Anatomy of Round Window in Micro Dissected Human Cadaveric Temporal Bones in the View of Cochlear Implant Surgery: An Indian Data
摘要
Round window anatomy and its relations have relevant implications for optimising the results of cochlear implant surgery. The anatomy of the round window, crista fenestra and the direction of the scala tympani needs to be well understood by surgeons performing cochlear implant surgery to ensure accurate electrode insertion. The micro dissection of human cadaveric temporal bones of Indian origin, for the round window anatomy and the radiological correlation in some of these temporal bones, is the highlight of this study. To study the anatomy of round window in micro dissected human cadaveric temporal bones of Indian origin in the view of Cochlear Implant surgery. 1) To study anatomy of round window in microdissected cadaveric human temporal bones for optimal insertion of cochlear implant array. 2) To study anatomy of crista fenestra. 3) To study relations of round window with oval window and facial nerve and its CT correlation. Thirty wet human cadaveric temporal bones were studied by dissection under an operating microscope for anatomy of round window and crista fenestra. 7 temporal bones were subjected to high resolution CT scan in the radiology department prior to the dissection. The dissected bones were photographed with a millimeter scale using a Nikon D3200-DSLR camera. The photographs were then imported to a computer, and by using a special Image processing and analysis software ImageJ with proper calibration, the parameters were measured and scaled from pixel-to-millimeter conversion. In our cadaveric study of temporal bones the shape of the round window was saddle shaped in 65%, oval in 17%, circular in 13% and triangular in 5% of the cases. The mean width of the round window (longer dimension) was 1.23 mm and mean height (smaller dimension) was 0.78 mm. This was correlated on HRCT where the mean width and height was 1.2 mm and 0.8 mm respectively. In most cases the direction of round window opening was posteroinferior (63%) followed by a posterior (23%) and inferior (14%) orientation. The mean area of the crista was found to be 0.33mm2. The mean shortest distance between round window and vertical facial was 3.1 mm in cadaveric temporal bones and on CT scan it was 3.3 mm. The mean distance between round window and oval window in cadaveric temporal bones was 2.34 mm and on HRCT the mean distance was found to be 2.6 mm. Study of round window with special reference to crista fenestra in human cadaveric temporal bones, can help a cochlear implant surgeon for a smooth round window insertion of the electrode array into scala tympani without damaging the delicate intracochlear structures.