Bilateral Cochlear Implants Research Articles

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.

Auditory performance and language skills in children with auditory brainstem implants and cochlear implants

PurposeThis study aims to evaluate school-age language skills and auditory performance in different listening situations in children with cochlear implants and auditory brainstem implants.MethodThe study included 60 children between the ages of 5 and 9 years with cochlear implants (CI) and auditory brainstem implants (ABI). The volunteer children were divided into two groups: bimodal CI-ABI and bilateral CI users. Test of Language Development: Primary (TOLD-P:4), which assesses components of language such as phonology, morphology, syntax and semantics, was used to evaluate school-age language skills. Children’s Auditory Performance Scale (CHAPS) was used to measure their listening performance in quiet, noisy, multi-stimulus environments and their auditory attention and memory skills in daily life. The correlations between language and auditory performance were analyzed and compared between the two groups.ResultsChildren with ABI showed poorer performance in school-age language skills and auditory performance in different listening environments (p < 0.05). Significant correlations were between school-age language skills and auditory performance (p < 0.05).ConclusionImproved auditory performance is crucial for the development of school-age language skills. To improve auditory performance in children with ABI in different listening environments, assistive listening devices, acoustic environmental arrangements, informative activities, etc., should be used.

Assessment of the main factors involved in the auditory-verbal rehabilitation process in children with cochlear implants

Abstract BACKGROUND. Children’s communication with the family and the environmental surroundings begins immediately after birth and development continues throughout life. Impairment of hearing due to the presence of congenital hypoacusis results in severe language development disorders. The purpose of the study was to identify the main factors involved in the auditory-verbal rehabilitation process of children with hearing impairment. MATERIAL AND METHODS. A descriptive, observational study was conducted on a group of 35 carers of hearing-impaired children proposed for auditory-verbal rehabilitation through cochlear implantation. The study carried out was based on the parents’ statements, analyzing the essential factors that can influence the quality of life of parents with hearing-impaired children: the child’s age at the time of the positive diagnosis, the child’s communication skills before implantation, the time elapsed from the intervention to implant activation, participation in auditory-verbal rehabilitation sessions with a speech therapist, parental commitment during the immediate pre- and post-implant period, the parent’s level of education. RESULTS. The dominance of the female gender can be noted - 91.43%. 60% of adult participants were college graduates, 20% discontinued their education after completing high school, 17.14% graduated from a post-secondary school. 57.14% of the parents reported being employed in some form of work during the period before and immediately after the cochlear implantation of their children. 82.85% reported the diagnosis of their child’s hypoacusis in the pre-kindergarten group. Out of the total number of children, 68.57% were recipients of bilateral cochlear implants, 31.43% had unilateral implants. The periods during which children benefited from post-implantation speech therapy were between 1 and 6 months (5.71%), 1 and 2 years (2.86%), &gt;2 years (17.14%). In 71.43% of cases, families were in the rehabilitation phase with speech therapy at the time of filling out the form. CONCLUSION. In the auditory-verbal rehabilitation process of a hearing-impaired child, there are a number of factors and conditions that must be considered in a specific manner for each individual patient.

Quality of Life With Cochlear Implantation Using the CIQOL-35 at a Tertiary Urban Medical Center: Our Experience.

Assessment of quality-of-life (QOL) outcomes after cochlear implantation (CI) using the Cochlear Implant Quality of Life-35 questionnaire (CIQOL-35). Retrospective cohort. Single-institution tertiary care center. Patients 18 years and older who have undergone CI and CIQOL-35 survey. Implementing CIQOL-35 from 2019 to 2022 to measure change in QOL after CI. Statistical analysis included nonparametric, univariate, and multivariate analyses. Significance was set at 0.05. Differences in QOL among CI patients in each of the CIQOL-35 domains. Ninety-three patients (40 female, 53 male) aged 20 to 93 years (median 70 years) turned in 164 QOL surveys (68 preactivation, 96 postactivation). Postactivation median QOL was 5 to 15 points higher across all domains ( p < 0.001). QOL score distributions among unilateral CI only, bilateral CI, and unilateral CI with contralateral hearing aid users were not statistically different ( p > 0.05). Multivariate analysis identified that male sex ( β = -2.0; 95% confidence interval, -3.9 to -0.1) was a negative predictor for environment scores and not being married ( β = 2.0; 95% confidence interval, 0.02 to 4.0) was a positive predictor for entertainment scores. Median follow-up time was 13 months post-CI (interquartile range [IQR], 7.1-21.5 months). CI patients experienced improved QOL postactivation among all QOL domains, whereas specific CI use pattern in regard to unilateral, bilateral, or bimodal did not affect QOL. Multivariate analysis identified marital status and sex as possible QOL predictors.

Outcomes and Measures of Children with Bilateral Cochlear Implants: A Single-center Experience in Bangladesh

Children dealing with hearing impairment encounter challenges associated with speech and language delays, significantly impacting their quality of life. Recent data from the World Health Organization indicate that 466 million people worldwide experience disabling hearing loss, with 34 million being children. Cochlear implantation (CI) is a novel approach for severe to profound sensorineural hearing loss. In pediatric CI, the main objective is to enable hearing-impaired children to perceive sound promptly, facilitating speech and language development. This study investigated the outcomes of bilateral pediatric cochlear implant (CI) users in Bangladesh, applying the Speech, Spatial, and Qualities of Hearing questionnaire and the Classification of Auditory Performance-II (CAP-II). Conducted at the Combined Military Hospital in Bangladesh, the study involved 10 children with bilateral cochlear implants. The results revealed commendable scores in speech understanding, spatial hearing, and qualities of hearing, underscoring the effectiveness of cochlear implant interventions. Deeply examining the implications is the topic of discussion of these findings, emphasizing the positive impact of early implantation and the adaptability of assessment tools in diverse cultural contexts.

Synchronizing Automatic Gain Control in Bilateral Cochlear Implants Mitigates Dynamic Localization Deficits Introduced by Independent Bilateral Compression.

The independence of left and right automatic gain controls (AGCs) used in cochlear implants can distort interaural level differences and thereby compromise dynamic sound source localization. We assessed the degree to which synchronizing left and right AGCs mitigates those difficulties as indicated by listeners' ability to use the changes in interaural level differences that come with head movements to avoid front-back reversals (FBRs). Broadband noise stimuli were presented from one of six equally spaced loudspeakers surrounding the listener. Sound source identification was tested for stimuli presented at 70 dBA (above AGC threshold) for 10 bilateral cochlear implant patients, under conditions where (1) patients remained stationary and (2) free head movements within ±30° were encouraged. These conditions were repeated for both synchronized and independent AGCs. The same conditions were run at 50 dBA, below the AGC threshold, to assess listeners' baseline performance when AGCs were not engaged. In this way, the expected high variability in listener performance could be separated from effects of independent AGCs to reveal the degree to which synchronizing AGCs could restore localization performance to what it was without AGC compression. The mean rate of FBRs was higher for sound stimuli presented at 70 dBA with independent AGCs, both with and without head movements, than at 50 dBA, suggesting that when AGCs were independently engaged they contributed to poorer front-back localization. When listeners remained stationary, synchronizing AGCs did not significantly reduce the rate of FBRs. When AGCs were independent at 70 dBA, head movements did not have a significant effect on the rate of FBRs. Head movements did have a significant group effect on the rate of FBRs at 50 dBA when AGCs were not engaged and at 70 dBA when AGCs were synchronized. Synchronization of AGCs, together with head movements, reduced the rate of FBRs to approximately what it was in the 50-dBA baseline condition. Synchronizing AGCs also had a significant group effect on listeners' overall percent correct localization. Synchronizing AGCs allowed for listeners to mitigate front-back confusions introduced by unsynchronized AGCs when head motion was permitted, returning individual listener performance to roughly what it was in the 50-dBA baseline condition when AGCs were not engaged. Synchronization of AGCs did not overcome localization deficiencies which were observed when AGCs were not engaged, and which are therefore unrelated to AGC compression.

The Benefit of Bimodal Hearing and Beamforming for Cochlear Implant Users

Plain Language SummaryCochlear implantation is the standard treatment for severe to profound hearing loss. While cochlear implant (CI) users can communicate effectively in quiet environments, speech understanding in noise remains challenging. Bimodal hearing, combining a CI in one ear and a hearing aid (HA) in the other, has shown advantages over unilateral electrical hearing, especially for speech understanding in noisy conditions. We analyzed the effect of the addition of the HA to the CI in this paper. There are also other processing techniques available to improve speech understanding in noise for this population. In this paper, one of these techniques, beamforming, is studied in different configurations. Therefore, 17 participants with a CI in one ear and a HA in the other ear are included. They performed a speech test for different configurations with and without beamforming to be able to analyze the effect of beamforming.

Tonal language experience facilitates the use of spatial cues for segregating competing speech in bimodal cochlear implant listeners.

English-speaking bimodal and bilateral cochlear implant (CI) users can segregate competing speech using talker sex cues but not spatial cues. While tonal language experience allows for greater utilization of talker sex cues for listeners with normal hearing, tonal language benefits remain unclear for CI users. The present study assessed the ability of Mandarin-speaking bilateral and bimodal CI users to recognize target sentences amidst speech maskers that varied in terms of spatial cues and/or talker sex cues, relative to the target. Different from English-speaking CI users, Mandarin-speaking CI users exhibited greater utilization of spatial cues, particularly in bimodal listening.

Predictive factors for broad binaural pitch fusion in adults with hearing aids and cochlear implants

Many adults with hearing loss who use hearing aids (HAs) and/or cochlear implants (CIs) have broad binaural pitch fusion, such that sounds with large pitch differences are fused across ears, leading to difficulties separating voices in multi-talker environments. However, there is individual variation. The goal of the current study was to investigate whether auditory experience factors explain this variation in broad binaural fusion. Binaural fusion was measured in adults with various hearing device combinations: 26 bilateral HA, 25 bimodal CI, and 27 bilateral CI users. Fusion ranges were measured by simultaneous, dichotic presentation of reference and comparison stimuli in opposite ears, and varying the comparison stimulus to find the range that fused with the reference stimulus. Factors examined included age at testing, degree of HL, amount of amplification, age of onset of HL, duration of HL without CI, and duration of HA, bimodal CI, and bilateral CI use. Preliminary analyses suggest that broad fusion is correlated with long durations of HA use; further analyses using multivariable models will be described. The findings will indicate how hearing device experience may influence binaural pitch fusion. [Work supported by NIH grant R01 DC013307.]

Listening-Related Fatigue in New and Experienced Adult Cochlear Implant Users.

Active listening in everyday settings is challenging and requires substantial mental effort, particularly in noisy settings. In some cases, effortful listening can lead to significant listening-related fatigue and negatively affect quality of life. However, our understanding of factors that affect the severity of fatigue is limited. Hearing aids and cochlear implants (CIs) can improve speech understanding and thus, potentially, reduce listening effort and fatigue. Some research supports this idea for adult hearing aid users with mild-to-moderate hearing loss, but similar work in CI users is very limited. This study examined (1) longitudinal changes in listening-related fatigue in new and established CI users, and (2) relationships between demographic and audiologic factors and preimplantation and postimplantation listening-related fatigue. Participants included an experimental group of 48 adult CI candidates receiving either a unilateral implant (n = 46) or simultaneous, bilateral implants (n = 2) and a control group of 96 experienced (>12 months experience) adult CI users (50 unilateral, 46 bilateral). Listening-related fatigue was evaluated using the 40-item version of the Vanderbilt Fatigue Scale for Adults. Experimental group ratings were obtained before implantation and again at 0.5-, 1-, 2-, 3-, 6-, and 12-month(s) postactivation. Control group participants completed the scale twice-upon study entry and approximately 3 months later. Additional measures, including a social isolation and disconnectedness questionnaire, hearing handicap inventory, and the Effort Assessment Scale, were also administered at multiple time points. The role of these measures and select demographic and audiologic factors on preimplant and postimplant fatigue ratings were examined. Adult CI candidates reported significantly more fatigue, greater self-perceived hearing handicap, greater listening effort, and more social isolation than experienced adult CI users. However, significant reductions in fatigue and effort were observed within 2 weeks postimplantation. By 3 months, there were no significant differences in fatigue, effort, hearing handicap, or social isolation between new CI recipients and experienced CI users. Secondary analyses revealed that age at onset of hearing loss (before or after 2 years of age) and subjective hearing handicap contributed significantly to the variance of preimplantation fatigue ratings (those with higher handicap reported higher fatigue). In contrast, variance in postimplantation fatigue ratings was not affected by age of hearing loss onset but was affected by gender (females reported more fatigue than males) and subjective ratings of effort, handicap, and isolation (those reporting more effort, handicap, and isolation reported more fatigue). Listening-related fatigue is a significant problem for many CI candidates, as well as for many experienced unilateral and bilateral CI users. Receipt of a CI significantly reduced listening-related fatigue (as well as listening effort, hearing handicap, and social isolation) as soon as 2 weeks post-CI activation. However, the magnitude of fatigue-related issues for both CI candidates and experienced CI users varies widely. Audiologic factors, such as hearing loss severity and aided speech recognition, were not predictive of individual differences in listening-related fatigue. In contrast, strong associations were observed between perceived hearing handicap and listening-related fatigue in all groups suggesting fatigue-related issues may be a component of perceived hearing handicap.

Importance of age at 2nd implantation and interimplant interval to the outcome of bilateral prelingually deafened pediatric cochlear implantation.

In Taiwan, the number of cases of sequential bilateral pediatric cochlear implantation (CI) is increasing but data regarding its effectiveness and impact of the reimbursement policy are lacking. We examined the speech perception and quality of life (QOL) of bilateral prelingually deaf children who underwent sequential CI, considering the effects of age at the time of second implantation and interimplant interval. We enrolled 124 Mandarin-speaking participants who underwent initial cochlear implant (CI1) in 2001-2019 and a second CI (CI2) in 2015-2020. Patients were followed up for ≥2 years and were categorized into groups based on age at the time of CI2 implantation (<3.5, 3.6-7, 7.1-10, 10.1-13, and 13.1-18 years) and interimplant interval (0.5-3, 3.1-5, 5.1-7, 7.1-10, and >10 years). We evaluated speech perception, device usage rates, and QOL using subjective questionnaires (Speech, Spatial, and Qualities of Hearing and Comprehension Cochlear Implant Questionnaire). Speech perception scores of CI2 were negatively correlated with ages at the time of CI1 and CI2 implantation and interimplant interval. Older age and a longer interimplant interval were associated with higher nonuse rates for CI2 and worse auditory performance and QOL. Among individuals aged >13 years with interimplant intervals >10 years, up to 44% did not use their second ear. Patients aged 7.1 to 10 years had better speech perception and higher questionnaire scores than those aged 10.1 to 13 and 13.1 to 18 years. Furthermore, patients aged 10.1 to 13 years had a lower rate of continuous CI2 usage compared to those aged 7.1 to 10 years. Timely implantation of CI2 is essential to achieve optimal outcomes, particularly among sequentially implanted patients with long-term deafness in the second ear and no improvement with hearing aids following CI1 implantation. For CI2 implantation, an upper limit of age of 10 years and interimplant interval of 7 years are essential to prevent suboptimal outcomes. These data can provide useful information to implant recipients, their families, and medical and audiological professionals, enabling a comprehensive understanding of the benefits and potential impacts of the timing of CI2 implantation.

Late Bilateral Sequential Cochlear Implant and Quality of Life.

Introduction Hearing impairment is one of the main disorders that can interfere with the development of speech and language. In an individual, it can cause significant communication difficulties, social isolation, negative feelings, and depressive disorders. The hearing aids (HAs) and cochlear implant (CI) are options for profound and severe hearing loss, and the CI can be indicated for individuals who do not obtain benefits from HAs. Objective To evaluate the quality of life of individuals who underwent sequential bilateral CIs with a long surgical interval between procedures. Methods Fifteen patients, aged 8 to 70 years old, who underwent sequential bilateral CI, with an interval ≥ 4 years between surgeries, were evaluated. Quality of life was evaluated using three questionnaires: WHOQOL-BREF, SSQ-12 and HHIA in Portuguese. Results The WHOQOL-BREF questionnaire showed that the study participants had a good quality of life in all domains assessed. According to the SSQ-12, few reported inability to listen in communication situations. Most individuals were classified as having medium disability by the HHIA, but the social and emotional effects did not significantly affect the quality of life. Conclusion The use of questionnaires to assess the quality of life of patients with hearing impairment is a valuable tool to measure adaptation to CI. Patients undergoing bilateral sequential CI, even with a long interval between procedures, presented high indices of quality of life.

Cochlear Implantation Outcomes in Pediatric Unilateral Hearing Loss: Impact of Device Use and Direct Input.

To investigate the impact of daily cochlear implant (CI) use on speech perception outcomes among children with unilateral hearing loss (UHL). Multi-institutional retrospective case series of pediatric patients with UHL who underwent CI between 2018 to 2022. Three tertiary children's hospitals. Demographics were obtained including duration of deafness and age at CI. Best consonant-nucleus-consonant (CNC) word scores and data logs describing hours of CI usage were assessed postimplantation. Use of direct audio input (DAI) during rehabilitation was recorded. Twenty-seven children were included, with a mean age at CI of 7.8 years. Mean datalogging time was 7.8 ± 3.0 hours/day. 40.7% of children utilized daily DAI. The mean CNC score using the best score during the study period was 34.9%. There was no significant correlation between hours of CI usage and CNC score. There was a significant improvement in CNC score associated with whether the child used DAI during rehabilitation (CNC 50.91% [yes] vs 23.81% [no]), which remained significant when adjusting for age at CI, duration of deafness, and data log hours. Unlike children with bilateral hearing loss and CI, children with UHL and CI demonstrate no significant correlation between hours of daily CI usage and CNC scores. However, children who used DAI during postoperative rehabilitation achieved significantly higher CNC scores than those who did not. This suggests that rehabilitation focused on isolated listening with the implanted ear maybe critical in optimizing outcomes with CI in UHL patients.

Psychophysical and Electrophysiological Parameters of the Auditory Analyzer as Indicators of the Effectiveness of Cochlear Implantation in Children with Bilateral Deafness

Background. The results of rehabilitation of patients with deafness after cochlear implantation (CI) depends on many factors related on both the individual characteristics of the patient and the technical parameters of auditory nerve stimulation — fitting of the CI system processor. Article presents the results of a study of the relationship between psychophysical (subjective) auditory sensations and electrophysiological (objective) responses of the structures of the auditory analyzer to electrical stimulation. Aims — to evaluate the relationship between the electrophysiological responses of the auditory analyzer and the psychophysical parameters of the thresholds of sound perception and speech intelligibility in patients with deafness after CI. Methods. The study involved 88 patients with IV bilateral sensorineural hearing loss, borderline with deafness, aged 6 to 17 years 11 months, among whom 54.5% (n = 48) of girls and 45.5% (n = 40) of boys. Of the patients included in the follow-up, 40% (n = 35) underwent unilateral CI; 60% (n = 53) of children underwent bilateral sequential CI. In our study, slightly more than half of the patients (51.1%) had experience using the CI system for more than 5 years. At the first stage of the study, we studied the relationship between sound perception thresholds (tonal audiometry in a free field) and registered ASSR (auditory steady state response) thresholds in patients with deafness receiving rehabilitation after CI surgery. The relationship between behavioral and electrophysiological (objective) thresholds was assessed by comparing the results of tonal threshold audiometry and the responses received during ASSR registration to acoustic stimulation in a free field. At the second stage, patients with indications for processor fitting (decreased speech intelligibility, uncomfortable sensations) underwent speech audiometry, evoked compound action potentials (ECAP) registration, according to the results of which the parameters of the CI processor were changed. Results. Research data showed the effectiveness of the approach of including the ECAP registration test, followed by the creation of a fitting card and correction of the level of auditory nerve stimulation under the control of speech audiometry in the protocol of fitting the CI processor. Conclusions. The results of the conducted studies allow us to recommend the use of the developed method of objective recording of sound perception thresholds in patients with CI as one of the indicators of the effectiveness of CI in the early period of auditory-speech rehabilitation in patients with undeveloped speech skills and when it is impossible to conduct objective tests accompanied by supra-threshold stimulation of the auditory nerve.

Language, cognitive, and speech in noise perception abilities of children with cochlear ımplants: a comparative analysis by implantation period and bilateral versus unilateral cochlear implants

PurposeThe purpose of this study was to compare the language, cognitive, and speech in noise (SiN) perception abilities of children with cochlear implants (CIs) to those of their peers with NH by grouping them according to their implantation period (12–18 months/19–24 months) and unilateral/bilateral CI use.MethodsThe sample comprised 50 children with cochlear implants (CIs) and 20 children with normal hearing (NH), ages 6–9 years. Children’s language, cognitive, and speech in noise (SiN) perception skills were assessed.ResultsChildren with CIs between 12 and 18 months and 19 and 24 months performed more poorly than children with NH on language, verbal memory (VM), verbal-short-term memory (V-STM), verbal working memory (V-WM), rapid naming, and speech in noise (SiN) perception abilities measures (p < 0.001). In addition, children with CIs between 19 and 24 months performed worse on rapid naming and V-WM tasks than children with CIs between 12 and 18 months (p < 0.017). Children with unilateral and bilateral CI performed more poorly than children with NH on language, VM, V-STM, V-WM, rapid naming, and SiN perception abilities assessments (p < 0.001). Additionally children with unilateral CI users performed poorly than children with bilateral CI users on SiN perception (p < 0.017).ConclusionsIn children with congenital hearing loss (CHL), cochlear implantation between 12 and 18 months or sequential bilateral implantation is not sufficient for these children to perform like their NH peers in language, cognitive, and SiN perception abilities. In addition, intervention approaches should focus not only on increasing language skills, but also on cognitive abilities.

Intraoperative Difficulties and Postoperative Complications Associated With Cochlear Implantations: A Study From Erbil City.

Background and objective Cochlear implants are highly effective for the treatment of severe to profound hearing loss. Cochlear implant surgery is a safe surgical procedure; however, due to many modifications over the years, it has been associated with certain minor and major complications. This study aimed to examine the intraoperative difficulties and postoperative complications in patients who received cochlear implants in Erbil City. Methods We conducted a retrospective descriptive study regarding complications of cochlear implants involving patients who received unilateral or bilateral cochlear Implants at the Rizgary Teaching Hospital and aprivate hospitalin Erbil City from January 2013 to July 2022. Their medical records were analyzed, and data on demographics, intraoperative difficulties, and postoperative complications were gathered. Results A total of 160 patients with cochlear implants (87 male, 54.4%; 73 female, 45.6%) were included in the study. The mean age of the patientsat the time of operation was6.76 ± 8.02 years (range: 1-53 years); 150 of these patients were children and 10 were adults (18 years and above). Intraoperative difficulties occurred in five patients (3.1%). The overall rate of complication was 10%, 7.5% of which was minor(the most common being wound infection) and 2.5%major(the most frequent being device extrusion). Conclusions Cochlear implant surgery is a safeprocedure performed to treat profoundly deaf patients. It is associatedwith a low rate of complications, most of which can be successfully managed with conservative measures or minimal intervention.

Variability in Receptive Language Development Following Bilateral Cochlear Implantation.

The primary aim was to investigate the variability in language development in children aged 5-7.5 years after bilateral cochlear implantation (CI) up to the age of 2 years, and any impact of the age at implantation and additional noncognitive or anatomical disorders at implantation. Data of 84 congenitally deaf children that had received simultaneous bilateral CI at the age of ≤ 24 months were included in this retrospective study. The results of language comprehension acquisition were evaluated using a standardized German language acquisition test for normal hearing preschoolers and first graders. Data on speech perception of monosyllables and sentences in quiet and noise were added. In a monosyllabic test, the children achieved a median performance of 75.0 ± 12.88%. In the sentence test in quiet, the median performance was 89 ± 12.69%, but dropped to 54 ± 18.92% in noise. A simple analysis showed a significant main effect of age at implantation on monosyllabic word comprehension (p < .001), but no significant effect of comorbidities that lacked cognitive effects (p = .24). Language acquisition values correspond to the normal range of children with normal hearing. Approximately 25% of the variability in the language acquisition tests is due to the outcome of the monosyllabic speech perception test. Congenitally deaf children who were fitted bilaterally in the 1st year of life can develop age-appropriate language skills by the time they start school. The high variability in the data is partly due to the age of implantation, but additional factors such as cognitive factors (e.g., working memory) are likely to influence the variability.

Localization of Low- and High-Frequency Sounds in Cochlear Implant Recipients Using a Contralateral Hearing Aid.

The ability to localize sounds is partly recovered in patients using a cochlear implant (CI) in one ear and a hearing aid (HA) on the contralateral side. Binaural processing seems effective at least to some extent, despite the difference between electric and acoustic stimulation in each ear. To obtain further insights into the mechanisms of binaural hearing in these listeners, localization of low- and high-frequency sounds was tested. The study used a within-subject design, where participants were tasked with localizing sound sources in the horizontal plane. The experiment was conducted in an anechoic chamber, where an array of seven loudspeakers was mounted along the 24 azimuthal angle span from -90° to +90°. Stimuli were applied with different frequencies: broadband noise and high- and low-frequency noise. Ten CI recipients participated in the study. All had an asymmetric hearing loss with a CI in the poorer ear and an HA on the contralateral side. Accuracy of sound localization in terms of angular error and percentage of correct localization scores. The median angular error was 40° in bimodal conditions for both broadband noise and high-frequency noise stimuli. The angular error increased to 47° for low-frequency noise stimuli. In the unilaterally aided condition with an HA, only a median angular error of 78° was observed. Irrespective of the frequency composition of the stimuli, this group of bimodal listeners showed some ability to localize sounds. Angular errors were larger than those reported in the literature for bilateral CI users or single-sided deaf listeners with a CI. In the unilateral listening condition with HA, only localization of sounds was not possible for most subjects.

Review of Binaural Processing With Asymmetrical Hearing Outcomes in Patients With Bilateral Cochlear Implants.

Bilateral cochlear implants (BiCIs) result in several benefits, including improvements in speech understanding in noise and sound source localization. However, the benefit bilateral implants provide among recipients varies considerably across individuals. Here we consider one of the reasons for this variability: difference in hearing function between the two ears, that is, interaural asymmetry. Thus far, investigations of interaural asymmetry have been highly specialized within various research areas. The goal of this review is to integrate these studies in one place, motivating future research in the area of interaural asymmetry. We first consider bottom-up processing, where binaural cues are represented using excitation-inhibition of signals from the left ear and right ear, varying with the location of the sound in space, and represented by the lateral superior olive in the auditory brainstem. We then consider top-down processing via predictive coding, which assumes that perception stems from expectations based on context and prior sensory experience, represented by cascading series of cortical circuits. An internal, perceptual model is maintained and updated in light of incoming sensory input. Together, we hope that this amalgamation of physiological, behavioral, and modeling studies will help bridge gaps in the field of binaural hearing and promote a clearer understanding of the implications of interaural asymmetry for future research on optimal patient interventions.

Previous binaural experience supports compensatory strategies in hearing-impaired children's auditory horizontal localization.

This study investigates auditory localization in children with a diagnosis of hearing impairment rehabilitated with bilateral cochlear implants or hearing aids. Localization accuracy in the anterior horizontal field and its distribution along the angular position of the source were analyzed. Participants performed a localization task in a virtual environment where they could move their heads freely and were asked to point to an invisible sound source. The source was rendered using a loudspeaker set arranged as a semi-circular array in the horizontal plane. The participants' head positions were tracked while their hands pointed to the auditory target; the preferred listening position and the onset of active strategies involving head movement were extracted. A significant correlation was found between age and localization accuracy and age and head movement in children with bilateral hearing aids. Investigating conditions where no, one, or both hearing devices were turned off, it was found that asymmetrical hearing caused the largest errors. Under this specific condition, head movement was used erratically by children with bilateral cochlear implants who focused on postures maximizing sound intensity at the more sensitive ear. Conversely, those with a consolidated binaural hearing experience could use dynamic cues even if one hearing aid was turned off. This finding may have implications for the clinical evaluation and rehabilitation of individuals with hearing impairments.