Cochlear Implantation is performed in patients with severe to profound unilateral or bilateral sensorineural hearing loss who fail to gain sufficient benefit from appropriate and well-fitting hearing aid 1. The Round Window is one of the natural openings from the middle ear into the inner ear. It is located at the end of Scala tympani and sealed by Round Window Membrane. The Round Window not only serves as another entrance to the inner ear and access to the cortical organ or auditory nerve but also a physiological exit to sound energy. The Round Window is regarded as the most reliable surgical landmark to locate the Scala Tympani and an access point for electrode insertion in Cochlear implantation.Currently two surgical approaches employed in Cochlear implantation are the Mastoidectomy with Posterior Tympanotomy Approach (MPTA) and the Suprameatal Approach (SMA). Transmastoid Posterior Tympanotomy is the standard way to access the Round Window.
The electrode array can be inserted into the Scala tympani through the Round Window with or without drilling its edges, or via a Cochleostomy adjacent to the Round Window. The visualisation of the Round Window Niche and Round Window Membrane is a prerequisite for the surgeon for inserting the electrode array into the Scala tympani of the cochlea2. The variation in the position of Round Window caused due to rotation of cochlea in horizontal and vertical axes can pose a problem in the visualisation of Round Window Niche1,2. The distance between the Short process of Incus and the Round Window Niche, distance between the Oval Window and the Round Window Niche can help in determining the extent of visibility of the Round Window seen during posterior tympanotomy2. These measurements can be used as a guide by the surgeons in locating the Round Window Niche pre-operatively2. Prior knowledge about the approximate location of the Round Window Niche will aid in planning surgery2.The present study was undertaken to correlate the radiological prediction of the Round Window with that at surgery and to evaluate the effectiveness of the High-Resolution Computed Tomography in assessing the orientation of the Round Window pre-operatively.
