Speech Detection in Noise and Spatial Unmasking in Children With Simultaneous Versus Sequential Bilateral Cochlear Implants

Objectives: To measure speech detection in noise performance for children with bilateral cochlear implants (BiCI), to compare performance in children with simultaneous implant versus those with sequential implant, and to compare performance to normal-hearing children. Study Design: Prospective cohort study. Setting: Tertiary academic pediatric center. Patients: Children with early-onset bilateral deafness and 2-year BiCI experience, comprising the "sequential'' group (>2 yr inter-implantation delay, n = 12) and "simultaneous group'' (no inter-implantation delay, n = 10) and normal-hearing controls (n = 8). Intervention: Thresholds to speech detection (at 0-degree azimuth) were measured with noise at 0-degree azimuth or +/- 90-degree azimuth. Main Outcome Measures: Spatial unmasking (SU) as the noise condition changed from 0-degree azimuth to +/- 90-degree azimuth and binaural summation advantage (BSA) of 2 over 1 CI. Results: Speech detection in noise was significantly poorer than controls for both BiCI groups (p < 0.0001). However, the SU in the simultaneous group approached levels found in normal controls (7.2 +/- 0.6 versus 8.6 +/- 0.6 dB, p > 0.05) and was significantly better than that in the sequential group (3.9 +/- 0.4 dB, p < 0.05). Spatial unmasking was unaffected by the side of noise presentation in the simultaneous group but, in the sequential group, was significantly better when noise was moved to the second rather than the first implanted ear (4.8 +/- 0.5 versus 3.0 +/- 0.4 dB, p < 0.05). This was consistent with a larger BSA from the sequential group's second rather than first CI. Conclusion: Children with simultaneously implanted BiCI demonstrated an advantage over children with sequential implant by using spatial cues to improve speech detection in noise.