Abstract
Bilateral Bone Anchored Hearing Aids (BAHA) provide more subjective patient satisfaction and outcome than unilateral BAHA. Initially, percutaneous BAHAs were used for many decades. Transcutaneous BAHAs were started later to overcome problems associated with percutaneous ones. The present report gives the outcome of bilateral BAHA in a patient with percutaneous BAHA on one side and transcutaneous BAHA on the other.
Keywords: BAHA (Bone Anchored Hearing Aid), Transcutaneous, Percutaneous
Introduction
Bone conduction implants are a widely accepted means of hearing rehabilitation in patients with conductive hearing loss which cannot be managed by conventional hearing aids. They work by transmission of sound by bone conduction to the skull bone and the cochlea [1]. Congenital aural atresia, chronic canal and middle ear infections, single sided deafness are some of the indications for bone conduction implants. Percutaneous bone conduction implants were first developed in 1977 in Gothenburg, Sweden [2]. They consist of osseointegrated titanium implant that is connected to the external speech processor by an abutment. They may produce minor complications such as skin overgrowth, recurrent infections and wound dehiscence. Transcutaneous devices were developed to overcome these problems, but they generate relatively less audiological gain [3]. They consist of an implanted magnet which is stimulated transcutaneously by a sound processor and magnetic fixture.
Bone conduction inter-aural attenuation although considered to be zero, actually lies in between − 5 decibels to + 20 decibels [4]. Hence, stimulation of one cochlea with a single BAHA may not help the patients with bilateral conductive hearing loss to detect the inter-aural time and intensity differences appropriately [5]. This brings us to the necessity of bilateral BAHA, which can give better sound quality and ability to have directional hearing. The present report is on one of the bilateral BAHA recipients who has a percutaneous BAHA (BI200/BAHA Connect)™ on right side and a transcutaneous BAHA (BAHA Attract)™ on the left. Functional and audiological outcomes of the bilateral BAHA have been assessed and reported.
Case Report
A six year old male child presented with left hemifacial microsomia and bilateral microtia and congenital aural atresia. He had bilateral maximal conductive hearing loss for which he underwent right BAHA implantation surgery in the year 2006 (Figs. 1, 2). Device used was the BAHA BI200/Connect™ system. Post operatively there were minor complications like soft tissue reaction and overgrowth of the skin over the abutment, which were revised. Ten years later he underwent BAHA Attract™ surgery on the left side (Figs. 3, 4). The patient is now using both the BAHAs on a day-to-day basis at both home and college environments. He is on follow up once in a year.
Fig. 1.
Right ear showing the abutment of the BAHA BI200/Connect™
Fig. 2.
Right ear showing the BAHA Sound Processor (3rd Generation)
Fig. 3.
Left ear showing the skin covering the BAHA aAttract™ Implant system
Fig. 4.
Left ear showing the BAHA Sound Processor and magnet of the BAHA Attract™ Implant system (4th Generation)
Functional Outcome
Functionally, the patient was assessed by two questionnaire.
Glasgow Benefit Inventory (GBI) is a post-interventional patient oriented questionnaire used to assess the patient satisfaction after a therapy or surgery [6]. GBI score ranges from − 100 (poorer outcome) to 0 (no change) to + 100 (best outcome). The score in this patient was + 40 which indicates enhanced wellbeing and improved quality of life after the bilateral BAHA.
Abbreviated Profile of Hearing Aid Benefit (APHAB) is a questionnaire list of twenty four, used to evaluate and document the hearing aid benefit. It consists of Ease of communication, background noise, reverberation and aversiveness subscales [7]. Here, APHAB was used to assess the benefit of each BAHA individually and then with both BAHAs together. Global mean benefit score is found to be 61% on the right side, 35% on the left side and 68% with the bilateral BAHA, indicating better benefit on the right side and more benefit with bilateral BAHA than unilateral BAHA.
Audiological Outcome
Aided thresholds were measured which lie within the speech spectrum with pure tone average threshold of 30–35 dB on both sides (Fig. 5).
Speech Recognition Score (SRS): Speech recognition in quiet and noise were measured. The results under different conditions are displayed in Table 1. It can be noted that the scores are better with bilateral BAHA when compared to unilateral BAHA.
Sound localization: Directional hearing was evaluated using eight speakers placed in a circle at 45° of interval in a clockwise direction. Stimuli were presented at 70 dB around a frequency of 2 kHz and tested for three options. 1. Right BAHA, 2. Left BAHA and 3. Bilateral BAHAs. Two trials were given and the average result is plotted in a graph (Fig. 6) where averaged response angle is plotted in relation to the stimulation angle. It was observed that there is an increase in ability to correctly localize the sound with bilateral BAHA.
Fig. 5.
Aided audiogram showing the pure tone average thresholds within the speech spectrum
Table 1.
Speech recognition scores
| Test condition | Right ear (percutaneous BAHA) | Left ear (transcutaneous BAHA) | Bilateral BAHA |
|---|---|---|---|
| Signal @ 70 dB | SRS in quiet: 95% | SRS in quiet: 95% | SRS in quiet: 100% |
|
SNR (Signal to Noise Ratio) 0 Signal @ 70 dB Noise @70 dB |
SRS in noise: 70% | SRS in noise: 65% | SRS in noise: 80% |
|
SNR -5 Signal @ 70 dB Noise @75 dB |
SRS: 60% | SRS: 60% | SRS: 70% |
|
SNR +5 Signal @75 dB Noise @70 dB |
SRS: 75% | SRS: 70% | SRS: 90% |
Fig. 6.
Sound localization test- x-axis represents the loud speaker angle and y-axis is the average angle of the two responses. Diagonal line indicates correct responses. The responses are closer to the diagonal line with bilateral BAHA
Discussion and Conclusion
Bone Anchored Hearing Aids remain an effective solution for hearing rehabilitation in adults or children with bilateral conductive hearing loss [8]. BAHA devices have evolved over the years from percutaneous to transcutaneous, which offer better maintenance, ease of use and aesthetic appearance [9, 10]. The present report shows that the patient has been a part of that evolution of BAHAs and is functionally satisfied with both the BAHAs, percutaneous better than transcutaneous, which is reflected in GBI and APHAB scores. Aided thresholds fall well within the speech spectrum and speech recognition scores are better with the bilateral BAHA when compared to unilateral BAHA. Bilateral BAHAs are also known to have improved the ability to lateralize and localize the sound to near-normal which is well appreciated in the localization angles of the directional hearing testing.
Compliance with Ethical Standards
Conflict of interest
All authors declare that they have no conflicts of interest.
Ethical Approval
This article does not contain any studies with human participants or animals performed by any of the authors, but includes a rare case report.
Informed Consent
Informed consent was obtained from the patient for the publication of the case report.
Footnotes
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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