Evidence for a right cochlear implant advantage in simultaneous bilateral cochlear implantation

The Best Users of Cochlear Implants

The aim of this descriptive-analytical study was to compare the categories of auditory performance (CAP) and speech intelligibility rating (SIR) in people with cochlear implants (CI) based on the implanted ear. CAP and SIR were evaluated in 184 people with CI of right (110) and left (74) ears every 6 to 24 months (6,12,18,24). The significance level was less than 0.05. People with CI in the right-ears had better mean CAP and SIR scores than the left-ears (P values6,12,18, 24= 0.001, 0.004, 0.004, 0.002, and 0.001, 0.010, 0.010, 0.006). There were the relationship between the means of language acquisition status at the time of surgery and the means of CAP and SIR scores (P values6,12,18, 24= 0.005, 0.031, 0.006, 0.019, and 0.000, 0.000, 0.000, 0.002). The highest mean SIR scores were found in people with high school education (P values6,12,18, 24= 0.000, 0.000, 0.000, 0.008). The means of CAP scores did not show a relationship with the level of education (P values6, 12, 18, 24= 0.388, 0.217, 0.297, 0.213).  Mean SIR and CAP scores were not related to gender. People who received right ear prostheses after the language learning age and have a higher level of education are the best users of cochlear implants. Compared to others who do not have these facilities, they gain more ability in auditory-speech skills. Gender, does not affect these capabilities.

Association between lateral wall electrode array insertion parameters and audiological outcomes in bilateral cochlear implantation

Purpose

The aims of this study were to compare speech recognition at different postoperative times for both ears in bilaterally implanted patients and to assess the influence of the time of deafness, frequency-to-place mismatch, angular insertion depth (AID) and angular separation between neighbouring electrode contacts on audiometric outcomes.

Methods

This study was performed at an academic tertiary referral centre. A total of 19 adult patients (6 men, 13 women), who received sequential bilateral implantation with lateral wall electrode arrays, were analysed in retrospective. Statistical analysis was performed using two-sided t test, Wilcoxon test, median test, and Spearman’s correlation.

Results

Postlingually deafened patients (deafness after the age of 10) had a significantly better speech perception (WRS65[CI]) than the perilingually deafened subjects (deafness at the age of 1–10 years) (p < 0.001). Comparison of cochlear duct length between peri- and postlingually deafened subjects showed a slightly significantly smaller cochleae in perilingual patients (p = 0.045). No association between frequency-to-place mismatch as well as angular separation and speech perception could be detected. There was even no significant difference between the both ears in the intraindividual comparison, even if insertion parameters differed.

Conclusion

The exact electrode position seems to have less influence on the speech comprehension of CI patients than already established parameters as preoperative speech recognition or duration of deafness.

Side-of-Implantation Effect on Functional Asymmetry in the Auditory Cortex of Single-Sided Deaf Cochlear-Implant Users

Cochlear implants (CIs) allow to restore the hearing function in profoundly deaf individuals. Due to the degradation of the stimulus by CI signal processing, implanted individuals with single-sided deafness (SSD) have the specific challenge that the input highly differs between their ears. The present study compared normal-hearing (NH) listeners (N = 10) and left- and right-ear implanted SSD CI users (N = 10 left, N = 9 right), to evaluate cortical speech processing between CI- and NH-ears and to explore for side-of-implantation effects. The participants performed a two-deviant oddball task, separately with the left and the right ear. Auditory event-related potentials (ERPs) in response to syllables were compared between proficient and non-proficient CI users, as well as between CI and NH ears. The effect of the side of implantation was analysed on the sensor and the source level. CI proficiency could be distinguished based on the ERP amplitudes of the N1 and the P3b. Moreover, syllable processing via the CI ear, when compared to the NH ear, resulted in attenuated and delayed ERPs. In addition, the left-ear implanted SSD CI users revealed an enhanced functional asymmetry in the auditory cortex than right-ear implanted SSD CI users, regardless of whether the syllables were perceived via the CI or the NH ear. Our findings reveal that speech-discrimination proficiency in SSD CI users can be assessed by N1 and P3b ERPs. The results contribute to a better understanding of the rehabilitation success in SSD CI users by showing that cortical speech processing in SSD CI users is affected by CI-related stimulus degradation and experience-related functional changes in the auditory cortex.

Effect of auditory feedback on speech intelligibility of adults with cochlear implants

PURPOSE

Auditory feedback (AF) contributes to speech intelligibility (SI) which is vital in social interactions to examine AF effect on SI of adults with cochlear implant (CI). The relationship between age of CI implantation and AF on SI was examined as well.

METHOD

Twenty native Hebrew speaker pre-lingual adults with a hearing loss using CIs from ages 2 to 19 years. Participants were recorded reading excerpts from a book and word lists from MIDBAR test in two situations-with and without using their CIs. Sixteen judges listened to the recordings and rated the speech characteristics of the participants reading the excerpts using an adapted version of Speech Intelligibility Test and Intelligibility Questionnaire for Teachers.

RESULTS

Significant differences were found between the SI of words of those who received CI before and after 3 years. AF effect was found only for the older implantation group. The questionnaire indicates good reliability among all the speech characteristics. The speech characteristics most affected by the AF are the disruption of consonants followed by the varied degrees of intonation precision and nasality.

CONCLUSIONS

AF affects speech characteristics differently and is vital to SI. The use of the adapted version of Speech Intelligibility Test and Intelligibility Questionnaire for Teachers can be used clinically to assess SI and rehabilitation of young adults with CI. AF accessed at a younger age decreases the dependency on AF in later years.

The Acoustic Change Complex in Response to Frequency Changes and Its Correlation to Cochlear Implant Speech Outcomes

One of the biggest challenges that face cochlear implant (CI) users is the highly variable hearing outcomes of implantation across patients. Since speech perception requires the detection of various dynamic changes in acoustic features (e.g., frequency, intensity, timing) in speech sounds, it is critical to examine the ability to detect the within-stimulus acoustic changes in CI users. The primary objective of this study was to examine the auditory event-related potential (ERP) evoked by the within-stimulus frequency changes (F-changes), one type of the acoustic change complex (ACC), in adult CI users, and its correlation to speech outcomes. Twenty-one adult CI users (29 individual CI ears) were tested with psychoacoustic frequency change detection tasks, speech tests including the Consonant-Nucleus-Consonant (CNC) word recognition, Arizona Biomedical Sentence Recognition in quiet and noise (AzBio-Q and AzBio-N), and the Digit-in-Noise (DIN) tests, and electroencephalographic (EEG) recordings. The stimuli for the psychoacoustic tests and EEG recordings were pure tones at three different base frequencies (0.25, 1, and 4 kHz) that contained a F-change at the midpoint of the tone. Results showed that the frequency change detection threshold (FCDT), ACC N1' latency, and P2' latency did not differ across frequencies (p > 0.05). ACC N1'-P2 amplitude was significantly larger for 0.25 kHz than for other base frequencies (p < 0.05). The mean N1' latency across three base frequencies was negatively correlated with CNC word recognition (r = -0.40, p < 0.05) and CNC phoneme (r = -0.40, p < 0.05), and positively correlated with mean FCDT (r = 0.46, p < 0.05). The P2' latency was positively correlated with DIN (r = 0.47, p < 0.05) and mean FCDT (r = 0.47, p < 0.05). There was no statistically significant correlation between N1'-P2' amplitude and speech outcomes (all ps > 0.05). Results of this study indicated that variability in CI speech outcomes assessed with the CNC, AzBio-Q, and DIN tests can be partially explained (approximately 16-21%) by the variability of cortical sensory encoding of F-changes reflected by the ACC.

Hearing Loss Is Associated with Increased Variability in Double Support Period in the Elderly

Hearing loss is a disabling condition that increases with age and has been linked to difficulties in walking and increased risk of falls. The purpose of this study is to investigate changes in gait parameters associated with hearing loss in a group of older adults aged 60 or greater. Custom-engineered footwear was used to collect spatiotemporal gait data in an outpatient clinical setting. Multivariable linear regression was used to determine the relationship between spatiotemporal gait parameters and high and low frequency hearing thresholds of the poorer hearing ear, the left ear, and the right ear, respectively, adjusting for age, sex, race/ethnicity, and the Dizziness Handicap Inventory–Screening version score. Worsening high and low frequency hearing thresholds were associated with increased variability in double support period. Effects persisted after adjusting for the effects of age and perceived vestibular disability and were greater for increases in hearing thresholds for the right ear compared to the left ear. These findings illustrate the importance of auditory feedback for balance and coordination and may suggest a right ear advantage for the influence of auditory feedback on gait.

Speech perception with simultaneous bilateral cochlear implants: Is there a unilateral predominance?

OBJECTIVES

To assess the audiological outcomes and speech performance among children with simultaneous bilateral cochlear implants (CIs).

METHODS

This was a retrospective case review of 41 patients with prelingual deafness who failed a hearing aid trial and received simultaneous bilateral CIs. Ear-specific responses in terms of pure tone average (PTA), speech reception thresholds (SRTs), and speech discrimination score (SDS) were recorded for both ears of all patients.

RESULTS

The PTA and SRT for the right and left CIs were comparable (P-value = 0.861 and P-value = 0.524, respectively). The SDS was slightly higher for the right ear, although it was not significantly different from that for the left ear (P-value = 0.375), yielding only a 2.42% difference.

CONCLUSION

We found no significant side preference in all assessment scores for children with simultaneous bilateral CIs. Therefore, we cautiously advise implanting the CI in the right ear in case of symmetrical hearing loss when other prognostic factors do not favor the left ear.

The Effect of Side of Implantation on the Cortical Processing of Frequency Changes in Adult Cochlear Implant Users

Cochlear implants (CI) are widely used in children and adults to restore hearing function. However, CI outcomes are vary widely. The affected factors have not been well understood. It is well known that the right and left hemispheres play different roles in auditory perception in adult normal hearing listeners. It is unknown how the implantation side may affect the outcomes of CIs. In this study, the effect of the implantation side on how the brain processes frequency changes within a sound was examined in 12 right-handed adult CI users. The outcomes of CIs were assessed with behaviorally measured frequency change detection threshold (FCDT), which has been reported to significantly affect CI speech performance. The brain activation and regions were also examined using acoustic change complex (ACC, a type of cortical potential evoked by acoustic changes within a stimulus), on which the waveform analysis and the standardized low-resolution brain electromagnetic tomography (sLORETA) were performed. CI users showed activation in the temporal lobe and non-temporal areas, such as the frontal lobe. Right-ear CIs could more efficiently activate the contralateral hemisphere compared to left-ear CIs. For right-ear CIs, the increased activation in the contralateral temporal lobe together with the decreased activation in the contralateral frontal lobe was correlated with good performance of frequency change detection (lower FCDTs). Such a trend was not found in left-ear CIs. These results suggest that the implantation side may significantly affect neuroplasticity patterns in adults.

[Dichotic speech recognition with cochlear implants]

BACKGROUND

Dichotic speech recognition of side-separated speech stimuli requires their central nervous processing and has been used since the 1950s in a variety of clinical settings.

OBJECTIVE

The objective of this study was to investigate the dichotic speech recognition of normal-hearing (NH) subjects, cochlear implant (CI) recipients with single-sided deafness (SSD), and bilateral CI (BilCI) recipients with the dichotic discrimination test according to Feldmann.

MATERIALS AND METHODS

The speech recognition of ten adult NH subjects, ten SSD CI recipients, and ten BilCI recipients was determined at 65 dB SPL or 65 dB SPL equivalent for monotic presentation of trisyllabic nouns of the Feldmann test (NH subjects: better ear, poorer ear; SSD CI recipients: NH ear, CI; BilCI recipients: better CI, poorer CI) and for dichotic, i.e., simultaneous side-separated, presentation.

RESULTS

The NH subjects showed significantly poorer speech recognition for dichotic presentation than for monotic presentation. Speech recognition of SSD CI recipients was significantly worse with the CI than with the NH ear for both monotic and dichotic presentation. For both presentation conditions, BilCI recipients obtained significantly lower speech recognition with the poorer CI compared to the better CI. With each of the two CI, BilCI recipients had significantly worse speech recognition for dichotic presentation than for monotic presentation.

CONCLUSION

All three study groups-NH subjects, SSD CI recipients, and BilCI recipients-were able to recognize dichotically presented speech with both ears. For SSD CI recipients, there was no negative effect of the CI on speech recognition with the NH ear for dichotic presentation.

Right Ear Advantage of Speech Audiometry in Single-sided Deafness

BACKGROUND

Postlingual single-sided deafness (SSD) is defined as normal hearing in one ear and severely impaired hearing in the other ear. A right ear advantage and dominance of the left hemisphere are well established findings in individuals with normal hearing and speech processing. Therefore, it seems plausible that a right ear advantage would exist in patients with SSD.

METHODS

The audiometric database was searched to identify patients with SSD. Results from the German monosyllabic Freiburg word test and four-syllabic number test in quiet were evaluated. Results of right-sided SSD were compared with left-sided SSD. Statistical calculations were done with the Mann-Whitney U test.

RESULTS

Four hundred and six patients with SSD were identified, 182 with right-sided and 224 with left-sided SSD. The two groups had similar pure-tone thresholds without significant differences. All test parameters of speech audiometry had better values for right ears (SSD left) when compared with left ears (SSD right). Statistically significant results (p < 0.05) were found for a weighted score (social index, 98.2 ± 4% right and 97.5 ± 4.7% left, p < 0.026), for word understanding at 60 dB SPL (95.2 ± 8.7% right and 93.9 ± 9.1% left, p < 0.035), and for the level at which 100% understanding was reached (61.5 ± 10.1 dB SPL right and 63.8 ± 11.1 dB SPL left, p < 0.022) on a performance-level function.

CONCLUSION

A right ear advantage of speech audiometry was found in patients with SSD in this retrospective study of audiometric test results.

Early auditory skills development in Mandarin speaking children after bilateral cochlear implantation

OBJECTIVES

The purpose of the present study was: (1) to investigate the early auditory preverbal behaviors of infants/toddlers with bilateral cochlear implants (BCI), and to compare their performance with that of unilateral cochlear implant (UCI) peers; (2) to investigate effects of age of implantation, education level of caregivers, living environment, and unaided behavioral threshold before operation on early auditory preverbal development.

METHODS

The evaluation material of the present study was the Mandarin version of the LittlEARS^® Auditory Questionnaire (LEAQ). Assessments were administrated at 0, 1, 2, 3, 6, 9, 12 and 24 months after cochlear implants (CIs) were switched on. A one-way ANOVA was used to analyze the differences of early auditory preverbal performance between each two contiguous test intervals. A two-sample t-test was used to analyze the difference of behaviors between infants/toddlers with BCI and UCI. Non-parametric tests were used to analyze the effects of potential affecting factors on auditory preverbal skills.

RESULTS

Nineteen subjects aging from 9 to 54 months (Mean = 22.7, SD = 13.7) were recruited in the study. At each evaluation time, the average scores of LEAQ were 4.58, 9.00, 16.00, 18.56, 22.00, 31.50, 29.67, and 34.35 respectively. The total score and semantic auditory behavior score increased significantly during the second months after CIs activation (the total score: LSD-t = 3.157, p = 0.030; semantic auditory behavior score: LSD-t = 1.972, p = 0.034). The score of BCI group was significantly higher than UCI group after 1, 3 and 6 months of CI use (1 month: t = 3.257, p = 0.002; 3 months: t = 5.042, p = 0.000; 6 months: t = 4.054, p = 0.000). Education level of caregivers had a positive effect on receptive auditory behavior (H = 6.538, p = 0.035) after CIs switched on for 3 months. The LEAQ performance was not significantly correlated with pre-operative behavioral threshold although they showed a trend of negative correlation in the first 3 months after activation.

CONCLUSION

The study indicated that infants and toddlers who underwent BCI had better auditory preverbal skills than their UCI peers. Higher caregivers' education level positively correlated with the early development of auditory preverbal skills. Better pre-operative behavioral threshold might also benefit early auditory preverbal skills development for BCI children.

Bilateral cochlear implants in children: Effects of auditory experience and deprivation on auditory perception

Spatial hearing skills are essential for children as they grow, learn and play. These skills provide critical cues for determining the locations of sources in the environment, and enable segregation of important sounds, such as speech, from background maskers or interferers. Spatial hearing depends on availability of monaural cues and binaural cues. The latter result from integration of inputs arriving at the two ears from sounds that vary in location. The binaural system has exquisite mechanisms for capturing differences between the ears in both time of arrival and intensity. The major cues that are thus referred to as being vital for binaural hearing are: interaural differences in time (ITDs) and interaural differences in levels (ILDs). In children with normal hearing (NH), spatial hearing abilities are fairly well developed by age 4-5 years. In contrast, most children who are deaf and hear through cochlear implants (CIs) do not have an opportunity to experience normal, binaural acoustic hearing early in life. These children may function by having to utilize auditory cues that are degraded with regard to numerous stimulus features. In recent years there has been a notable increase in the number of children receiving bilateral CIs, and evidence suggests that while having two CIs helps them function better than when listening through a single CI, these children generally perform worse than their NH peers. This paper reviews some of the recent work on bilaterally implanted children. The focus is on measures of spatial hearing, including sound localization, release from masking for speech understanding in noise and binaural sensitivity using research processors. Data from behavioral and electrophysiological studies are included, with a focus on the recent work of the authors and their collaborators. The effects of auditory plasticity and deprivation on the emergence of binaural and spatial hearing are discussed along with evidence for reorganized processing from both behavioral and electrophysiological studies. The consequences of both unilateral and bilateral auditory deprivation during development suggest that the relevant set of issues is highly complex with regard to successes and the limitations experienced by children receiving bilateral cochlear implants. This article is part of a Special Issue entitled .

Persistent Language Delay Versus Late Language Emergence in Children With Early Cochlear Implantation

PURPOSE

The purpose of the present investigation is to differentiate children using cochlear implants (CIs) who did or did not achieve age-appropriate language scores by midelementary grades and to identify risk factors for persistent language delay following early cochlear implantation.

MATERIALS AND METHOD

Children receiving unilateral CIs at young ages (12-38 months) were tested longitudinally and classified with normal language emergence (n = 19), late language emergence (n = 22), or persistent language delay (n = 19) on the basis of their test scores at 4.5 and 10.5 years of age. Relative effects of demographic, audiological, linguistic, and academic characteristics on language emergence were determined.

RESULTS

Age at CI was associated with normal language emergence but did not differentiate late emergence from persistent delay. Children with persistent delay were more likely to use left-ear implants and older speech processor technology. They experienced higher aided thresholds and lower speech perception scores. Persistent delay was foreshadowed by low morphosyntactic and phonological diversity in preschool. Logistic regression analysis predicted normal language emergence with 84% accuracy and persistent language delay with 74% accuracy.

CONCLUSION

CI characteristics had a strong effect on persistent versus resolving language delay, suggesting that right-ear (or bilateral) devices, technology upgrades, and improved audibility may positively influence long-term language outcomes.

Asymmetric Hearing During Development: The Aural Preference Syndrome and Treatment Options

Deafness affects ∼2 in 1000 children and is one of the most common congenital impairments. Permanent hearing loss can be treated by fitting hearing aids. More severe to profound deafness is an indication for cochlear implantation. Although newborn hearing screening programs have increased the identification of asymmetric hearing loss, parents and caregivers of children with single-sided deafness are often hesitant to pursue therapy for the deaf ear. Delayed intervention has consequences for recovery of hearing. It has long been reported that asymmetric hearing loss/single-sided deafness compromises speech and language development and educational outcomes in children. Recent studies in animal models of deafness and in children consistently show evidence of an "aural preference syndrome" in which single-sided deafness in early childhood reorganizes the developing auditory pathways toward the hearing ear, with weaker central representation of the deaf ear. Delayed therapy consequently compromises benefit for the deaf ear, with slow rates of improvement measured over time. Therefore, asymmetric hearing needs early identification and intervention. Providing early effective stimulation in both ears through appropriate fitting of auditory prostheses, including hearing aids and cochlear implants, within a sensitive period in development has a cardinal role for securing the function of the impaired ear and for restoring binaural/spatial hearing. The impacts of asymmetric hearing loss on the developing auditory system and on spoken language development have often been underestimated. Thus, the traditional minimalist approach to clinical management aimed at 1 functional ear should be modified on the basis of current evidence.

Clinical and logopaedic results of simultaneous and sequential bilateral implants in children with severe and/or profound bilateral sensorineural hearing loss: A literature review

This article carries out a literature review of the advantages and limitations of the simultaneous bilateral cochlear implantation (SCI) compared to those of the sequential bilateral cochlear implantation (SBCI) and the unilateral cochlear implantation (UCI). The variables analysed in said comparison are: safety and surgical technique, SCI incidence, effectiveness, impact of the inter-implant interval, costs and financing, impact on brain plasticity, impact on speech and language development, main benefits, main disadvantages and concerns, and predictive factors of prognosis. Although the results are not conclusive, all variables analysed seem to point towards observable benefits of SCI in comparison with SBCI or UCI. This tendency should be studied in more depth in multicentre studies with higher methodological rigour, more comprehensive samples and periods and other determining variables (age at the time of implantation, duration and degree of the hearing loss, rehabilitation methodologies used, family involvement, etc.).