Predicting round window visibility by HRCT during cochlear implantation in children.

Objective: The present study aimed to radiologically evaluate the visibility of round window during cochlear implantation by high-resolution computed tomography (HRCT) imaging of temporal bone. Study design: This was a cross-sectional descriptive analytic study. Methods: Two new radiologic measurements were evaluated on the presurgical HRCT of temporal bone, including (1) the angle between the line parallel to coronal axis that passes through the middle of the round window niche (RWN) and the line that connects the anterior portion of facial nerve (FN) to the middle of the RWN (RWN angle) and (2) the vertical distance between this coronal plane and the anterior portion of the FN, modified facial recess distance (MFRD). The measurements were then compared with the visibility of the round window (RW) during operation, as reported by the surgeon. Result: The present study compared the abovementioned CT scan findings of cochlear implanted children in visible (n = 21) and nearly invisible (n = 21) RW during surgery, as reported by the surgeon. The analysis revealed that both MFRD (P < 0.01) and RWN angle (P < 0.04) were significantly different between the two groups. Conclusion: the RWN angle and MFRD are fairly reliable predictors of round window visibility during cochlear implantation.