Horizontal sound localisation accuracy in individuals with conductive hearing loss: effect of the bone conduction implant

Objective: The objective of this study is to quantify the effect of the Bone Conduction Implant (BCI) on sound localisation accuracy in subjects with conductive hearing loss (CHL).Design: The subjects were tested in a horizontal sound localisation task in which localisation responses were objectively obtained by eye-tracking, in a prospective, cross-sectional design. The tests were performed unaided and unilaterally aided. The stimulus used had a spectrum similar to female speech and was presented at 63 and 73dB SPL. The main outcome measure was the error index (EI), ranging from 0 to 1 (perfect to random performance).Study sample: Eleven subjects (aged 21-75 years, five females) with BCI participated in the study. Their mixed/conductive hearing loss was either unilateral (n=5) or bilateral (n=6).Results: Three of five subjects (60%) with unilateral CHL, and four of six subjects (67%) with bilateral CHL showed significantly improved sound localisation when using a unilateral BCI (p<.05). For the subjects with bilateral CHL, a distinct linear relation between aided sound localisation and hearing thresholds in the non-implant ear existed at 73dB SPL (18% decrease in the EI per 10dB decrease in pure-tone average, r=0.98, p<.001).Conclusions: Individuals with mixed/conductive hearing loss may benefit from a unilateral BCI in sound localisation.