Sequential Bilateral Cochlear Implantation in Children: Outcome of the Second Implant and Long-Term Use.

OBJECTIVES: The aim of this retrospective cohort study was to assess speech perception outcomes of second-side cochlear implants (CI2) relative to first-side implants (CI1) in 160 participants who received their CI1 as a child. The predictive factors of CI2 speech perception outcomes were investigated. In addition, CI2 device use predictive models were assessed using the categorical variable of participant's decision to use CI2 for a minimum of 5 years after surgery. Findings from a prospective study that evaluated the bilateral benefit for speech recognition in noise in a participant subgroup (n = 29) are also presented. DESIGN: Participants received CI2 between 2003 and 2009 (and CI1 between 1988 and 2008), and were observed from surgery to a minimum of 5 years after sequential surgery. Group A (n = 110) comprised prelingually deaf children (severe to profound) with no or little acquired oral language before implantation, while group B (n = 50) comprised prelingually deaf children with acquired language before implantation, in addition to perilingually and postlingually deaf children. Speech perception outcomes included the monosyllable test score or the closed-set Early Speech Perception test score if the monosyllable test was too difficult. To evaluate bilateral benefit for speech recognition in noise, participants were tested with the Hearing in Noise test in bilateral and "best CI" test conditions with noise from the front and noise from either side. Bilateral advantage was calculated by subtracting the Hearing in Noise test speech reception thresholds in noise obtained in the bilateral listening mode from those obtained in the unilateral "best CI" mode. RESULTS: On average, CI1 speech perception was 28% better than CI2 performance in group A, the same difference was 20% in group B. A small bilateral speech perception benefit of using CI2 was measured, 3% in group A and 7% in group B. Longer interimplant interval predicted poorer CI2 speech perception in group A, but only for those who did not use a hearing aid in the interimplant interval in group B. At least 5 years after surgery, 25% of group A and 10% of group B did not use CI2. In group A, prediction factors for nonuse of CI2 were longer interimplant intervals or CI2 age. Large difference in speech perception between the two sides was a predictor for CI2 nonuse in both groups. Bilateral advantage for speech recognition in noise was mainly obtained for the condition with noise near the "best CI"; the addition of a second CI offered a new head shadow benefit. A small mean disadvantage was measured when the noise was located opposite to the "best CI." However, the latter was not significant. CONCLUSIONS: Generally, in both groups, if CI2 did not become comparable with CI1, participants were more likely to choose not to use CI2 after some time. In group A, increased interimplant intervals predicted poorer CI2 speech perception results and increased the risk of not using CI2 at a later date. Bilateral benefit was mainly obtained when noise was opposite to CI2, introducing a new head shadow benefit.

Sound localising ability in children with bilateral sequential cochlear implants.

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.

Comparison of bilateral and unilateral cochlear implants in children with sequential surgery.

OBJECTIVE: The objective of this study was to evaluate the effect of bilateral versus unilateral cochlear implants and the importance of the inter-implant interval. METHODS: Seventy-three prelingually deaf children received sequential bilateral cochlear implants. Speech recognition in quiet with the first, second and with both implants simultaneously was evaluated at the time of the second implantation and after 12 and 24 months. RESULTS: Mean bilateral speech recognition 12 and 24 months after the second implantation was significantly higher than that obtained with either the first or the second implant. The addition of a second implant was demonstrated to have a beneficial effect after both 12 and 24 months. Speech recognition with the second implant increased significantly during the first year. A small, non-significant improvement was observed during the second year. The inter-implant interval significantly influenced speech recognition with the second cochlear implant both at 12 and 24 months, and bilateral speech recognition at 12 months, but not at 24 months. CONCLUSIONS: A small, but statistically significant improvement in speech recognition was found with bilateral cochlear implants compared with a unilateral implant. A major increase in speech recognition occurred with the second cochlear implant during the first year. A shorter time interval between the two implantations resulted in better speech recognition with the second implant. However, no definitive time-point was found for when the second implant could no longer add a positive effect.