What Is the Sensitive Period to Initiate Auditory Stimulation for the Second Ear in Sequential Cochlear Implantation?

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Objectives:Bilateral cochlear implants (CI) are the standard treatment for bilaterally deaf children, but it is unclear how much the second CI can be delayed in sequential bilateral CI. We investigated the performances of sequential CI to answer this question.Study Design:Retrospective case series review.Setting:Tertiary referral center.Methods:We studied a cohort of congenitally deaf children (n = 73) who underwent sequential CI without any inner ear anomaly or combined disabilities. Hearing threshold levels and speech perception were evaluated by aided pure tone audiometry and Asan-Samsung Korean word recognition test. The scores were analyzed by the ages at surgery and compared among the different age groups.Results:When the second CI was performed before 3.5 years (the optimal period for the first CI), the second CI scores (96.9%) were comparable to the first CI scores. Although the first CI scores were more than or equal to 80% when the first CI was implanted before the age of 7 years, the second CI scores were more than or equal to 80% when the second CI was implanted before the age of 12 to 13 years. The hearing threshold levels were not different regardless of the ages and between the first and second CIs.Conclusion:Our cohort demonstrated that the second CI showed comparable results to the first CI when implanted before 3.5 years, suggesting that optimal periods for the first CI and the second CI are same. However, the sensitive period (12–13 yr) for the second CI with good scores (≥80%) was much longer than that (7 yr) of the first CI, suggesting that the first CI prolongs the sensitive period for the second CI. The second CI should be implanted early, but considered even at a later age.

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