Binaurality in middle ear implant recipients using contralateral digital hearing AIDS

OBJECTIVE: For some patients, conventional hearing aids might have disadvantages that clearly limit the benefit of using them. The middle ear implant, Vibrant Soundbridge hearing prosthesis offers an approach to help such patients. Our study's objective was to identify the binaurality in a well-fitted digital hearing aid worn in the contralateral ear in recipients experienced with use of the Vibrant Soundbridge middle ear implant device. STUDY DESIGN: In a prospective study, warble-tone thresholds and stereophony were evaluated for the following conditions: (1) binaural unaided-with the middle ear implant inactive and the behind-the-ear hearing aid removed; (2) middle ear implant alone-middle ear implant active, behind-the-ear hearing aid removed; (3) middle ear implant plus behind-the-ear omnidirectional-middle ear implant active, behind-the-ear active; and (4) behind-the-ear omnidirectional alone-middle ear implant inactive, behind-the-ear omnidirectional active. Behind-the-ear omnidirectional and behind-the-ear is defined as the behind-the-ear active in the omnidirectional or directional response, respectively. Behind-the-ear is a contralateral digital hearing aid to the middle ear implant. Benefits such as improved sound detection, speech perception in quiet and in noise, and sound quality were investigated. The evaluation of subjective hearing benefit was based on the Abbreviated Profile of Hearing Aid Benefit (APHAB) test. Paired t tests (subject) were used to analyze the differences between mean thresholds for the different test conditions. SETTING: Tertiary referral center. PATIENTS: Eight adults (aged 45-68 yr) had undergone implantation with a single Vibrant Soundbridge at least 12 months before starting the study. These eight subjects presented no contraindication for contralateral hearing aid use. Patients were fitted 5 weeks before testing with a Siemens Signia digital behind-the-ear hearing aid in the side contralateral to the Vibrant Soundbridge. RESULTS: Five weeks after use of the contralateral hearing aid together with the middle ear implant, mean differences in warble-tone thresholds between Conditions 2 and 3 and between Conditions 3 and 4 were both statistically significant. The mean differences in speech reception thresholds were in line with the mean differences in average warble-tone thresholds. The mean speech reception threshold for the middle ear implant plus behind-the-ear omnidirectional condition was slightly worse (3 dB) than that for the middle ear implant alone condition; however, this difference was not statistically significant. Whereas speech reception threshold difference between Condition 1 and Condition 4 was not statistically significant (60 dB and 61 dB, respectively). The mean difference for the 0-degree azimuth alone was statistically significant (p < 0.05) for the conditions middle ear implant alone and middle ear implant plus behind-the-ear omnidirectional. The middle ear implant alone appears to give good sensitivity at 2 kHz for any direction. Increasing scores indicate greater percentages of problems. Percentages of problems were on average lower for the middle ear implant when used with the contralateral digital hearing aid based on the global score. CONCLUSION: The use of a middle ear implant Vibrant Soundbridge together with a contralateral digital hearing aid improved functional gain and speech perception thresholds in quiet, especially for the sound coming from the front of the patient. The use of a middle ear implant together with a contralateral digital hearing did not significantly improve hearing in noise.