Publication:

A clinical study of cochlear implant electrode placement via posterior tympanotomy approach in cases with varying types of round window visibility

Background Cochlear implantation (CI) is an established intervention for severe to profound hearing loss not benefiting from hearing aids. Posterior tympanotomy is the standard surgical approach to access the basal turn of the cochlea for electrode insertion via the round window or cochleostomy. However, the visibility and accessibility of the Round window membrane (RWM) may vary depending on anatomical variations. This study aimed to evaluate the utility of the Saint Thomas Hospital (STH) classification in assessing round window visibility and its relationship to the practical ease of electrode insertion.

Methods This retrospective study analysed 511 cochlear implantations performed via the posterior tympanotomy approach in 476 children. The round window was classified according to the STH classification. The method of electrode insertion used in each case was documented and analysed.

Results Type IIA round window was the most common variant, observed in 282 cases (55.2%), while Type III was the least common, occurring in 64 cases (12.5%). Direct round window insertion was feasible in all cases with Type I and Type IIA round windows. In 96 cases with Type IIB round window, an extended round window technique was required for electrode insertion. All 64 cases with Type III round window required cochleostomy due to inadequate round window access.

Conclusions The study demonstrates the clinical utility of the STH classification in predicting the feasibility of round window electrode insertion during cochlear implantation. This classification can assist surgeons in determining the most appropriate method of electrode insertion based on intraoperative STH classification.