Assessment of the preoperative computed tomographic predictability for round window membrane visibility and accessibility during cochlear implant surgery

Objectives The aim of the present study was to assess the preoperative predictability of multi-slice computed tomography for round window membrane (RWM) visibility and accessibility through round window niche (RWN) intraoperatively. Patients and methods Computed tomographic scans of 61 adult cochlear implant patients with otherwise normal temporal bone anatomy were studied for RWN extent using two methods. The first was a modification of a method by Park and colleagues and another simple method proposed by our group. The visibility of the RWN through RWN was assessed intraoperatively after performing the posterior tympanotomy and good exposure of the RWN. Statistical analysis was then performed. Results Modified Park and colleagues method was statistically significant in predicting RWM visibility ( P =0.018) and a cutoff point was detected at more than or equal to 0.7 with a specificity of 69.23% for low or no visibility of RWM. Our proposed method was also statistically significant ( P =0.001) with a cutoff point of more than or equal to 1.43mm with a specificity of 96.15%. Discussion RWN depth has been studied repeatedly in the literature with only rarely correlation to intraoperative findings. These methods were also frequently either cadaveric or radiological with complex reconstruction, thus were with doubtful clinical value. In the present study, two methods were used and were found to be significant to predict the degree of visibility of RWN visibility through RWM. Conclusion The modified Park’s and our proposed methods can statistically significantly predict RWM visibility through RWN. However, our proposed method had higher specificity and smaller P value.