Anatomical Variations of Carotid Artery and Optic Nerve in Sphenoid Sinus Using Computerized Tomographic Imaging

Background: Sphenoid sinus is surrounded by many vital vascular and nervous structures. In more than 20% of patients with chronic sinusitis, involvement of sphenoid sinus has been observed. Besides, sphenoid sinus is an appropriate route to access anterior and middle cranial fossa in surgery. Therefore, it is important to have an adequate knowledge about the contents of sphenoid sinus and its proximity for nasal endoscopy, sinus surgeries and neurosurgeries. Objectives: The aim of this study was to study sphenoid sinus proximity with carotid artery and the optic nerve using computerized tomographic imaging. Materials and Methods: In this prospective study, computerized tomographic images of sphenoid sinus of patients referred to Imam Khomeini and Apadana hospitals were studied. The images were studied regarding any bulging, as well as not having a bone covering in sphenoid sinus regarding internal carotid artery and optic nerve. Furthermore, unilateralness or bilateralness of their relationships was studied. Results: Among 468 coronal and axial CT scan images of sphenoid sinus, 365 (78%) showed post-sellar pneumatization and 103 (22%) pre-sellar pneumatization. Regarding existence of internal septa, 346 (74%) cases showed multiple septation, and the remaining images were reported to have a single septum. According to the reports of CT scan images, the existence of bulging as a result of internal carotid artery and uncovered artery were 4.22% and 5.8% in the right sinus, 4.9% and 5.4% in the left sinus, and 4.34% and 4.6% in both sinuses, respectively. According to the reports of CT scan images, existence of bulging as a result of optic nerve and uncovered nerve were 5.7% and 4.3% in the right sinus, 6% and 5.4% in the left sinus, and 12% and 3.2% in both sinuses, respectively. Conclusions: Due to variability of sphenoid sinus pneumatization and the separator blade of the two sinus cavities, careful attention is required during sinus surgery to avoid damage to neural and vascular structures in its proximity.