Extended‐duration deafness is correlated with better subjective satisfaction in CROS‐tBAHI recipients

• This study aimed to assess subjective satisfaction regarding CROS‐tBAHI and identify positive predictive factors for successful fitting of tBAHI devices after surgery.
• CROS‐tBAHI showed better hearing threshold in the aided ears and improved the SNR in speech perception in noise; nevertheless, the increased signal‐to‐ratio was not associated with better subjective satisfaction regarding CROS‐tBAHI.
• Duration of deafness was a positive predictive factor for better subjective satisfaction regarding CROS‐tBAHIs, probably explained by relatively lower expectation about the surgery in patients with extended‐duration deafness
• Patients with longer durations of single‐sided deafness or asymmetric hearing loss would be good candidates for CROS‐tBAHI implantation.

Key points

INTRODUCTION

A bone‐anchored hearing system (BAHS) is an option for audiological rehabilitation of patients with sensorineural, conductive and mixed hearing loss.[1] Profound unilateral sensorineural deafness is specifically a good indication for contralateral routing of signal (CROS) by means of bone‐anchored hearing implants (BAHI) or headbands. Unilateral deafness includes both single‐sided deafness (SSD) and asymmetric hearing loss (AHL) with normal and impaired hearing in the contralateral ear, respectively, both of which could benefit from CROS through a BAHS.

In the past, percutaneous BAHIs (pBAHIs) were the primary choice for BAHS implantation. The audiological performance of pBAHIs is comparable with that of wireless CROS hearing aids in terms of subjective and objective benefits.[2] However, pBAHIs have several potential drawbacks, including skin problems and stigmatisation originating from implantation of a permanent percutaneous titanium abutment. To overcome the disadvantages of pBAHIs, transcutaneous BAHIs (tBAHIs) without percutaneous abutments have been developed over the last 10 years.[3] Examples of tBAHIs include Sophono, Bonebridge and BAHA Attract.

Although tBAHIs help overcome many of the limitations associated with pBAHIs, it is still a big challenge to persuade patients with SSD to undergo BAHI implantation. The main reasons for avoidance of tBAHI implantation include anxiety over surgery, limited audiological benefits at low frequencies and cosmetic appearance.[4] In this study, we attempted to identify predictive factors for successful rehabilitation of patients with unilateral deafness, including SSD and AHL, through tBAHI implantation.

MATERIALS AND METHODS

Ethical consideration

This study was approved by the ethical committee of Yonsei University (4‐2016‐1000).

Subjects

Between August 2014 and January 2016, 28 patients with unilateral sensorineural deafness underwent tBAHI implantation surgery at the Department of Otorhinolaryngology, Severance Hospital, Seoul, Korea (Table). Devices were implanted in the deaf ear in the CROS‐tBAHI (contralateral routing of signal‐transcutaneous bone‐anchored hearing implant). All patients experienced subjective satisfaction in headband testing using band BAHAs for 2 weeks and agreed to undergo BAHI surgery. While 12 patients were diagnosed with SSD with normal hearing in the contralateral ear [PTA4 (pure‐tone average at 500, 1000, 2000 and 4000 Hz), 12.8 ± 8.5 dB HL], 16 were diagnosed with AHL; patients with AHL had mild sensorineural hearing loss in the contralateral ear (PTA4 in AHL, 37.2 ± 9.6 dB HL) and had not previously utilised hearing aids in the contralateral ear. All patients with both SSD and AHL exhibited air‐bone gaps of <5 dB HL at all frequencies in the contralateral ears. The mean follow‐up period from the date of surgery was 12.8 ± 4.4 months. Subjective outcomes were determined using the Korean version (properly translated and validated) of the International Outcome Inventory for Hearing Aids (IOI‐HA). Responses to the IOI‐HA were obtained 6‐9 months after tBAHI implantation.

Characteristics of patients with unilateral deafness with tBAHI

Characteristics	N = 28
Age at tBAHI implantation (y)	49.6 ± 15.0
Sex, n (%)
Male	11 (39.3)
Female	17 (60.7)
Aetiology of unilateral deafness (PTA4 >90 dB HL) n (%)
Chronic otitis media	12 (42.9)
Sudden hearing loss	3 (10.7)
Trauma	2 (7.1)
Congenital deafness	2 (7.1)
Surgery of hemifacial spasm	2 (7.1)
Surgery of vestibular schwannoma	2 (7.1)
Meniere's disease	1 (3.6)
Unknown origin	4 (14.3)
Type of tBAHI, n (%)
Bonebridge (Medel)	25 (89.3)
BAHA Attract (Cochlear)	2 (7.1)
Sophono (Medtronic)	1(3.6)
Side of tBAHI (contralateral to the deaf ear), n (%)
Right	17 (60.7)
Left	11 (39.3)
Type of hearing loss, n (%)
Single‐sided deafness (SSD)	12 (42.9)
Asymmetric hearing loss (AHL)	16 (57.1)
PTA4 in the better ear (dB HL)
SSD	12.8 ± 8.5
AHL	37.2 ± 9.6

1 Abbreviations: HL, hearing level; tBAHI, transcutaneous bone‐anchored hearing implant; PTA4, pure‐tone average at four frequency thresholds (0.5, 1, 2 and 4 Hz).

Audiological analysis

Audiological evaluations, including pure‐tone audiometry (PTA) and speech audiometry, were performed before and after surgery. Postoperative best‐fitting data of tBAHI implantation, acquired at least 3 months after initial fitting, were used for statistical analysis. In the tBAHI‐aided condition, PTA was administered by sound‐field testing through a loudspeaker, with the tBAHI switched on and the contralateral ear plugged. Efficacy of speech perception in a noisy environment was evaluated with the Korean version of the Hearing in Noise Test (K‐HINT), a validated Korean version of the HINT Pro 7 (Bio‐Logic Systems Co).[5] Speech was designed to always originate in front of the subject, with the noise generated in front of and 90 degrees to the ipsilateral (in reference to the site of tBAHI implantation) and contralateral sides of the subject. When K‐HINT was evaluated, both ears were open without plugging or masking noise.

Statistical analysis

Statistical analysis was performed with the SPSS software for PC, version 21 (SPSS Inc). Data are presented as mean values ± standard deviations (SDs). P values <0.05 were considered significant.

RESULTS

Comparison of audiological performance of tBAHIs between SSD and AHL

This study included 28 patients with unilateral deafness, who underwent tBAHI implantation in the deaf ear. The patients were categorised into the SSD and AHL groups. In the 12 subjects with SSD, the aided PTA4 in the tBAHI‐aided condition was 25.1 ± 8.8 dB HL (Figure A). In the 16 subjects with AHL, tBAHI‐aided PTA4 was 38.0 ± 8.4 dB HL (Figure B). There was no significant difference in IOI‐HA scores between the SSD and AHL groups (21.8 ± 7.6 and 22.1 ± 8.2, respectively; P = 0.949; Figure C). Notably, satisfaction scores were not associated with hearing thresholds in the tBAHI‐aided condition (P = 0.341), indicating that contralateral hearing function had no effect on the subjective performance of tBAHIs in patients with unilateral deafness (Figure D).

Predictive factors for improving subjective satisfaction after CROS‐tBAHI implantation

Subjective satisfaction among patients with tBAHIs might be affected by several parameters such as speech perception in noise. Therefore, we analysed the improvement in speech perception in noisy conditions using the HINT. Relative to the unaided condition, there was no improvement in signal‐to‐noise ratio (SNR) in the tBAHI‐aided condition when noise was delivered from the ipsilateral direction; in contrast, delivery of noise from the contralateral and frontal positions resulted in significant improvements in speech perception in the tBAHI‐aided condition (Figure A). Composite scores recorded in the tBAHI‐aided condition were also significantly better than those recorded in the unaided condition (P < 0.01). However, the improvement in composite scores of the HINT had no effect on IOI‐HA scores (P = 0.598; Figure B), which indicates that, despite the increase in speech perception ability in noise, improvement in SNR after CROS‐tBAHI implantation is not a critical parameter for subjective satisfaction.

Meanwhile, analysis of IOI‐HA scores according to the duration of deafness revealed that the longer the duration of deafness, the greater the satisfaction regarding tBAHI implantation, with the correlation being statistically significant (P = 0.0051). Interestingly, none of the patients with deafness for more than 20 years exhibited IOI‐HA scores <24 points (Figure), which indicates that duration of deafness is an important factor that influences patient satisfaction regarding CROS‐tBAHI implantation.

DISCUSSION

The longer the deaf duration, the better the subjective satisfaction in CROS‐tBAHI

The present study revealed duration of deafness to be a critical predictive factor for better satisfaction regarding CROS‐tBAHI implantation in patients with unilateral deafness. This result could be an important clue for clinicians to select the best candidates for CROS‐tBAHI implantation from among patients with unilateral deafness. For instance, patients with recent sudden hearing loss would experience poor satisfaction with CROS‐tBAHI rehabilitation, whereas those with several decades of deafness due to chronic otitis media would be better satisfied.

There have been several reports that deafness duration does not influence patients' decisions regarding surgery for pBAHI.[[6]] In addition, Desmet et al have shown that postoperative satisfaction is not correlated with duration of deafness, whereas Martin et al showed that >10 years of duration of deafness significantly correlates with an increased Glasgow Benefit Inventory score, following pBAHI.[[9]] The present study shows that extended duration of deafness is significantly correlated with higher subjective satisfaction after tBAHI. These conflicting results may be explained by several points. First, the enrolled patient group differs in characteristics among studies; some studies investigate whether deafness duration influences the decision for surgery, using a two‐group comparison of surgery and non‐surgery groups. In contrast, other studies—including the present study—describe the influence of the duration of deafness on postoperative satisfaction within the surgery group. Second, the aetiologies of the deafness, as well as the mean duration of deafness in enrolled patients, were quite different in each study; in the present study, the most common aetiology of deafness was chronic otitis media, whereas vestibular schwannoma, sudden hearing loss and Meniere's disease were most common in the study by Desmet et al23 Third, there is a difference in the type of BAHI device among studies; the previous references were all related to pBAHI, but the present study utilised tBAHI. Thus, these factors may contribute to the different and debatable results.

Notably, the increased speech perception ability in noise rarely determines the subjective satisfaction about CROS‐tBAHI; possibly, the improved SNR may be too small to make a difference in subjective outcome or only acquired in the limited condition of signal at the implanted ear. Nevertheless, it is worthwhile to emphasise that the improvement in SNR is the essential advantage of CROS‐tBAHI.

This study is limited by the absence of preoperative or serial survey data regarding handicap due to deafness. The outcome from the IOI‐HA questionnaire would have been useful during application of the preoperative headband test. The results would be more defined and accurate if decreased handicap due to deafness were to be evaluated in tandem. Additionally, a larger sample size would provide more concrete conclusions in future studies.

CONCLUSION

Extended duration of deafness should be considered as an important predictive factor for better subjective satisfaction during patient selection for CROS‐tBAHI implantation in patients with SSD or AHL.

ACKNOWLEDGEMENTS

The authors acknowledge the participants of this study.

This work was supported by a National Research Foundation of Korea grant awarded by the Korean Government (2017M3A9E8029714) and the Korea Health Technology R&D Project, Ministry of Health & Welfare, Republic of Korea (HI16C0142).

CONFLICTS OF INTEREST

The authors declare no competing interests.

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By Jinsei Jung; Hyun Ji Kim; Young Ho Lee; In Seok Moon and Jae Young Choi

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