Round Window Accessibility Prediction in Cochlear Implant Surgery

Clear identification of the round window (RW) through the facial recess is a key surgical step for successful cochlear implantation (CI) surgery, which may be very challenging in some cases. Objective is to predict round window (RW) accessibility during CI surgery using high-resolution computed tomography (HRCT).

We retrospectively reviewed preoperative HRCT scans of 142 patients who underwent CI surgery via the standard posterior tympanotomy approach at our ENT Head and Neck Surgery department. Surgical accessibility of the RW was assessed according to 2 methods, similar to the ones introduced by Mandour et al and Elzayat et al. Pre-operative imaging findings were then compared to the actual surgical accessibility of the RW by reviewing surgical notes and video recordings.

Difficult surgical access to the RW was correctly predicted in our series by Mandour's method in 81.8% of the cases, with a sensitivity and specificity of 56.3% and 96.4%, respectively, and by Elzayat's method in 72.2% of the cases, with a sensitivity and specificity of 50% and 94.5%, respectively. Combining both methods showed an increase in sensitivity levels (Se=71.9%). When the 2 methods both predicted difficult RW access, there was a strong probability that drilling a cochleostomy would be necessary for safe electrode insertion along the scala tympani of the basal turn of the cochlea (P < .001).

These 2 methods are both simple and reliable tools that can help the surgeon anticipate difficult surgical access and prepare for the potential use of alternative techniques.