Early-deafened adult cochlear implant users: assessment of outcomes

OBJECTIVE: To determine whether adults deafened in the prelingual and perilingual stages of speech development realize objective and subjective benefits from cochlear implantation. METHOD: Retrospective analysis of the open-set speech recognition and subjective data such as use and quality of life. RESULTS: Between 1989 and 1999, 198 deafened adults underwent cochlear implantation at Sunnybrook and Women's College Health Sciences Centre. Of these, 44 patients were deafened pre- or perilingually. These subjects were implanted with a Nucleus 22, Nucleus 24 (Cochlear Corporation, Denver, Colorado, USA), or Clarion (Advanced Bionics Corporation, Sylmar, California, USA) device. The average age at implantation was 34 years (range 14-62 years). Significant differences in speech perception, as measured by a composite score of open-set word, phoneme, and sentence recognition, were found among groups who differed by type of education and communication training received in childhood. CONCLUSION: By and large, open-set speech recognition in prelingually and perilingually deafened adults is inferior to that achieved in postlingually deafened adults and varies according to the type of communication training they received. However, cochlear implants have significantly improved the overall communication skills and quality of life in all subgroups of patients.     

Mandarin Chinese speech recognition by pediatric cochlear implant users

Objectives

Because of difficulties associated with pediatric speech testing, most pediatric cochlear implant (CI) speech studies necessarily involve basic and simple perceptual tasks. There are relatively few studies regarding Mandarin-speaking pediatric CI users’ perception of more difficult speech materials (e.g., words and sentences produced by multiple talkers). Difficult speech materials and tests necessarily require older pediatric CI users, who may have different etiologies of hearing loss, duration of deafness, CI experience. The present study investigated how pediatric CI patient demographics influence speech recognition performance with relatively difficult test materials and methods.

Methods

In this study, open-set recognition of multi-talker (two males and two females) Mandarin Chinese disyllables and sentences were measured in 37 Mandarin-speaking pediatric CI users. Subjects were grouped according to etiology of deafness and previous acoustic hearing experience. Group 1 subjects were all congenitally deafened with little-to-no acoustic hearing experience. Group 2 subjects were not congenitally deafened and had substantial acoustic hearing experience prior to implantation. Multiple linear regression analyses were performed within each group using subject demographics such as age at implantation and age at testing.

Results

Pediatric CI performance was generally quite good. For Group 1, mean performance was 82.3% correct for disyllables and 82.8% correct for sentences. For Group 2, mean performance was 76.6% correct for disyllables and 84.4% correct for sentences. For Group 1, multiple linear regression analyses showed that age at implantation predicted disyllable recognition, and that age at implantation and age at testing predicted sentence recognition. For Group 2, neither age at implantation nor age at testing predicted disyllable or sentence recognition. Performance was significantly better with the female than with the male talkers.

Conclusions

Consistent with previous studies’ findings, early implantation provided a significant advantage for profoundly deaf children. Performance for both groups was generally quite good for the relatively difficult materials and tasks, suggesting that open-set word and sentence recognition may be useful in evaluating speech performance with older pediatric CI users. Differences in disyllable recognition between Groups 1 and 2 may reflect differences in adaptation to electric stimulation. The Group 1 subjects developed speech patterns exclusively via electric stimulation, while the Group 2 subjects adapted to electric stimulation relative to previous acoustic patterns.     

Temporal characteristics of stop consonants in pediatric cochlear implant users

Objectives: The benefits of Cochlear Implant (CI) in improving speech production abilities in children with hearing impairment can be reflected through acoustic analysis. The primary aim of the study was to investigate the temporal characteristics of stop consonants in Malayalam speaking children using CI.

Methods: Twelve children using CI and 12 age- and gender-matched typically developing children (TDC) participated in the study. Simple bisyllabic words with selected target consonants were elicited through a picture naming task and were recorded. Acoustic analysis was carried out using Praat software to derive the acoustic measures – Voice Onset Time (VOT), Burst duration and Closure duration.

Results: The results of the study revealed that children using CI differed significantly from TDC for a few target consonants in burst duration and closure duration. However, VOT did not show any significant difference between children using CI and TDC.

Conclusion: With early implantation and intensive speech intervention, there is a significant improvement in the speech of children using CI. Yet may have minor deficits which could impact the naturalness of speech. The study highlights the importance of acoustic analyses in identifying these speech errors at a finer level and utilizing the same to evaluate intervention efficacy.     

Speech production intelligibility of early implanted pediatric cochlear implant users

Objectives

To investigate the influence of age, and age-at-implantation, on speech production intelligibility in prelingually deaf pediatric cochlear implant recipients.

Methods

Forty prelingually, profoundly deaf children who received cochlear implants between 8 and 40 months of age. Their age at testing ranged between 2.5 and 18 years. Children were recorded repeating the 10 sentences in the Beginner's Intelligibility Test. These recordings were played back to normal-hearing listeners who were unfamiliar with deaf speech and who were instructed to write down what they heard. They also rated each subject for the intelligibility of their speech production on a 5-point rating-scale. The main outcome measures were the percentage of target words correctly transcribed, and the intelligibility ratings, in both cases averaged across 3 normal-hearing listeners.

Results

The data showed a strong effect of age at testing, with older children being more intelligible. This effect was particularly pronounced for children implanted in the first 24 months of life, all of whom had speech production intelligibility scores of 80% or higher when they were tested at age 5.5 years or older. This was true for only 5 out of 9 children implanted at age 25-36 months.

Conclusions

Profoundly deaf children who receive cochlear implants in the first 2 years of life produce highly intelligible speech before the age of 6. This is also true for most, but not all children implanted in their third year.     

Comparing eSRT and eCAP measurements in pediatric MED-EL cochlear implant users

Introduction: Electrically evoked compound action potentials (eCAP) and electrically evoked stapedius reflexes are the most frequently used objective measurements for programming a cochlear implant (CI) audio processor. Objective methods are particularly beneficial for children and CI users that encounter difficulties in providing feedback. In this study, we compared the threshold and the slope of the eCAP amplitude growth function with the electrically evoked stapedius reflex threshold (eSRT) in pediatric CI users. Furthermore, the duration times required to perform eCAP and eSRT recordings were compared.

Methods: During a regular fitting session, 52 pediatric CI users with recordable eSRTs having MED-EL devices (MED-EL GmbH, Innsbruck, Austria) were programmed using the eSRT fitting method. The eCAP thresholds and the slopes of the amplitude growth function were measured across one apical, one medial, and one basal electrode contact.

Results: There was a weak to medium correlation between eCAP thresholds and eSRTs. The eCAP threshold profile did not correlate with the eSRT profile. Typically ECAP thresholds were at a lower stimulation charge than eSRTs with only 4/152 being higher. An eCAP threshold was found on 152/156 electrode contacts with eSRTs. On average, the eCAP measurements took 4.2 times longer to record per electrode than eSRT measurements (median durations 35?s vs. 120?s).

Conclusion: eSRTs were significantly higher than eCAP thresholds and eSRT and eCAP profiles were generally different from each other reducing the clinical relevance of eCAP testing for setting MCLs across the array. Additionally, the eSRT measurements were faster to record than the eCAP threshold and slope determination measurements.     

Acoustic and perceptual appraisal of speech production in pediatric cochlear implant users

OBJECTIVE: The purpose of the present study was to examine the relationship between objectively measurable acoustic changes in speech production and subjective speech production accuracy and perceived intelligibility immediately following a disruption in auditory feedback normally provided to subjects from a cochlear implant. METHODS: Six children with profound sensorineural hearing loss participated in the study. Their task was to produce speech samples in two conditions: (1) with auditory feedback from their cochlear implants, and (2) without auditory feedback from their cochlear implants. Samples were subjected to both objective and subjective analyses. Objectively, measures were made of duration, fundamental frequency, and the first and second formants of the vowels. Subjectively, two groups of listeners, one familiar with the speech of children with hearing loss and the other unfamiliar, transcribed the productions and provided ratings of intelligibility. RESULTS: All the children in this study exhibited significant differences from the cochlear implant-on to the cochlear implant-off condition, although these changes were not always in the predicted direction, nor were they always perceptually salient. CONCLUSIONS: Consistent with previous studies, children in this investigation demonstrated variable acoustic voice and speech changes following deactivation of their cochlear implant device. Few of these acoustic changes affected speech intelligibility. The results of this study overall suggest that during the initial years following implantation children who are deaf rely to some extent on the auditory feedback provided by a cochlear implant to control and modify F0, duration, and vowel formant production.     

Inconsistent device use in pediatric cochlear implant users: Prevalence and risk factors

Objectives: Cochlear implants (CIs) afford an opportunity for children with a significant hearing loss to access spoken language through auditory input, but challenges post-implantation could impede success. Inconsistent device use occurs when a child wears their device less than full-time (<8 hours per day). Previous studies may underestimate the prevalence of inconsistent device use in pediatric CI users due to methodological issues (subjective parent report vs. objective measures).

Methods: This retrospective chart review identifies risk factors (demographic, audiologic, and device) associated with poorer daily device use in children with CI using objective datalogging. Non-parametric correlations, Mann–Whitney U, and Kruskal–Wallis H tests were used to evaluate effects of demographic, audiologic, and device factors on daily device use via datalogging.

Results: Participants included 71 children (age M?=?7.0 years) with mean implantation age of 4.0 years and mean device experience of 3.0 years. Children with CIs used their device, on average, 7.6 hours/day (range: 0.1–15.5 hours). Half of the participants wore their device less than full-time. Fewer hours of device use coincided with younger chronologic age, presence of additional disabilities, lower maternal education, younger age at CI, use of Medicaid, and smaller dynamic range.

Discussion: The prevalence of inconsistent device use may exceed previous estimations based on parent report.

Conclusion: Professionals working with pediatric CI users should consider incorporating datalogging into clinical practice to counsel families at risk for poorer device use. Future studies should compare objective device use with communication outcomes in pediatric CI users.     

Speech recognition outcomes in Mandarin-speaking cochlear implant users with fine structure processing

Conclusion: Mandarin-speaking adults can use the Fine Structure Processing (FSP) coding strategy as well as the Continuous Interleaved Sampling (CIS+) coding strategy. No loss in performance was observed after switch-over. Tone identification improves over time with the FSP coding strategy, which is of benefit to tonal-language users. After some time, fine structure was preferred.

Objective: This study aimed to determine speech perception, tone perception, and the subjective preferences of Mandarin-speaking adults who received the FSP coding strategy, at upgrade from the CIS?+?coding strategy.

Methods: Thirteen Mandarin-speaking subjects were tested at switch-over from CIS?+?to the FSP coding strategy ～1-month after switch-over, 2-months after switch-over, and 3-months after switch-over with the Mandarin Hearing in Noise Test (M-HINT), the Mandarin Tone Identification in Noise Test (M-TINT), and a visual analogue scale assessing Sound and Speech Assessment (SSA).

Results: There were no significant differences in the M-HINT between presentation levels (62?dB SPL vs 65?dB SPL), over time, nor when compared to the CIS?+?coding strategy. Tone perception improved significantly over time with the FSP coding strategy. Subjects rated the FSP coding strategy with the OPUS 2 as significantly more ‘full’ and ‘rich’ than with the CIS?+?coding strategy after 3-months.     

Modeling spoken word recognition performance by pediatric cochlear implant users using feature identification

OBJECTIVE: Computational simulations were carried out to evaluate the appropriateness of several psycholinguistic theories of spoken word recognition for children who use cochlear implants. These models also investigate the interrelations of commonly used measures of closed-set and open-set tests of speech perception. DESIGN: A software simulation of phoneme recognition performance was developed that uses feature identification scores as input. Two simulations of lexical access were developed. In one, early phoneme decisions are used in a lexical search to find the best matching candidate. In the second, phoneme decisions are made only when lexical access occurs. Simulated phoneme and word identification performance was then applied to behavioral data from the Phonetically Balanced Kindergarten test and Lexical Neighborhood Test of open-set word recognition. Simulations of performance were evaluated for children with prelingual sensorineural hearing loss who use cochlear implants with the MPEAK or SPEAK coding strategies. RESULTS: Open-set word recognition performance can be successfully predicted using feature identification scores. In addition, we observed no qualitative differences in performance between children using MPEAK and SPEAK, suggesting that both groups of children process spoken words similarly despite differences in input. Word recognition ability was best predicted in the model in which phoneme decisions were delayed until lexical access. CONCLUSIONS: Closed-set feature identification and open-set word recognition focus on different, but related, levels of language processing. Additional insight for clinical intervention may be achieved by collecting both types of data. The most successful model of performance is consistent with current psycholinguistic theories of spoken word recognition. Thus it appears that the cognitive process of spoken word recognition is fundamentally the same for pediatric cochlear implant users and children and adults with normal hearing.     

Early listening and speaking skills predict later reading proficiency in pediatric cochlear implant users

OBJECTIVES: Previous studies have reported that children who use cochlear implants (CIs) tend to achieve higher reading levels than their peers with profound hearing loss who use hearing aids. The purpose of this study was to investigate the influences of auditory information provided by the CI on the later reading skills of children born with profound deafness. The hypothesis was that there would be a positive and predictive relationship between earlier speech perception, production, and subsequent reading comprehension. DESIGN: The speech perception and production skills at the vowel, consonant, phoneme, and word level of 72 children with prelingual, profound hearing loss were assessed after 48 mos of CI use. The children's reading skills were subsequently assessed using word and passage comprehension measures after an average of 89.5 mos of CI use. A regression analysis determined the amount of variance in reading that could be explained by the variables of perception, production, and socioeconomic status. RESULTS: Regression analysis revealed that it was possible to explain 59% of the variance of later reading skills by assessing the early speech perception and production performance. The results indicated that early speech perception and production skills of children with profound hearing loss who receive CIs predict future reading achievement skills. Furthermore, the study implies that better early speech perception and production skills result in higher reading achievement. It is speculated that the early access to sound helps to build better phonological processing skills, which is one of the likely contributors to eventual reading success.     

Non-auditory stimulation in adult cochlear implant users

This is a retrospective case review of all 163 adults to have received multichannel cochlear implants on the Manchester University/Manchester Royal Infirmary programme between 1988 and 1998. The aims were to investigate the incidence of unwanted non-auditory effects of electrical stimulation (NAS) of the cochlea, and to try to identify any factors that seemed to be related to these effects. The effectiveness of programming strategies in eliminating unwanted effects was also studied. Most of the devices were Nucleus CI 22M or CI 24M. The remainder were Med-el Combi 40 or Combi 40+. NAS occurred in 23.9% of implantees. There were 20 cases of facial nerve stimulation (12.3%), 18 cases of pain in the ear or throat (11.0%) and one case of vestibulospinal spinal stimulation (0.6%). Two aetiologies were significantly associated with NAS. Otosclerosis tended to be associated with facial nerve stimulation and skull base fracture was associated with pain. Pain was associated with electrodes stimulated in the base turn of the cochlea and facial nerve stimulation tended to occur with more distally situated electrodes, close to labyrinthine segment of the nerve. There was no association with one particular make of device. The T and C levels for the rogue electrodes were in the normal range. It is concluded that the unwanted effects result from shorting of current through areas of low electrical resistance in the temporal bone. A number of different strategies were employed to prevent the effect, including alteration of current levels, removal of electrodes from the map and changing the stimulation mode, and this was successfully achieved in all cases. There was no difference between the performance of patients who had had NAS and those who had not, as assessed on open-set BKB sentence scores.     

Neural plasticity in blind cochlear implant users

Abstract

This study, using positron emission tomography, investigates the cortical activation generated by auditory stimulation in two congenitally blind cochlear implant users. In the patient with a relatively short history of deafness, activity increased in both auditory cortices and fell in the visual cortices. The patient with a longer period of deafness had greater activation of the visual cortices than the auditory cortices. A similar pattern of activity was seen when this patient subsequently had a second cochlear implant inserted into the opposite ear. The neural pathways formed after the restoration of auditory input in the congenitally blind can activate either the auditory or visual cortices. We suggest that the visual cortical activation demonstrated is of functional significance. Copyright © 2008 John Wiley & Sons, Ltd.     

Neural response telemetry in cochlear implant users

Programming of multichannel cochlear implants requires subjective responses to a series of sophisticated psychophysical percepts. It is often difficult for cochlear implant patients (especially young prelinguistically deaf children) to provide adequate responses for device fitting. However, the neural response telemetry (NRT) system renders possible the measurement of the compound action potential threshold. We performed NRT examinations in 27 cochlear implant users with Nucleus 24-channel cochlear implants. Measurements were obtained from five electrodes (3, 5, 10, 15, and 20) in each patient. Our goal was to look for correlation between behavioral subjective thresholds and compound action potentials. The action potentials could be elicited in 23 patients in all measured electrodes. The NRT threshold values were highly correlated with electrical threshold levels obtained through subjective responses. Our results suggest that the electrically elicited neural responses may yield very important information for device fitting in patients with cochlear implants.