After more than 25 years of clinical experience, the BAHA (bone-anchored hearing aid) system is a well-established treatment for hearing-impaired patients with conductive or mixed hearing loss. Owing to its success, the use of the BAHA system has spread and the indications for application have gradually become broader. New indications, as well as clinical applications, were discussed during scientific roundtable meetings in 2004 by experts in the field, and the outcomes of these discussions are presented in the form of statements. The issues that were discussed concerned BAHA surgery, the fitting range of the BAHA system, the BAHA system compared to conventional devices, bilateral application, the BAHA system in children, the BAHA system in patients with single-sided deafness, and, finally, the BAHA system in patients with unilateral conductive hearing loss.

The poor sound-localization results in an audiologic test setting illustrated the inability of patients with unilateral inner ear deafness to localize sounds. The speech-in-noise measurements demonstrated the efficacy of the BAHA CROS to lift the head shadow. Patients were still satisfied at 1-year follow-up, according to the four instruments.

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

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

Some patients with congenital unilateral conductive hearing impairment had such good directional hearing and speech-in-noise scores in the unaided situation that no overall significant improvement occurred after BAHA fitting in our setup. Of the 18 patients with a complete data set, 6 did not show any significant improvement at all. However, compliance with BAHA use in this patient group was remarkably high. Observations of consistent use of the device are highly suggestive of patient benefit. Further research is recommended to get more insight into these findings.