Benefits Of Binaural Hearing Research Articles

Cochlear implantation for children with single-sided deafness: parents’ perspectives

ABSTRACT Historically, cochlear implantation is reserved for those with bilateral severe to profound hearing loss. However, indications have expanded to include Single-Sided Deafness (SSD) because of the known benefits of binaural hearing and the limitations of unilateral hearing, especially for children developing linguistic and cognitive skills. This study aimed to provide a qualitative perspective of lived experiences of children with SSD who use a cochlear implant (CI), as perceived and reported by their parents. An online questionnaire was developed and distributed to evaluate outcomes of cochlear implantation in children with SSD residing in New Zealand and the United States. Qualitative content analysis of open-ended questions identified themes, including: (1) motivating factors; (2) benefits of amplification; (3) challenges associated with the CI journey; and (4) advice to parents. Parents described benefits and challenges as a result of cochlear implantation, such as access to sound and academic and psychosocial development, as well as subjective improvements in spatial hearing, reduced listening fatigue, enhanced academic performance, and changes in quality of life. The difference that bilateral hearing makes to a child’s development is difficult to precisely define but parental insights offer valuable perspective to healthcare providers when considering what some consider an elective procedure.

Validation of the Pediatric Spatial Hearing Questionnaire.

Spatial hearing is necessary for adequate sound awareness and speech perception abilities; however, research indicates that children have difficulties on these spatial hearing tasks that affect functioning in their daily environment. The purpose of this study was to validate a pediatric version of the Spatial Hearing Questionnaire (P-SHQ) for determining binaural hearing benefits and spatial hearing ability in children. We recruited parents and guardians of 68 children ages kindergarten through eighth grade to participate. Parents completed the P-SHQ, the Speech, Spatial and Qualities of Hearing Scale-Parent version, and a demographic questionnaire. To determine the factor structure of the P-SHQ, we conducted an exploratory factor analysis and reliability was assessed by calculating correlation coefficients. Three factors emerged during factor analysis: Factor 1 = sound localization, Factor 2 = speech-in-noise perception, and Factor 3 = speech perception in quiet. The P-SHQ has good internal consistency reliability (α = .97), and high item-total correlations were found. The correlation between scores from the P-SHQ questionnaire and the SSQ-Spatial subscale questionnaire provides evidence for the construct validity of the P-SHQ. The P-SHQ is a reliable and valid questionnaire to assess spatial hearing ability in children. This quick-to-administer tool can be incorporated into audiological care to determine the spatial hearing skills of a child and assist in counseling, making it a valuable assessment for hearing health care professionals.

Unilateral crosstalk cancellation via bone conduction: Methods and evaluation

Bone conduction hearing aids (BCHAs) offer an alternative solution for individuals with outer or middle ear issues who cannot benefit from traditional air conduction hearing aids. However, the phenomenon of “crosstalk,” where sound intended for one ear is mistakenly transmitted to the other ear through bone conduction, presents a challenge. This unintended transmission may limit the benefits of binaural hearing that can be achieved using two BCHAs, such as accurately detecting a sound source's direction. In this article, we present a method to suppress “crosstalk” within the human head using an adaptive algorithm to control two audiometric bone transducers.•Our method involves positioning an error sensor at a location considered close to the cochlea, such as the ear canal or the mastoid, and utilizing an adaptive algorithm to estimate the crosstalk compensation filter. This filter generates an anti-signal, which is then transmitted to one of the two transducers, effectively cancelling the crosstalk.•To verify whether the crosstalk cancellation reaches the cochlea in the inner ear, we provide a procedure for measuring hearing thresholds with and without crosstalk cancellation. This acts as a subjective measure of the efficacy of our crosstalk cancellation method.By leveraging an adaptive algorithm, this approach provides personalized cancellation and has the potential to enhance the performance of binaural BCHAs.

The Benefit of Binaural Hearing Among Listeners with Sensorineural Hearing Loss

The performance of binaural processing may be disturbed in the presence of hearing loss, especially of sensorineural type. To assess the impact of hearing loss on speech perception in noise regarding binaural processing, series of speech recognition measurements in controlled laboratory conditions were carried out. The spatial conditions were simulated using dummy head recordings played back on headphones. The Intelligibility Level Difference (ILD) was determined by measuring the change in the speech reception thresholds (SRT) between two configurations of a masking signal source (N) and a speech source (S), namely the S0N90 condition (where numbers stand for angles in horizontal plane) and the co-located condition (S0N0). To disentangle the head shadow effect (better ear effect) from binaural processing in the brain, the difference between binaural and monaural S0N90 condition (so-called Binaural Intelligibility Level Difference, BILD) value was calculated. Measurements were performed with a control group of normal-hearing listeners and a group of sensorineural hearing-impaired subjects. In all conditions performance of the hearing-impaired listeners was significantly lower than normal-hearing ones, resulting in higher SRT values (3 dB difference in the S0N0 configuration, 7.6 dB in S0N90 and 5 dB in monaural S0N90). The SRT improvement due to the spatial separation of target and masking signal (ILD) was also higher in the control group (8.1 dB) than in hearing-impaired listeners (3.5 dB). Moreover, a significant deterioration of the binaural processing described by BILD was found in people with sensorineural deficits. This parameter for normal-hearing listeners reached a value of 3 to 6 dB (4.6 dB on average) and decreased more than two times in the hearing-impaired group to 1.9 dB on average (with a deviation of 1.4 dB). These findings could not be explained by individual average hearing threshold (standard in audiological diagnostics) only. The outcomes indicate that there is a contribution of suprathershold deficits and it may be useful to consider binaural SRT measurements in noise in addition to the pure tone audiometry resulting in better diagnostics and hearing aid fitting.

Cochlear implantation in single-sided deafness: a single-center experience of 138 cases.

Assess the outcomes in patients who underwent cochlear implant (CI) for single-sided deafness (SSD). All patients affected by SSD who underwent CI at Gruppo Otologico, Piacenza, from October 2012 to May 2022 with at least 6months of follow-up were selected in the study group. The analysis included subjective and objective measures performed pre-operative and up to 24months after surgery. Hearing threshold on both sides was evaluated with a weighted four-frequency average (PTA [0.5kHz + 1kHz + 2kHz + 4kHz]/4) on pure tone audiometry and speech audiometry (Speech Discrimination Score, SDS). The Speech Spatial and Qualities of Hearing scale (SSQ Questionnaire) for binaural hearing benefits and sound localization, the Tinnitus Handicap Inventory Questionnaire (THI) and Dizziness Handicap Inventory Questionnaire (DHI) were used for subjective assessment. Data from 138 patients, 69 males and 69 females, (mean age 49years, range 17-77years) underwent CI for SSD were examined. Single-sided hearing deprivation average before undergoing CI surgery was 2.5years (range 3months-35years). There was a significant reduction of THI and DHI scores compared to pre-operative scores alongside a referred improvement in social, physical, and emotional well-being through the SSQ questionnaire. To the best of our knowledge, this paper descried the largest cohort of SSD who underwent CI in a single institution. According to our findings CI in patients affected by SSD represents a valuable tool for an overall improvement of tinnitus and dizziness but also quality of life, after at least 6months of follow-up. Further studies are desirable to improve rehabilitation pathways and possibly set new standards of care of this condition.

Effect of cochlear implantation on speech recognition under different listening modes in children

Objective:To investigate speech recognition among children with a unilateral cochlear implant（CI）, bilateral CI, and bimodal hearing and identify the benefits of binaural hearing. Methods:A total of 67 children with severe sensorineural hearing loss who received bilateral CI, bimodal hearing, and unilateral CI from 2012 to 2021 were recruited, including 23 cases with unilateral CI, 25 cases of bimodal hearing, and 19 cases of bilateral CI. The aided hearing threshold at 250-4000 Hz and speech recognition performance of two-syllable words and short sentences in quiet and noisy environments were tested, respectively. Results:There was no significant difference in the hearing threshold results of the bilateral CI group, the bimodal hearing group, and the unilateral CI group by ANOVA（P>0.05）. According to the paired t-test within the group, the speech recognition of disyllabic words and short sentences in quiet and noisy environments were significantly different among the three groups（P<0.05）. There was no significant difference in the speech recognition rates of disyllabic words and short sentences among the three groups in a quiet environment（P>0.05）, but there was a statistically significant difference in a noisy environment（P<0.05）. Additional multiple linear regression analysis showed no significant difference in the recognition rates of disyllabic words and short sentences between the bimodal group and the bilateral CI group in quiet and noisy environments（β=-0.567, P>0.05; β=-0.643, P>0.05）. There was a statistically significant difference in speech recognition of disyllabic words and short sentences between the bimodal group and the unilateral CI group in the noise environment（β=-0.124, P<0.05）, but the difference was not statistically significant in a quiet environment（β=-0.671, P>0.05）; there was a statistically significant difference in the recognition rate of disyllabic words and short sentences between the bilateral CI group and the unilateral CI group in the noise environment（β=-0.226, P<0.05）, but the difference was not statistically significant in a quiet environment（β=-0.341, P>0.05）. Conclusion:Clinicians and guardians are encouraged to provide the most comprehensive audiological evaluation for children with hearing loss. Bilateral CI and bimodal hearing have demonstrated enormous advantages over unilateral CI regarding speech recognition in noise. Bimodal hearing deems a strong recommendation if the contralateral ear has sufficient speech recognition capability. Bilateral CI should be warranted if hearing aids deemed to be ineffective.

A Study of Event-Related Potentials During Monaural and Bilateral Hearing in Single-Sided Deaf Cochlear Implant Users.

Single-sided deafness (SSD) is characterized by a profoundly deaf ear and normal hearing in the contralateral ear. A cochlear implant (CI) is the only method to restore functional hearing in a profoundly deaf ear. In a previous study, we identified that the cortical processing of a CI signal differs from the normal-hearing ear (NHE) when directly compared using an auditory oddball paradigm consisting of pure tones. However, exactly how the brain integrates the electrical and acoustic signal is not well investigated. This study aims to understand how the provision of the CI in combination with the NHE may improve SSD CI users' ability to discriminate and evaluate auditory stimuli. Electroencephalography from 10 SSD-CI participants (4 participated in the previous pure-tone study) were recorded during a semantic acoustic oddball task, where they were required to discriminate between odd and even numbers. Stimuli were presented in four hearing conditions: directly through the CI, directly to the NHE, or in free field with the CI switched on and off. We examined task-performance (response time and accuracy) and measured N1, P2, N2N4, and P3b event-related brain potentials (ERPs) linked to the detection, discrimination, and evaluation of task relevant stimuli. Sound localization and speech in noise comprehension was also examined. In direct presentation, task performance was superior during NHE compared with CI (shorter and less varied reaction times [~720 versus ~842 msec], higher target accuracy [~93 versus ~70%]) and early neural responses (N1 and P2) were enhanced for NHE suggesting greater signal saliency. However, the size of N2N4 and P3b target-standard effects did not differ significantly between NHE and CI. In free field, target accuracy was similarly high with the CI (FF-On) and without the CI (FF-Off) (~95%), with some evidence of CI interference during FF-On (more variable and slightly but significantly delayed reaction times [~737 versus ~709 msec]). Early neural responses and late effects were also greater during FF-On. Performance on sound localization and speech in noise comprehension (S CI N NHE configuration only) was significantly greater during FF-On. Both behavioral and neural responses in the semantic oddball task were sensitive to CI in both direct and free-field presentations. Direct conditions revealed that participants could perform the task with the CI alone, although performance was suboptimal and early neural responses were reduced when compared with the NHE. For free-field, the addition of the CI was associated with enhanced early and late neural responses, but this did not result in improved task performance. Enhanced neural responses show that the additional input from the CI is modulating relevant perceptual and cognitive processes, but the benefit of binaural hearing on behavior may not be realized in simple oddball tasks which can be adequately performed with the NHE. Future studies interested in binaural hearing should examine performance under noisy conditions and/or use spatial cues to allow headroom for the measurement of binaural benefit.

Improved Low-Frequency Crosstalk Cancellation in Bone Conduction Using Bone Transducers and Probe Microphone

A bone conduction (BC) sound presented on either side of the head will travel to the cochleae in both ears, and this crosstalk phenomenon is considered one factor limiting the benefits of binaural hearing with BC. Previous studies have demonstrated the feasibility of measuring the phase and level required for crosstalk cancellation at the cochlea; however, given a human subject&#x2019;s inability to consistently detect low frequencies, this method is limited to cancellations at frequencies above 1000 Hz. This study describes an alternative approach for implementing a crosstalk cancellation system for low frequencies by measuring ear-canal sound pressure (ECSP). Since the ear canal is close to the cochlea, we hypothesized that altering ECSP in response to a BC stimulation may be used to achieve crosstalk cancellation at the cochlea. Our approach relies on ECSP measurements to estimate impulse responses (IRs) from bone transducers to a probe microphone in the ear canal. The IRs are then used to predict the phase and level required for crosstalk cancellation at the probe microphone&#x2019;s location. To confirm the hypothesis, we measured tone reception threshold (TRT), the lowest tone level participants could detect, under two conditions: with and without crosstalk cancellation. Although crosstalk cancellation was designed to occur at the probe microphone and not at the cochlea, the TRT results showed that participants were still able to perceive cancellations at frequencies below 1000 Hz.

Benefits of Cartilage Conduction Hearing Aids for Speech Perception in Unilateral Aural Atresia.

Severe conductive hearing loss due to unilateral aural atresia leads to auditory and developmental disorders, such as difficulty in hearing in challenging situations. Bone conduction devices compensate for the disability but unfortunately have several disadvantages. The aim of this study was to evaluate the benefits of cartilage conduction (CC) hearing aids for speech perception in unilateral aural atresia. Eleven patients with unilateral aural atresia were included. Each participant used a CC hearing aid in the atretic ear. Speech recognition scores in the binaural hearing condition were obtained at low speech levels to evaluate the contribution of aided atretic ears to speech perception. Speech recognition scores were also obtained with and without presentation of noise. These assessments were compared between the unaided and aided atretic ear conditions. Speech recognition scores at low speech levels were significantly improved under the aided atretic ear condition (p < 0.05). A CC hearing aid in the unilateral atretic ear did not significantly improve the speech recognition score in a symmetrical noise presentation condition. The binaural hearing benefits of CC hearing aids in unilateral aural atresia were predominantly considered a diotic summation. Other benefits of binaural hearing remain to be investigated.

An introductory overview of bimodal fitting

Background and Aim: In a bimodal fitting, one ear is stimulated acoustically with a hearing aid and the other is stimulated electrically with a cochlear implant. This paper provides a brief summary of the concept of bimodal fitting, binaural hearing and its importance, the hearing benefits of binaural hearing in bimodal fitting, candidacy and hearing aid adjustment in bimodal fitting cases. Recent Findings: Researches have shown that bimodal fitting offers a wide range of hearing benefits over unilateral cochlear implants, such as better speech perception in noise, better musical perception, and a better understanding of pitch and tone perception and naturalness of sound perception. Conclusion: Considering the binaural hearing advantages in bimodal fitting users, it can be concluded that users of unilateral cochlear implants who have measurable residual hearing in their non-implanted ear can use a hearing aid in that ear and enjoy binaural hearing advantages. The hearing aid should be fitted in a way to complement the information obtained through cochlear implantation. Keywords: Bimodal fitting; cochlear implant; binaural hearing

The Temporal Limits Encoder as a Sound Coding Strategy for Bilateral Cochlear Implants.

The difference in binaural benefit between bilateral cochlear implant (CI) users and normal hearing (NH) listeners has typically been attributed to CI sound coding strategies not encoding the acoustic fine structure (FS) interaural time differences (ITD). The Temporal Limits Encoder (TLE) strategy is proposed as a potential way of improving binaural hearing benefits for CI users in noisy situations. TLE works by downward-transposition of mid-frequency band-limited channel information and can theoretically provide FS-ITD cues. In this work, the effect of choice of lower limit of the modulator in TLE was examined by measuring performance on a word recognition task and computing the magnitude of binaural benefit in bilateral CI users. Performance listening with the TLE strategy was compared with the commonly used Advanced Combinational Encoder (ACE) CI sound coding strategy. Results showed that setting the lower limit to ≥200 Hz maintained word recognition performance comparable to that of ACE. While most CI listeners exhibited a large binaural benefit (≥6 dB) in at least one of the conditions tested, there was no systematic relationship between the lower limit of the modulator and performance. These results indicate that the TLE strategy has potential to improve binaural hearing abilities in CI users but further work is needed to understand how binaural benefit can be maximized.

Cost-effectiveness analysis of bilateral cochlear implants for children with severe-to-profound sensorineural hearing loss in both ears in Singapore.

A cochlear implant is a small electronic device that provides a sense of sound for the user, which can be used unilaterally or bilaterally. Although there is advocacy for the benefits of binaural hearing, the high cost of cochlear implant raises the question of whether its additional benefits over the use of an acoustic hearing aid in the contralateral ear outweigh its costs. This cost-effectiveness analysis aimed to separately assess the cost-effectiveness of simultaneous and sequential bilateral cochlear implantations compared to bimodal hearing (use of unilateral cochlear implant combined with an acoustic hearing aid in the contralateral ear) in children with severe-to-profound sensorineural hearing loss in both ears from the Singapore healthcare payer perspective. Incremental quality-adjusted life year (QALYs) gained and costs associated with bilateral cochlear implants over the lifetime horizon were estimated based on a four-state Markov model. The analysis results showed that, at the 2017 mean cost, compared to bimodal hearing, patients receiving bilateral cochlear implants experienced more QALYs but incurred higher costs, resulting in an incremental cost-effectiveness ratio (ICER) of USD$60,607 per QALY gained for simultaneous bilateral cochlear implantation, and USD$81,782 per QALY gained for sequential bilateral cochlear implantation. The cost-effectiveness of bilateral cochlear implants is most sensitive to utility gain associated with second cochlear implant, and cost of bilateral cochlear implants. ICERs increased when the utility gain from bilateral cochlear implants decreased; ICERs exceeded USD$120,000 per QALY gained when the utility gain was halved from 0.03 to 0.015 in both simultaneous and sequential bilateral cochlear implantations. The choice of incremental utility gain associated with the second cochlear implant is an area of considerable uncertainty.

Effect of channel separation and interaural mismatch on fusion and lateralization in normal-hearing and cochlear-implant listeners.

Bilateral cochlear implantation has provided access to some of the benefits of binaural hearing enjoyed by normal-hearing (NH) listeners. However, a gap in performance still exists between the two populations. Single-channel stimulation studies have shown that interaural place-of-stimulation mismatch (IPM) due to differences in implantation depth leads to decreased binaural fusion and lateralization of interaural time and level differences (ITDs and ILDs, respectively). While single-channel studies are informative, multi-channel stimulation is needed for good speech understanding with cochlear implants (CIs). Some multi-channel studies have shown that channel interaction due to current spread can affect ITD sensitivity. In this work, we studied the effect of IPM and channel spacing, along with their potential interaction, on binaural fusion and ITD/ILD lateralization. Experiments were conducted in adult NH listeners and CI listeners with a history of acoustic hearing. Results showed that IPM reduced the range of lateralization for ITDs but not ILDs. CI listeners were more likely to report a fused percept in the presence of IPM with multi-channel stimulation than NH listeners. However, no effect of channel spacing was found. These results suggest that IPM should be accounted for in clinical mapping practices in order to maximize bilateral CI benefits.

Early Speech Perception Test Outcome in Children with Severe Sensorineural Hearing Loss with Unilateral Cochlear Implants Alone versus Bimodal Stimulation.

Bilateral stimulation of the auditory system has clear advantages over unilateral hearing. Hearing-impaired children are, therefore, generally fitted with hearing aids in both ears so that they can have the benefits of binaural hearing. Children who use acochlear implant in one ear and no acoustic stimulation in the opposite ear are at a definite disadvantage. This study was undertaken to determine the advantages of bimodal stimulation in pediatric population especially in terms of speech recognition. This study comprised of 30 children between 3 and 6years of age with profound bilateral sensorineural hearing loss with cochlear implant in one ear and fitted with digital hearing aid in non-implanted ear. Speech recognition performance was compared in unilateral cochlear implant only and with bimodal hearing stimulation in the same set of children. A statistically significant difference was found between speech reception scores in children with a unilateral cochlear implant only and those with a cochlear implant in one ear and a hearing aid in the non implanted ear in quiet surroundings. It is suggested that the use of bimodal fitting be considered as an effective management method to obtain the advantage of binaural hearing in children who undergo unilateral cochlear implantation.

Dichotic listening performance and listening effort for asymmetrical inputs

Binaural hearing typically improves speech understanding in difficult listening situations. Cochlear-implant (CI) recipients seek to gain binaural hearing benefits through bilateral implantation. However, the standard of care is currently sequential implantation, possibly with a long difference in the duration of deafness between the ears. Sequential implantation may cause interaural asymmetry in the quality of the signal, which could limit binaural benefits. A range of bilateral CI listeners, from those who experience binaural benefits to those who demonstrate interference, were recruited for this experiment. Listeners attended to one ear and reported digits heard in monotic and dichotic conditions. Perceptual performance and listening effort (via pupillometry) were measured. A control group of normal-hearing listeners were tested and were presented unprocessed, four-, and eight-channel vocoded digits, and the processing was independent across ears. It was hypothesized that attending to a poorer-quality signal in the presence of a better-quality signal would lead to poorer performance than in the monotic condition. Pupillometry was hypothesized to reflect the listener’s ability to perceive the poorer-quality signal in the presence of a better-quality signal. Results will inform strategies to maximize binaural hearing in bilateral CI listeners.

Horizontal Localization in Simulated Unilateral Hearing Loss.

Background and ObjectivesThe ability to localize a sound source is one of the binaural hearing benefits in a horizontal plane based on interaural time difference and interaural intensity difference. Unilateral or bilateral asymmetric hearing loss will affect binaural hearing and lead to sound locating errors. In this cross sectional analytical descriptive study, the localization error was investigated when participants turned their heads to the sound source with closed eyes and after simulating unilateral hearing loss by placing earplugs inside the right ear canal. Subjects and MethodsThis cross sectional analytical descriptive study was carried out on 30 right-handed adults, 22 female and 8 male (average: 25 years, standard deviation: 3.16). They were selected with the available random access method. Horizontal localization was evaluated with five speakers located at 0, ±30, and ±60 degree azimuths at a 1-meter distance from the examinee. Narrow-band noise signals were delivered at 35 dB SL in two “without earplug” and “with earplug” situations and the results were compared. The study was performed between September and December 2016 in Tehran, Iran. ResultsSignificant differences were observed in localization errors between the “with earplug” and “without earplug” situations. The localization differences were greater for left-side speakers (-30 and -60 degrees) compared with right-side speakers (+30 and +60 degrees). The differences were more apparent at 4,000 and 6,000 Hz, which confirmed the effect of unilateral simulated hearing loss on interaural latency differences. ConclusionsSimulating hearing loss by using an earplug in one ear (right) increased localization errors at all frequencies. The errors increased at higher frequencies.

Pre- and Postoperative Binaural Unmasking for Bimodal Cochlear Implant Listeners.

Cochlear implants (CIs) are increasingly recommended to individuals with residual bilateral acoustic hearing. Although new hearing-preserving electrode designs and surgical approaches show great promise, CI recipients are still at risk to lose acoustic hearing in the implanted ear, which could prevent the ability to take advantage of binaural unmasking to aid speech recognition in noise. This study examined the tradeoff between the benefits of a CI for speech understanding in noise and the potential loss of binaural unmasking for CI recipients with some bilateral preoperative acoustic hearing. Binaural unmasking is difficult to evaluate in CI candidates because speech perception in noise is generally too poor to measure reliably in the range of signal to noise ratios (SNRs) where binaural intelligibility level differences (BILDs) are typically observed (<5 dB). Thus, a test of audiovisual speech perception in noise was employed to increase performance to measureable levels. BILDs were measured preoperatively for 11 CI candidates and at least 5 months post-activation for 10 of these individuals (1 individual elected not to receive a CI). Audiovisual sentences were presented in speech-shaped masking noise between -10 and +15 dB SNR. The noise was always correlated between the ears, while the speech signal was either correlated (N0S0) or inversely correlated (N0Sπ). Stimuli were delivered via headphones to the unaided ear(s) and, where applicable, via auxiliary input to the CI speech processor. A z test evaluated performance differences between the N0S0 and N0Sπ conditions for each listener pre- and postoperatively. For listeners showing a significant difference, the magnitude of the BILD was characterized as the difference in SNRs required to achieve 50% correct performance. One listener who underwent hearing-preservation surgery received additional postoperative tests, which presented sound directly to both ears and to the CI speech processor. Five of 11 listeners showed a significant preoperative BILD (range: 2.0 to 7.3 dB). Only 2 of these 5 showed a significant postoperative BILD, but the mean BILD was smaller (1.3 dB) than that observed preoperatively (3.1 dB). Despite the fact that some listeners lost the preoperative binaural benefit, 9 out of 10 listeners tested postoperatively had performance equal to or better than their best pre-CI performance. The listener who retained functional acoustic hearing in the implanted ear also demonstrated a preserved acoustic BILD postoperatively. Approximately half of the CI candidates in this study demonstrated preoperative binaural hearing benefits for audiovisual speech perception in noise. Most of these listeners lost their acoustic hearing in the implanted ear after surgery (using nonhearing-preservation techniques), and therefore lost access to this binaural benefit. In all but one case, any loss of binaural benefit was compensated for or exceeded by an improvement in speech perception with the CI. Evidence of a preoperative BILD suggests that certain CI candidates might further benefit from hearing-preservation surgery to retain acoustic binaural unmasking, as demonstrated for the listener who underwent hearing-preservation surgery. This test of binaural audiovisual speech perception in noise could serve as a diagnostic tool to identify CI candidates who are most likely to receive functional benefits from their bilateral acoustic hearing.

Sound localization performance in children with cochlear implants using bimodal stimulation

Introduction: There are clear benefits of having bilateral inputs to the auditory nervous system. Hearing-impaired children are, therefore, generally fitted with two hearing aids so that they can benefit from hearing binaurally. Children who use a cochlear implant in one ear and no amplification in the opposite ear are, however, deprived of these advantages. The current study was undertaken to determine the benefits of bimodal stimulation in pediatric population. Methods and Materials: This study comprised of 20 children between 6-11 years of age with profound bilateral sensorineural hearing loss with cochlear implant in one ear and fitted with digital hearing aid in non-implanted ear. Mean sound localization score was compared in children with cochlear implant only and those with both cochlear implant and hearing aid. Result: A statistically significant difference was found between mean sound localization in both test condition under quiet surrounding. Conclusion: Hence it is suggested that the use of bimodal fitting can be considered as an effective management option in order to obtain binaural hearing benefits in children who undergo unilateral cochlear implantation.

Effect of cochlear implantation on sound localization for patients with unilateral sensorineural hearing loss

The aim of this review was to examine the current literature regarding application of cochlear implantation on patients with unilateral sensorineural hearing loss (USNHL) for improvement on sound localization. The literature were searched in the PubMed database with 'cochlear implantation AND single-sided deafness' or 'cochlear implantation AND unilateral deafness' as keywords. The publication date of the articles was up to 2015-2-12. A total of 12 articles were included. The results show that the ability of sound localization for most of the USNHL subjects (90%) with cochlear implantation was significantly improved than that without CI, which suggests that CI is a superior auditory rehabilitation treatment than BAHA and CROS hearing aids for patients with USNHL, because of the re-establishment of the benefits of binaural hearing. In addition, the benefit of CI for USNHL requires a period of auditory experience or training. About 30% subjects showed significantly improvement on sound localization ability after CI worked for three months. For most of the patients (90%), the sound localization ability improved after CI worked for six months. When CI worked for nine months, all the subjects would show improvement on sound localization ability. Sound localization of the USNHL subjects with a CI is based primarily on interaural level differences (ILD) while interaural time differences (ITD) provide little advantage or probably not perceptible at all. The younger subject suffers from USNHL, the stronger the plasticity of the auditory center shows, which results in more obvious degeneration of the affected side and adaptive enhancement of the contralateral side of the auditory pathway. Similarly, the longer duration of USNHL lead to more obvious degeneration of the affected side and adaptive enhancement of the contralateral side. An adaptive enhancement of auditory pathway corresponding to the healthy ear will rely more on the monaural spatial cues that available to the intact ear to improve the sound localization in the horizontal plane. Contrarily, the degeneration of auditory pathway corresponding to the USNHL may be limited to re-reorganize from auditory deprivation even after CI, which may increase the risk that a few subjects cannot re-establish the binaural benefits after CI. Therefore, patients with USNHL should accept CI as soon as possible to obtain good binaural benefits, especially for sound localization.

Cochlear implantation in children with congenital unilateral deafness: Mid-term follow-up outcomes

ObjectivesAlthough cochlear implantation is widely used to treat unilateral deafness in adults, very little literature exists on its use and effects on the paediatric population. This report adds to the literature showing the mid-term follow-up outcomes achieved by these children. Material and methodsThree children with congenital unilateral deafness were studied after implantation. Speech perception in noise, and sound localization ability were evaluated using age-appropriate materials. ResultsThe preliminary data of our small group of 3 children with congenital unilateral profound hearing loss revealed that up to 3 years post-implantation, congenitally deaf children who received a cochlear implant after 4 years of age do not demonstrate binaural hearing benefits. ConclusionEarly intervention in the prelingual phase may be crucial for the development of binaural hearing.