الفهرس 
ANATOMY OF THE COCHLEA AND MEDIIALOnly 14 pages are availabe for public view
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Abstract
Background: Insertion trauma in cochlear implant surgery is a feared surgical risk, also the round window niche is used as a primary guide to cochleostomy for cochlear implantation, but it has many anatomical variations.
Aim of work: To study the detailed anatomy of the cochlea in relation to medial wall of middle ear in order to identify anatomical landmarks that help the surgeon in performing the optimal cochleostomy for inserting the electrode array of cochlear implant in non obliterated and obliterated cochleae
Methods: Twenty temporal bones were dissected and drilled under the operating microscope in the temporal bone lab of Ain shams specialized hospital. Eight cochleostomies were done on the promontory in relation to round window and processus cochleariformis. 3 parameters were measured: the depth, the direction of drilling and the cochlear partition that opened after decaping of overlying bone of the promontory.
Results: The findings are summarized in tables and statistical analysis was done for the quantitative and qualitative data. 3 parameters were observed: 1- depth of drilling which shows that cochleostomy 5 has the highest depth with mean 2mm, cochleostomy 2 has least depth mean 1.6mm in the 20 studied bones.2- direction of drilling 90% of cochleostomy 1,2,3, and 4 need vertical direction. 3-the cochlear partition that was opened after decaping 100% of cochleostomy 1,3 and 4 opened in scala tympani and 100% of cochleostomy 2 opened in scala vestibuli.
Conclusion: Cochleostomy 1, 2 and 3 needs the least amount of drilling and need vertical direction of drilling, 1, 3 and 4 usually opened in scala tympani best place for electrode insertion. Cochleostomy 5 and 6 are deep and opened outside cochlear lumen in hypotympanum. Cochleostomy 7 and 8 opened in scala vestibuli of the middle turn and needs inferior direction of drilling.
Keywords: cochleostomy-cochlear implants-human temporal bone-round window niche-Round window insertion.