Sound localization with bilateral bone conduction devices

Over three-year outcomes of Bonebridge implantation in children and adolescents with congenital bilateral conductive hearing loss

OBJECTIVE

Investigation of the long-term performance and safety of Bonebridge in children and adolescents with congenital bilateral conductive hearing loss (BCHL) over 3 years post-implantation.

METHODS

20 children and adolescents diagnosed with congenital BCHL underwent Bonebridge implantation over 36 months were enrolled. Preoperative and final follow-up pure-tone average (PTA) results were recorded, and whether postoperative complications occurred. All patients tested under two listening conditions: (1) unaided, (2) Bonebridge aided. The speech reception thresholds (SRTs), speech discrimination scores (SDSs) and sound field hearing thresholds (SFHTs) were measured. The mean absolute error (MAE) of sound source localization was calculated to assess the sound localization accuracy.

RESULTS

The median age of 20 patients underwent Bonebridge implantation was 9 years old, and follow-up time was 55 months. There were no difference in PTA air conduction and bone conduction between preoperative with postoperative. The performance in SRTs, SDSs and SFHTs were significantly higher in the Bonebridge aided condition than that in the unaided. Concerning sound source localization, the accuracy of localization exhibited a sharp decline when using a single side Bonebridge. However, their sound localization abilities on the Bonebridge implantation same side remained unaffected. One patient had implant exposure, and completed the experiment with the exposed Bonebridge, then underwent a revision surgery. All other complications were resolved by conservative treatment.

CONCLUSION

The performance and safety of Bonebridge were established in children and adolescents with congenital BCHL over 3 years post-implantation.

Evaluating binaural hearing capabilities in individuals with sensorineural hearing loss through bilateral bone conduction stimulation

This study investigated the impact of bilateral bone conduction (BC) stimulation and sensorineural hearing loss on spatial release from masking, binaural intelligibility level difference, and lateralization. The study involved two groups of adults with mild to moderate sensorineural hearing loss: one group of 21 participants with symmetric hearing loss and another group of nine participants with asymmetric hearing loss. All tests were conducted through BC and air conduction (AC) headsets with non-individualized virtual positions of the sound sources and linear amplification based on individual hearing thresholds. The findings revealed a bilateral benefit for both groups of hearing-impaired individuals, with symmetric hearing loss yielding better results than asymmetric hearing loss. AC stimulation provided approximately twice the benefit in terms of dB compared to BC stimulation. A large part of this benefit originated from a favorable signal-to-noise ratio due to noise reduction from the head shadow. However, binaural processing was present in both hearing-impaired groups with bilateral BC stimulation. The ability to lateralize sounds based on interaural time delays was significantly impaired in participants with both types of hearing loss when stimulation was by BC. Despite these challenges, the study underscores the benefits of bilateral fitting of BC hearing aids, even in individuals with mild to moderate sensorineural hearing loss, whether symmetric or asymmetric.

The Merits of Bilateral Application of Middle Ear Implants in Patients With Bilateral Conductive and/or Mixed Hearing Loss

This study investigated sound localization abilities in patients with bilateral conductive and/or mixed hearing loss (BCHL) when listening with either one or two middle ear implants (MEIs). Sound localization was measured by asking patients to point as quickly and accurately as possible with a head-mounted LED in the perceived sound direction. Loudspeakers, positioned around the listener within a range of +73°/-73° in the horizontal plane, were not visible to the patients. Broadband (500 Hz-20 kHz) noise bursts (150 ms), roved over a 20-dB range in 10 dB steps was presented. MEIs stimulate the ipsilateral cochlea only and therefore the localization response was not affected by crosstalk. Sound localization was better with bilateral MEIs compared with the unilateral left and unilateral right conditions. Good sound localization performance was found in the bilaterally aided hearing condition in four patients. In two patients, localization abilities equaled normal hearing performance. Interestingly, in the unaided condition, when both devices were turned off, subjects could still localize the stimuli presented at the highest sound level. Comparison with data of patients implanted bilaterally with bone-conduction devices, demonstrated that localization abilities with MEIs were superior. The measurements demonstrate that patients with BCHL, using remnant binaural cues in the unaided condition, are able to process binaural cues when listening with bilateral MEIs. We conclude that implantation with two MEIs, each stimulating only the ipsilateral cochlea, without crosstalk to the contralateral cochlea, can result in good sound localization abilities, and that this topic needs further investigation.

Evaluating the effectiveness of bone conduction hearing implants in rehabilitation of hearing loss

PURPOSE

Implantable hearing devices are indicated for candidates who could not benefit from conventional hearing aids. This study aimed at evaluating their effectiveness in rehabilitation of hearing loss.

METHODS

This study included patients who received bone conduction implants at Tertiary Teaching Hospitals, between December 2018 and November 2020. Data were collected prospectively, and patients were assessed both subjectively using COSI and GHABP questionnaires and objectively using bone conduction and air conduction thresholds, unaided and aided free field speech thresholds. Outcomes of transcutaneous (tBCHD) and percutaneous (pBCHD) bone conduction hearing devices were compared as well as outcomes of unilateral versus bilateral fitting. Postoperative skin complications were recorded and compared.

RESULTS

A total of seventy patients were included, thirty-seven of them were implanted with tBCHD and thirty-three with pBCHD. Fifty-five patients were fitted unilaterally compared to 15 bilateral fitting. Preoperative mean of bone conduction (BC) of the overall sample was 23.27 ± 10.91 dB, the Air conduction (AC) mean was 69.27 ± 13.75 dB. There was significant difference between unaided free field speech score (88.51% ± 7.92) and the aided score (96.79 ± 2.38) with P value = 0.00001. The postoperative assessment using GHABP showed a benefit score mean of 70.95 ± 18.79, patient satisfaction score mean of 78.15 ± 18.39. The disability score improved significantly from a mean of 54.08 ± 15.26 to residual score of only 12.50 ± 10.22 with P < 0.00001 postoperatively. There was significant improvement in all parameters of COSI questionnaire following fitting. Comparison of pBCHDs vs tBCHDs showed a non-significant difference regarding FF speech as well as GHABP parameters. Comparison of the post-operative skin complications was in favor of tBCHDs as (86.5%) of the patients had normal skin postoperatively, compared to 45.5% of patients with pBCHDs devices. Bilateral implantation showed significant improvement of FF speech scores, GHABP satisfaction score, as well as COSI score results.

CONCLUSION

Bone conduction hearing devices are effective solution for rehabilitation of hearing loss. Bilateral fitting yields satisfactory outcomes in suitable candidates. Transcutaneous devices carry significantly lower skin complication rates compared to percutaneous devices.

Long-term Outcome of Sound Localization with Baha ® Attract System

BACKGROUND

Spatial hearing is a critical feature in daily life. However, there is quite a range in hearing loss patients regarding the effect of bone conduction device on localization performance.

OBJECTIVES

To analyze the localization performance in patients with bilateral conductive or mixed hearing loss fitted with one Baha® Attract system.

MATERIALS AND METHODS

This prospective study included 12 patients who had followed up for more than one year. The parameters analyzed included (1) audiological results: sound field threshold, speech discrimination scores (SDSs), and sound localization test, and (2) functional results: scores for the Speech, Spatial and Qualities of Hearing Scale (SSQ) and the Chinese translation of the Spatial Hearing Questionnaire (C-SHQ).

RESULTS

The audiological assessments showed a reduction of 28.5 dB in the mean sound field thresholds and improvements of 61.7% in the SDSs for disyllabic words. The root mean square error improved slightly with the Baha® Attract system. Patients showed promising results in the functional questionnaire assessments, with significant improvements in the SSQ and C-SHQ scores.

CONCLUSIONS

Although most patients were not able to localize sound accurately after surgery, the change in the scores of the SSQ and C-SHQ indicated that the Baha® Attract system could improve spatial hearing.

The continued importance of comparative auditory research to modern scientific discovery

A rich history of comparative research in the auditory field has afforded a synthetic view of sound information processing by ears and brains. Some organisms have proven to be powerful models for human hearing due to fundamental similarities (e.g., well-matched hearing ranges), while others feature intriguing differences (e.g., atympanic ears) that invite further study. Work across diverse "non-traditional" organisms, from small mammals to avians to amphibians and beyond, continues to propel auditory science forward, netting a variety of biomedical and technological advances along the way. In this brief review, limited primarily to tetrapod vertebrates, we discuss the continued importance of comparative studies in hearing research from the periphery to central nervous system with a focus on outstanding questions such as mechanisms for sound capture, peripheral and central processing of directional/spatial information, and non-canonical auditory processing, including efferent and hormonal effects.

Analysis of cross-talk cancellation of bilateral bone conduction stimulation

When presenting a stereo sound through bilateral stimulation by two bone conduction transducers (BTs), part of the sound at the left side leaks to the right side, and vice versa. The sound transmitted to the contralateral cochlea becomes cross-talk, which can affect space perception. The negative effects of the cross-talk can be mitigated by a cross-talk cancellation system (CCS). Here, a CCS is designed from individual bone conduction (BC) transfer functions using a fast deconvolution algorithm. The BC response functions (BCRFs) from the stimulation positions to the cochleae were obtained by measurements of BC evoked otoacoustic emissions (OAEs) of 10 participants. The BCRFs of the 10 participants showed that the interaural isolation was low. In 5 of the participants, a cross-talk cancellation experiment was carried out based on the individualized BCRFs. Simulations showed that the CCS gave a channel separation (CS) of more than 50 dB in the 1-3 kHz range with appropriately chosen parameter values. Moreover, a localization test showed that the BC localization accuracy improved using the CCS where a 2-4.5 kHz narrowband noise gave better localization performance than a broadband 0.4-10 kHz noise. The results indicate that using a CCS with bilateral BC stimulation can improve interaural separation and thereby improve spatial hearing by bilateral BC.

Bilateral adhesive bone conduction devices in patients with congenital bilateral conductive hearing loss

PURPOSE

This study aims to characterize the hearing benefits and sound localization accuracy of bilateral adhesive bone conduction devices (aBCDs) compared to unilateral devices in patients with congenital bilateral conductive hearing loss (BCHL).

METHODS

Sixteen children and adolescents with congenital BCHL were enrolled and tested under four listening conditions: (1) unaided, (2) R aided: aided with a right-side aBCD, (3) L aided: aided with a left-side aBCD, and (4) B aided: aided with aBCDs on both sides. The sound field hearing threshold (SFHT, in dB hearing level [HL]) and the word recognition score (WRS) were measured. The mean absolute error (MAE) of sound source localization was calculated to assess the sound localization accuracy.

RESULTS

The performance in SFHT and WRS was significantly higher in the B aided condition than that in the unaided, R and L aided conditions; moreover, no significant difference was observed between the R and L aided conditions. Concerning sound source localization, the accuracy of localization exhibited a sharp decline when using a single aBCD, while the application of bilateral aBCDs (B aided condition) resulted in a significantly improved localization accuracy as compared to the unilaterally aided conditions (both R and L); however, no significant difference was found between the unaided and B aided condition.

CONCLUSION

Patients with congenital BCHL experienced suboptimal hearing benefits and manifested significant challenges in sound source localization when utilizing a single aBCD, as compared to the utilization of bilateral aBCDs.

Evaluation of the Benefits of Bilateral Fitting in Bone-Anchored Hearing System Users: Spatial Resolution and Memory for Speech

OBJECTIVES

The purpose of this study was to evaluate the benefits of bilateral implantation for bone-anchored hearing system (BAHS) users in terms of spatial resolution abilities and auditory memory for speech.

DESIGN

This is a prospective, single-center, comparative, single-blinded study where the listeners served as their own control. Twenty-four experienced bone-anchored users with a bilateral conductive or mixed hearing loss participated in the study. After fitting the listeners unilaterally and bilaterally with BAHS sound processor(s) (Ponto 3 SuperPower), spatial resolution was estimated by measuring the minimum audible angle (MAA) to achieve an 80% correct response via a two-alternative-forced choice task (right-left discrimination of noise bursts) in two conditions: both sound processors active (bilateral condition) and only one sound processor active (unilateral condition). In addition, a memory recall test, the Sentence-final Word Identification and Recall (SWIR) test was performed with five lists of seven sentences for each of the two conditions (unilateral and bilateral). Self-reported performance in everyday life with the listener's own sound processors was also evaluated via a questionnaire (the abbreviated version of the Speech, Spatial and Qualities of Hearing scale).

RESULTS

The MAA to discriminate noise bursts improved significantly from 75.04° in the unilateral condition to 3.61° in the bilateral condition ( p < 0.0001). The average improvement in performance was 54.28°. The SWIR test results showed that the listeners could recall, on average, 55.03% of the last words in a list of seven sentences in the unilateral condition and 57.23% in the bilateral condition. While the main effect of condition was not significant, there was a significant interaction between condition and repetition (list), revealing a significantly higher recall performance in the bilateral condition than in the unilateral condition for the second repetition/list out of five (10.2% difference; p = 0.022). Self-reported performance with bilateral BAHS obtained via the Speech, Spatial and Qualities of Hearing scale questionnaire was, on average, 4.4 for speech, 3.7 for spatial, and 5.1 for qualities of hearing. There was no correlation between self-reported performance in everyday life and bilateral performance in the MAA test, while significant correlations were obtained between self-reported performance and recall performance in the SWIR test.

CONCLUSIONS

These results showed a large benefit in spatial resolution for users with symmetric BC thresholds when being fitted with two BAHS, although their self-reported performance with bilateral BAHS in everyday life was rather low. In addition, there was no overall benefit of bilateral fitting on memory for speech, despite observing a benefit in one out of five repetitions of the SWIR test. Performance in the SWIR test was correlated with the users' self-reported performance in everyday life, such that users with higher recall ability reported to achieve better performance in real life. These findings highlight the advantages of bilateral fitting on spatial resolution, although bilaterally fitted BAHS users continue to experience some difficulties in their daily lives, especially when locating sounds, judging distance and movement. More research is needed to support a higher penetration of bilateral BAHS treatment for bilateral conductive and mixed hearing losses.

Sound Localization and Lateralization by Bilateral Bone Conduction Devices, Middle Ear Implants, and Cartilage Conduction Hearing Aids

Sound localization in daily life is one of the important functions of binaural hearing. Bilateral bone conduction devices (BCDs), middle ear implants, and cartilage conduction hearing aids have been often applied for patients with conductive hearing loss (CHL) or mixed hearing loss, for example, resulting from bilateral microtia and aural atresia. In this review, factors affecting the accuracy of sound localization with bilateral BCDs, middle ear implants, and cartilage conduction hearing aids were classified into four categories: (1) types of device, (2) experimental conditions, (3) participants, and (4) pathways from the stimulus sound to both cochleae. Recent studies within the past 10 years on sound localization and lateralization by BCDs, middle ear implants, and cartilage conduction hearing aids were discussed. Most studies showed benefits for sound localization or lateralization with bilateral devices. However, the judgment accuracy was generally lower than that for normal hearing, and the localization errors tended to be larger than for normal hearing. Moreover, it should be noted that the degree of accuracy in sound localization by bilateral BCDs varied considerably among patients. Further research on sound localization is necessary to analyze the complicated mechanism of bone conduction, including suprathreshold air conduction with bilateral devices.