Auditory brainstem activity in children with 9-30 months of bilateral cochlear implant use

Bilateral cochlear implants aim to restore binaural processing along the auditory pathways in children with bilateral deafness. We assessed auditory brainstem activity evoked by single biphasic pulses delivered by an apical or basal electrode from the left, right and both cochlear implants in 13 children. Repeated measures were made over the first 9-30 months of bilateral implant use. In children with short or long periods of unilateral implant use prior to the second implantation, Wave eV of the auditory brainstem response was initially prolonged when evoked by the na?ve versus experienced side. These differences tended to resolve in children first implanted <3 years of age but not in children implanted at older ages with long delays between implants. Latency differences were projected to persist for longer periods in children with long delays between implants compared with children with short delays. No differences in right versus left evoked eV latency were found in 2 children receiving bilateral implants simultaneously and their response latencies decreased over time. Binaural interaction responses showed effects of stimulating electrode position (responses were more detectable when evoked by an apical than basal pair of implant electrodes), and duration of delay between implants (measured by latency delays). The trends shown here suggest a negative impact of unilateral implant use on bilateral auditory brainstem plasticity.     

Importance of age and postimplantation experience on speech perception measures in children with sequential bilateral cochlear implants.

OBJECTIVES: Clinical trials in which children received bilateral cochlear implants in sequential operations were conducted to analyze the extent to which bilateral implantation offers benefits on a number of measures. The present investigation was particularly focused on measuring the effects of age at implantation and experience after activation of the second implant on speech perception performance. STUDY DESIGN: Thirty children aged 3 to 13 years were recipients of 2 cochlear implants, received in sequential operations, a minimum of 6 months apart. All children received their first implant before 5 years of age and had acquired speech perception capabilities with the first device. They were divided into 3 age groups on the basis of age at time of second ear implantation: Group I, 3 to 5 years; Group II, 5.1 to 8 years; and Group III, 8.1 to 13 years. Speech perception measures in quiet included the Multisyllabic Lexical Neighborhood Test (MLNT) for Group I, the Lexical Neighborhood Test (LNT) for Groups II and III, and the Hearing In Noise Test for Children (HINT-C) sentences in quiet for Group III. Speech perception in noise was assessed using the Children's Realistic Intelligibility and Speech Perception (CRISP) test. Testing was performed preoperatively and again postactivation of the second implant at 3, 6, and 12 months (CRISP at 3 and 9 mo) in both the unilateral and bilateral conditions in a repeated-measures study design. Two-way repeated-measures analysis of variance was used to analyze statistical significance among device configurations and performance over time. SETTING: US Multicenter. RESULTS: Results for speech perception in quiet show that children implanted sequentially acquire open-set speech perception in the second ear relatively quickly (within 6 mo). However, children younger than 8 years do so more rapidly and to a higher level of speech perception ability at 12 months than older children (mean second ear MLNT/LNT scores at 12 months: Group I, 83.9%; range, 71-96%; Group II, 59.5%; range, 40-88%; Group III, 32%; range, 12-56%). The second-ear mean HINT-C score for Group III children remained far less than that of the first ear even after 12 months of device use (44 versus 89%; t, 6.48; p<0.001; critical value, 0.025). Speech intelligibility for spondees in noise was significantly better under bilateral conditions than with either ear alone when all children were analyzed as a single group and for Group III children. At the 9-month test interval, performance in the bilateral configuration was significantly better for all noise conditions (13.2% better for noise at first cochlear implant, 6.8% better for the noise front and noise at second cochlear implant conditions, t=2.32, p=0.024, critical level=0.05 for noise front; t=3.75, p<0.0001, critical level=0.05 for noise at first implant; t=2.73, p = 0.008, critical level=0.05 for noise at second implant side). The bilateral benefit in noise increased with time from 3 to 9 months after activation of the second implant. This bilateral advantage is greatest when noise is directed toward the first implanted ear, indicating that the head shadow effect is the most effective binaural mechanism. The bilateral condition produced small improvements in speech perception in quiet and for individual Group I and Group II patient results in noise that, in view of the relatively small number of subjects tested, do not reach statistical significance. CONCLUSION: Sequential bilateral cochlear implantation in children of diverse ages has the potential to improve speech perception abilities in the second implanted ear and to provide access to the use of binaural mechanisms such as the head shadow effect. The improvement unfolds over time and continues to grow during the 6 to 12 months after activation of the second implant. Younger children in this study achieved higher open-set speech perception scores in the second ear, but older children still demonstrate bilateral benefit in noise. Determining the long-term impact and cost-effectiveness that results from such potential capabilities in bilaterally implanted children requires additional study with larger groups of subjects and more prolonged monitoring.     

1-year postactivation results for sequentially implanted bilateral cochlear implant users.

OBJECTIVE: Evaluate speech recognition in quiet and in noise for a group of 12 children, all of whom underwent sequential bilateral cochlear implantation at various ages (range, 1 yr, 8 mo to 9 yr, 6 mo at time of second implant). STUDY DESIGN: Retrospective. SETTING: Outpatient cochlear implant clinic. PATIENTS: Children who underwent sequential bilateral cochlear implantation. INTERVENTION: Rehabilitative. MAIN OUTCOME MEASURES: Speech recognition in quiet was evaluated for each ear separately using single-word speech recognition assessments (Multisyllabic Lexical Neighborhood Test and Early Speech Perception Test) via recorded presentation. Speech recognition in noise was assessed for each ear separately and in the bilateral condition by obtaining a spondee recognition threshold in the presence of speech-weighted noise presented at 45 dB hearing level. The primary outcome measure for speech recognition in noise assessment was the signal-to-noise ratio for 50% performance, which was calculated by determining the difference between the presentation level of the noise and the presentation level at which the speech recognition threshold was obtained. The results of these assessments were contrasted between children receiving their second cochlear implant before 4 years of age and children receiving their second cochlear implant after 4 years of age. RESULTS: A statistically significant difference for speech recognition scores in quiet was obtained between the early-implanted ear and the late-implanted ears for children receiving their second cochlear implant after 4 years of age. There was not a statistically significant difference in speech recognition scores in quiet between the early-implanted and late-implanted ears of children receiving their second cochlear before 4 years of age. Both groups of children possessed better speech recognition scores in noise (statistically significant at an alpha = 0.05) in the bilateral condition relative to either unilateral condition. However, there was not a statistically significant relationship between speech recognition performance in noise and the duration of deafness of the later implanted ear. CONCLUSION: Bilateral cochlear implantation allowed for better speech recognition in noise relative to unilateral performance for a group of 12 children who underwent sequential bilateral cochlear implantation at various ages. There was not a statistically significant relationship between speech recognition in noise benefit, which was defined as the difference in performance between the first implanted ear and the bilateral condition and the age at which the second implant was received. Children receiving bilateral cochlear implants younger than 4 years of age achieved better speech recognition in quiet performance for the later implanted ear as compared with children receiving their second cochlear implant after 4 year of age.     

Central auditory development in children with bilateral cochlear implants

OBJECTIVE: To examine the time course of maturation of P1 latencies in infant sequential and simultaneous bilateral cochlear implant recipients. DESIGN: Retrospective case series. SETTING: Pediatric collaborative cochlear implant program. PATIENTS: Four children who received bilateral cochlear implants prior to age 2 years. INTERVENTION: Cortical auditory evoked potential was completed to determine the latency of the P1 response in 4 children with bilateral cochlear implants. MAIN OUTCOME MEASURES: Longitudinal development of the latency of the P1 cortical auditory evoked potential in children who received bilateral cochlear implants prior to age 2 years. RESULTS: In 2 patients who received sequential bilateral implants, P1 latencies recorded from the first implanted ear were within normal limits after 3 to 6 months of implant use. By comparison, P1 latencies from the second implanted ear reached normal limits as early as 1 month after implant use. In 2 patients who received simultaneous bilateral implants, P1 latencies from both ears were also within normal limits in a very short time frame (ie, by 1 month poststimulation). CONCLUSIONS: Our data suggest a high degree of plasticity of the central auditory pathways after early bilateral implantation. We find that P1 latencies provide a clinically useful biomarker of central auditory system development in children after cochlear implantation.     

Bilateral cochlear implantation in children

AIMS: to determine the benefit of bilateral cochlear implantation in a child on speech and language development. METHOD: This child got her first implant, a Nucleus 24-system, on the right side at the age of 2.5 years. The left side was implanted at the age of 4.4 years with a Nucleus 24Contour-system. On the right side she's now wearing an Esprit 24-speechprocessor (SPR). On the left side she has a Sprint-SPR. M. goes to a mainstream school and receives Speech and Language therapy in a Speech and Hearing Rehab Centre. The etiology of her deafness was hyperbilirubinemia. Auditory capacity and speech recognition tests were performed for both ears separately and together. RESULTS: Aided thresholds give a PTA of 28 dBA with the first implant, 22 dBA with the second implant and with both implants we get a PTA of 23 dBA. Results for speech identification and recognition demonstrated an increased performance when both implants are used together. Speech and language development was equivalent to the mean of age 4.5. At the time of testing M. was 4.8 years. At this time the speech and language development show no delays with normal hearing children. CONCLUSIONS: bilateral cochlear implantation in children may have additional value for their speech and language development. Also, implantation may be considered when auditory neuropathy is likely.     

Comparison of bilateral and unilateral cochlear implants in children with sequential surgery

Objective

The objective of this study was to evaluate the effect of bilateral versus unilateral cochlear implants and the importance of the inter-implant interval.

Methods

Seventy-three prelingually deaf children received sequential bilateral cochlear implants. Speech recognition in quiet with the first, second and with both implants simultaneously was evaluated at the time of the second implantation and after 12 and 24 months.

Results

Mean bilateral speech recognition 12 and 24 months after the second implantation was significantly higher than that obtained with either the first or the second implant. The addition of a second implant was demonstrated to have a beneficial effect after both 12 and 24 months. Speech recognition with the second implant increased significantly during the first year. A small, non-significant improvement was observed during the second year. The inter-implant interval significantly influenced speech recognition with the second cochlear implant both at 12 and 24 months, and bilateral speech recognition at 12 months, but not at 24 months.

Conclusions

A small, but statistically significant improvement in speech recognition was found with bilateral cochlear implants compared with a unilateral implant. A major increase in speech recognition occurred with the second cochlear implant during the first year. A shorter time interval between the two implantations resulted in better speech recognition with the second implant. However, no definitive time-point was found for when the second implant could no longer add a positive effect.     

Speech intelligibility of Mandarin-speaking deaf children with cochlear implants

OBJECTIVE: Speech intelligibility, the extent to which the speakers can be understood verbally by their listeners, is an evaluator for the effectiveness of cochlear implantation. Thus, our goals were to evaluate the result of a tonal language through comparing the speech intelligibility between normal-hearing and implanted children who speak Mandarin, and to evaluate the relationship between speech intelligibility and duration of implants use. The effects of the age at implantation were also evaluated. METHODS: Twenty-six children (mean age of 5.9 years), who were congenitally deaf and implanted age at 3.5 years, were compared with 26 normal-hearing children (mean age of 5.84 years). The average post-implanted time was more than 6 months. Speech intelligibility was represented with the speech intelligibility ratings (SIR) and the correct percentage of dictation. The relationships between speech intelligibility, age at implantation and duration of implant were evaluated by linear regression analysis. RESULTS: Speech intelligibility of most subjects ranked from SIR category 3-5. The average correct perception rate (CI group/normal group) of words, consonants, vowels, and tones were 42.5%, 64.9%, 73.5%, and 72.3%, respectively. These differences were statistically significant (p<0.001). Speech intelligibility was positively correlated with age only in the normal-hearing group. Speech intelligibility in the implanted group was negatively correlated with age at implantation but positively correlated with the duration of implant. CONCLUSIONS: Speech intelligibility of tonal language was poorer in implanted children than normal-hearing children, but their communication outcomes were satisfactory when measured with SIR. Speech intelligibility is better if the age at implantation is younger or duration of implants use is longer.     

Reading abilities after cochlear implantation: the effect of age at implantation on outcomes at 5 and 7 years after implantation

OBJECTIVES: The reading skills of deaf children have typically been delayed and this delay has been found to increase with age. This study explored the reading ability of a large group of children who had received cochlear implants 7 years earlier and investigated the relationship between reading ability and age at implantation. METHODS: The reading ages of 105 children, with age at implantation less than 7 years and onset of deafness below the age of three, were assessed 5 and 7 years after implantation using the Edinburgh reading test. Net reading age was calculated by using the difference between chronological age and reading age. Non-verbal intelligence was measured for a subset of 71 children, using Raven's coloured progressive matrices. Further investigation of this subset looked at the association of nonverbal intelligence, age at implantation and reading ability. RESULTS: There was a strong negative correlation at both 5 and 7 years after implant between net reading score and age at implantation. In the subset of 71 children who had an IQ score within normal range, those implanted at or before 42 months had age-appropriate reading both 5 and 7 years post-implant. This was not the case for children implanted after 42 months. Reading progress at the two post-implant assessment intervals were found to be highly related. CONCLUSIONS: Age at implantation was a significant factor in the development of reading skills in this group. In children implanted below the age of 42 months, reading progress was in line with chronological age, which has not been the case previously with profoundly deaf children. With earlier implantation more common in present groups, and improved technology, there is every reason to be optimistic about the influence of cochlear implantation on the development of reading skills in deaf children.     

Systematic review of the literature on the clinical effectiveness of the cochlear implant procedure in paediatric patients

The aim of this systematic review of the literature was to summarize the results of scientific publications on the clinical effectiveness of the cochlear implant (CI) procedure in children. The members of the Working Group first examined existing national and international literature and the principal international guidelines on the procedure. They considered as universally-accepted the usefulness/effectiveness of unilateral cochlear implantation in severely-profoundly deaf children. Accordingly, they focused attention on systematic reviews addressing clinical effectiveness and cost/efficacy of the CI procedure, with particular regard to the most controversial issues for which international consensus is lacking. The following aspects were evaluated: post-CI outcomes linked to precocity of CI; bilateral (simultaneous/ sequential) CI vs. unilateral CI and vs. bimodal stimulation; benefits derived from CI in deaf children with associated disabilities. With regard to the outcomes after implantation linked to precocity of intervention, there are few studies comparing post-CI outcomes in children implanted within the first year of life with those of children implanted in the second year. The selected studies suggest that children implanted within the first year of life present hearing and communicative outcomes that are better than those of children implanted after 12 months of age. Concerning children implanted after the first year of life, all studies confirm an advantage with respect to implant precocity, and many document an advantage in children who received cochlear implants under 18 months of age compared to those implanted at a later stage. With regard to bilateral CI, the studies demonstrate that compared to unilateral CI, bilateral CI offers advantages in terms of hearing in noise, sound localization and during hearing in a silent environment. There is, however, a wide range of variability. The studies also document the advantages after sequential bilateral CI. In these cases, a short interval between interventions, precocity of the first CI and precocity of the second CI are considered positive prognostic factors. In deaf children with associated disabilities, the studies analyzed evidence that the CI procedure is also suitable for children with disabilities associated with deafness, and that even these children may benefit from the procedure, even if these may be slower and inferior to those in children with isolated deafness, especially in terms of high communicative and perceptive skills.     

Sequential bilateral cochlear implantation in children: development of the primary auditory abilities of bilateral stimulation

The advantages of sequential bilateral cochlear implantation were assessed in 29 children with a severe to profound hearing loss. The effect of age at second implantation and the effect of duration of bilateral implant use on the outcomes in speech perception and directional hearing were investigated. The children received their second cochlear implant at an age ranging from 2.8 to 8.5 years. Measurements were carried out preoperatively and postoperatively after 6, 12 and 24 months of bilateral implant use. A matched control group of 9 children with a unilateral implant were also measured over time and were compared with the study group after 12 and 24 months. Speech reception in both quiet and in noise and lateralization were measured. After 24 months, a minimum audible angle task was carried out. Bilateral advantages with regard to speech reception in quiet and in noise were already present after 6 months of bilateral implant use and improved thereafter. After 24 months, speech reception in noise had significantly improved with bilateral implants compared to that of children with a unilateral implant. The percentage of children that could accurately lateralize increased from 57% after 6 months to 83% after 24 months. With regard to the minimum audible angle task, loudspeakers were placed on average at ±42°. Age at second implantation did not have an influence on all outcomes. From the results it can be concluded that the advantages of bilateral hearing occur after sequential bilateral implantation and that age at second implantation does not influence the amount of bilateral advantage. Furthermore, it can be concluded that longer periods of bilateral implant use lead to greater bilateral advantages.     

Cochlear implants in children, adolescents, and prelinguistically deafened adults: speech perception.

A group of 10 children, adolescents, and prelinguistically deafened adults were implanted with the 22-electrode cochlear implant (Cochlear Pty Ltd) at the University of Melbourne Cochlear Implant Clinic and have used the prosthesis for periods from 12 to 65 months. Postoperative performance on the majority of closed-set speech perception tests was significantly greater than chance, and significantly better than preoperative performance for all of the patients. Five of the children have achieved substantial scores on open-set speech tests using hearing without lipreading. Phoneme scores in monosyllabic words ranged from 30% to 72%; word scores in sentences ranged from 26% to 74%. Four of these 5 children were implanted during preadolescence (aged 5:5 to 10:2 years) and the fifth, who had a progressive loss, was implanted during adolescence (aged 14:8 years). The duration of profound deafness before implantation varied from 2 to 8 years. Improvements were also noted over postoperative data collection times for the younger children. The remaining 5 patients who did not demonstrate open-set recognition were implanted after a longer duration of profound deafness (aged 13:11 to 20:1 years). The results are discussed with reference to variables that may affect implant performance, such as age at onset of loss, duration of profound loss, age at implantation, and duration of implantation. They are compared with results for similar groups of children using hearing aids and cochlear implants.     

The benefits of sequential bilateral cochlear implantation for hearing-impaired children

CONCLUSION: Sequential bilateral implantation offers listening advantages demonstrable on speech recognition in noise and for lateralization. Whilst the trend was for shorter inter-implant intervals and longer implant experience to positively impact binaural advantage, we observed no contraindications for binaural advantage. OBJECTIVE: To evaluate the benefits of sequential bilateral cochlear implantation over unilateral implantation in a multicentre study evaluating speech recognition in noise and lateralization of sound. SUBJECTS AND METHODS: Twenty children, implanted bilaterally in sequential procedures, had the following characteristics: they were native German-speaking, were3 years or older and had a minimum of 1 year inter-implant interval and had between 2 months and 4 years 7 months binaural listening experience. Binaural advantage was assessed including speech recognition in noise using the Regensburg modification of the Oldenburger Kinder-Reimtest (OLKI) and lateralization of broadband stimuli from three speakers. RESULTS: A significant binaural advantage of 37% was observed for speech recognition in noise. Binaural lateralization ability was statistically superior for the first and second implanted ear (p = 0.009, p = 0.001, respectively). Binaural experience was shown to correlate moderately with absolute binaural speech recognition scores, with binaural advantage for speech recognition and with binaural lateralization ability. The time interval between implants correlated in an inverse direction with binaural advantage for speech recognition.     

Sound localization ability of young children with bilateral cochlear implants.

OBJECTIVE: To evaluate the benefit of bilateral cochlear implantation in young children. STUDY DESIGN: Clinical trial comparing a group of bilaterally implanted children with a group of unilaterally implanted children. SETTING: Tertiary referral center. PATIENTS: Five bilaterally implanted children (mean age at testing, 3 yr 7 mo) were compared with 5 unilaterally implanted children (mean age at testing, 5 yr 3 mo). Meningitis was the cause of deafness in all of the children. METHODS: Children were asked to localize a prerecorded melody band limited from 500 to 4,000 Hz presented from loudspeakers placed at either -90 or 90 degrees or -30 or 30 degrees azimuth. Their parents filled in the Speech, Spatial and Qualities of Hearing Scale (SSQ) and PedsQL questionnaires on hearing and health-related quality of life of their children. RESULTS: The bilaterally implanted children had significantly better scores on the localization test than the children with unilateral cochlear implants. The scores of the children with bilateral cochlear implants were also significantly higher on the spatial domain of the SSQ, which concerns localization. No significant differences were found in the speech and quality of hearing domains and the total scores on the SSQ or the PedsQL between the two groups. CONCLUSION: Children with bilateral cochlear implantation already demonstrate an advantage over unilaterally implanted children at a young age.     

United Kingdom national paediatric bilateral project: Demographics and results of localization and speech perception testing

Objectives: To assess longitudinal outcomes in a large and varied population of children receiving bilateral cochlear implants both simultaneously and sequentially.

Methods: This observational non-randomized service evaluation collected localization and speech recognition in noise data from simultaneously and sequentially implanted children at four time points: before bilateral cochlear implants or before the sequential implant, 1 year, 2 years, and 3 years after bilateral implants. No inclusion criteria were applied, so children with additional difficulties, cochleovestibular anomalies, varying educational placements, 23 different home languages, a full range of outcomes and varying device use were included.

Results: 1001 children were included: 465 implanted simultaneously and 536 sequentially, representing just over 50% of children receiving bilateral implants in the UK in this period. In simultaneously implanted children the median age at implant was 2.1 years; 7% were implanted at less than 1 year of age. In sequentially implanted children the interval between implants ranged from 0.1 to 14.5 years. Children with simultaneous bilateral implants localized better than those with one implant. On average children receiving a second (sequential) cochlear implant showed improvement in localization and listening in background noise after 1 year of bilateral listening. The interval between sequential implants had no effect on localization improvement although a smaller interval gave more improvement in speech recognition in noise. Children with sequential implants on average were able to use their second device to obtain spatial release from masking after 2 years of bilateral listening. Although ranges were large, bilateral cochlear implants on average offered an improvement in localization and speech perception in noise over unilateral implants.

Conclusion: These data represent the diverse population of children with bilateral cochlear implants in the UK from 2010 to 2012. Predictions of outcomes for individual patients are not possible from these data. However, there are no indications to preclude children with long inter-implant interval having the chance of a second cochlear implant.     

Implantes cocleares bilaterales en la población infantil: adquisición de la binauralidad

Introduction and objectivesSeveral studies have indicated the benefit of bilateral cochlear implants in the acquisition of binaural hearing and bilateralism. In children with cochlear implants, is it possible to achieve binaurality after a second implant? When is the ideal time to implant them? The objective of this study was to analyse the binaural effect in children with bilateral implants and the differences between subjects with simultaneous and sequential implants with both short and long intervals.Patients and methodsThere were 90 patients between 1 and 2 years of age (the first surgery), implanted between 2000 and 2008. Of these, 25 were unilateral users and 65 bilateral; 17 patients had received simultaneous implants, 29 had sequential implants before 12 months after the first one (short interimplant period) and 19 after 12 months (long period). All of them were tested for silent and noisy verbal perception and a tonal threshold audiometry was performed.ResultsThe silent perception test showed that the simultaneous and short period sequential implant patients (mean: 84.67%) versus unilateral and long period sequential implants (mean: 79.66%), had a statistically-significant difference (P = 0,23). Likewise, the noisy perception test showed a difference with statistical significance (P = 0,22) comparing the simultaneous implanted and short period sequential implants (mean, 77.17%) versus unilateral implanted and long period sequential ones (mean: 69.32%).ConclusionsThe simultaneous and sequential short period implants acquired the advantages of binaural hearing.     

Brief Assessment of Parental Perception (BAPP): Development and validation of a new measure for assessing paediatric outcomes after bilateral cochlear implantation

Objective: In contrast to previous clinical practice, current guidelines recommend bilateral cochlear implantation in children, resulting in a cohort of children who initially received one implant, but have subsequently had a second, contralateral implant. This study aimed to explore satisfaction and quality of life in children implanted simultaneously or sequentially. Design: A novel measure of satisfaction and quality of life following paediatric bilateral cochlear implantation (the Brief Assessment of Parental Perception; BAPP) was developed and preliminary validation undertaken as part of a large, national project of bilateral implantation. Children’s parents completed the measure yearly for up to three years following implantation. Study sample: Children from 14 UK implant centres were recruited into the study; data were available for 410 children one year post-implantation. Results: The BAPP was found to have good face and convergent validity, and internal consistency. Results indicated very high levels of satisfaction with the devices, and improvements in quality of life. However there was evidence that children implanted sequentially were less willing to wear their second implant in the first two years than those children receiving simultaneous implants. Conclusion: Simultaneous and sequential cochlear implants have a positive impact on the quality of life of deaf children.     

Speech recognition outcomes following bilateral cochlear implantation in adults aged over 50 years old

Abstract

Objective: To examine the speech recognition benefit of bilateral cochlear implantation over unilateral implantation in adults aged over 50 years old, and to identify potential predictors of successful bilateral implantation in this group. Design: Retrospective cohort study using data collected during standard clinical practice. Bilateral performance was compared to the unilateral performance with the first and second implanted ear and examined in relation to potential predictive variables. Study sample: Sixty-seven cochlear implant users who received a second implant after the age of 50 years old. Results: Participants obtained significantly greater speech recognition scores with the use of bilateral cochlear implants compared to the use of each individual implant. The score obtained with the first implanted ear was the most reliable predictor of the score obtained with the second and with bilateral implants. Conclusions: Older adults can obtain speech recognition benefits from sequential bilateral cochlear implantation.     

Sound localization in bilateral users of MED-EL COMBI 40/40+ cochlear implants

OBJECTIVE: The purpose of the study was to investigate sound localization with bilateral and unilateral cochlear implants. DESIGN: Sound localization tests were performed on 20 bilaterally implanted MED-EL COMBI 40/40+ users. All subjects were bilaterally implanted during adolescence or later. Sound localization was tested in the frontal horizontal plane by using 9 equally spaced loudspeakers and speech-shaped noise bursts at randomized levels. RESULTS: The group of subjects who were bilaterally deafened after 5 to 6 yr of age (18 subjects) showed a statistically significant improvement in sound localization when using both implants, compared with when using only one. The mean deviation between the presentation azimuth and the response azimuth was 16.6 degrees when using both implants, which was on average 37.1 degrees smaller than when using one implant only. When adjusted for the localization error that was constant across loudspeakers, the mean deviation was 15.9 degrees for bilateral implant use, representing an improvement of 30.1 degrees over unilateral implant use. Statistical analysis showed that in this group, performance measures were not correlated with subject details such as age at onset of deafness or duration of unilateral implant use. In contrast, subjects who were bilaterally deafened before 6 yr of age (2 subjects) did not show a benefit in sound localization from bilateral implants. CONCLUSIONS: Bilateral cochlear implants offer a substantial benefit in sound localization to late-deafened, late-implanted subjects. The very limited data from early-deafened subjects implanted at a later age could suggest that these subjects may not benefit in sound localization from bilateral cochlear implants. It is possible that early implantation for early deafened subjects might allow better acquisition of spatial hearing, thus leading to improved localization performance.     

Bilateral versus unilateral cochlear implantation in young children

Objectives

To compare the preverbal communication skills of two groups of young implanted children: those with unilateral implantation and those with bilateral implantation.

Material and methods

The study assessed 69 children: 42 unilaterally and 27 bilaterally implanted with age at implantation less than 3 years. The preverbal skills of these children were measured before and 1 year after implantation, using Tait Video Analysis that has been found able to predict later speech outcomes in young implanted children.

Results

Before implantation there was no significant difference between the unilateral group and the bilateral group. There was still no difference at 12 months following implantation where vocal autonomy is concerned, but a strongly significant difference between the groups for vocal turn-taking and non-looking vocal turns, the bilateral group outperforming the unilateral group. Regarding gestural turn-taking and gestural autonomy, there was a strongly significant difference between the two groups at the 12 month interval, and also a difference before implantation for gestural autonomy, the unilateral group having the higher scores. Multiple regression of non-looking vocal turns revealed that 1 year following implantation, bilateral implantation contributed to 51% of the variance (p < 0.0001), after controlling for the influence of age at implantation and length of deafness which did not reach statistical significance.

Conclusions

Profoundly deaf bilaterally implanted children are significantly more likely to use vocalisation to communicate, and to use audition when interacting vocally with an adult, compared with unilaterally implanted children. These results are independent of age at implantation and length of deafness.     

Abnormal timing delays in auditory brainstem responses evoked by bilateral cochlear implant use in children.

HYPOTHESIS: A period of unilateral implant use before bilateral implantation affects timing of brainstem processes measured by the electrically evoked auditory brainstem response (EABR). BACKGROUND: EABR latencies decrease with unilateral implant use potentially disrupting binaural timing cues important in auditory brainstem processing of bilateral input. METHODS: EABRs were evoked by electrical pulses from the left, right, and both implants simultaneously in 3 groups of children. All were initially implanted at ages younger than 3 years and had the following: 1) a long delay (>2 yr [n = 16]), 2) a short delay (<1 yr [n = 15]), or 3) no delay (n = 15) between left and right ear implantation. Responses were recorded on the first day of bilateral implant use and 3 and 9 months thereafter. RESULTS: Relative to responses evoked in the experienced ear, the naive ear showed prolonged latency in both the EABR peaks and the binaural difference response. After 3 and 9 months of bilateral implant use, the relative prolongation decreased in the long and short delay groups, but significant differences persisted in the former. No clear differences in latencies evoked by the left versus right implant were found at any time point in children receiving bilateral implants simultaneously. CONCLUSION: Results suggest potential disruptions to binaural brainstem processing based on timing cues in children receiving a second cochlear implant after more than 2 years of unilateral implant use that persist through at least the first 9 months of bilateral implant use.