Masked Speech Perception with Bone Conduction Device, Contralateral Routing of Signals Hearing Aid, and Cochlear Implant Use in Adults with Single-Sided Deafness: A Prospective Hearing Device Comparison using a Unified Testing Framework
Authors: Wesarg Thomas , Kuntz Iris , Jung Lorenz , Wiebe Konstantin , Schatzer Reinhold , Brill Stefan , Aschendorff Antje , Arndt Susan 
Published: February 2024

<b><i>Introduction:</i></b> For the treatment of single-sided deafness (SSD), common treatment choices include a contralateral routing of signals (CROS) hearing aid, a bone conduction device (BCD), and a cochlear implant (CI). The primary aim of this study was to compare speech understanding in noise and binaural benefits in adults with postlingual SSD between preoperative unaided baseline, preoperative CROS and BCD trial devices, and CI, following recommendations from a consensus protocol. In addition, we investigated the effect of masker type on speech understanding. <b><i>Methods:</i></b> This was a prospective study with twelve participants. Binaural effects of head shadow, squelch, summation, and spatial release from masking were assessed by measuring speech reception thresholds (SRTs) in five different spatial target-masker configurations using two different maskers: two-talker babble (TTB), and speech-shaped noise (SSN). Preoperatively, participants were assessed unaided and with CROS and BCD trial devices. After cochlear implantation, participants were assessed at 1, 3, and 6 months post-activation. <b><i>Results:</i></b> For TTB, significant improvements in SRT with a CI relative to preoperatively unaided were found in all spatial configurations. With CI at 6 months, median benefits were 7.8 dB in S<sub>SSD</sub>N<sub>AH</sub> and 5.1 dB in S<sub>0</sub>N<sub>AH</sub> (head shadow), 3.4 dB in S<sub>0</sub>N<sub>0</sub> (summation), and 4.6 dB in S<sub>0</sub>N<sub>SSD</sub> and 5.1 dB in S<sub>AH</sub>N<sub>SSD</sub> (squelch). CROS yielded a significant head shadow benefit of 2.4 dB in S<sub>SSD</sub>N<sub>AH</sub> and a significant deterioration in squelch of 2.5 dB in S<sub>0</sub>N<sub>SSD</sub> and S<sub>AH</sub>N<sub>SSD</sub>, but no summation effect. With BCD, there was a significant summation benefit of 1.5 dB, but no head shadow nor squelch effect. For SSN, significant improvements in SRT with CI compared to preoperatively unaided were found in three spatial configurations. Median benefits with CI at 6 months were: 8.5 dB in S<sub>SSD</sub>N<sub>AH</sub> and 4.6 dB in S<sub>0</sub>N<sub>AH</sub> (head shadow), 1.4 dB in S<sub>0</sub>N<sub>0</sub> (summation), but no squelch. CROS showed a significant head shadow benefit of 1.7 dB in S<sub>SSD</sub>N<sub>AH</sub>, but no summation effect, and a significant deterioration in squelch of 2.9 dB in S<sub>0</sub>N<sub>SSD</sub> and 3.2 dB in S<sub>AH</sub>N<sub>SSD</sub>. With BCD, no binaural effect was obtained. Longitudinally, we found significant head shadow benefits with a CI in S<sub>SSD</sub>N<sub>AH</sub> in both maskers at all postoperative intervals and in S<sub>0</sub>N<sub>AH</sub> at 3 and 6 months post-activation. <b><i>Conclusion:</i></b> With a CI, a clear benefit for masked speech perception was observed for all binaural effects. Benefits with CROS and BCD were more limited. CROS usage was detrimental to the squelch effect.