Technology-Limited and Patient-Derived Versus Audibility-Derived Fittings in Bone-Anchored Hearing Aid Users: A Validation Study

Examining Force Level Output of Skin-Drive Bone Conduction Hearing Devices in Adults With Simulated Conductive Hearing Loss

PURPOSE

Bone conduction hearing devices (BCDs) that deliver sound across the skin (i.e., transcutaneous) are suitable for some individuals who have conductive or mixed hearing losses. Prescriptive targets for percutaneous devices are available, for example, from the Desired Sensation Level-Bone Conduction Hearing Device (DSL-BCD) algorithm. These targets, however, may require modification for use with transcutaneous BCDs. The current study investigated three key variables that may inform target modification: (a) comparison of thresholds measured using an audiometric bone conduction (BC) transducer versus transcutaneous BCDs that offer in situ threshold measurement, (b) transcutaneous BCD default force level outputs versus recommended DSL percutaneous BC targets, and (c) the preferred listening levels (PLLs) of adults wearing transcutaneous BCDs in a laboratory setting.

METHOD

Bilateral conductive hearing loss was simulated in 20 normal-hearing adults via earplugs. Thresholds were measured using a B-71 BC transducer and two commercially available BCDs coupled to a soft headband. DSL percutaneous BC targets were generated, and PLLs were obtained for a 60-dB SPL speech stimulus. Force level outputs were measured using a skull simulator on the Audioscan Verifit2 at the hearing aids' default settings and at the participants' PLL for each device.

RESULTS

On average, audiometric BC thresholds were significantly better than those measured in situ with each BCD. PLLs were similar to prescribed targets for one device with the smoother response shape and agreed in the high frequencies for both devices.

CONCLUSIONS

In situ thresholds are significantly higher than audiometric BC thresholds, suggesting that device-based in situ measurement more accurately accounts for the signal transmission from transcutaneous BCDs. PLLs differed from the percutaneous targets and varied between devices, which may indicate that either target modifications or manipulations of device frequency response shaping are needed to approximate PLL with transcutaneous BCD devices.

High-Frequency Gain and Maximum Output Effects on Speech Recognition in Bone-Conduction Hearing Devices: Blinded Study

INTRODUCTION

Bone-conduction hearing device (BCHD) uses natural sound transmission through bone and soft tissue, directly to the cochlea, via an external processor that captures and processes sound, which is converted into mechanical vibrations. Key parameters, as maximum power output (MPO) and broader frequency range (FR), must be considered when indicating a BCHD because they can be decisive for speech recognition, especially under listening challenge conditions.

OBJECTIVES

Compare hearing performance and speech recognition in noise of two sound processors (SPs), with different features of MPO and FR, among BCHD users.

MATERIALS AND METHODS

This single-blinded, comparative, observational study evaluated 21 individuals Baha 4 system users with conductive or mixed hearing impairment. The free-field audiometry and speech recognition results were blindly collected under the following conditions: unaided, with Baha 5, and with Baha 6 Max SP.

RESULTS

In free-field audiometry, significant differences were observed between the SP at 0.25, 3, 4, 6, and 8 kHz, with Baha 6 Max outperforming Baha 5. The Baha 6 Max provided significantly better speech recognition than Baha 5 under all the speech in noise conditions evaluated. Separating the transcutaneous from the percutaneous users, Baha 6 Max Attract SP provided the best results and significantly lowered the free-field thresholds than Baha 5 Attract. The Baha 6 Max also significantly improved speech recognition in noise, among both Attract and Connect users.

CONCLUSION

The present study revealed that the greater MPO and broader FR of the Baha 6 Max device helped increase high-frequency gain and improved speech recognition in BCHD-experimented users.

NAL-NL2 Prescriptive Targets for Bone Conduction Devices With an Adaptation to Device Constraints in the Low Frequencies

OBJECTIVES

To study the effectivity of a transformed NAL non-linear version 2 (NAL-NL2) gain prescription for percutaneous bone conduction devices (BCDs) and to investigate how to take into account output constraints for the lower frequencies.

DESIGN

The NAL-NL2 prescription was converted to a bone conduction prescription rule. Adaptations were needed, as this converted rule prescribes more output at low frequencies than the device delivers. Three adaptations with different audibility and compression were compared. Setting 1 (S1, "optimal audibility") had most audibility due to adapted frequency-dependent compression, setting 2 (S2, "moderate audibility") had moderate output reduction below 1 kHz, and setting 3 (S3, "reduced audibility, least distortion") had most output reduction. Eighteen experienced BCD users rated their relative sound quality in paired comparisons for different sounds (own voice, mixed voices, traffic noise, and music). In addition speech intelligibility in quiet and noise were assessed.

RESULTS

The relative sound quality rating for the adapted prescriptions varied between the stimuli: more low-frequency sound was preferred for music (S1 over S3), and less low-frequency sound was preferred for the own voice (S2 and S3 over S1). No differences in quality rating were found for mixed voices or traffic noise. Speech intelligibility in quiet scores at 45 dB SPL was significantly lower for S3 than for S1. Speech intelligibility in noise was significantly reduced in all settings and S3 yielded significantly better speech intelligibility in noise than S1.

CONCLUSIONS

With a moderate gain reduction for low frequencies to comply with device constraints the transformed NAL-NL2 prescription was found suitable for fitting BCDs. Perceived sound quality depended on the gain settings, but also on the sound spectra and how the sound was appreciated. A moderate gain reduction below 1 kHz seems to be the optimal adaptation as it has a neutral or positive relative sound quality for all stimuli without negative effects on Speech intelligibility. The NAL-NL2-BC prescribed a sufficient amount of gain, as indicated by the speech tests.

A novel method for objective in-situ measurement of audibility in bone conduction hearing devices - a pilot study using a skin drive BCD

OBJECTIVE

Objective measurement of audibility (verification) using bone conduction devices (BCDs) has long remained an elusive problem for BCDs. For air conduction hearing aids there are well-defined and often used objective methods, and the aim of this study is to develop an objective method for BCDs.

DESIGN

In a novel setup for audibility measurements of bone-anchored hearing aid (BAHA) attached via a soft band, we used a skin microphone (SM) on the forehead measuring in-situ sound field thresholds, maximum power output (MPO) and international speech test signal (ISTS) responses.

STUDY SAMPLE

Five normal-hearing persons.

RESULT

Using the electrical output of SM it was possible to objectively measure the audibility of a skin drive BCD, presented as an eSPL-o-gram showing thresholds, MPO and ISTS response. Normalised eSPL-o-gram was verified against corresponding FL-o-grams (corresponding force levels from skull simulator and artificial mastoid (AM)).

CONCLUSION

The proposed method with the SM can be used for objective measurements of the audibility of any BCDs based on thresholds, MPO and speech response allowing for direct comparisons of hearing and BCD output on the same graph using an eSPL-o-gram. After normalisation to hearing thresholds, the audibility can be assessed without the need for complicated calibration procedures.

Influence of Compression Thresholds and Maximum Power Output on Speech Understanding with Bone-Anchored Hearing Systems

Bone-anchored hearing systems (BAHS) transmit sound via osseointegrated implants behind the ear. They are used to treat patients with conductive or mixed hearing loss, but speech understanding may be limited especially in users with substantial additional cochlear hearing losses. In recent years, BAHS with higher maximum power output (MPO) and more advanced digital processing including loudness compression have become available. These features may be useful to increase speech understanding in users with mixed hearing loss. We have tested the effect of 4 combinations of two different MPO levels (highest level available and level reduced by 12 dB) and two different compression thresholds (CT) levels (50 dB and 65 dB sound pressure level) in 12 adult BAHS users on speech understanding in quiet and in noise. We have found that speech understanding in quiet was not influenced significantly by any of the changes in these two fitting parameters. In contrast, in users with average bone-conduction (BC) threshold of 25 dB or more, speech understanding in noise was improved by +0.8 dB to +1.1 dB (p < 0.03) when using the higher MPO level. In this user group, there may be an additional, but very small benefit of +0.1 dB to +0.4 dB when using the lower rather than the higher CT value, but the difference was not statistically significant (p > 0.27). In users with better average BC thresholds than 25 dB, none of the improvement was statistically significant. Higher MPOs and possibly, to a lesser degree, lower CTs seem to be able to improve speech understanding in noise in users with higher BC thresholds, but even their combined effect seems to be limited.

Effects of extended high frequency bandwidth in osseointegrated bone conduction device users

High-frequency hearing above 5000 Hz improves the detection and discrimination of high frequency phonemes. Improved access to high-frequency hearing may be particularly advantageous in unilaterally deafened listeners who experience reduced access to high frequency speech cues on their impaired side and decreased speech perception abilities in competing noise. This study aimed to investigate the effects of extended high-frequency bandwidth on speech perception in unilaterally deafened osseointegrated bone conduction hearing device recipients. To study the effect of extended high-frequency bandwidth, participants underwent aided testing in narrow bandwidth and extended high-frquency bandwidth BCD listening conditions. Aided word and phoneme recognition in quiet was assessed at soft and conversational speech levels with the better ear plugged. Aided thresholds and Ling 6 phoneme sounds were also assessed in quiet with the better ear plugged. Speech perception in noise was assessed at ± 90° and co-located at 0° using the adaptive Hearing in Noise Test. Findings demonstrate a significant improvement in speech perception outcomes when listening with extended high-frequency bandwidth. Extended high-frequency bandwidth significantly improved word and phoneme recognition for soft and average conversational speech. The largest effects were observed for voiceless phonemes. Results suggest use of bone conduction devices with extended high-frequency bandwidth result in improved hearing outcomes when compared with narrow bandwidth bone conduction devices.

Increased maximum power output may improve speech recognition with bone conduction hearing devices

OBJECTIVE

To investigate the influence of maximum power output of bone conduction hearing devices on speech recognition in quiet and in noise in experienced users of bone conduction hearing devices.

DESIGN

Prospective, randomised cross-over investigation comparing speech recognition performance, subjective sound quality, and device preference between two bone conduction hearing devices with different maximum power outputs.

STUDY SAMPLE

Sixteen adult subjects with conductive or mixed hearing loss.

RESULTS

Both speech recognition in quiet and speech recognition in noise improved significantly when using the device with high vs. lower maximum power output. Mean improvement in word recognition score in quiet was 10.5% and the mean speech reception threshold in noise improved by 0.9 dB SNR. Compared to the device with lower maximum power output, the sound quality was rated significantly higher with the device with high maximum power output, which was also the device of preference for 81% of the subjects.

CONCLUSION

Bone conduction hearing devices with higher maximum power output have the potential to improve speech recognition in both quiet and noisy listening environments.

Clinical consensus document for fitting non-surgical transcutaneous bone conduction hearing devices to children

This clinical consensus document addresses the assessment, selection, and fitting considerations for non-surgical bone conduction hearing devices (BCHD) for children under the age of 5 years identified as having unilateral or bilateral, permanent conductive or mixed hearing losses. Children with profound unilateral sensorineural hearing losses are not addressed. The document was developed based on evidence review and consensus by The Paediatric Bone Conduction Working Group, which is composed of audiologists from North America who have experience working with BCHDs in children. The document aims to provide clinical direction for an area of paediatric audiology practice that is under development and is therefore lacking in standard protocols or guidelines. This work may serve as a basis for future research and clinical contributions to support prospective paediatric audiology practices.

Development of a Novel Bone Conduction Verification Tool Using a Surface Microphone: Validation With Percutaneous Bone Conduction Users

Objectives:

To determine if a newly-designed, forehead-mounted surface microphone would yield equivalent estimates of audibility when compared to audibility measured with a skull simulator for adult bone conduction users.

Design:

Data was analyzed using a within subjects, repeated measures design. There were two different sensors (skull simulator and surface microphone) measuring the same hearing aid programmed to the same settings for all subjects. We were looking for equivalent results.

Patients:

Twenty-one adult percutaneous bone conduction users (12 females and 9 males) were recruited for this study. Mean age was 54.32 years with a standard deviation of 14.51 years. Nineteen of the subjects had conductive/mixed hearing loss and two had single-sided deafness.

Methods:

To define audibility, we needed to establish two things: (1) in situ–level thresholds at each audiometric frequency in force (skull simulator) and in sound pressure level (SPL; surface microphone). Next, we measured the responses of the preprogrammed test device in force on the skull simulator and in SPL on the surface mic in response to pink noise at three input levels: 55, 65, and 75 dB SPL. The skull simulator responses were converted to real head force responses by means of an individual real head to coupler difference transform. Subtracting the real head force level thresholds from the real head force output of the test aid yielded the audibility for each audiometric frequency for the skull simulator. Subtracting the SPL thresholds from the surface microphone from the SPL output of the test aid yielded the audibility for each audiometric frequency for the surface microphone. The surface microphone was removed and retested to establish the test–retest reliability of the tool.

Results:

We ran a 2 (sensor) × 3 (input level) × 10 (frequency) mixed analysis of variance to determine if there were any significant main effects and interactions. There was a significant three-way interaction, so we proceeded to explore our planned comparisons. There were 90 planned comparisons of interest, three at each frequency (3 × 10) for the three input levels (30 × 3). Therefore, to minimize a type 1 error associated with multiple comparisons, we adjusted alpha using the Holm–Bonferroni method. There were five comparisons that yielded significant differences between the skull simulator and surface microphone (test and retest) in the estimation of audibility. However, the mean difference in these effects was small at 3.3 dB. Both sensors yielded equivalent results for the majority of comparisons.

Conclusions:

Models of bone conduction devices that have intact skin cannot be measured with the skull simulator. This study is the first to present and evaluate a new tool for bone conduction verification. The surface microphone is capable of yielding equivalent audibility measurements as the skull simulator for percutaneous bone conduction users at multiple input levels. This device holds potential for measuring other bone conduction devices (Sentio, BoneBridge, Attract, Soft headband devices) that do not have a percutaneous implant.

Vestibulotomy with ossiculoplasty versus round window vibroplasty procedure in children with oval window aplasia

OBJECTIVE

To review the surgical procedures and outcomes in children with bilateral oval window aplasia (OWA).

STUDY DESIGN

Retrospective cohort review.

SETTING

Tertiary referral center.

PATIENTS

Children suffering from OWA between 1990 and 2010.

INTERVENTION

Vestibulotomy with ossiculoplasty (V-OPL) or round window vibroplasty (RWV).

MAIN OUTCOME MEASURES

Findings at radiology and surgery, preoperative and postoperative bone conduction (BC), air conduction (AC), and RWV-air conduction (RWV-AC) thresholds and speech discrimination scores (SDSs).

RESULTS

Among 23 children, 11 underwent V-OPL and 8 RWV. Four children in the V-OPL group had aborted surgery and were excluded from the study. In all the remaining 19 children, the 6-month follow-up time showed postoperative AC and SDS values significantly better than the preoperative thresholds in both groups. At the 36-month long-term follow-up, AC and SDS were stable in the RWV group but showed a significant worsening in the V-OPL children compared with the 6-month follow-up results. Preoperative versus postoperative BC values showed a significant difference between the 2 groups at 36 months; 5 of the V-OPL group underwent revision following the same surgical principles, which did not result in improved outcome.

CONCLUSION

In children with OWA, V-OPL provides modest long-term results and carries higher risks of BC degradation compared to RWV. Both procedures are technically challenging but considering the respective hearing results and morbidity of primary and revision surgery, we have abandoned the V-OPL procedure in favor of RWV. In infants and children younger than 5 years with OWA previously not considered candidates for hearing restoration, we consider RWV as the first-choice surgery. It has shown to provide significantly better hearing outcomes than traditional atresia surgery with minimal complication rate.

Long-term outcome of round window Vibrant SoundBridge implantation in extensive ossicular chain defects

OBJECTIVE

To evaluate retrospectively the long-term safety and efficacy of the first 50 patients, all suffering from severe ossicular chain defects and with moderate to severe mixed hearing loss, who received the Vibrant SoundBridge with the floating mass transducer located on the round window membrane. To evaluate differences in outcome versus etiology and age of the patient population.

STUDY DESIGN

Case series with planned data collection.

SETTING

Tertiary referral medical center.

SUBJECTS AND METHODS

Patients eligible for implantation of the floating mass transducer on the round window membrane ranged in age from 2 months to 74 years with a moderate to severe conductive or mixed hearing loss from different etiologies. For each adult patient, preoperative versus postoperative bone and air conduction thresholds, air-bone gaps, and speech understanding scores were evaluated at 24-month follow-up. At 60-month follow-up, data were available from 33 patients. Preoperative and postoperative free-field auditory brainstem responses were studied in infants and children. Intraoperative and short- and long-term postoperative complications are presented.

RESULTS

There were significant improvements in speech perception and pure-tone audiometry in adults and auditory brainstem response thresholds in infants immediately after surgery and at follow-up examinations (12 to 71 months). No significant complications or device extrusions were observed in the present series.

CONCLUSIONS

Infants, children, and adults with moderate to severe conductive or mixed hearing loss obtained substantial benefit from implantation of the floating mass transducer on the round window membrane regardless of the etiology of hearing loss and previous surgery.

Are Open-Fit Hearing Aids a Possible Alternative to Bone-Anchored Hearing Devices in Patients with Mild to Severe Hearing Loss? A Preliminary Trial

Open-fit hearing aids (OFHAs) may be of benefit for some individuals with chronic outer and middle ear conditions for which boneanchored hearing devices (BAHDs) are normally recommended. The purpose of this study was to compare performance between OFHAs and BAHDs. A Starkey Destiny 800 OFHA was fit on eight adult BAHD users and speech perception measures in quiet and in background noise were compared under two different test conditions: i) BAHD only and ii) OFHA only. Equivalent outcome measure performance between these two conditions suggests that the OFHA was able to provide sufficient amplification for mild to moderate degrees of hearing loss (pure-tone averages (PTAs) less than 47 dB HL). The improved speech perception performances and increased loudness ratings observed for several of the participants with moderately-severe to severe degrees of hearing loss (PTAs of 47 dB HL or greater) in the BAHD only condition suggest that the OFHA did not provide sufficient amplification for these individuals. Therefore, OFHAs may be a successful alternative to the BAHD for individuals with no more than a moderate conductive hearing loss who are unable or unwilling to undergo implant surgery or unable to wear conventional hearing aids due to allergies, irritation, or chronic infection associated with the ear being blocked with a shell or earmold.

The effect of stimulus choice on cortical auditory evoked potentials (CAEP): consideration of speech segment positioning within naturally produced speech

OBJECTIVE

Cortical auditory evoked potentials (CAEPs) can be elicited to stimuli generated from different parts of speech. The aim of this study was to compare the phoneme /ʃ/ from word medial and word initial positions and its influence on the CAEP.

DESIGN

Stimuli from word medial positions were found to have shorter rise times compared to the same phonemes from word initial positions. A repeated measures design was carried out with CAEPs elicited using /ʃ/ from a word initial and a word medial position.

STUDY SAMPLE

Sixteen individuals with audiometric thresholds within normal limits participated in the study.

RESULTS

Stimuli /ʃ/ from a word medial position elicited CAEPs with significantly larger amplitudes and shorter latencies compared to /ʃ/ from a word initial position (p < 0.05).

CONCLUSIONS

Findings from this study, incorporating naturally produced speech sounds, suggest the need to consider spectral and temporal variations when choosing stimuli to optimize the amplitude and latency characteristics of the CAEP. Overall, findings illustrate good test-retest reliability of CAEP measures using speech stimuli with clinical equipment.

Treatment of the atretic ear with round window vibrant soundbridge implantation in infants and children: electrocochleography and audiologic outcomes

OBJECTIVE

To evaluate the long-term outcomes of the first 5 infants and 9 children with congenital aural atresia (CAA) who had undergone hearing rehabilitation using the MED-EL Vibrant Soundbridge with intraoperative assistance of electrocochleography (ECoG) for optimal fitting of the floating mass transducer (FMT) on the round window (RW) membrane.

STUDY DESIGN

Tertiary referral medical center; retrospective case series.

PATIENTS

Infants and children ranging in age from 2 months to 16 years with a moderate-to-severe conductive or mixed hearing loss with CAA. For comparison, the study population was divided into 2 groups: older children (≥5 yr of age; 5 patients) and younger children/infants (<5 yr of age; 9 subjects) who were submitted to different audiologic tests appropriate for their age and general condition.

INTERVENTION

RW implantation.

MAIN OUTCOME MEASURES

Compound action potential threshold and amplitude were assessed as a function of different methods for stabilizing the FMT on the RW. Pure tone audiogram at 0.5, 1, 2, and 4 kHz, free-field speech testing (older children), bone conduction and free-field auditory brainstem response (ABR; younger children and infants), intraoperative and postoperative complications, and FMT displacement or extrusion rate.

RESULTS

Statistically significant differences were observed with ECoG recordings between pre- and post-FMT-RW membrane optimization with fascia and cartilage (p < 0.001). Significant improvements were observed in speech perception and pure-tone and ABR threshold, immediately after surgery and at follow-up intervals (12-65 mo) in children and infants (p < 0.01). No complications or instances of device extrusion were observed.

CONCLUSION

Infants and children with moderate-to-severe conductive or mixed hearing loss, not suitable or unwilling to accept Bone-Anchored Hearing Aids and who would not tolerate traditional bone and air conduction hearing aids, obtain substantial benefit with the FMT-RW implantation procedure. Intraoperative ECoG is of significant help in achieving the best FMT-RW fitting.