Round Window Membrane Visibility and its Implications in Cochlear Implant Surgery

With increasing number of patients with residual hearing being implanted, there is a renewed interest in round window (RW) as the preferred route for electrode insertion to reduce intracochlear trauma. The degree of round window membrane (RWM) visibility and its orientation might hamper the accessibility of RW for electrode insertion. This study is an attempt to identify the various factors affecting the accessibility of RW for electrode insertion. 30 children fulfilling the CI candidacy criteria were recruited for the study. All the surgeries were performed by the standard posterior tympanotomy technique. Round window membrane (RWM) visibility was graded into four types from grade I to grade IV. The membrane visibility was assessed prior to niche drilling. Grade III RW was the most common type. RW insertion could be achieved in 66.7% cases, while extended RW was performed in 33.3% cases. Bony cochleostomy was not required in any of the cases. There was no significant association between grade of RWM visibility and the route of electrode insertion. RW insertion could be achieved in most cases with normal cochlear anatomy. We observed that the grades of RWM visibility did not affect the route of electrode insertion. RW insertion can be performed in a manner that is potentially less traumatic by following the surgical steps meticulously. Both RWM visualization and insertion angle can be improved with careful bone removal in RW niche region making the round window a viable option, when minimizing insertion trauma in patients.