Sound Localization in Active Transcutaneous Bone Conduction Implant Users with Single-Sided Deafness

Objective: Evaluate sound localization accuracy of subjects with single-sided deafness (SSD) with active transcutaneous bone conduction implants (atBCIs). Study Design: Prospective case-control study. Setting: Tertiary referral center. Patients: Ten SSD patients (with ATBCIS) and 10 controls. Interventions: Localization was assessed in a semianechoic chamber using a 24-speaker array. Stimuli included broadband noise (BBN) and narrowband noise (NBN). Perceived stimulus angle was recorded and compared with presented location. Statistical analyses were performed using ANOVA and Wilcoxon rank sum tests. Main Outcome Measures: The primary outcome measures were as follows: 1) mean angular error (MAE) error (degrees) and regression slope and 2) subjective benefit assessment (Speech Spatial Qualities questionnaire). Results: Subjects with SSD demonstrated worse localization by MAE and regression slope compared with controls for both broadband noise (p < 0.0001) and narrowband noise at 500 Hz and 1000 kHz (p < 0.0001). There was no statistically significant difference (p = 0.1090) in slope between all groups at 4000 Hz. There was no significant difference in slope or MAE aided compared with unaided. Localization ability varied widely within the SSD cohort, with some individuals showing some ability in the unaided condition, best at 4000 Hz. Although SSQ confirmed particular difficulty in the spatial hearing domain, all domains improved with device use. Conclusions: Localization ability for individuals with SSD falls into a somewhat bimodal distribution. Some have fair localization, particularly at high frequencies, that is preserved but not improved with the atBCI. Others have minimal to no localization ability at any frequency, with no apparent device benefit.