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 73 dB 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 73 dB SPL (18% decrease in the EI per 10 dB 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.