Sound localising ability in children with bilateral sequential cochlear implants

Abstract

Objectives: To evaluate the sound localisation ability in children with sequential bilateral cochlear implants and the potential influence of age at the time of the first implantation, years of experience with the first implanted ear and the inter-implant interval (time between the first and the second cochlear implantation).

Methods: Sixty-three prelingually deaf children (mean age, 11.03; range, 6.5-17 years; SD, 3.09) were tested after 12 and 24 months of using bilateral cochlear implants. Every child was tested with each ear alone and both ears together. Five loudspeakers were placed in a 180° horizontal arch with 45° of separation between each loudspeaker. The child was placed 1.5m from the speakers. For each test run, three stimuli were presented at 65dB (A) from each speaker for a total of 15 stimulus presentations. For each test run, we calculated the mean angular error (MAE) and the proportion of correct speakers identified (CSS: correct speaker score). Performance by chance for the MAE was 72° and for the CSS was 20% (1 of 5 speakers).

Results: After 12 months of using bilateral CIs, the added effect of the second CI in the MAE was minor, and there was no significant difference in CSS between listening in the unilateral condition and listening in bilateral condition. After 24 months, however, the added effect of the second CI in the MAE was significant (mean diff=12.2°; 95% CI; 4.5-20.0°, p=0.003). The mean bilateral CSS increased significantly to 38% (diff=7.7%; 95% CI; 1.4-14.0%; p=0.019) while the mean unilateral CSS remained at a similar level (27%). The influence of age at the time of the first implantation on CSS after 24 months was not significant (p=0.96). However, the inter-implant interval showed a significant decrease in score by 1.4% per year between the two implants (p=0.04).

Conclusion: Sound localisation with two versus one CI in children with a sequential bilateral cochlear implantation was significantly improved 24 months (but not 12 months) after the second implantation. A shorter inter-implant interval showed a small but significant beneficial effect on sound localisation.