Relationship of the optic nerve to the posterior ethmoid and sphenoid sinuses - A CT based anatomical study

Background: A meticulous knowledge of the anatomy of sphenoid sinus and its related adjacent structures preoperatively is crucial in order to prevent unintentional damage to the vital structures like optic nerve which can result in blindness and injury to internal carotid artery which can result in fatal haemorrhage. Material and Method: Our CT scan based study was conducted by Postgraduate Department of Anatomy in collaboration with Department of Radiodiagnosis and Imaging, Government Medical College, Srinagar for a period of 1 year. Since the aim of our study was to evaluate normal variations, cases found to harbor pathology or disease enough to distort or obscure the regional anatomy were excluded from the study. Relationship of optic nerve with sphenoid sinus was studied using De Lano’s classification. Result: In our study of 200 cases (400 sides), in majority of sides i.e. 286 (71.50%) optic nerves of type1 were found, type 2 optic nerves were found in 88(22%) sides, type 3 in 19 (4.75%) sides and least 7(1.75%)optic nerves were of type 4. Protrusion of optic nerve into sphenoid sinus was seen in 20 (10%) cases, bony wall dehiscence of optic nerve was seen in 8 (4.00%) cases, protrusion of internal carotid artery (ICA) into sphenoid sinus was seen in 25 (12.50%) cases, bony wall dehiscence of internal carotid artery was seen in 4 (2.00%) cases and pneumatization of anterior clinoid process was seen in 50 (25%) cases. Conclusion: Detailed preoperative analysis of anatomy and knowledge of individual variations of the sphenoid sinus and its boundaries is essential to prevent serious complications in surgical area.