Radiological Parameters Predicting the Round Window Niche Visibility through Facial Recess Approach in Cochlear Implantation

Aim The aim was to study the radiological parameters using High Resolution Computed Tomography (HRCT) temporal bone to predict the Round Window Niche (RWN) visibility through the facial recess approach and to study radiological types of the round window niche. Materials and Methods Prospective study was done in the patients underwent CI surgery from 2019 to 2021. HRCT radiological parameters of the patients and their intraoperative visualisation from video recordings were compared to predict the most feasible parameters to predict good visualisation of RWN. Results Among 51 patients (34 males, 17 females) in 48 children round window membrane insertion was done and in three children cochleostomy was done and in two children partial canal wall drilling was done due to poor visualisation of RWN area. Multiple parameters to assess the visibility of the RWN were used. Facial recess width (4.2 mm), location of the mastoid segment of facial nerve (2 mm), external auditory canal to basal turn of cochlea angle (< 13.5 0 ) and the radiological types (tunnel shape and semi-circular shape) of the RWN by HRCT were found to be significant parameters in predicting a good visualisation of the RWN. Conclusion HRCT parameters prepare the surgeon to face the possibility of a difficult surgery and plan to deal with difficult situations. This would eventually lead to better preparedness of surgeons for management of complications.