Results of the Bone-Anchored Hearing Aid in Unilateral Hearing Loss

The Laryngoscope Lippincott Williams & Wilkins, Inc., Philadelphia © 2001 The American Laryngological, Rhinological and Otological Society, Inc.

Results of the Bone-Anchored Hearing Aid in Unilateral Hearing Loss Jack J. Wazen, MD; Jaclyn Spitzer, PhD; Soha N. Ghossaini, MD; Ashutrosh Kacker, MD; Anne Zschommler

Objectives: The advantages of binaural hearing are well established and universally accepted. However, a tendency remains to withhold the benefits of binaural hearing to adults and children with one normal ear. The purpose of this study is to demonstrate the benefit of the bone-anchored hearing aid (BAHA) in a group of patients with unilateral conductive or mixed hearing loss. Study Design: This is a prospective study of nine patients (five males and four female patients) with conductive or mixed hearing loss who met the criteria for BAHA except for having normal hearing in the other ear. They had congenital aural atresia or mastoidectomies secondary to chronic ear infections with or without cholesteatoma or had a temporal bone tumor excised Methods: Patients had evaluations before and after implantation, including audiological testing and responses to a standardized hearing handicap questionnaire. Statistical analyses of the data were made using the Wilcoxon signed rank test and the paired Student t test for repeated measures. Results: All patients had tonal and spondee threshold improvement with BAHA when compared with thresholds before treatment. Speech recognition performance in BAHA-aided conditions was comparable to the patient’s best score in unaided condition. Patients reported a significant improvement in their hearing handicap scores with the BAHA. Conclusions: The use of BAHA has significantly improved the hearing handicap scores in patients with unilateral conductive or mixed hearing loss. The proven safety and efficacy of the device promote its use in unilateral cases that traditionally had been left unaided. Key Words: Bone-anchored hearing aid, unilateral conductive hearing loss, binaural hearing, hearing handicap. Laryngoscope, 111:955–958, 2001

Presented at the Meeting of the Eastern Section of the American Laryngological, Rhinological and Otological Society, Inc., Toronto, Ontario, Canada, January 28, 2001. From the Department of Otolaryngology—Head and Neck Surgery (J.S., A.J.M., A.Z.), Columbia University College of Physicians and Surgeons, the New York–Presbyterian Hospital, and the Research Institute for Hearing and Balance Disorders Limited (J.J.W., S.N.G.), New York, NY, U.S.A. Editor’s Note: This Manuscript was accepted for publication February 27, 2001. Send Correspondence to Jack J. Wazen, MD, 111 East 77th Street, New York, NY 10021, U.S.A.

Laryngoscope 111: June 2001

INTRODUCTION The benefits of binaural hearing in sound localization and improved speech perception in noise have been well established. Although eyeglasses replaced the “monocle ” decades ago, the use of binaural hearing aids has lagged behind. In the last few years, however, there has been a significant trend toward the fitting of binaural hearing aids. Reconstructive surgery for unilateral hearing loss has also been met with conflicting opinions. Although performing a stapedectomy in unilateral otosclerosis is widely acceptable, some authorities have argued against operating in cases of unilateral congenital aural atresia. Other authorities have argued against bilateral stapedectomies despite stapedectomy on the first side being quite successful. Although the impact of unilateral deafness has sometimes been minimized, other authors have measured conceptual, vocabulary, and speech deficits in unilaterally impaired children.1,2 Similar deficits were also observed in children with unilateral deafness in a study done by American Speech and Hearing Association (ASHA) (ASHA’s Interdisciplinary Pre-School Project, unilateral hearing loss in children: concerns and suggestions for management). Furthermore, there has been little investigation using contemporary methods such as self-rating scales or handicap assessment to evaluate the subjective impact of unilateral hearing loss in children or adults.3,4 The purpose of this study was to evaluate the effectiveness of the bone-anchored hearing aid (BAHA) in providing binaural hearing in patients with unilateral conductive or mixed hearing losses.

PATIENTS AND METHODS This prospective study was designed to investigate the benefits of BAHA in patients with unilateral conductive or mixed hearing loss who received implants between December 1999 and December 2000. Patients were included if they met the following criteria: unilateral conductive or mixed hearing loss, inability to wear an air-conduction hearing aid because of recurrent infections, congenital atresia or surgical defects disallowing use of a conventional hearing aid, and bone-conduction thresholds less than or equal to 45 dB HL. In a series of 42 patients referred for evaluation for BAHA, 9 patients (5 male and 4 female patients) met the criteria just mentioned and were included in this study. Their mean age was 45 years, with an age range of 23 to 76 years. Four patients had

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a unilateral congenital aural atresia. Two patients had temporal bone tumors (a meningioma and a squamous cell carcinoma) that were resected with a resultant conductive hearing loss. Two patients had cholesteatoma, and one patient had a chronic otitis media. Preoperative hearing thresholds for the operated ear are displayed in Table I; preoperative speech perception performance (i.e., spondee threshold and speech recognition in quiet) is displayed in Table II. All subjects received implants on the side of the ear with the conductive hearing loss. The implantation was completed in two stages. The first stage was performed with the patient under general anesthesia, and a 4-mm titanium screw was implanted in the postauricular area, 50 mm from the external auditory canal. The hair-bearing skin around the screw was excised and replaced by a full-thickness skin graft. A 3-month period was allowed for osseointegration of the screw before the second stage was done. This second stage was performed with the patient under local anesthesia and included exteriorization of the titanium screw and attachment of the abutment. After healing, the hearing aid was attached to the abutment with a bayonet or snap mount.

Audiological Tests All patients had preoperative audiological testing under headphones including pure-tone air-conduction and boneconduction thresholds, spondee threshold, and speech recognition using Northwestern University list-6 (NU-6) words. Administration level for speech recognition varied in an effort to record the maximum score for phonetically balanced words. The technique for audiological measures followed accepted practices. When feasible, the patient was evaluated to determine aided benefit with his or her current hearing aid or an appropriate stock behindthe-ear aid. The contralateral ear was occluded using a noiserated earplug noise reduction range [NRR] ⫽ 28 dB). Sound field testing was performed with the patient seated at 3 feet and 0° from the speaker. Sound field measures included thresholds for FM tones, spondee threshold, and speech recognition for NU-65 words at 70 dB HL. Preoperative and postoperative audiological studies followed the same protocol, using equivalent lists of stimuli. All patients completed the Hearing Handicap Inventory for Adults (HHIA)4 before and after BAHA use. The HHIA has been demonstrated to have high test-retest reliability, making it a sensitive measure for detection of changes in perceived handicap. All equipment was calibrated to the American National Standards Institute standard ANSI S.3–1996.6 Statistical analyses of the data were made using the Wilcoxon signed rank test and the paired Student t test for repeated measures.

RESULTS Tonal Thresholds Treatment thresholds before and after BAHA implantation for individual patients were analyzed at each of

TABLE I. Preoperative Hearing Thresholds (in dB Hearing Level, HL). Frequency (Hz)

Mean Range SD

250

500

1000

2000

4000

8000

68.89 35–95 16.7

68.30 25–95 19.53

68.89 40–105 17.99

74.40 40–115 25.30

79.44 55–115 25.30

97.30 55–110 17.90

SD ⫽ standard deviation.


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TABLE II. Preoperative Speech Perception Performance (N ⫽ 9).

Mean SD Range

SRT (dB HL)

Speech Recognition (%)*

60.63 14.99 35–90

82.22 15.38 60–96

*NU-6 words. SRT ⫽ speech reception threshold; HL ⫽ hearing level; SD ⫽ standard deviation.

the octave frequencies (500, 1000, 2000, and 4000 Hz). Analysis revealed lower thresholds with BAHA (Wilcoxon signed rank test, P ⬍.05 [one-tailed]). These data are shown in Table III, which indicates that the mean gain (preoperative threshold for the operated side minus postoperative aided threshold) is substantial at each of these frequencies. The greatest gain (66.3 dB) was obtained at 1000 Hz.

Speech Perception The BAHA-aided performance for speech perception tasks demonstrated that sensitivity was enhanced and speech recognition was maintained from its maximum preoperative scores. The spondee threshold dropped significantly (Wilcoxon signed rank test, P ⫽ .008 [onetailed]) from preoperative to BAHA-aided conditions. Regarding the speech recognition performance, the maximum preoperative score for phonetically balanced words (as obtained under headphones or in sound field) was compared with the BAHA-aided response. The best measurable performance preoperatively was compared with the BAHA outcome. The BAHA-aided speech recognition performance for each patient was approximately comparable to or better than their best preoperative condition as shown in Figure 1 (Wilcoxon signed rank test result was nonsignificant, P ⬎.05 [one-tailed]).

Handicap Perception The average score on the HHIA preoperatively was 25 (range, 10 – 40), a score falling in the “moderate” handicapped range. The postoperative mean (10 [range, 0 –14]) fell in the borderline of “mild to moderate” handicap perception range. The reduction in handicap for the individual data for these unilaterally impaired listeners was dramatic (Student t test for paired samples, P ⫽ .04 [two-

TABLE III. Mean Gain* in Hearing Thresholds (dB). Frequency (Hz)

Mean

Range

500 1000 2000 4000

41.9 66.3 49.4 45.6

5–80 40–100 15–75 20–80

*Preoperative unaided thresholds—postoperative thresholds. BAHA ⫽ bone-anchored hearing aid.

BAHA-aided


Fig. 1. Comparison of speech recognition for individuals before and after bone-anchored hearing aid.

tailed]). Five patients reported that their difficulty in daily living decreased from “severely” handicapped to a handicap of “mild to none” while using the BAHA. Two subjects (subjects S7 and S11) showed no significant change in the comparisons before and after implantation (Fig. 2). The results indicated the following: 1) There was marked improvement in tonal thresholds over preoperative (unaided) results; 2) similarly, spondee threshold improvement reflected improved sensitivity; 3) speech recognition performance in BAHA-aided conditions was comparable to the patient’s best unaided score; and 4) there was a reduction of hearing handicap from preoperative to BAHA-aided perception.

DISCUSSION The use of both ears for binaural hearing has been recognized in the otological and audiological literature as important for sound localization and improved speech perception in noise.7–9 Silman et al.10 presented powerful evidence that a form of sensory deprivation occurs, in mature individuals as well as in children, through nonstimulation of the auditory pathway. In a series of studies,

the authors showed that failure to wear binaural conventional hearing aids resulted in significantly decreased speech recognition in the unaided ear. All patients who were included in this study reported a significant handicap with their unilateral loss to warrant a surgical procedure to recover binaural hearing. All patients were very satisfied with their outcome, and when tested with the hearing handicap questionnaire, most scored a significant handicap reduction. The patients who did not score a reduction indicated, nevertheless, that there was an improvement in communicative skills and that they were pleased with the outcome. In reviewing their characteristics, one of the two was acclimated to their lifestyle as a unilateral listener (patients with congenital aural atresia) and may have required a longer timeline to perceive benefit as described in the questionnaire. The second patient stated that she needed more experience before being able to perceive a change in her life as a result of the BAHA. It is also possible that the HHIA is not the ideal instrument for detection of the problems faced by unilateral listeners because much of its content is focused on a more generalized impact of hearing loss.

Fig. 2. Comparison of handicap before and after bone-anchored hearing aid.



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There were no complications observed. Patients reported satisfaction with the procedure and the device and indicated their willingness to have the procedure again or to recommend the procedure to a friend. Furthermore, the results of this study reassured us that wearing the BAHA did not interfere with the function of the normal contralateral ear through bone conduction. Indeed, binaural stimulation may also occur, as reported by Chasin,11 who documented that binaural summation was obtained while the BAHA was being worn in unilateral conductive hearing loss. Other measurements are currently underway on this same patient sample to evaluate objectively sound localization benefit of the device and to reassess patients’ handicap at a minimum of 3 months after beginning BAHA use. Our next step is to increase sample size to apply parametric analyses. We have had a long and positive experience with the Branemark system (Goteborg, Sweden) for either BAHA12 or craniofacial applications.13 Our patients’ main wish is for the device to be made smaller. The positive patient response and acceptance, the safety and efficacy of the device, and the acknowledged benefits of binaural hearing should pave the way for more BAHA applications in unilateral hearing loss.

CONCLUSION The use of the BAHA in patients with unilateral conductive or mixed hearing loss has proven to be successful in achieving binaural hearing with no complications and no interference with the function of the normal ear. The indications for the device ought to be expanded to include unilateral hearing losses.


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