A pilot study on spatial hearing in children with congenital unilateral aural atresia

Abstract

Despite normal hearing in one ear, individuals with congenital unilateral aural atresia may perceive difficulties in everyday listening conditions typically containing multiple sound sources. While previous work shows that intervention with bone conduction devices may aid spatial hearing for some children, testing conditions are often arranged to maximize any benefit and are not very similar to daily life. The benefit from amplification on spatial tasks has been found to vary between individuals, for reasons not entirely clear. This study has sought to expand on the limited knowledge on how children with unilateral aural atresia recognize speech masked by competing speech, and how horizontal sound localization accuracy is affected by the degree of unilateral hearing loss and by amplification using unilateral bone conduction devices when fitted before 3 years of age. In a within-subject, repeated measures design, including 11 children (mean age = 7.9 years), bone conduction hearing device (BCD) amplification did not negatively affect horizontal sound localization accuracy. The effect on speech recognition scores showed greater inter-individual variability. No benefit from amplification on a group level was found. There was no association between age at fitting and the benefit of the BCD. For children with poor unaided sound localization accuracy, there was a greater BCD benefit. Unaided localization accuracy increased as a function of decreasing hearing thresholds in the atretic ear. While it is possible that low sound levels in the atretic ear provided access to interaural localization cues for the children with the lowest hearing thresholds, the association has to be further investigated in a larger sample of children.

Keywords: BCD; UCHL; bone conduction device; early fitting; sound localization; speech recognition; unilateral aural atresia; unilateral conductive hearing loss.

Figure 1

Flow chart for inclusion in the study. Thirteen eligible participants declined participation due to different reasons. Four patients were between 5 and 10 years old in 2018 but could not make it to any of the appointments available at that time and had grown too old to include in the study when more opportunities opened in 2021. *One participant did not perform any aided measurements due to lack of time and was therefore excluded from analysis.

Figure 2

Setup for testing of SLA. Twelve loudspeakers each coupled to a 7-inch video display (LD pairs) were placed in a 110° arc in the frontal horizontal plane relative to the subject who was seated facing the loudspeaker array. The distance from the LD pairs to the head of the study participant was approximately 1.2 (loudspeaker) and 1.1 m (screen). The LD pairs were adjusted to be at ear level of the study participant.

Figure 3

Setup for testing of SRT. Participants were seated facing a loudspeaker presenting target speech at 0° azimuth. Interfering speech was presented from four spatially symmetrically separated loudspeakers at ±30° and ±150° azimuth at a fixed overall level of 63 dB SPL measured at the position of the subject's head.

Figure 4

(A) Individual values of unaided and aided SLA performance. A lower EI indicates a better performance. There was no significant benefit from amplification on a group level (Spearman correlation, p > 0.05). In the aided setting, the three individuals with the highest unaided EI had intra-individual statistically significant benefit compared to the unaided measurements (p < 0.05). (B) There was a high degree of inter-individual variability on SRT both aided and unaided. A more negative SRT (dB) value indicates a better performance.

Figure 5

(A) SLA performance unaided and aided correlated to age. An EI value of 0 indicates a perfect performance and a value of 1 a random performance. Two of the youngest participants (6 and 9) had the worst unaided SLA performance, but there was no significant correlation between SLA and age. The youngest individuals had the most benefit from amplification. (B) SRT correlated with age. A more negative value indicates better speech discrimination. Both aided and unaided SRTs were correlated to age (p < 0.05), where the older study participants had lower (better) SRTs.

Figure 6

(A) Unaided SLA was correlated to unaided PTA₄ (p < 0.05). (B) There was no correlation between aided PTA₄ and aided SLA performance. (C) Unaided SRT related to unaided PTA₄. There was no significant correlation between unaided audibility in the atretic ear and unaided speech recognition thresholds (p > 0.05, Spearman correlation). (D) No significant correlation was found between aided SRTs and aided PTA₄ (p > 0.05, Spearman correlation).

Figure 7

Comparison of unaided PTA₄ (A) and SLA (B) between children from the present study and adults from the study by Siegbahn et al. (25). The adults had a tendency toward a higher PTA₄ and lower EI compared to the children in the present study where the spread tends to approach lower PTA₄ and a higher EI.