Evaluation of a super powerful bone-anchored hearing system and its users: A retrospective study.

INTRODUCTION: Although the Baha 5SP has been commercially available for six years, very few studies have been performed on the device's efficacy. The current study aims to evaluate the characteristics and audiological results in patients with severe-to-profound mixed hearing loss fitted with this superpower sound processor. METHODS: This retrospective evaluation was conducted at a tertiary referral centre where a series of 82 adult patients with severe-to-profound mixed hearing loss were implanted with a percutaneous bone-anchored hearing system and fitted with a superpower sound processor between 2016 and 2019. Patients with incomplete or unreliable audiological data (n = 24) were excluded, resulting in 58 data sets for analysis. The main outcome measures were unaided and aided pure-tone thresholds and aided free-field speech perception in quiet. RESULTS: The median unaided air conduction (AC) threshold averaged across 0.5, 1 and 2 kHz (PTA0.5-2kHz) of all patients was 75 dB hearing loss (HL); the median unaided AC averaged across 1, 2 and 4 kHz (PTA1-4kHz) was 84 dB HL. For bone conduction and direct bone conduction, the median PTA0.5-2kHz was 52 and 47 dB HL, respectively. With the superpower device, the median free-field speech reception threshold was 54 dB sound pressure level (SPL), and the median speech perception score at 65 dB SPL was 80%. CONCLUSIONS: At least 75% of the patients reached a maximum phoneme score of 70%. For patients with lower scores, the superpower device still provides a substantial hearing benefit. This makes the superpower device particularly suitable for patients with severe-to-profound mixed hearing loss with a contraindication for conventional hearing aids and/or cochlear implants.

Measurement and optimisation of the perceptual equivalence of the Dutch consonant-vowel-consonant (CVC) word lists using synthetic speech and list pairs.

OBJECTIVES: (1) to determine whether the standard Dutch word lists for speech audiometry are equally intelligible in normal-hearing listeners (Experiment 1), (2) to investigate whether synthetic speech can be used to create word lists (Experiment 1) and (3) to determine whether the list effect found in Experiment 1 can be reduced by combining two lists into pairs (Experiment 2). DESIGN: Participants performed speech tests in quiet with the original (natural) and synthetic word lists (Experiment 1.). In Experiment 2, new participants performed speech tests with list pairs from the original lists constructed from the results of Experiment 1. STUDY SAMPLES: Twenty-four and twenty-eight normal-hearing adults. RESULTS: There was a significant list effect in the natural speech lists; not in the synthetic speech lists. Variability in intelligibility was significantly higher in the former, with list differences up to 20% at fixed presentation levels. The 95% confidence interval of a list with a score of approximately 70% is around 10%-points wider than of a list pair. CONCLUSIONS: The original Dutch word lists show large variations in intelligibility. List effects can be reduced by combining two lists per condition. Synthetic speech is a promising alternative to natural speech in speech audiometry in quiet.

Investigating Real-World Benefits of High-Frequency Gain in Bone-Anchored Users with Ecological Momentary Assessment and Real-Time Data Logging.

PURPOSE: To compare listening ability (speech reception thresholds) and real-life listening experience in users with a percutaneous bone conduction device (BCD) with two listening programs differing only in high-frequency gain. In situ real-life experiences were recorded with ecological momentary assessment (EMA) techniques combined with real-time acoustical data logging and standard retrospective questionnaires. METHODS: Nineteen experienced BCD users participated in this study. They all used a Ponto 4 BCD from Oticon Medical during a 4-week trial period. Environmental data and device parameters (i.e., device usage and volume control) were logged in real-time on an iPhone via a custom iOS research app. At the end of the trial period, subjects filled in APHAB, SSQ, and preference questionnaires. Listening abilities with the two programs were evaluated with speech reception threshold tests. RESULTS: The APHAB and SSQ questionnaires did not reveal any differences between the two listening programs. The EMAs revealed group-level effects, indicating that in speech and noisy listening environments, subjects preferred the default listening program, and found the program with additional high-frequency gain too loud. This finding was corroborated by the volume log-subjects avoided the higher volume control setting and reacted more to changes in environmental sound pressure levels when using the high-frequency gain program. Finally, day-to-day changes in EMAs revealed acclimatization effects in the listening experience for ratings of "sound quality" and "program suitability" of the BCD, but not for ratings of "loudness perception" and "speech understanding". The acclimatization effect did not differ among the listening programs. CONCLUSION: Adding custom high-frequency amplification to the BCD target-gain prescription improves speech reception in laboratory tests under quiet conditions, but results in poorer real-life listening experiences due to loudness.

The Merits of Bilateral Application of Bone-Conduction Devices in Children With Bilateral Conductive Hearing Loss.

OBJECTIVES: This study aims to characterize lateralization of sounds and localization of sounds in children with bilateral conductive hearing loss (BCHL) when listening with either one or two percutaneous bone conduction devices (BCDs). DESIGN: Sound lateralization was measured with the minimum audible angle test in which children were asked to indicate from which of the two visible speakers the sound originated. Sound localization was measured with a test in which stimuli were presented from speakers that were not visible to the children. In the sound localization test, 150 ms broadband noise bursts were presented, and sound level was roved over a 20-dB range. Because speakers were not visible the localization response was not affected by any visual cue. The sound localization test provides a clear distinction between lateralization and localization of sounds. Ten children with congenital BCHL and one child with acquired BCHL participated. RESULTS: Both lateralization and sound localization were better with bilateral BCDs compared with the unilaterally aided conditions. In the bilateral BCD condition, lateralization was close to normal in nearly all the children. The localization test demonstrated lateralization rather than sound localization behavior when listening with bilateral BCDs. Furthermore, in the unilateral aided condition, stimuli presented at different sound levels were mainly perceived at the same location. CONCLUSIONS: This study demonstrates that, in contrast to listening with two BCDs, children demonstrated difficulties in lateralization of sounds and in sound localization when listening with just one BCD (i.e., one BCD turned off). Because both lateralization and sound localization behavior were tested, it could be demonstrated that these children are more able to lateralize than localize sounds when listening with bilateral BCDs. The present study provides insight in (sub-optimal) sound localization capabilities of children with congenital BCHL in the unilateral-aided and bilateral-aided condition. Despite the sub-optimal results on sound localization, this study underlines the merits of bilateral application of BCDs in such children.

Controlled Clinical Trial on Bone-anchored Hearing Implants and a Surgical Technique With Soft-tissue Preservation.

OBJECTIVE: To compare the clinical and audiological outcomes after linear incision with soft-tissue preservation and standard linear incision with soft-tissue reduction for placement of percutaneous bone-anchored hearing implants. STUDY DESIGN: Clinical trial with historical control-group from a previous randomized controlled trial. SETTING: Tertiary referral center. PATIENTS AND INTERVENTIONS: Twenty-five patients were enrolled in a prospective cohort of bone-anchored hearing implant placement with linear incision and tissue preservation with a follow-up of 6 months. The control-group consisted of 25 patients from a previous randomized controlled trial in the same tertiary referral center. All sound processors were fitted 3 weeks after surgery. MAIN OUTCOME MEASURES: Numbness around the abutment, length of surgery, soft-tissue reactions according to Holgers' classification, Patient and Observer Scar Assessment Scale, implant loss, Implant Stability Quotient, and audiological outcome. RESULTS: Tissue preservation resulted in better results on sensibility (mean percentage correct responses 98% [SD 4.4] versus 89% [SD 15.0], p = 0.003), on the Patient and Observer Scar Assessment Scale (mean observer score 15.3 [SD 4.3] versus 19.4 [SD 6.3], p = 0.006), and shorter total surgery time (mean 24.6 min [SD 6.2] versus 31.9 min [SD 6.5], p < 0.001). More adverse soft-tissue reactions as measured by the Holgers classification were observed in the test-group (n = 7 [28%] versus n = 1 [4%], p = 0.049). For Implant Stability Quotient and audiology the study did not provide evidence that tissue preservation is better or worse compared with tissue reduction. CONCLUSION: Tissue preservation compared with tissue reduction leads to a generally favorable clinical outcome, comparable audiology results, and significantly shorter surgery time. Longer follow-up is warranted to conclude on the increased adverse soft-tissue reactions after 6 months.

Wireless and acoustic hearing with bone-anchored hearing devices.

OBJECTIVE: The efficacy of wireless connectivity in bone-anchored hearing was studied by comparing the wireless and acoustic performance of the Ponto Plus sound processor from Oticon Medical relative to the acoustic performance of its predecessor, the Ponto Pro. STUDY SAMPLE: Nineteen subjects with more than two years' experience with a bone-anchored hearing device were included. Thirteen subjects were fitted unilaterally and six bilaterally. DESIGN: Subjects served as their own control. First, subjects were tested with the Ponto Pro processor. After a four-week acclimatization period performance the Ponto Plus processor was measured. In the laboratory wireless and acoustic input levels were made equal. In daily life equal settings of wireless and acoustic input were used when watching TV, however when using the telephone the acoustic input was reduced by 9 dB relative to the wireless input. RESULTS: Speech scores for microphone with Ponto Pro and for both input modes of the Ponto Plus processor were essentially equal when equal input levels of wireless and microphone inputs were used. Only the TV-condition showed a statistically significant (p <5%) lower speech reception threshold for wireless relative to microphone input. In real life, evaluation of speech quality, speech intelligibility in quiet and noise, and annoyance by ambient noise, when using landline phone, mobile telephone, and watching TV showed a clear preference (p <1%) for the Ponto Plus system with streamer over the microphone input. Due to the small number of respondents with landline phone (N = 7) the result for noise annoyance was only significant at the 5% level. CONCLUSION: Equal input levels for acoustic and wireless inputs results in equal speech scores, showing a (near) equivalence for acoustic and wireless sound transmission with Ponto Pro and Ponto Plus. The default 9-dB difference between microphone and wireless input when using the telephone results in a substantial wireless benefit when using the telephone. The preference of wirelessly transmitted audio when watching TV can be attributed to the relatively poor sound quality of backward facing loudspeakers in flat screen TVs. The ratio of wireless and acoustic input can be easily set to the user's preference with the streamer's volume control.

Evaluation of a new powerful bone-anchored hearing system: a comparison study.

BACKGROUND: The recent introduction of digital hearing aid technology for bone-conduction devices employing percutaneous stimulation may be beneficial for patients with conductive and mixed hearing loss and single sided deafness. PURPOSE: Performance of a recently released sound processor for bone-anchored implants, the Ponto Pro Power from Oticon Medical (bone-conduction device 2 [BCD2]), was compared with that of the Baha Intenso from Cochlear (bone-conduction device 1 [BCD1]). RESEARCH DESIGN: Direct comparison of the subject's own device (BCD1) with the new device (BCD2) was examined in a nonrandomized design. Subjects were initially tested with BCD1. BCD2 was tested after a 4 wk acclimatization period. STUDY SAMPLE: Eighteen subjects with mixed hearing loss and with at least 4 mo experience with BCD1 completed the study. Mean air-conduction and bone-conduction thresholds averaged across the frequencies of 500, 1000, 2000, and 4000 Hz were 73.9 and 34.2 dB HL, respectively. DATA COLLECTION AND ANALYSIS: Performance of the two devices was evaluated objectively by measuring aided free-field thresholds, speech perception in quiet, and speech perception in noise. A subjective evaluation was carried out with the Abbreviated Profile of Hearing Aid Benefit (APHAB) (Cox and Alexander, 1995) and the Speech, Spatial and Qualities of Hearing Scale (SSQ) questionnaire (Gatehouse and Noble, 2004). In addition, user experiences, user satisfaction, and device preference were obtained via proprietary questionnaires. Statistical significance was established with analysis-of-variance (ANOVA) and paired t-statistics with Bonferroni correction. RESULTS: Aided free-field thresholds and speech reception thresholds (SRTs) in quiet were not statistically significantly different for either device (p > 0.05). In contrast, SRTs in noise were 2.0 dB lower (p < 0.001) for BCD2 than for BCD1. APHAB questionnaire scores on all subscales provided statistically significantly greater benefit (p < 0.05) for BCD2 than for BCD1. Also, with the SSQ most items in the speech and sound quality domain were significantly more favorable (p < 0.05) for BCD2 than for BCD1. Finally, all subjects preferred BCD2 over BCD1 with 14 subjects reporting a strong preference and four subjects an average preference for the digital signal processing provided by BCD2 over previous technology provided by BCD1.

Comparison of sound processing strategies for osseointegrated bone conduction implants in mixed hearing loss: multiple-channel nonlinear versus single-channel linear processing.

OBJECTIVES: Evaluation of a single-channel linear bone conduction implant sound processor (S-BCI) and a multiple-channel nonlinear bone conduction implant sound processor (M-BCI) with objective and subjective measures in patients with mixed hearing loss. STUDY DESIGN: In total, 20 patients with mixed hearing loss were included in the study. For either sound processor aided thresholds and speech perception in quiet with monosyllables were measured. Speech perception in noise was measured with sentences. Two different configurations were used: speech and noise at 0° (S0N0) and speech at 0° and noise at 180° (S0N180). The M-BCI was tested in both omnidirectional and directional mode. Patients were first fitted with the S-BCI and evaluated 3 weeks later. The M-BCI was fitted and, again 3 weeks later, evaluated. Subjectively, patients compared both sound processors with the APHAB questionnaire. RESULTS: Aided thresholds were similar for both sound processors in the low- and mid-frequency range. For speech in quiet, no significant differences between both sound processors were observed. For speech in noise in the S0N0 condition, the M-BCI-thresholds were 1.7 dB (SD, 2.2dB; p = 0.002) more favorable than with S-BCI. For the S0N180 configuration, an improvement of 5.8 dB (SD, 2.8 dB; p < 0.001) was seen for the directional mode relative to S-BCI. The APHAB showed statistically significant subjective improvement with the M-BCI on all subscales relative to S-BCI. CONCLUSION: Speech intelligibility in noise is better with M-BCI than with S-BCI. This was attributed to better high-frequency gain provided by the M-BCI. Improved signal processing strategies may have contributed to subjective preference for the M-BCI.

Bone-anchored hearing aids in patients with acquired and congenital unilateral inner ear deafness (Baha CROS): clinical evaluation of 56 cases.

OBJECTIVES: We performed an evaluation of the audiological and subjective benefits of the bone-anchored hearing aid (Baha) as a device for transcranial routing of sound (Baha CROS) in 56 patients with unilateral inner ear deafness. METHODS: We performed a prospective clinical follow-up study in a tertiary referral center. Previously reported results of 29 patients were supplemented with a second series of 30 patients with unilateral inner ear deafness; 3 patients dropped out during the evaluation. Audiometric measurements were taken before and after Baha CROS fitting. Subjective benefits were quantified with 4 different patient questionnaires. RESULTS: The sound localization results in a well-structured test setting were not differentiable from chance. The 5 patients with congenital hearing loss showed better scores in the unaided sound localization measurements. Overall, most patients reported some subjective improvement in their capacity to localize sounds with the Baha CROS in daily life. The main effect of the Baha CROS was to alleviate the head shadow effect during the speech-in-noise test. CONCLUSIONS: Poor sound localization in this larger series of patients confirms the findings of previous studies. Improvements in the speech-in-noise scores corroborated the efficacy of the Baha CROS in alleviating the head shadow effect. The 4 different patient questionnaires revealed subjective benefit and satisfaction in various domains.

Fitting range of the BAHA Intenso.

Audiometric characteristics of a recently introduced more powerful, behind-the-ear, BAHA sound processor, the BAHA Intenso, were evaluated in 23 patients with contra-indications for using conventional hearing aids. All patients had mixed hearing loss with boneconduction thresholds ranging between 30 and 50 dB HL. Boneconduction gain, defined as the difference in aided free-field detection thresholds and unaided boneconduction thresholds, was calculated at the octave frequencies between 500 Hz and 4 kHz. Median boneconduction gain of the Intenso ranges from 0 dB at 500 ;Hz to 12 ;dB at 2 kHz with substantial interindividual variability. The upper limit of the BAHA Intenso's fitting range was established by requiring aided speech reception thresholds with CVC-monosyllables of at most 60 dB SPL. The fitting range of the BAHA Intenso appeared to be limited to 42, 44, 58, and 48 dB HL for boneconduction thresholds at 0.5, 1, 2, and 4 ;kHz, respectively. Loudness growth functions at 0.5 and 3 kHz as obtained with 7-point categorical scaling showed an adequate aided dynamic range.

Audiometric characteristics of USH2a patients.

Temporal processing, frequency discrimination and frequency resolution, three basic mechanisms involved in speech perception, were studied in 11 USH2a patients from 10 Dutch families. Measurements included loudness scaling, gap detection, determination of auditory filter shapes and difference limen for frequency. The results were compared to values obtained from listeners with normal hearing, DFNA8/12 patients, DFNA13 patients and unselected patients with presbyacusis. Overall, the results for USH2a were most similar to those obtained in patients with sensorineural hearing loss caused by hair cell defects. To our knowledge, this is the first study that presents results on audiometric measurements combined with psychophysical measurements in a group of USH2a patients.

Audiological evaluation of affected members from a Dutch DFNA8/12 (TECTA) family.

In DFNA8/12, an autosomal dominantly inherited type of nonsyndromic hearing impairment, the TECTA gene mutation causes a defect in the structure of the tectorial membrane in the inner ear. Because DFNA8/12 affects the tectorial membrane, patients with DFNA8/12 may show specific audiometric characteristics. In this study, five selected members of a Dutch DFNA8/12 family with a TECTA sensorineural hearing impairment were evaluated with pure-tone audiometry, loudness scaling, speech perception in quiet and noise, difference limen for frequency, acoustic reflexes, otoacoustic emissions, and gap detection. Four out of five subjects showed an elevation of pure-tone thresholds, acoustic reflex thresholds, and loudness discomfort levels. Loudness growth curves are parallel to those found in normal-hearing individuals. Suprathreshold measures such as difference limen for frequency modulated pure tones, gap detection, and particularly speech perception in noise are within the normal range. Distortion otoacoustic emissions are present at the higher stimulus level. These results are similar to those previously obtained from a Dutch DFNA13 family with midfrequency sensorineural hearing impairment. It seems that a defect in the tectorial membrane results primarily in an attenuation of sound, whereas suprathreshold measures, such as otoacoustic emissions and speech perception in noise, are preserved rather well. The main effect of the defects is a shift in the operation point of the outer hair cells with near intact functioning at high levels. As most test results reflect those found in middle-ear conductive loss in both families, the sensorineural hearing impairment may be characterized as a cochlear conductive hearing impairment.

Fitting range of the BAHA Cordelle.

The performance of the most powerful Bone-Anchored Hearing Aid (BAHA) currently available, the BAHA Cordelle, was evaluated in 25 patients with severe to profound mixed hearing loss. Patients showed bone conduction thresholds at 500, 1000 and 2000 Hz, ranged between 30 and 70 dB HL, and an additional air-bone gap of about at least 30 dB. With the BAHA Cordelle, free-field thresholds improve relative to bone-conduction thresholds with 1.5, 5.0, 17.8, and 4.3 dB at 500, 1000, 2000, and 4000 Hz, respectively, with substantial inter-individual variability. The differences in unaided air conduction thresholds and aided free-field thresholds amount to 45.3, 45.8, 47.5, and 43.5 dB at 500, 1000, 2000, and 4000 Hz, respectively. Speech perception, measured both with monosyllables of the consonant-vowel-consonant type and with bisyllables, showed highly similar results. The fitting range of a (linear) hearing aid is determined by its gain characteristics. Requiring aided speech reception thresholds at or better than 65 dB SPL results in an upper limit of the fitting range of the BAHA Cordelle for bone-conduction thresholds of 51, 56, 67, and 58 dB HL at 500, 1000, 2000, and 4000 Hz, respectively. The dynamic range provided by the BAHA Cordelle was estimated from loudness growth functions at 500, 1500, and 3000 Hz employing 7-point categorical scaling. On average, aided loudness growth functions exhibit normal slopes but they level off at input levels of about 80, 70, 65 dB SPL for 500, 1500, and 3000 Hz stimuli, respectively. Measurements with a skull simulator demonstrated that the levelling-off reflects saturation of the output of the Cordelle. The relatively low saturation levels of the device suggest that increasing maximum output levels may be a worthwhile consideration for candidates with more profound sensorineural loss.

Bone-anchored hearing aids in unilateral inner ear deafness: an evaluation of audiometric and patient outcome measurements.

OBJECTIVE: To evaluate the benefit of a bone-anchored hearing aid contralateral routing of sound hearing aid (BAHA CROS hearing aid) in 29 patients with unilateral inner ear deafness. STUDY DESIGN: Prospective clinical follow-up study. SETTING: Tertiary referral center. PATIENTS: Thirty patients were recruited. There were 19 patients with a history of acoustic neuroma surgery and 11 patients with unilateral inner ear deafness due to other causes; 1 patient was excluded. The first 21 patients had also participated in a previous evaluation. INTERVENTION: Audiometric measurements were taken before intervention, when fitted with a conventional CROS, and after BAHA implementation. Patients' subjective benefit was quantified with four different hearing aid-specific instruments: the Abbreviated Profile of Hearing Aid Benefit, the Glasgow Hearing Aid Benefit Profile, the International Outcome Inventory for Hearing Aids, and the Single-Sided Deafness questionnaire. MAIN OUTCOME MEASURES: The same instruments were used at a mean long-term follow-up of 1 year after BAHA implantation. RESULTS: Sound localization in an audiologic test setting was no different from chance level. The main effect of the BAHA CROS that was found was the "lift the head shadow" effect in the speech-in-noise measurements. All instruments also showed positive results in favor of the BAHA CROS at long-term follow-up. CONCLUSIONS: The poor sound-localization results in an audiologic test setting illustrated the inability of patients with unilateral inner ear deafness to localize sounds. The speech-in-noise measurements demonstrated the efficacy of the BAHA CROS to lift the head shadow. Patients were still satisfied at 1-year follow-up, according to the four instruments.

Audiological characteristics of some affected members of a Dutch DFNA13/COL11A2 family.

Members of a Dutch DFNA13/COL11A2 family were evaluated with pure tone audiometry, stapedial reflexes, otoacoustic emissions, loudness scaling, difference limen for frequency, gap detection, and speech perception in quiet and noise. The tone audiometry showed a predominant loss for the low and middle frequencies, with only a few otoacoustic emissions at thresholds better than 25 dB hearing level. The stapedial reflexes appeared elevated, and loudness growth curves were shifted parallel to those for normal-hearing subjects, indicating a shift of the dynamic range toward higher presentation levels. The data for the difference limen for frequency, gap detection, and speech perception in noise fell within the (near-)normal range. Despite elevated thresholds, all suprathreshold functions showed fairly normal properties, suggesting an attenuation of signal energy in the cochlea with limited degradation of the cochlea's signal analyzing capabilities. The effect of DFNA13/COL11A2 may thus be characterized as a cochlear conductive loss.

Bone-anchored hearing aid in unilateral inner ear deafness: a study of 20 patients.

OBJECTIVE: To evaluate the benefit of a bone-anchored hearing aid (BAHA) contralateral routing of sound (CROS) in 20 patients with unilateral inner ear deafness. SUBJECTS: 21 patients were recruited; 15 had undergone acoustic neuroma surgery and 6 patients had unilateral profound hearing loss due to other causes; 1 patient was excluded. Only patients with thresholds of better than 25 dB HL (500-2000 Hz) and an air-bone gap of less than 10 dB in the best ear were included. METHODS: Evaluation involved audiometric measurements before intervention, when fitted with a conventional CROS and after implementation and quantification of the patients' subjective benefit with a hearing aid-specific instrument: the Abbreviated Profile of Hearing Aid Benefit (APHAB). RESULTS: Lateralization scores were not significantly different from chance (50%) in any of the three conditions. Measurements of speech perception in noise showed an increase in the signal to noise ratio (S/N ratio) with the conventional CROS (p = 0.001) and with the BAHA CROS compared to the unaided condition when speech was presented at the front with noise on the poor hearing side. On the other hand, a lower S/N ratio was seen with the BAHA CROS (p = 0.003) compared to the unaided situation when noise was presented at the front with speech on the poor hearing side. The patient outcome measure (APHAB) showed improvement, particularly with the BAHA CROS. CONCLUSIONS: The poor sound localization results illustrate the inability of patients with unilateral inner ear deafness to localize sounds. The speech-in-noise measurements reflect the benefit of a BAHA CROS in lifting the head shadow while avoiding some of the disadvantages of a conventional CROS. The benefit of the BAHA CROS was most clearly reflected in the patients' opinion measured with the APHAB.

Candidacy for the bone-anchored hearing aid.

The BAHA (bone-anchored hearing aid) is a bone conduction hearing aid with percutaneous transmission of sound vibrations to the skull. The device has been thoroughly evaluated by various implant groups. These studies showed that, in audiological terms, the BAHA is superior to conventional bone conduction devices. In comparison with air conduction devices, the results are ambiguous. However, a positive effect is found with respect to aural discharge. The most powerful BAHA can be applied to patients with a sensorineural hearing loss component of up to 60 dB HL. It was shown that bilateral BAHA application leads to binaural sound processing. Preliminary results on the application of the BAHA in patients with unilateral conductive hearing loss suggest that stereophonic hearing can be re-established. The application of the BAHA as a transcranial CROS (contralateral routing of signal) device in unilateral deafness minimizes head shadow effects.

Bone-anchored hearing aids in unilateral inner ear deafness.

In nine patients with unilateral deafness and normal hearing in the contralateral ear, measurements of sound localization and speech perception were obtained before intervention, with a conventional contralateral routing of sound (CROS) hearing aid and later with a bone-anchored hearing aid (BAHA) implanted in the deaf ear. Sound localization did not show any differences between the three conditions. Speech perception using short, everyday sentences showed a reduction in the head-shadow effect of 2 dB for both the conventional CROS hearing aid and the BAHA in comparison to the unaided condition. Patients' real-life experiences of the three conditions were evaluated using the Abbreviated Profile of Hearing Aid Benefit (APHAB) questionnaire. The results showed a significant benefit with the BAHA in situations involving background noise and reverberation and a reduced aversion to loud sounds in comparison to the unaided and conventional CROS conditions.