clinical profile for affected patients. In particular it examines the perceptual consequences of auditory neuropathy/dys-synchrony, which are quite different from those associated with sensorineural hearing loss, and considers currently available, and future management options.

Cochlear implants and brain stem implants

This chapter describes the development of two implantable prosthetic neurostimulators which, in the last 20 years, have revolutionised the management of severe-to-profound sensorineural deafness. We have witnessed their rapid evolution from the realms of esoteric laboratory abstraction, with many critics and little perceived clinical use, to a routine treatment which is safe, effective and, indeed, cost effective. It is one of the great triumphs of biomedical and surgical collaboration, and is without any doubt the greatest ever advance in the treatment of deafness.