Experimental Framework for the Setup and Validation of Individualized Bone Conduction Hearing Computational Models

The purpose of this study is to evaluate binaural hearing ability in adults with normal hearing when bone conduction (BC) stimulation is bilaterally applied at the bone conduction hearing aid (BCHA) implant position as well as at the audiometric position on the mastoid. The results with BC stimulation are compared with bilateral air conduction (AC) stimulation through earphones. Binaural hearing ability is investigated with tests of spatial release from masking and binaural intelligibility level difference using sentence material, binaural masking level difference with tonal chirp stimulation, and precedence effect using noise stimulus. In all tests, results with bilateral BC stimulation at the BCHA position illustrate an ability to extract binaural cues similar to BC stimulation at the mastoid position. The binaural benefit is overall greater with AC stimulation than BC stimulation at both positions. The binaural benefit for BC stimulation at the mastoid and BCHA position is approximately half in terms of decibels compared with AC stimulation in the speech based tests (spatial release from masking and binaural intelligibility level difference). For binaural masking level difference, the binaural benefit for the two BC positions with chirp signal phase inversion is approximately twice the benefit with inverted phase of the noise. The precedence effect results with BC stimulation at the mastoid and BCHA position are similar for low frequency noise stimulation but differ with high-frequency noise stimulation. The results confirm that binaural hearing processing with bilateral BC stimulation at the mastoid position is also present at the BCHA implant position. This indicates the ability for binaural hearing in patients with good cochlear function when using bilateral BCHAs.

The present study aimed to evaluate and compare the outcome of different bone conduction hearing implants (BCHIs) in subjects with mixed hearing loss (MHL) and single-sided deafness (SSD) in terms of audiometric results and compliance. Twenty-one subjects with MHL and 18 subjects with SSD undergoing implantation of Baha connect, Baha attract, or Bonebridge were enrolled. Functional gain, effective gain, and usage rate of BCHIs were retrospectively reviewed. As for MHL, the functional gain of three devices was not significantly different (p = 0.477), while the effective gain of Bonebridge was higher (- 8.8 [- 15.0, - 3.5] dB) than that of Baha connect (- 20.0 [- 26.3, - 11.3] dB, p = 0.037), especially at 0.5kHz (p = 0.010) and 1kHz (p = 0.014). In SSD subjects, the effective gain of Bonebridge was significantly higher than that of Baha attract (- 11.3 [- 15.0, - 7.5] vs - 21.3 [- 21.3, - 16.3] dB, p = 0.012), while the functional gain of Bonebridge and Baha attract was not different. The constant usage rate of BCHIs tends to be higher in MHL subjects [17/21 (82%)] than that in SSD subjects [10/18 (56%)]. In SSD subjects, the constant user group showed higher functional gain than the non-constant user group, with a significant difference at 3kHz (35.0 [33.8, 45.0] vs 17.5 [10.0, 27.5] dB, p = 0.006). Bonebridge shows a higher effective gain than Baha connect in the MHL group and Baha attract in the SSD group. The usage rate of BCHIs is lower in SSD than that in MHL. In SSD subjects, the constant user group tended to show higher functional gain than the non-constant user group. Irrespective of the device type, the tendency of higher functional gain of BCHIs, especially at mid frequencies, may potentially lead to yield good compliance in SSD, mandating a meticulous fitting strategy ensuring a sufficient mid-frequency functional gain in SSD.

ObjectivesTo characterize cervical vestibular evoked myogenic potentials (c-VEMPs) in bone conduction (BC) and air conduction (AC) in healthy children, to compare the responses to adults and to provide normative values according to age and sex.DesignObservational study in a large cohort of healthy children (n = 118) and adults (n = 41). The c-VEMPs were normalized with the individual EMG traces, the amplitude ratios were modeled with the Royston-Wright method.ResultsIn children, the amplitude ratios of AC and BC c-VEMP were correlated (r = 0.6, p < 0.001) and their medians were not significantly different (p = 0.05). The amplitude ratio was higher in men than in women for AC (p = 0.04) and BC (p = 0.03). Children had significantly higher amplitude ratios than adults for AC (p = 0.01) and BC (p < 0.001). Normative values for children are shown. Amplitude ratio is age-dependent for AC more than for BC. Confidence limits of interaural amplitude ratio asymmetries were less than 32%. Thresholds were not different between AC and BC (88 ± 5 and 86 ± 6 dB nHL, p = 0.99). Mean latencies for AC and BC were for P-wave 13.0 and 13.2 msec and for N-wave 19.3 and 19.4 msec.ConclusionThe present study provides age- and sex-specific normative data for c-VEMP for children (6 months to 15 years of age) for AC and BC stimulation. Up to the age of 15 years, c-VEMP responses can be obtained equally well with both stimulation modes. Thus, BC represents a valid alternative for vestibular otolith testing, especially in case of air conduction disorders.

The objective of this study is to evaluate the safety and efficacy of a new transcutaneous bone-conduction implant (BCI BB) in patients with conductive and mixed hearing loss or with single-sided deafness (SSD), 1year after surgical implantation. The study design is multicentric prospective, intra-subject measurements. Each subject is his/her own control. The setting is nine university hospitals: 7 French and 2 Belgian. Sixteen subjects with conductive or mixed hearing loss with bone-conduction hearing thresholds under the upper limit of 45dB HL for each frequency from 500 to 4000Hz, and 12 subjects with SSD (contralateral hearing within normal range) were enrolled in the study. All subjects were older than 18years. The intervention is rehabilitative. The main outcome measure is the evaluation of skin safety, audiological measurements, benefit, and satisfaction questionnaires with a 1-year follow up. Skin safety was rated as good or very good. For the mixed or conductive hearing loss groups, the average functional gain (at 500Hz, 1, 2, 4kHz) was 26.1dB HL (SD 13.7), and mean percentage of speech recognition in quiet at 65dB was 95% (vs 74% unaided). In 5/6 SSD subjects, values of SRT in noise were lower with BB. Questionnaires revealed patient benefit and satisfaction. The transcutaneous BCI is very well tolerated at 1-year follow up, improves audiometric thresholds and intelligibility for speech in quiet and noise, and gives satisfaction to both patients with mixed and conductive hearing loss and patients with SSD.

Objectives. This study aimed to compare the audiological benefits of a non-implantable wearable option for a bone conduction (BC) implant mounted on an arch (SoundArc) to those of traditional BC hearing aids (HAs) mounted on eyeglasses (BCHAs) in patients with moderate to severe conductive or mixed hearing loss. Methods: A preliminary cross-sectional observational prospective cohort study was conducted in the Tertiary Audiological Department, University Hospital. Fourteen adults with conductive or mixed hearing loss (PTA at 0.5-1-2-4 KHz = 67 ± 15 dB HL) who had been wearing conventional BCHAs mounted on eyeglasses for at least 3 years and had declined surgical implantation of a bone conduction hearing implant (BCHI) were included in the study. Unaided and aided pure-tone air conduction (AC) and bone conduction (BC) thresholds, as well as speech tests in quiet and noise, were recorded at baseline and in two different settings: with a BCHI mounted on SoundArc® and with their own BCHAs mounted on eyeglasses using two couplers. Participants completed questionnaires in both conditions, including the International Inventory for Hearing Aids (IOI-HA), the Hearing Handicap Inventory for Adults/Elderly (HHIA/E), the Speech, Spatial, and Qualities of Hearing Scale (SSQ), a 10-point visual analog scale (VAS), and the Fatigue Impact Scale (FIS). Results: A significant functional gain was observed in both settings (p = 0.0001). Better speech perception in quiet and noise was observed with SoundArc compared to conventional BCHAs on eyeglasses (improvements in word repetition scores in noise: +19.3 at SNR +10 dB, p = 0.002; +12.1 at SNR 0 dB, p = 0.006; and +11.4 at SNR −10 dB, p = 0.002). No significant differences were found in IOI-HA, FIS, and HHIA/E scores. However, significantly better SSQ scores were reported for SoundArc in all domains (p = 0.0038). Conclusions: Although patients were accustomed to using BCHAs mounted on eyeglasses, the bone conduction wearable option of the BCHI (SoundArc) proved to be a viable alternative for adult patients with conductive or mixed hearing loss who are unable or unwilling to undergo BCHI surgery.

3D finite element modeling of earplug-induced occlusion effect in the human ear

Objective: To develop an algorithm that prescribes targets for bone conduction frequency response shape, compression, and output limiting, along with a clinical method that ensures accurate transforms between assessment and verification stages of the clinical workflow. Design: Technical report of target generation and validation. Study sample: We recruited 39 adult users of unilateral percutaneous bone conduction hearing aids with a range of unilateral, bilateral, mixed and conductive hearing losses across the sample. Results: The initial algorithm over-prescribed output compared to the user’s own settings in the low frequencies, but provided a good match to user settings in the high frequencies. Corrections to the targets were derived and implemented as a low-frequency cut aimed at improving acceptance of the wearer’s own voice during device use. Conclusions: The DSL-BCD prescriptive algorithm is compatible with verification of devices and fine-tuning to target for percutaneous bone conduction hearing devices that can be coupled to a skull simulator. Further study is needed to investigate the appropriateness of this prescriptive algorithm for other input levels, and for other clinical populations including those with single-sided deafness, bilateral devices, children and users of transcutaneous bone conduction hearing aids.

Current research on sound source externalization primarily focuses on air conduction (AC). As bone conduction (BC) technology advances and BC headphones become more common, the perception of externalization for BC-generated virtual sound sources has emerged as an area of significant interest. However, there remains a shortage of relevant research in this domain. The current study investigates the impact of reverberant sound components on the perception of externalization for BC virtual sound sources, both with the ear open (BC-open) and with the ear canals occluded (BC-blocked). To modify the reverberant components of the Binaural Room Impulse Responses (BRIRs), the BRIRs were either truncated or had their reverberation energy scaled. The experimental findings suggest that the perception of externalization does not significantly differ across the three stimulation modalities: AC, BC-open, and BC-blocked. Across both AC and BC transmission modes, the perception of externalization for virtual sound sources was primarily influenced by the reverberation present in the contralateral ear. The results were consistent between the BC-open and BC-blocked conditions, indicating that air radiated sounds from the BC transducer did not impact the results. Regression analyses indicated that under AC stimulation, sound source externalization ratings exhibited strong linear relationships with the Direct-to-Reverberant Energy Ratio (DRR), Frequency-to-Frequency Variability (FFV), and Interaural Coherence (IC). The results suggests that BC transducers provide a similar degree of sound source externalization as AC headphones.

Objective:To confirm the long-term safety and performance of the Bonebridge BCI 602 in patients suffering from conductive or mixed hearing loss (CMHL) or single-sided deafness (SSD) over a 12-month period post-implantation.Study design:Multicentric, multinational, ambidirectional, observational Post-Market Clinical Follow-Up (PMCF) study.Setting:Eight tertiary referral hospitals.Participants:Fifty-two participants in 3 categories: adults CMHL (N=24), children CMHL (N=17), and SSD (N=11; 9 adults and 2 children).Intervention:Participants were implanted with the Bonebridge BCI 602 device.Main outcome measure(s):Outcome measures focused on sound field thresholds (SF), word recognition scores (WRS), speech reception thresholds (SRT) in both quiet and noise, adverse events, and subjective satisfaction (SSQ and AQoL questionnaires) at initial activation and at 3-month and 12-month post-implantation.Results:Safety was established by stable bone conduction (BC) thresholds and a low adverse event rate with no unanticipated events. Safety was underlined by clinically relevant improvements in the health-related assessment of Quality of Life (AQoL) questionnaire of mean+0.1 (adults and children CMHL) and +0.07 (SSD). Hearing significantly improved in sound field thresholds with mean functional gains of 24.05±8.68 dB (adults CMHL), 21.34±25.43 dB (children CMHL), and 32.89±25.87 dB (SSD). Mean word recognition scores improved by 65.83±28.62 percent points (PP) for adult CMHL and 65.77±27.53 PP for children CMHL and speech reception thresholds (SRT) in quiet by 15.4±9.34 dB and 19.96±14.66 dB, respectively. SRT in noise improved by −5.57±4.23 dB (adults; S0°N0°), −5.12±5.08 dB (children, S0°N0°), and −3.05±3.06 dB (SSD, SSSDNNH). Subjective hearing ability tested with the Speech, Spatial, and Qualities (SSQ) of Hearing questionnaire improved and was clinically relevant for the adult (+2.23) and children (+1.51) CMHL groups.Conclusions:The Bonebridge BCI 602 demonstrates significant enhancements in hearing and speech understanding 12 months postoperatively, showing high user satisfaction and safety.

The Bonebridge hearing aid (Med-EL, Innsbruck, Austria) is a semi-implantable hearing system with transcutaneous bone conduction that was implemented in Europe in 2012. It is indicated for patients with conductive and mixed hearing loss or unilateral profound sensorineural hearing loss, who do not obtain adequate benefits with conventional hearing aids and are not candidates for middle ear reconstructive surgery. The Bonebridge device, being an active transcutaneous bone conduction implant, can overcome the disadvantages of percutaneous bone conduction devices. The Vibrant Soundbridge hearing aid (Med-EL, Innsbruck, Austria) was implemented in Europe in 1996 as an implantable hearing device in the middle ear in patients with mild to severe sensorineural, conductive or mixed hearing loss with medical and audiological contraindications for the use of conventional hearing aids or with rapidly progressive sensorineural hearing loss. The Bonebridge and Vibrant Soundbridge devices, used in patients with the same indication criteria, had similar audiological results – adequate hearing rehabilitation with improvement of subjective hearing (perception of silent and noisy speech, spatial hearing, hearing quality, sound localization), a significant increase in perceived quality of life and patients’ satisfaction with the hearing aid (comfort, sound quality, cosmetic appearance). Because the Vibrant Soundbridge device requires the floating mass transducer to be coupled to the ossicles, round window, or oval window, this surgery carries a higher risk of inner ear injury than surgery with the Bonebridge device. The advantages of the Vibrant Soundbridge system, compared to the Bonebridge device, are the potential for greater stimulation power, especially at high frequencies, unilaterally stimulating the affected ear without influencing the contralateral ear through bone conduction.

Patients with air-bone gaps or combined hearing loss that cannot be corrected by tympanoplasty can be treated with bone conduction hearing aids. The disadvantages of conventional and percutaneous systems are, on one hand, the obvious external fixation components and on the other hand, the biological and psychosocial problems of open implants. This project was therefore set up to develop a semi-implantable, magnetically anchored transcutaneous bone conduction device, introduce it into clinical application and follow-up the results. The principle of this bone conduction device is the magnetic coupling of an external vibrator via implanted double magnets. After extensive laboratory tests, this method was introduced into the clinic in 2006. Following the initial pilot study, 184 implantations in 143 patients have been performed in Recklinghausen since 2008. Long-term evaluation of 20 congenital atresia patients treated with these devices was possible. Worldwide, more than 3000 of these devices have been implanted. The operative implantation technique is relatively simple. With the new "upside down technique", bone removal is no longer necessary. The 2.6-mm thin implants are hardly noticeable. The hearing improvement is similar to that of other bone conduction hearing aids. This semi-implantable transcutaneous bone conduction hearing device is another option for patients with air-bone gaps, combined hearing loss or single-sided deafness.

ObjectiveA new prototype bone conduction (BC) transducer B250, with an emphasized low-frequency response, is evaluated in vestibular evoked myogenic potential (VEMP) investigations. The aim was to compare cervical (cVEMP) and ocular (oVEMP) responses using tone bursts at 250 and 500 Hz with BC stimulation using the B250 and the conventional B81 transducer and by using air conduction (AC) stimulation.MethodsThree normal subjects were investigated in a pilot study. BC stimulation was applied to the mastoids in cVEMP, and both mastoid and forehead in oVEMP investigations.ResultsBC stimulation was found to reach VEMP thresholds at considerably lower hearing levels than in AC stimulation (30–40 dB lower oVEMP threshold at 250 Hz). Three or more cVEMP and oVEMP responses at consecutive 5 dB increasing mastoid stimulation levels were only obtained in all subjects using the B250 transducer at 250 Hz. Similar BC thresholds were obtained for both ipsilateral and contralateral mastoid stimulation. Forehead stimulation, if needed, may require a more powerful vibration output.ConclusionViable VEMP responses can be obtained at a considerably lower hearing level with BC stimulation than by AC stimulation. The cVEMP and oVEMP responses were similar when measured on one side and with the B250 attached to both ipsilateral and contralateral mastoids.

Round window membrane motion with air conduction and bone conduction stimulation

The aim of this study was to evaluate the performance and limits of an adhesive bone conduction hearing aid in patients implanted with an active transcutaneous bone conduction implant. Therefore, hearing performance and subjective benefit of patients with mixed and conductive hearing loss were assessed with both bone conduction devices. This cohort study was conducted at a tertiary care center. Fifteen subjects, who had been implanted with an active transcutaneous device previously, were included and used the adhesive hearing device for 3 weeks instead of the implant. Subjects underwent two sets of audiological tests as well as assessments of quality of life at the beginning and at the end of the testing period. Audiological results showed a significantly greater improvement in regards to functional hearing gain and word recognition scores with the transcutaneous bone conduction device than the nonimplantable adhesive device. Regression analysis showed a trend toward greater improvement with the transcutaneous device compared with the adhesive device in patients with an increasing bone conduction threshold. Hearing-specific and general quality-of-life questionnaires revealed no significant difference between the two devices. Patients with mixed or conductive hearing loss experience hearing gain with both, the adhesive device and the active transcutaneous device. The adhesive device may be a valuable alternative to the active transcutaneous device, depending on the individual bone conduction threshold.

In the past 30 years, a large amount of clinical and audiological research on bone conduction hearing devices has been performed. In this review, we give a brief history of the developments in indications, surgical techniques and sound processors with respect to implantable bone conduction devices like the bone-anchored hearing aid or Baha. Starting with the use of Baha in patients with bilateral conductive or mixed hearing loss (HL), the indications for such devices have been extended to patients with unilateral HL, children and moderate mentally retarded patients. Bilateral fitting has been shown to be beneficial in restoring binaural hearing in patients with bilateral acquired or congenital conductive HL. In addition, the surgical techniques used to implant the titanium fixture for Baha application have been modified and further developed to reach two main goals: (a) optimal osseointegration, and (b) preparation of the implant site to minimize the occurrence of soft tissue reactions. Currently, the most used techniques are the pedicled skin flap, dermatome and linear incision techniques. Several generations of the Baha(®) sound processor have been developed by Cochlear(TM) to provide sufficient amplification in different hearing situations. Improvements in sound quality, aesthetics and handling have been major points of interest. The Baha sound processors most often used today are the Baha(®) Divino, the Baha(®) Intenso and the Baha(®) Cordelle. Recently, the more flexible Baha(®) BP100 sound processor was launched.