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Management of single-sided deafness with the bone-anchored hearing aid
Otolaryngology–Head and Neck Surgery (2009) 141, 16-23
ORIGINAL RESEARCH—OTOLOGY AND NEUROTOLOGY
Management of single-sided deafness with the bone-anchored hearing aid Heng-Wai Yuen, MBBS, MRCS, DOHNS, Daniel Bodmer, MD, PhD, Kari Smilsky, MclSci, Julian M. Nedzelski, MD, FRCSC, and Joseph M. Chen, MD, FRCSC, Toronto, ON, Canada Sponsorships or competing interests that may be relevant to content are disclosed at the end of this article. ABSTRACT OBJECTIVES: The benefits of the bone-anchored hearing aid (BAHA) for rehabilitation of conductive and mixed hearing loss are well established. Recently, the BAHA was used to rehabilitate patients with single-sided deafness (SSD). In this study, the benefits of the BAHA in SSD are presented. STUDY DESIGN: Case series with planned data collection. SETTING: Tertiary referral center. SUBJECTS AND METHODS: Twenty-one consecutive adult patients with SSD underwent single-stage BAHA implantation on the side of deafness. Testing in sound field was performed using the hearing-in-noise test (HINT) in both unaided and aided conditions. Speech and noise signals were delivered through two speakers oriented in two test paradigms. The outcomes were expressed as signal-to-noise (S/N) ratios. Subjective benefit analyses were determined through two questionnaires: the Abbreviated Profile of Hearing Aid Benefit (APHAB) and the Glasgow Hearing Aid Benefit Profile (GHABP). RESULTS: All subjects demonstrated significant improvement in speech reception thresholds with the HINT using the BAHA, especially with the 90/270 speaker paradigm, in which the mean improvement over the unaided condition was 5.5 dB SPL (range, 2.0-11.0 dB; P ⫽ 0.00001). Qualitative subjective outcome measures demonstrated additional benefits. CONCLUSION: In SSD patients, the BAHA provides significant subjective benefits and improves speech understanding in noise. © 2009 American Academy of Otolaryngology–Head and Neck Surgery Foundation. All rights reserved.
A
ural rehabilitation in the context of single-sided deafness (SSD) is very challenging because of the limited options available. Historically, rerouting sound from the deafened side to the hearing ear with hearing aids such as the contralateral routing of sound (CROS) device was the mainstay of treatment for this condition.1,2 There were divergent reports of success and patient satisfaction with a CROS hearing aid,1 and the overall acceptance rate of the CROS aids has remained low. Attempts to use a single,
tightly-fitted canal aid to achieve transcranial CROS hearing proved unpopular due to discomfort and insufficient gain.2,3 Limited subjective and objective benefits from the transcutaneous loss of energy led to the discontinued use of the Audiant implantable device.4 The use of conventional boneconducting hearing aids is constrained by several factors including pain, headache, and skin irritation at the site of contact. Sound quality and fidelity varied with sound attenuation as a function of scalp thickness, vibrator location, and the tension of the securing device.5,6 The advent of the bone-anchored hearing aid (BAHA) resolved a number of issues related to the quality of sound perception. Through a percutaneous abutment, a direct coupling of the sound processor to an implanted screw led to minimal attenuation. Short- and long-term studies have confirmed that the BAHA is a viable and preferable alternative to traditional amplification to remediate conductive or mixed hearing loss, especially for those who cannot wear a conventional hearing aid.1,7-11 Vaneecloo et al12 reported the first series of aural rehabilitation for SSD using a BAHA on the deaf side. Subsequently, increased awareness in North America led to the expanded use of this device in SSD.6,13 In the United States, the BAHA was approved by the Food and Drug Administration (FDA) for use in patients with bilateral conductive or mixed hearing loss in 1996, and for SSD in 2002. In Canada, the BAHA was approved by Health Canada for SSD in 2003. In this report, patients with SSD treated with the BAHA device were evaluated in a prospective manner through subjective and objective indices of auditory performance.
MATERIAL AND METHODS Twenty-one consecutive adult patients with SSD were included in the study. Those with unilateral severe to profound sensorineural hearing loss and a speech discrimination score of less than 30 percent were included. The better
Received October 15, 2008; revised December 31, 2008; accepted February 20, 2009.
0194-5998/$36.00 © 2009 American Academy of Otolaryngology–Head and Neck Surgery Foundation. All rights reserved. doi:10.1016/j.otohns.2009.02.029
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Management of single-sided deafness with the . . .
ear had a pure-tone threshold of 35 dB HL or better and a speech discrimination score of at least 80 percent. Institutional review board approval was obtained. All patients underwent standard audiometric testing in a double-walled sound booth. Pure-tone air- and bone-conduction thresholds were measured using the standard Hughson-Westlake procedure. Speech recognition was established using a 25-item W-22 word list presented at the patient’s most comfortable listening level, or at 30 to 40 dB SPL. Surgical candidacy was established by audiologic criteria and the patient’s subjective response to two separate trials of listening to speech and environmental sounds using the BAHA sound processor. Trials were done with the better ear occluded and open. At the initial visit, a test band was used; at the second visit, a bite bar was placed firmly over the mastoid cortex on the deafened side. None of our patients had a home trial with the headband prior to implantation. Only subjects who expressed a significantly heightened sense of improvement and satisfaction, and those who were not put off by the cosmetic challenges of a BAHA, were deemed suitable for this device. Complete audiologic tests and questionnaires were administered prior to surgery. All subjects underwent a standard, one-stage procedure to implant the one-piece titanium screw with abutment on the side of SSD. External sound-processor fitting was scheduled for three months following surgery to allow osseointegration to occur.
Speech Recognition Testing The hearing-in-noise test (HINT) was used for speech recognition testing about three months after BAHA fitting in all
17
21 patients. Noise was presented at a fixed level of 65 dB, and sentences varied around the noise depending on the response of the patients. The HINT threshold is defined as the decibel signal-to-noise (S/N) ratio whereby the subject correctly identifies half of the sentences. Two signal-to-noise delivery paradigms were used with speakers oriented in the 0/180-degree positions (front-back) and 90/270-degree positions (left-right). For the 0/180 paradigm, speech signal was presented at 0 degree (front) and noise at 180 degrees (Fig 1a). In the 90/270 paradigm, speech was presented at 90 degrees (deaf side) and noise at 270 degrees (hearing side) (Fig 1b). No other speaker paradigms were used as sound localization test was not conducted. Patients were evaluated both with the BAHA system turned off (unaided) and with it turned on (aided). In each test condition, the speech reception thresholds were measured twice, and the results were averaged. The sound field and speech levels were calibrated for each patient. Positioning in the sound booth did not change between the aided and unaided conditions. The volume setting of the BAHA was set to the patient’s preference and optimal level; this setting was at 2 1/2 out of 3 in the majority of patients.
Patient Subjective Outcome Analysis In addition to audiometric evaluation, patients were asked to complete user-benefit questionnaires. Two questionnaires were administered: 1) Abbreviated Profile of Hearing Aid benefit (APHAB)14 pre- and post-fitting, and 2) Glasgow
Figure 1 Speaker paradigms used in the study. (A) The 0/180 paradigm showing a patient with a left BAHA. (B) The 90/270 paradigm showing a patient with a left BAHA.
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Hearing Aid Benefit Profile (GHABP)15 post-fitting. Both post-fitting questionnaires were administered via mail approximately three months following fitting. The APHAB consists of 24 items to evaluate hearing benefit across four different domains: ease of communication (EC), reverberant conditions (RV), background noise (BN), and aversiveness of sound (AV). A higher score indicates greater difficulty.14 The GHABP evaluates initial hearing disability, handicap, hearing aid use, hearing aid benefit, residual disability, and patients’ satisfaction with their hearing aids.15 This questionnaire consists of two parts: the first covers four predetermined environments and in the second part the patient is asked to identify up to four additional situations in which they experience hearing difficulties. A score is calculated based on the answers.15 Higher scores in the initial disability, handicap, and residual disability domains suggest greater difficulties, whereas higher scores in the domains of use, benefit, and satisfaction are more desirable.
Statistical Analysis The paired t test was applied to the results of the speech perception measurements and tests and was used to compare mean values in the different domains of the APHAB and GHABP. A P value of less than 0.05 was chosen as the level of significance.
RESULTS Between July 2004 and May 2008, 65 patients with SSD fulfilled the candidacy criteria for a BAHA; 34 patients received the BAHA implantation surgery. Complete one-year data were available for 21 patients. Demographic data of the 21 consecutive SSD patients who underwent rehabilitation with a BAHA system are shown in Table 1. There were eight male and 13 female subjects. Mean age at implantation was 54.5 years (range, 33.1 to 72.1 years). The BAHA was implanted on the right side in 15 cases and on the left side in six cases. The first two patients were fitted with the BAHA Compact sound processor, and the remaining patients were fitted with the BAHA Divino sound processor (Cochlear Nordic AB, Molnlycke, Sweden) when it became available. The etiologies of SSD included: translabyrinthine cerebellopontine angle tumor surgery (n ⫽ 10), idiopathic sudden sensorineural hearing loss (n ⫽ 3), cholesteatoma (n ⫽ 2), mastoidectomy for chronic suppurative otitis media (n ⫽ 2), mumps (n ⫽ 1), congenital SSD (n ⫽ 1), labyrinthectomy for Menière’s disease (n ⫽ 1), and gentamicin treatment for Menière’s disease (n ⫽ 1). The mean duration of deafness was 11 years (range, 4 months to 59 years); the longest duration of deafness occurred in the patient with congenital SSD. There was no notable difference in performance of this patient compared with those with noncongenital causes.
Table 1 Patient characteristics
Patient
Age at surgery (years)
Gender
Ear implanted
1 2 3 4 5 6 7 8 9
57 42 59 51 72 70 60 34 59
M F F F M F M F M
L R R R R L R L R
10 11
72 33
F F
L L
12 13 14 15 16 17 18 19 20
47 59 52 72 38 65 44 50 42
F M F F M F F M M
L R R R R R R R R
21
66
F
R
Cause of loss Cholesteatoma Cholesteatoma Acoustic neuroma Acoustic neuroma Acoustic neuroma Acoustic neuroma Acoustic neuroma ISSNHL Congenital hearing loss Chronic otitis media Gentamicin treatment for Menière’s Acoustic neuroma Acoustic neuroma Meningioma Acoustic neuroma Chronic otitis media Labyrinthectomy Mumps ISSNHL Acoustic neuroma excision ISSNHL
PTA [dB] (better ear)
PTA [dB] (SSD ear)
Speech recognition (SSD ear)
8.33 10.00 1.67 20.00 20.00 5.00 13.33 11.67 15.33
BTL BTL 90.00 BTL BTL BTL 90.00 80.00 BTL
0% 0% 0% 0% 0% 0% 24% 0% 0%
15 years 10 years
38.33 40.00
76.67 BTL
0% 0%
12 9 4 12 10 10 35 17 6
months months months years years years years years years
11.67 16.67 16.67 18.33 31.67 8.33 6.67 5.00 10.00
BTL BTL BTL BTL 110.00 BTL 103.33 108.33 BTL
0% 0% 0% 0% 28% 0% 0% 0% 0%
36 months
21.67
BTL
0%
Duration of deafness 22 16 5 7 10 5 10 19 59
months months years years years years years months years
PTA, pure-tone average over frequencies 500, 1000, 2000, 4000 Hz; ISSNHL, idiopathic sudden sensorineural hearing loss; BTL, beyond test limits.
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Management of single-sided deafness with the . . .
Five of the patients had previous experience with a CROS hearing aid; none had maintained the use of such a device. All patients had severe to profound hearing loss in their poorer ear. Nineteen of the subjects had no speech recognition (0%) in the poorer ear, and the remaining two subjects had speech recognition scores of 24 percent and 28 percent, respectively. Nineteen patients had normal hearing in their better ear (pure-tone average [PTA] ⬍ 20 dB HL). Two patients had mild hearing loss (PTA ⫽ 20-40 dB HL). Surgeries were uneventful in all 21 patients with no implant extrusion, intraoperative hemorrhage, cerebrospinal fluid leakage, or infection. One patient required minor flap revision to debulk tissues adjacent to the percutaneous abutment to improve fitting of the external sound processor. The mean interval between surgery and BAHA fitting was 4.4 months (range, 3-15 months). One patient waited for 15 months to fit the BAHA because of financial constraints. The mean duration of follow-up after BAHA fitting was 22.4 months (range, 7.0-48.0 months). At the conclusion of this study, there were no nonusers.
Speech Recognition Testing Speech perception thresholds with noise during the HINT tests are expressed as signal-to-noise (S/N) ratios. As the noise level was fixed, the S/N ratio was recorded as a positive or negative value. If a patient could hear the speech signal at a lower level than the background noise, the S/N ratio would be presented as a negative number. Similarly, if the patient could hear the speech signal at a higher level than the background noise, the S/N ratio was positive. When the BAHA-aided condition was compared with the unaided condition, a decrease in S/N ratio reflected an improvement in speech recognition and, thus, a better outcome. Complete audiometric data were available in all the patients. In the 0/180 paradigm, there was an increase of S/N ratio (ie, hearing deterioration) of 1.6 dB SPL (range, 0-5 dB) when the BAHA was turned on compared to when it was turned off (Fig 2). This was statistically significant (P ⫽ 0.01). In the 90/270 paradigm, all patients demonstrated an improvement of speech reception thresholds using the BAHA device. The mean decrease in S/N ratio was 5.5 dB SPL (range, 2-11 dB) when the BAHA was turned on compared to when it was turned off. This difference in the HINT tests in the 90/270 paradigm was statistically significant (P ⫽ 0.00001) (Fig 2). The changes in the HINT scores are summarized in Table 2.
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Figure 2 Results of HINT test in 20 patients in the unaided and BAHA-aided condition. Signal-to-noise (S/N) ratios were derived by numerically subtracting the noise level (fixed at 65 dB) from the speech reception thresholds. Therefore, negative S/N ratio values denote speech reception thresholds lower than noise level, and vice versa (see text for further details). The difference between the unaided and aided conditions was statistically significant for the 90/270 paradigm (*).
consistently higher (ie, less favorable) in all four domains than in the aided situation. In addition, the difference was statistically significant in the communication performance domains EC (P ⫽ 0.001), RV (P ⫽ 0.0007), and BN (P ⫽ 0.0002). The positive impact of the BAHA has a borderline significance on aversiveness of sound (P ⫽ 0.04). The changes in scores in the domains are summarized in Table 3. The patients’ scores on the GHABP questionnaire were scaled to lie between 0 and 100 to represent categorical levels of benefit, from small to large.15 There were large standard deviations in the scores reflecting the highly variable range of reported experience with the BAHA. A mean initial disability score of 58.5 (⫾ 9.7) was obtained in the initial disability domain. In the initial handicap domain the mean score was 60.1 (⫾ 16.3). Measures obtained after BAHA fitting revealed a mean score of 33.8 (⫾ 12.2) in the residual disability domain. In the domain that probed the proportion of time the BAHA was used in the given situation, a mean score of 82.4 (⫾ 23.2) was obtained. In the benefit domain, the mean score was 48.5 (⫾ 20.5), while in the satisfaction domain the mean score was 58.9 (⫾ 25.5).
Patient Subjective Outcome Analysis Sixteen patients completed and returned both questionnaires, giving a response rate of 67 percent. These patients used BAHAs an average of 5.6 days a week (range, 1.0-7.0 days), for an estimated mean duration of 11.4 hours per day (range, 4.0-16.0 hours). The mean scores on the four domains of the APHAB are shown in Figure 3. In the unaided situation, the scores are
DISCUSSION It is well documented that monaural hearing does not provide normal hearing in many listening situations,16 especially hearing in noise. The greatest difficulties for monaural listeners occur when the sound source is positioned on the
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Table 2 Hearing in noise test (HINT) scores in patients (n ⴝ 21) in the unaided (preoperative) and BAHA situations) Signal-to-noise (S/N) ratio (dB), testing paradigm 0/180 paradigm Patient 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
Unaided
BAHA
90/270 paradigm Change*
⫺10.0 ⫺12.0 2.0 ⫺6.0 ⫺6.0 0.0 ⫺6.0 ⫺3.0 3.0 ⫺2.0 3.0 5.0 ⫺5.0 ⫺5.0 0.0 ⫺6.0 ⫺6.0 0.0 ⫺6.0 ⫺5.0 1.0 ⫺6.0 ⫺4.0 2.0 ⫺1.0 0.0 1.0 3.0 5.0 2.0 ⫺6.0 ⫺4.0 2.0 ⫺6.0 ⫺3.0 3.0 0.0 ⫺1.0 1.0 ⫺4.0 0.0 4.0 4.0 5.0 1.0 ⫺3.0 0.0 3.0 ⫺1.0 0.0 1.0 ⫺5.0 ⫺5.0 0.0 0.0 ⫺2.0 2.0 ⫺1.0 ⫺1.0 0.0 0.0 0.0 0.0 Change* S/N ratio ⫽ 1.6 (95% CI, 1.0-2.3)
Unaided
BAHA
Change*
⫺8.0 ⫺14.0 6.0 0.0 ⫺7.0 7.0 3.0 ⫺4.0 7.0 6.0 ⫺2.0 8.0 2.0 ⫺3.0 5.0 4.0 ⫺1.0 5.0 4.0 ⫺3.0 7.0 2.0 ⫺6.0 8.0 2.0 0.0 2.0 12.0 2.0 10.0 2.0 ⫺6.0 8.0 6.0 4.0 2.0 4.0 0.0 4.0 ⫺1.0 ⫺4.0 3.0 5.0 3.0 2.0 4.0 ⫺7.0 11.0 5.0 1.0 4.0 2.0 ⫺4.0 6.0 6.0 0.0 6.0 4.0 2.0 2.0 6.0 3.0 3.0 Change* S/N ratio ⫽ 5.5 (95% CI, 4.3-6.7)
*Change is denoted in absolute values.
side of impairment due to the exaggerated head shadow effect.17 The BAHA system allows direct transmission of electromechanical energy to the skull without the dampening effects of the overlying soft tissues, effectively becoming a transcranial conductive device that expands the sound field through contralateral routing of the offside signal. The energy transfer is efficient since interaural attenuation for bone conduction is essentially nil.12 The relative benefits of the BAHA over the CROS device have been shown in previous studies.6,13 Both Niparko et al6 and Wazen et al13 showed that BAHA provided significantly greater speech intelligibility compared to CROS amplification as demonstrated in speech recognition with HINT testing. Niparko et al6 also demonstrated that CROS amplification does not provide benefits compared to the monaural unaided conditions. In this study, four patients were previously rehabilitated with a CROS device for an average duration of 1 month to 2 years; all four had abandoned the CROS device at the time of BAHA assessment. A direct comparison of auditory performance using the CROS with a BAHA was not attempted in this study. However, all four patients indicated better sound resolution with the BAHA and showed improvement based on the APHAB and GHABP questionnaires. We utilized specific speaker paradigms representing challenging real-life hearing situations to evaluate the audiometric benefits of the BAHA. The benefit of the BAHA
was best exemplified in the 90/270 test paradigm when the speech signals were presented to the deaf ear with the BAHA turned on, and when the noise signals were presented only to the hearing ear. The S/N ratio improvement of 5.5 dB SPL when the BAHA was on vs when it was off was highly significant (P ⫽ 0.00001). Given that a 1-dB decrease in S/N ratio reflects a 10 percent improvement in speech recognition,18 this clearly translates into a significant clinical benefit. The same observations were reported by others, including Wazen et al13 and Lin et al.19 In these studies, when the HINT was conducted with noise directly in front of the listener (coincident with the speech), no hearing aid advantage was conferred by the BAHA. In contrast, when the noise source was placed near the functional ear, significant benefit from the BAHA was realized. This showed that the BAHA system effectively expands the sound field through routing of offside auditory signal. Generally, patients with SSD do not experience much hindrance when noise is presented to the deaf side. Following BAHA fitting, the amplified noise could in fact become bothersome. A previous study13 showed that this situation could result in reduced speech intelligibility compared to the unaided situation. We did not test the situation in which noise is presented to the BAHA-aided side while speech is presented to the functional ear; in the real-life situation, a patient could turn down the level of amplification or turn off
Yuen et al
Management of single-sided deafness with the . . .
Figure 3 Mean scores of 14 patients in the following domains: ease of communication (EC), background noise (BN), reverberation (RV), and aversiveness of sound (AV) on the APHAB in the unaided and BAHA-aided conditions. Lower scores indicate more favorable situations. (**) indicates the domains in which the difference between the unaided and aided conditions is statistically significant (P ⬍ 0.05).
the BAHA completely in the presence of overwhelming noise. This is a common theme among our patients. Nevertheless, none had sufficient aversion to noise to become a nonuser. Another reason is the considerable time involved
21
in testing too many speaker paradigms. The 90/270-degree paradigm is what we were most interested in to ensure that the BAHA was offering a release from the head shadow effect. Interestingly, we reported a slight but statistically significant worsening of S/N ratio with the BAHA turned on compared to off in the 0/180 test paradigm. In this scenario, the noise stimulus presented behind the subject may be perceived as a distraction to the BAHA side, as the sound processor is set 5 to 6 cm behind the pinna, which cannot shield the microphone. These observations were not noted by previous studies13,19 in which patients were only tested with noise coincident with the speech in the 0-degree azimuth. The same effect was also observed with the use of directional microphones (data not shown). Patients in our study essentially performed equally well in both the omnidirectional and directional microphone settings when speech was presented from the front and noise from 180 degrees behind. Many patients subjectively prefer the directional microphone setting as it has a softer, more natural sound quality, especially in noise. Patients were all tested in the omnidirectional setting in the 90/270 paradigm for consistency even if patients expressed a preference for the directional mode. We did not assess sound localization in our study as previous studies have demonstrated that the expanded sound field provided by BAHA in unilateral hearing loss did not confer binaural hearing to permit significant sound localiza-
Table 3 Abbreviated Profile of Hearing Aid Benefit (APHAB) domain scores among respondents in the unaided (preoperative) and BAHA (postoperative) situations APHAB domain scores Ease of communication (EC)
Reverberant condition (RV)
Background noise (BN)
Aversiveness to sound (AV)
Patient Unaided Aided Change Unaided Aided Change Unaided Aided Change Unaided Aided Change 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
54.2 14.2 40.0 18.5 27.0 ⫺8.5 20.5 8.7 11.8 31.2 6.5 24.7 22.8 14.7 8.1 6.8 1.0 5.8 10.8 6.8 4.0 18.5 10.2 8.3 10.8 6.5 4.3 27.0 18.5 8.5 16.3 10.2 6.1 8.3 2.8 5.5 60.2 16.5 43.7 41.3 27.0 14.3 45.7 1.0 44.7 60.3 22.8 37.5 Change score ⫽ 16.2 (95% CI, 7.4-25.0)
68.6 62.4 6.2 35.3 60.3 ⫺25.0 45.9 20.7 25.2 58.2 18.7 39.5 25.0 16.3 8.7 43.8 27.2 16.6 25.0 12.0 13.0 33.3 16.3 17.0 47.8 20.5 27.3 45.8 22.7 23.1 25.0 17.2 7.8 20.8 5.0 15.8 74.7 35.2 39.5 87.0 79.8 7.2 85.0 47.5 37.5 72.7 41.7 31.0 Change score ⫽ 18.2 (95% CI, 9.5-26.9)
79.0 66.5 12.5 52.0 68.5 ⫺16.5 56.2 33.2 23.0 78.8 45.7 33.1 43.7 37.5 6.2 78.7 14.7 64.0 54.2 24.8 29.4 62.5 33.3 29.2 66.5 39.5 27.0 66.7 41.7 25.0 29.2 14.2 15.0 80.8 18.5 62.3 68.3 54.0 14.3 74.5 56.0 18.5 68.7 35.2 33.5 80.8 35.3 45.5 Change score ⫽ 26.4 (95% CI, 15.8-37.0)
70.3 70.3 0.0 8.7 15.0 ⫺6.3 24.7 24.7 0.0 50.0 43.7 6.3 24.7 35.3 ⫺10.6 25.5 2.8 22.7 43.7 27.2 16.5 6.5 6.5 0.0 9.0 9.0 0.0 83.0 52.0 31.0 74.7 37.4 37.3 58.2 8.3 49.9 82.5 80.5 2.0 18.8 17.0 1.8 10.2 12.8 ⫺2.6 66.2 62.5 3.7 Change score ⫽ 9.5 (95% CI, 0.4-18.6)
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tion.6,13,19 The improvement in speech recognition using the two test paradigms clearly demonstrated that speech signals were effectively conveyed transcranially by the BAHA device in the presence of competing noise. This has also been shown by Lin et al19 and is likely due to the elimination of the acoustic head shadow effect. Debate continues as to the best assessment method for evaluating subjective hearing aid benefit.20 There is no standardized questionnaire specifically designed to assess the unique difficulties posed by SSD. During the last few years, the APHAB has become a popular and practical tool to evaluate hearing aid benefit.6,11,14,19 In our study, the APHAB showed a significant improvement in the domains of EC, RV, and BN but not in the AV domain, an observation that was also made by Hol et al,11 who found no statistical significance in the AV domain in the aided vs unaided situation. The aversion to sound reflects a subjective overamplification of noise by the BAHA. The GHABP questionnaire was also employed in this cohort to determine subjective improvement. Among the 16 patients who responded to the questionnaire, the subjective benefits in our patients were substantial, with consistent high scores in the use, perception of benefit, and satisfaction with the BAHA, and a low score with residual disability. These scores were similar to that observed by Hol et al.11 Although the scale scores produced by the GHABP are thought to be more informative with respect to withinpatient trends and changes in scores on individual questions, they are informative in their own right. The mean GHABP scores obtained in this study suggested a consistent trend of advantages and subjective benefits provided by the BAHA in SSD. A further sub-analysis of the patient-specific concerns identified by part two of the GHABP may reveal greater benefits of the BAHA for SSD that are not probed by standardized situations. As indicated by the APHAB and GHABP surveys of benefit, the subjects in this study found BAHA amplification to be consistently useful in a variety of listening environments experienced in daily life.
CONCLUSION The BAHA system improves speech reception threshold levels in the presence of noise in the situation of SSD by overcoming the head shadow effect and expanding the sound field. In addition, subjective benefit was consistently reported, as indicated by qualitative measures through questionnaires.
AUTHOR INFORMATION From the Department of Otolaryngology–Head and Neck Surgery, Sunnybrook Health Sciences Centre, University of Toronto.
Corresponding author: Joseph M. Chen, MD, FRCSC, Department of Otolaryngology–Head and Neck Surgery, Sunnybrook Health Sciences Centre, University of Toronto, 2075 Bayview Avenue, M1-102, Toronto, ON M4N 3M5, Canada. E-mail address: [email protected].
AUTHOR CONTRIBUTIONS Heng-Wai Yuen, data collection, study design, writer; Daniel Bodmer, data collection, writer; Kari Smilsky, data collection, critical review; Julian M. Nedzelski, data collection, critical review; Joseph M. Chen, study design, data collection, writer, critical review.
DISCLOSURES Competing interests: None. Sponsorships: Heng-Wai Yuen was supported by a fellowship grant under the Health Manpower Development Program (HMDP) from the Ministry of Health, Republic of Singapore. Daniel Bodmer was supported by a fellowship grant from the University of Zurich, Switzerland (StiefelZangger-Stiftung).
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14. Cox RM, Alexander GC. The abbreviated profile of hearing aid benefit. Ear Hear 1995;16:176 – 86. 15. Gatehouse S. Glasgow Hearing Aid Benefit Profile: derivation and validation of a client-centered outcome measure for hearing aid services. J Am Acad Audiol 1999;10:80 –103. 16. Giolas T. Aural rehabilitation of adults with hearing impairment. In: Katz J, editor. Handbook of clinical audiology. 4th ed. Baltimore: Williams and Wilkins; 1994. p. 776 –92. 17. Sargent EW, Herrmann B, Hollenbeak CS, et al. The minimum speech test battery in profound unilateral hearing loss. Otol Neurotol 2001;22:480 – 6.
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18. Nilsson M, Soli SD, Sullivan J. Development of a hearing in noise test for the measurement of speech reception threshold. J Acoust Soc Am 1994;95:1085–99. 19. Lin LM, Bowditch S, Anderson MJ, et al. Amplification in the rehabilitation of unilateral deafness: speech in noise and directional hearing effects with bone-anchored hearing and contralateral routing of signal amplification. Otol Neurotol 2006;27:172– 82. 20. Hol MK, Spath MA, Krabbe PF, et al. The bone-anchored hearing aid. Quality-of-life assessment. Arch Otolaryngol Head Neck Surg 2004; 130:394 –9.
ORIGINAL RESEARCH—OTOLOGY AND NEUROTOLOGY
Management of single-sided deafness with the bone-anchored hearing aid Heng-Wai Yuen, MBBS, MRCS, DOHNS, Daniel Bodmer, MD, PhD, Kari Smilsky, MclSci, Julian M. Nedzelski, MD, FRCSC, and Joseph M. Chen, MD, FRCSC, Toronto, ON, Canada Sponsorships or competing interests that may be relevant to content are disclosed at the end of this article. ABSTRACT OBJECTIVES: The benefits of the bone-anchored hearing aid (BAHA) for rehabilitation of conductive and mixed hearing loss are well established. Recently, the BAHA was used to rehabilitate patients with single-sided deafness (SSD). In this study, the benefits of the BAHA in SSD are presented. STUDY DESIGN: Case series with planned data collection. SETTING: Tertiary referral center. SUBJECTS AND METHODS: Twenty-one consecutive adult patients with SSD underwent single-stage BAHA implantation on the side of deafness. Testing in sound field was performed using the hearing-in-noise test (HINT) in both unaided and aided conditions. Speech and noise signals were delivered through two speakers oriented in two test paradigms. The outcomes were expressed as signal-to-noise (S/N) ratios. Subjective benefit analyses were determined through two questionnaires: the Abbreviated Profile of Hearing Aid Benefit (APHAB) and the Glasgow Hearing Aid Benefit Profile (GHABP). RESULTS: All subjects demonstrated significant improvement in speech reception thresholds with the HINT using the BAHA, especially with the 90/270 speaker paradigm, in which the mean improvement over the unaided condition was 5.5 dB SPL (range, 2.0-11.0 dB; P ⫽ 0.00001). Qualitative subjective outcome measures demonstrated additional benefits. CONCLUSION: In SSD patients, the BAHA provides significant subjective benefits and improves speech understanding in noise. © 2009 American Academy of Otolaryngology–Head and Neck Surgery Foundation. All rights reserved.
A
ural rehabilitation in the context of single-sided deafness (SSD) is very challenging because of the limited options available. Historically, rerouting sound from the deafened side to the hearing ear with hearing aids such as the contralateral routing of sound (CROS) device was the mainstay of treatment for this condition.1,2 There were divergent reports of success and patient satisfaction with a CROS hearing aid,1 and the overall acceptance rate of the CROS aids has remained low. Attempts to use a single,
tightly-fitted canal aid to achieve transcranial CROS hearing proved unpopular due to discomfort and insufficient gain.2,3 Limited subjective and objective benefits from the transcutaneous loss of energy led to the discontinued use of the Audiant implantable device.4 The use of conventional boneconducting hearing aids is constrained by several factors including pain, headache, and skin irritation at the site of contact. Sound quality and fidelity varied with sound attenuation as a function of scalp thickness, vibrator location, and the tension of the securing device.5,6 The advent of the bone-anchored hearing aid (BAHA) resolved a number of issues related to the quality of sound perception. Through a percutaneous abutment, a direct coupling of the sound processor to an implanted screw led to minimal attenuation. Short- and long-term studies have confirmed that the BAHA is a viable and preferable alternative to traditional amplification to remediate conductive or mixed hearing loss, especially for those who cannot wear a conventional hearing aid.1,7-11 Vaneecloo et al12 reported the first series of aural rehabilitation for SSD using a BAHA on the deaf side. Subsequently, increased awareness in North America led to the expanded use of this device in SSD.6,13 In the United States, the BAHA was approved by the Food and Drug Administration (FDA) for use in patients with bilateral conductive or mixed hearing loss in 1996, and for SSD in 2002. In Canada, the BAHA was approved by Health Canada for SSD in 2003. In this report, patients with SSD treated with the BAHA device were evaluated in a prospective manner through subjective and objective indices of auditory performance.
MATERIAL AND METHODS Twenty-one consecutive adult patients with SSD were included in the study. Those with unilateral severe to profound sensorineural hearing loss and a speech discrimination score of less than 30 percent were included. The better
Received October 15, 2008; revised December 31, 2008; accepted February 20, 2009.
0194-5998/$36.00 © 2009 American Academy of Otolaryngology–Head and Neck Surgery Foundation. All rights reserved. doi:10.1016/j.otohns.2009.02.029
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ear had a pure-tone threshold of 35 dB HL or better and a speech discrimination score of at least 80 percent. Institutional review board approval was obtained. All patients underwent standard audiometric testing in a double-walled sound booth. Pure-tone air- and bone-conduction thresholds were measured using the standard Hughson-Westlake procedure. Speech recognition was established using a 25-item W-22 word list presented at the patient’s most comfortable listening level, or at 30 to 40 dB SPL. Surgical candidacy was established by audiologic criteria and the patient’s subjective response to two separate trials of listening to speech and environmental sounds using the BAHA sound processor. Trials were done with the better ear occluded and open. At the initial visit, a test band was used; at the second visit, a bite bar was placed firmly over the mastoid cortex on the deafened side. None of our patients had a home trial with the headband prior to implantation. Only subjects who expressed a significantly heightened sense of improvement and satisfaction, and those who were not put off by the cosmetic challenges of a BAHA, were deemed suitable for this device. Complete audiologic tests and questionnaires were administered prior to surgery. All subjects underwent a standard, one-stage procedure to implant the one-piece titanium screw with abutment on the side of SSD. External sound-processor fitting was scheduled for three months following surgery to allow osseointegration to occur.
Speech Recognition Testing The hearing-in-noise test (HINT) was used for speech recognition testing about three months after BAHA fitting in all
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21 patients. Noise was presented at a fixed level of 65 dB, and sentences varied around the noise depending on the response of the patients. The HINT threshold is defined as the decibel signal-to-noise (S/N) ratio whereby the subject correctly identifies half of the sentences. Two signal-to-noise delivery paradigms were used with speakers oriented in the 0/180-degree positions (front-back) and 90/270-degree positions (left-right). For the 0/180 paradigm, speech signal was presented at 0 degree (front) and noise at 180 degrees (Fig 1a). In the 90/270 paradigm, speech was presented at 90 degrees (deaf side) and noise at 270 degrees (hearing side) (Fig 1b). No other speaker paradigms were used as sound localization test was not conducted. Patients were evaluated both with the BAHA system turned off (unaided) and with it turned on (aided). In each test condition, the speech reception thresholds were measured twice, and the results were averaged. The sound field and speech levels were calibrated for each patient. Positioning in the sound booth did not change between the aided and unaided conditions. The volume setting of the BAHA was set to the patient’s preference and optimal level; this setting was at 2 1/2 out of 3 in the majority of patients.
Patient Subjective Outcome Analysis In addition to audiometric evaluation, patients were asked to complete user-benefit questionnaires. Two questionnaires were administered: 1) Abbreviated Profile of Hearing Aid benefit (APHAB)14 pre- and post-fitting, and 2) Glasgow
Figure 1 Speaker paradigms used in the study. (A) The 0/180 paradigm showing a patient with a left BAHA. (B) The 90/270 paradigm showing a patient with a left BAHA.
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Hearing Aid Benefit Profile (GHABP)15 post-fitting. Both post-fitting questionnaires were administered via mail approximately three months following fitting. The APHAB consists of 24 items to evaluate hearing benefit across four different domains: ease of communication (EC), reverberant conditions (RV), background noise (BN), and aversiveness of sound (AV). A higher score indicates greater difficulty.14 The GHABP evaluates initial hearing disability, handicap, hearing aid use, hearing aid benefit, residual disability, and patients’ satisfaction with their hearing aids.15 This questionnaire consists of two parts: the first covers four predetermined environments and in the second part the patient is asked to identify up to four additional situations in which they experience hearing difficulties. A score is calculated based on the answers.15 Higher scores in the initial disability, handicap, and residual disability domains suggest greater difficulties, whereas higher scores in the domains of use, benefit, and satisfaction are more desirable.
Statistical Analysis The paired t test was applied to the results of the speech perception measurements and tests and was used to compare mean values in the different domains of the APHAB and GHABP. A P value of less than 0.05 was chosen as the level of significance.
RESULTS Between July 2004 and May 2008, 65 patients with SSD fulfilled the candidacy criteria for a BAHA; 34 patients received the BAHA implantation surgery. Complete one-year data were available for 21 patients. Demographic data of the 21 consecutive SSD patients who underwent rehabilitation with a BAHA system are shown in Table 1. There were eight male and 13 female subjects. Mean age at implantation was 54.5 years (range, 33.1 to 72.1 years). The BAHA was implanted on the right side in 15 cases and on the left side in six cases. The first two patients were fitted with the BAHA Compact sound processor, and the remaining patients were fitted with the BAHA Divino sound processor (Cochlear Nordic AB, Molnlycke, Sweden) when it became available. The etiologies of SSD included: translabyrinthine cerebellopontine angle tumor surgery (n ⫽ 10), idiopathic sudden sensorineural hearing loss (n ⫽ 3), cholesteatoma (n ⫽ 2), mastoidectomy for chronic suppurative otitis media (n ⫽ 2), mumps (n ⫽ 1), congenital SSD (n ⫽ 1), labyrinthectomy for Menière’s disease (n ⫽ 1), and gentamicin treatment for Menière’s disease (n ⫽ 1). The mean duration of deafness was 11 years (range, 4 months to 59 years); the longest duration of deafness occurred in the patient with congenital SSD. There was no notable difference in performance of this patient compared with those with noncongenital causes.
Table 1 Patient characteristics
Patient
Age at surgery (years)
Gender
Ear implanted
1 2 3 4 5 6 7 8 9
57 42 59 51 72 70 60 34 59
M F F F M F M F M
L R R R R L R L R
10 11
72 33
F F
L L
12 13 14 15 16 17 18 19 20
47 59 52 72 38 65 44 50 42
F M F F M F F M M
L R R R R R R R R
21
66
F
R
Cause of loss Cholesteatoma Cholesteatoma Acoustic neuroma Acoustic neuroma Acoustic neuroma Acoustic neuroma Acoustic neuroma ISSNHL Congenital hearing loss Chronic otitis media Gentamicin treatment for Menière’s Acoustic neuroma Acoustic neuroma Meningioma Acoustic neuroma Chronic otitis media Labyrinthectomy Mumps ISSNHL Acoustic neuroma excision ISSNHL
PTA [dB] (better ear)
PTA [dB] (SSD ear)
Speech recognition (SSD ear)
8.33 10.00 1.67 20.00 20.00 5.00 13.33 11.67 15.33
BTL BTL 90.00 BTL BTL BTL 90.00 80.00 BTL
0% 0% 0% 0% 0% 0% 24% 0% 0%
15 years 10 years
38.33 40.00
76.67 BTL
0% 0%
12 9 4 12 10 10 35 17 6
months months months years years years years years years
11.67 16.67 16.67 18.33 31.67 8.33 6.67 5.00 10.00
BTL BTL BTL BTL 110.00 BTL 103.33 108.33 BTL
0% 0% 0% 0% 28% 0% 0% 0% 0%
36 months
21.67
BTL
0%
Duration of deafness 22 16 5 7 10 5 10 19 59
months months years years years years years months years
PTA, pure-tone average over frequencies 500, 1000, 2000, 4000 Hz; ISSNHL, idiopathic sudden sensorineural hearing loss; BTL, beyond test limits.
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Five of the patients had previous experience with a CROS hearing aid; none had maintained the use of such a device. All patients had severe to profound hearing loss in their poorer ear. Nineteen of the subjects had no speech recognition (0%) in the poorer ear, and the remaining two subjects had speech recognition scores of 24 percent and 28 percent, respectively. Nineteen patients had normal hearing in their better ear (pure-tone average [PTA] ⬍ 20 dB HL). Two patients had mild hearing loss (PTA ⫽ 20-40 dB HL). Surgeries were uneventful in all 21 patients with no implant extrusion, intraoperative hemorrhage, cerebrospinal fluid leakage, or infection. One patient required minor flap revision to debulk tissues adjacent to the percutaneous abutment to improve fitting of the external sound processor. The mean interval between surgery and BAHA fitting was 4.4 months (range, 3-15 months). One patient waited for 15 months to fit the BAHA because of financial constraints. The mean duration of follow-up after BAHA fitting was 22.4 months (range, 7.0-48.0 months). At the conclusion of this study, there were no nonusers.
Speech Recognition Testing Speech perception thresholds with noise during the HINT tests are expressed as signal-to-noise (S/N) ratios. As the noise level was fixed, the S/N ratio was recorded as a positive or negative value. If a patient could hear the speech signal at a lower level than the background noise, the S/N ratio would be presented as a negative number. Similarly, if the patient could hear the speech signal at a higher level than the background noise, the S/N ratio was positive. When the BAHA-aided condition was compared with the unaided condition, a decrease in S/N ratio reflected an improvement in speech recognition and, thus, a better outcome. Complete audiometric data were available in all the patients. In the 0/180 paradigm, there was an increase of S/N ratio (ie, hearing deterioration) of 1.6 dB SPL (range, 0-5 dB) when the BAHA was turned on compared to when it was turned off (Fig 2). This was statistically significant (P ⫽ 0.01). In the 90/270 paradigm, all patients demonstrated an improvement of speech reception thresholds using the BAHA device. The mean decrease in S/N ratio was 5.5 dB SPL (range, 2-11 dB) when the BAHA was turned on compared to when it was turned off. This difference in the HINT tests in the 90/270 paradigm was statistically significant (P ⫽ 0.00001) (Fig 2). The changes in the HINT scores are summarized in Table 2.
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Figure 2 Results of HINT test in 20 patients in the unaided and BAHA-aided condition. Signal-to-noise (S/N) ratios were derived by numerically subtracting the noise level (fixed at 65 dB) from the speech reception thresholds. Therefore, negative S/N ratio values denote speech reception thresholds lower than noise level, and vice versa (see text for further details). The difference between the unaided and aided conditions was statistically significant for the 90/270 paradigm (*).
consistently higher (ie, less favorable) in all four domains than in the aided situation. In addition, the difference was statistically significant in the communication performance domains EC (P ⫽ 0.001), RV (P ⫽ 0.0007), and BN (P ⫽ 0.0002). The positive impact of the BAHA has a borderline significance on aversiveness of sound (P ⫽ 0.04). The changes in scores in the domains are summarized in Table 3. The patients’ scores on the GHABP questionnaire were scaled to lie between 0 and 100 to represent categorical levels of benefit, from small to large.15 There were large standard deviations in the scores reflecting the highly variable range of reported experience with the BAHA. A mean initial disability score of 58.5 (⫾ 9.7) was obtained in the initial disability domain. In the initial handicap domain the mean score was 60.1 (⫾ 16.3). Measures obtained after BAHA fitting revealed a mean score of 33.8 (⫾ 12.2) in the residual disability domain. In the domain that probed the proportion of time the BAHA was used in the given situation, a mean score of 82.4 (⫾ 23.2) was obtained. In the benefit domain, the mean score was 48.5 (⫾ 20.5), while in the satisfaction domain the mean score was 58.9 (⫾ 25.5).
Patient Subjective Outcome Analysis Sixteen patients completed and returned both questionnaires, giving a response rate of 67 percent. These patients used BAHAs an average of 5.6 days a week (range, 1.0-7.0 days), for an estimated mean duration of 11.4 hours per day (range, 4.0-16.0 hours). The mean scores on the four domains of the APHAB are shown in Figure 3. In the unaided situation, the scores are
DISCUSSION It is well documented that monaural hearing does not provide normal hearing in many listening situations,16 especially hearing in noise. The greatest difficulties for monaural listeners occur when the sound source is positioned on the
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Table 2 Hearing in noise test (HINT) scores in patients (n ⴝ 21) in the unaided (preoperative) and BAHA situations) Signal-to-noise (S/N) ratio (dB), testing paradigm 0/180 paradigm Patient 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
Unaided
BAHA
90/270 paradigm Change*
⫺10.0 ⫺12.0 2.0 ⫺6.0 ⫺6.0 0.0 ⫺6.0 ⫺3.0 3.0 ⫺2.0 3.0 5.0 ⫺5.0 ⫺5.0 0.0 ⫺6.0 ⫺6.0 0.0 ⫺6.0 ⫺5.0 1.0 ⫺6.0 ⫺4.0 2.0 ⫺1.0 0.0 1.0 3.0 5.0 2.0 ⫺6.0 ⫺4.0 2.0 ⫺6.0 ⫺3.0 3.0 0.0 ⫺1.0 1.0 ⫺4.0 0.0 4.0 4.0 5.0 1.0 ⫺3.0 0.0 3.0 ⫺1.0 0.0 1.0 ⫺5.0 ⫺5.0 0.0 0.0 ⫺2.0 2.0 ⫺1.0 ⫺1.0 0.0 0.0 0.0 0.0 Change* S/N ratio ⫽ 1.6 (95% CI, 1.0-2.3)
Unaided
BAHA
Change*
⫺8.0 ⫺14.0 6.0 0.0 ⫺7.0 7.0 3.0 ⫺4.0 7.0 6.0 ⫺2.0 8.0 2.0 ⫺3.0 5.0 4.0 ⫺1.0 5.0 4.0 ⫺3.0 7.0 2.0 ⫺6.0 8.0 2.0 0.0 2.0 12.0 2.0 10.0 2.0 ⫺6.0 8.0 6.0 4.0 2.0 4.0 0.0 4.0 ⫺1.0 ⫺4.0 3.0 5.0 3.0 2.0 4.0 ⫺7.0 11.0 5.0 1.0 4.0 2.0 ⫺4.0 6.0 6.0 0.0 6.0 4.0 2.0 2.0 6.0 3.0 3.0 Change* S/N ratio ⫽ 5.5 (95% CI, 4.3-6.7)
*Change is denoted in absolute values.
side of impairment due to the exaggerated head shadow effect.17 The BAHA system allows direct transmission of electromechanical energy to the skull without the dampening effects of the overlying soft tissues, effectively becoming a transcranial conductive device that expands the sound field through contralateral routing of the offside signal. The energy transfer is efficient since interaural attenuation for bone conduction is essentially nil.12 The relative benefits of the BAHA over the CROS device have been shown in previous studies.6,13 Both Niparko et al6 and Wazen et al13 showed that BAHA provided significantly greater speech intelligibility compared to CROS amplification as demonstrated in speech recognition with HINT testing. Niparko et al6 also demonstrated that CROS amplification does not provide benefits compared to the monaural unaided conditions. In this study, four patients were previously rehabilitated with a CROS device for an average duration of 1 month to 2 years; all four had abandoned the CROS device at the time of BAHA assessment. A direct comparison of auditory performance using the CROS with a BAHA was not attempted in this study. However, all four patients indicated better sound resolution with the BAHA and showed improvement based on the APHAB and GHABP questionnaires. We utilized specific speaker paradigms representing challenging real-life hearing situations to evaluate the audiometric benefits of the BAHA. The benefit of the BAHA
was best exemplified in the 90/270 test paradigm when the speech signals were presented to the deaf ear with the BAHA turned on, and when the noise signals were presented only to the hearing ear. The S/N ratio improvement of 5.5 dB SPL when the BAHA was on vs when it was off was highly significant (P ⫽ 0.00001). Given that a 1-dB decrease in S/N ratio reflects a 10 percent improvement in speech recognition,18 this clearly translates into a significant clinical benefit. The same observations were reported by others, including Wazen et al13 and Lin et al.19 In these studies, when the HINT was conducted with noise directly in front of the listener (coincident with the speech), no hearing aid advantage was conferred by the BAHA. In contrast, when the noise source was placed near the functional ear, significant benefit from the BAHA was realized. This showed that the BAHA system effectively expands the sound field through routing of offside auditory signal. Generally, patients with SSD do not experience much hindrance when noise is presented to the deaf side. Following BAHA fitting, the amplified noise could in fact become bothersome. A previous study13 showed that this situation could result in reduced speech intelligibility compared to the unaided situation. We did not test the situation in which noise is presented to the BAHA-aided side while speech is presented to the functional ear; in the real-life situation, a patient could turn down the level of amplification or turn off
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Management of single-sided deafness with the . . .
Figure 3 Mean scores of 14 patients in the following domains: ease of communication (EC), background noise (BN), reverberation (RV), and aversiveness of sound (AV) on the APHAB in the unaided and BAHA-aided conditions. Lower scores indicate more favorable situations. (**) indicates the domains in which the difference between the unaided and aided conditions is statistically significant (P ⬍ 0.05).
the BAHA completely in the presence of overwhelming noise. This is a common theme among our patients. Nevertheless, none had sufficient aversion to noise to become a nonuser. Another reason is the considerable time involved
21
in testing too many speaker paradigms. The 90/270-degree paradigm is what we were most interested in to ensure that the BAHA was offering a release from the head shadow effect. Interestingly, we reported a slight but statistically significant worsening of S/N ratio with the BAHA turned on compared to off in the 0/180 test paradigm. In this scenario, the noise stimulus presented behind the subject may be perceived as a distraction to the BAHA side, as the sound processor is set 5 to 6 cm behind the pinna, which cannot shield the microphone. These observations were not noted by previous studies13,19 in which patients were only tested with noise coincident with the speech in the 0-degree azimuth. The same effect was also observed with the use of directional microphones (data not shown). Patients in our study essentially performed equally well in both the omnidirectional and directional microphone settings when speech was presented from the front and noise from 180 degrees behind. Many patients subjectively prefer the directional microphone setting as it has a softer, more natural sound quality, especially in noise. Patients were all tested in the omnidirectional setting in the 90/270 paradigm for consistency even if patients expressed a preference for the directional mode. We did not assess sound localization in our study as previous studies have demonstrated that the expanded sound field provided by BAHA in unilateral hearing loss did not confer binaural hearing to permit significant sound localiza-
Table 3 Abbreviated Profile of Hearing Aid Benefit (APHAB) domain scores among respondents in the unaided (preoperative) and BAHA (postoperative) situations APHAB domain scores Ease of communication (EC)
Reverberant condition (RV)
Background noise (BN)
Aversiveness to sound (AV)
Patient Unaided Aided Change Unaided Aided Change Unaided Aided Change Unaided Aided Change 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
54.2 14.2 40.0 18.5 27.0 ⫺8.5 20.5 8.7 11.8 31.2 6.5 24.7 22.8 14.7 8.1 6.8 1.0 5.8 10.8 6.8 4.0 18.5 10.2 8.3 10.8 6.5 4.3 27.0 18.5 8.5 16.3 10.2 6.1 8.3 2.8 5.5 60.2 16.5 43.7 41.3 27.0 14.3 45.7 1.0 44.7 60.3 22.8 37.5 Change score ⫽ 16.2 (95% CI, 7.4-25.0)
68.6 62.4 6.2 35.3 60.3 ⫺25.0 45.9 20.7 25.2 58.2 18.7 39.5 25.0 16.3 8.7 43.8 27.2 16.6 25.0 12.0 13.0 33.3 16.3 17.0 47.8 20.5 27.3 45.8 22.7 23.1 25.0 17.2 7.8 20.8 5.0 15.8 74.7 35.2 39.5 87.0 79.8 7.2 85.0 47.5 37.5 72.7 41.7 31.0 Change score ⫽ 18.2 (95% CI, 9.5-26.9)
79.0 66.5 12.5 52.0 68.5 ⫺16.5 56.2 33.2 23.0 78.8 45.7 33.1 43.7 37.5 6.2 78.7 14.7 64.0 54.2 24.8 29.4 62.5 33.3 29.2 66.5 39.5 27.0 66.7 41.7 25.0 29.2 14.2 15.0 80.8 18.5 62.3 68.3 54.0 14.3 74.5 56.0 18.5 68.7 35.2 33.5 80.8 35.3 45.5 Change score ⫽ 26.4 (95% CI, 15.8-37.0)
70.3 70.3 0.0 8.7 15.0 ⫺6.3 24.7 24.7 0.0 50.0 43.7 6.3 24.7 35.3 ⫺10.6 25.5 2.8 22.7 43.7 27.2 16.5 6.5 6.5 0.0 9.0 9.0 0.0 83.0 52.0 31.0 74.7 37.4 37.3 58.2 8.3 49.9 82.5 80.5 2.0 18.8 17.0 1.8 10.2 12.8 ⫺2.6 66.2 62.5 3.7 Change score ⫽ 9.5 (95% CI, 0.4-18.6)
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tion.6,13,19 The improvement in speech recognition using the two test paradigms clearly demonstrated that speech signals were effectively conveyed transcranially by the BAHA device in the presence of competing noise. This has also been shown by Lin et al19 and is likely due to the elimination of the acoustic head shadow effect. Debate continues as to the best assessment method for evaluating subjective hearing aid benefit.20 There is no standardized questionnaire specifically designed to assess the unique difficulties posed by SSD. During the last few years, the APHAB has become a popular and practical tool to evaluate hearing aid benefit.6,11,14,19 In our study, the APHAB showed a significant improvement in the domains of EC, RV, and BN but not in the AV domain, an observation that was also made by Hol et al,11 who found no statistical significance in the AV domain in the aided vs unaided situation. The aversion to sound reflects a subjective overamplification of noise by the BAHA. The GHABP questionnaire was also employed in this cohort to determine subjective improvement. Among the 16 patients who responded to the questionnaire, the subjective benefits in our patients were substantial, with consistent high scores in the use, perception of benefit, and satisfaction with the BAHA, and a low score with residual disability. These scores were similar to that observed by Hol et al.11 Although the scale scores produced by the GHABP are thought to be more informative with respect to withinpatient trends and changes in scores on individual questions, they are informative in their own right. The mean GHABP scores obtained in this study suggested a consistent trend of advantages and subjective benefits provided by the BAHA in SSD. A further sub-analysis of the patient-specific concerns identified by part two of the GHABP may reveal greater benefits of the BAHA for SSD that are not probed by standardized situations. As indicated by the APHAB and GHABP surveys of benefit, the subjects in this study found BAHA amplification to be consistently useful in a variety of listening environments experienced in daily life.
CONCLUSION The BAHA system improves speech reception threshold levels in the presence of noise in the situation of SSD by overcoming the head shadow effect and expanding the sound field. In addition, subjective benefit was consistently reported, as indicated by qualitative measures through questionnaires.
AUTHOR INFORMATION From the Department of Otolaryngology–Head and Neck Surgery, Sunnybrook Health Sciences Centre, University of Toronto.
Corresponding author: Joseph M. Chen, MD, FRCSC, Department of Otolaryngology–Head and Neck Surgery, Sunnybrook Health Sciences Centre, University of Toronto, 2075 Bayview Avenue, M1-102, Toronto, ON M4N 3M5, Canada. E-mail address: [email protected].
AUTHOR CONTRIBUTIONS Heng-Wai Yuen, data collection, study design, writer; Daniel Bodmer, data collection, writer; Kari Smilsky, data collection, critical review; Julian M. Nedzelski, data collection, critical review; Joseph M. Chen, study design, data collection, writer, critical review.
DISCLOSURES Competing interests: None. Sponsorships: Heng-Wai Yuen was supported by a fellowship grant under the Health Manpower Development Program (HMDP) from the Ministry of Health, Republic of Singapore. Daniel Bodmer was supported by a fellowship grant from the University of Zurich, Switzerland (StiefelZangger-Stiftung).
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