PP808 - Effectiveness of Bilateral Stimulation with Bone-Anchored Hearing Aids

Abstract: This longitudinal observational study evaluated the effectiveness of bilateral stimulation in patients with bilateral conductive or mixed hearing loss using bone-anchored hearing systems (BAHS) or middle ear implants (MEI) and compared their auditory performance under unilateral and bilateral conditions. Thirteen users (8 BAHS, 5 MEI; aged 16–56 years) were assessed through free-field audiometry, speech recognition index, and sentence recognition in silence and noise. Results showed significant bilateral advantages in audibility and speech recognition, supporting the clinical benefit of bilateral stimulation.

Summary: Bone-anchored hearing systems (BAHS) and middle ear implants (MEI) have demonstrated efficacy in restoring hearing for individuals with conductive or mixed hearing loss. However, despite the known benefits of binaural hearing, the specific contribution of bilateral stimulation remains poorly established in this population. Understanding whether bilateral adaptation provides measurable auditory advantages can support evidence-based clinical recommendations. This study aimed to evaluate the effectiveness and auditory performance of bilateral stimulation in users of BAHS and MEI compared with unilateral fitting, and to determine the binaural benefit in speech perception and audibility. This longitudinal observational study analyzed the clinical records of 13 participants (8 BAHS and 5 MEI users), aged 16 to 56 years (5 male, 8 female). Free-field audiometry, monosyllabic word recognition (Lacerda list), and sentence recognition in quiet and in noise (Maristela test) were conducted at activation and after 3, 6, and 12 months of device use. Each participant was evaluated in three conditions: unaided, unilateral, and bilateral. Statistical analyses included Friedman’s test, post-hoc Durbin-Conover pairwise comparisons, and Kendall’s W for effect size estimation. Free-field audiometry demonstrated significant global differences among conditions (p < .001; large effect, W = 0.69), with improved thresholds in both unilateral and bilateral fittings compared to unaided listening. Across frequencies, bilateral stimulation consistently produced lower thresholds, independent of coupling type (BAHS or MEI). For speech recognition of monosyllables, both groups showed significant improvement with device use (BAHS: p < .001; MEI: p = .004). Speech recognition scores increased from approximately 40% to 90% with bilateral fittings, indicating a large effect (W = 0.71). In sentence recognition in quiet, thresholds improved significantly in both groups, bilateral MEI users demonstrated slightly greater gains (p = .026), while bilateral BAHS users performed similarly to unilateral left fittings but better than right fittings. Under the noise condition (0°/0°), although no overall difference emerged across all configurations, significant improvements were found for bilateral MEI users versus unaided listening, and for BAHS users in both unilateral and bilateral fittings (p = .042; moderate-to-large effect W = 0.60). In the 0°/180° condition, numerical improvements were observed across all aided conditions, though differences between unilateral and bilateral fittings were not statistically significant. The findings suggest that bilateral auditory rehabilitation, whether with BAHS or MEI, enhances audibility and speech perception performance compared to unilateral use. The evidence supports the clinical recommendation of bilateral fitting for individuals with bilateral conductive or mixed hearing loss. Future research with larger samples and controlled designs is warranted to confirm the binaural benefits and to optimize fitting protocols for bilateral users.