Speech development in children and insertion depth of the cochlear implantelectrode array.

Background: The goal in pediatric cochlear implantation is improved hearing leading to better speech development, which may allow their integration in to mainstream schools. Whether the intracochlear position of the electrode array has an influence on speech development or not is controversially disc ussed. Patients: Between 1996 and 1998 29 children ranging from 1.5 to 11.8 years (median 4 years) were provided with a Nucleus 22M or 24M cochlear im plant system. Speech and language skills were assessed by a closed-set test (Mainzer test) and by the Schmid-Giovannini score for hearing development pre-implantation and at 6, 12, 18 and 24 months post-implantation. The posi tion of the electrode array was determined by the surgical record and by a post-operative transorbital x-ray. Since the promontory has a thickness of one to two electrode bands, we defined deep insertion as more than 24 bands intracochlear. Results: The patients were divided into 2 groups according to the insertion depth: Group 1 (n = 8) 24 bands (22 electrodes and 2 stiff ening rings correspond to less than or equal to 18 mm) or less and group 2 (n = 21) more than 24 bands intracochlear correspond to >18 mm). The mean c losed-set test scores 12 months post-implantation were 51.4% and 68.5 % for group 1 and group 2, respectively. Schmid-Giovannini test scores were 8,7 for group 1 and 10,1 for group 2. There was no significant statistical diff erence in the closed-set and Schmid-Giovannini test scores. We observed inc omplete insertion (i.e. less than 22 active bands are intracochlear) becaus e of electrode extrusion in only one child. Conclusion: Speech development in children does not improve with deeper insertion of the cochlear implant electrode array.