Predictors of round window membrane visibility in pediatric cochlear implant surgery using temporal bone HRCT: A retrospective study.

Objective: To predict round window membrane (RWM) visibility and electrode insertion sites using high-resolution computed tomography (HRCT) in pediatric cochlear implant surgery.

Methods: Sixty-two ears of 36 infants less than 1 year old were included in our study. Intraoperative RWM visibility was classified into three types corresponding to three different surgical approaches. Radiologic parameters were measured on preoperative axial temporal HRCT images and correlated with RWM visibility and surgical approaches.

Results: A significant correlation was found between the degree of RWM visibility and the following two parameters: 1) a line (lw) was drawn from the posterior margin of the RWM to the intersection point of the posterior wall of the external auditory canal (EAC) and mastoid cortex. Another line (lf) was drawn between the posterior margin of the RWM and the lateral margin of the FN. The angle between lw and lf was measured as angle A, P < 0.01, R2 = -0.809; 2) a line (lm) was drawn from the anterior to posterior margin of the RWM, and the angle between lm and lf was measured as angle B, P < 0.01, R2 = -0.850. A nonsignificant correlation was found between the degree of RWM visibility and the facial recess width, p > 0.05, R2 = -0.00015.

Conclusions: RWM visibility showed a high correlation with the two angular measurements (angle A and angle B) and was associated with electrode insertion sites. In children less than one year old, surgeons can depend on those two parameters in predicting the RWM visibility.