Background
Children with unilateral conductive hearing loss (UCHL) experience degraded binaural hearing, impairing speech perception and spatial listening. Bone conduction implants (BCIs) aim to restore access to sound on the impaired side, yet the extent to which they facilitate spatial cue use and compensate for binaural deficits remains uncertain, particularly in dynamic, noisy environments.

Methods
10 children with UCHL and 10 age-matched normal-hearing (NH) peers completed a dynamic speech-in-noise task with a head tracker. Target sentences were presented at 0° and ±60° azimuth amidst diffuse babble at decreasing signal-to-noise ratios (SNRs). NH children were tested under binaural and monauralized (plug+muff) conditions. UCHL participants were assessed unaided and with BCI. Primary outcomes were speech reception thresholds and head-orienting responses.

Results
BCIs significantly improved speech perception for signals presented to the impaired ear (p<0.05). Both groups required more favorable SNRs for impaired-side targets during unilateral listening. UCHL children achieved comparable SRTs to NH peers in aided conditions moderate SNRs, though performance declined more steeply at poorer SNRs. NH children required higher SNRs in monauralized conditions, possibly reflecting compensatory adaptation in UCHL. Head-orienting behavior revealed that NH children orient efficiently with minimal turns with binaural input but cease movement when cues become ambiguous. UCHL children showed increased head movements when unaided and greater variability when aided, suggesting unreliable spatial cues and limited binaural integration.

Conclusion
BCIs improve speech perception and support compensatory orientation strategies in UCHL but fall short of restoring reliable binaural hearing. Spatial cue ambiguity and residual asymmetries limit effectiveness in complex listening environments.

Bilateral conductive/mixed hearing loss (BCHL) limits speech perception in complex listening conditions and directional hearing. Potentially these patients can benefit from a second bone-conduction devices (BCDs) or (active) middle ear implants (AMEIs). However, many studies demonstrate that treatment does not result in optimal hearing. Patients implanted with bilateral BCDs demonstrate lateralization instead of localization of sounds, and when one BCD is turned off, patients perceive the stimuli mainly coming from one location. Surprisingly, and in contrast to earlier studies in which BCHL patients were tested in the acute unilateral aided condition, at group level, patients with BCHL do not demonstrate a significant improvement in their sound localization abilities when listening with a second BCD on a softband compared to listening with their single BCD. This apparent difference is due to much better localization in the chronic unilateral condition compared to the acute unilateral BCD condition of patients tested in earlier studies. Furthermore, good localization in azimuth was found in the bilateral AMEI condition. The measurements suggest that patients implanted with AMEIs are able to process binaural cue, and that patients with one BCD or one VSB can use monaural cues when they are not tested in an acute unilateral condition. We conclude that implantation with devices stimulating only the ipsilateral cochlea in patients with pure conductive hearing loss can result in optimal sound localization abilities, and that this topic needs further investigation.

Background: The study aimed to quantify hearing benefits of bilateral bone conduction devices in children. Because bone conducted stimuli has limited interaural attention, bilateral bone conduction devices may not provide accurate interaural timing and level cues needed for spatial hearing and speech perception in noise.

Methods: Participants were 11 children (14.7(3.5) years of age) with bilateral atresia/microtia who received bilateral bone conduction devices (BCD: 6 bilateral Osia, 5 Osia/BAHA) and 11 children with typical hearing (controls: 14.9 (1.9) years of age). Outcome measures were: 1) spondee word reception thresholds (SRTs) in 3 noise conditions (front, -90°, +90°), 2) word recognition scores (WRS) in co-located noise (+10 dB SNR) with either device alone or bilaterally and 3) localization of stationary and moving sound (bandpass-filtered white noise) with no visual cues within a frontal-horizontal arc of 120°.

Results: SRTs were significantly higher in the BCD than control group (8.6 (1.9) dB, p<0.001) but both groups showed similar benefits of spatial separation from noise (2.1 (2.7) dB, p=0.43) and right ear advantage (4.8 (0.8) dB, p<0.001). The BCD group had better WRS in noise when using both devices than either one alone (Bilateral-Left: 7.4(2.7)%, p<0.05; Bilateral-Right: 7.6 (2.7)%, p<0.05) and localized stationary sound significantly better in the bilateral versus unilateral device conditions (Bilateral-Left error: -15.8 (3.8)°, p<0.001; Bilateral-Right error: -13.4 (4.0)°, p<0.01). Spatial hearing remained poorer than in controls for both stationary (32.6 (4.3)°, p<0.001) and moving sound (33.1 (4.1)°, p<0.001).

Conclusion: Bilateral bone conduction devices provide significant hearing benefits in children with bilateral atresia/microtia.