الفهرس 
IntroductionOnly 14 pages are availabe for public view
Abstract
S
uccessful cochlear implantation by posterior tympanotomy round window approach is a main technique for cochlear implantation. This approach depends on conclusive identification of the round window niche (RWN).
The round window exposure is a critical step in success of this surgery. Preoperative radiological predication of RW visibility helps the surgeon to anticipate the degree of difficulty in cochlear implant.
In this work the possibility of preoperative assessment of round window visibility in relation to the facial recess this was done in order to anticipate the type of round window exposure before surgery by using High-resolution computed tomography (HRCT) scan, was studied.
This study included 50 children, aged 3 to 5 years who underwent unilateral cochlear implant with round window electrode insertion.
Pre-operative high-resolution temporal bone CT scan was used to predict round window exposure according to ST Thomas’ Hospital classification as the round window visibility is graded in to three grades. Two parameters were measured α value and d value by using CT scan. A correlation was done between the intraoperative degree of round window membrane exposure and the measured values.
In the present study, a comparison were done between class III (no round window exposure) and class I/IIa/IIb collectively (completely and partially exposed round window) regarding the two parameters. Another comparison was done regarding the two measures in class I (complete exposed RW) compared with both class IIa/IIb (partial exposed RW).
from this study, we conclude that the (α) value can help in determining the extent of visibility of the round window seen during posterior tympanotomy round window insertion approach .While (d) value was not significant in predicating exposure of round window.
We recommend searching for other radiological measures to help predicting round window exposure. Also, studies including and comparing adults & children are highly recommended.