Surgical nuances and functional outcomes of cochlear implantation with incomplete separation of type II cochlea (Mondini)

INTRODUCTION: The modern classification of abnormalities in the development of the inner ear gives an idea of the diversity of such pathology, is useful in determining indications for cochlear implantation, surgical access and the method of insertion of an active electrode array. OBJECTIVE: To describe the surgical features and results of CI in patients with incomplete cochlea type II separation, with special attention to the prevention and control of intraoperative cerebrospinal fluid and electrode placement. Materials and Methods: From 2020 to 2025, 25 patients were examined and operated on at the NMICO of the FMBA of Russia, including 11 boys and 14 girls aged 8 months to 6 years, most of them were children aged 1-3 years (18 patients). Discussion. Our study has demonstrated that cochlear implantation in patients with incomplete type II separation (Mondini), despite the high risk of intraoperative cerebrospinal fluid, is technically feasible and leads to a significant improvement in auditory-speech function. Preventive surgical tactics and adaptation of the electrode insertion method proved to be key to success. CONCLUSIONS: CI in case of incomplete separation of the type II cochlea is highly effective, but it requires the surgeon to be prepared for the «gusher» phenomenon and precise electrode installation techniques to achieve optimal results. CONFLICT OF INTEREST: The authors declare no conflict of interest.