Anatomical Variations of the Optic Nerve in the Sphenoid Sinus: Do Ethnic Variations Matter?

There are several variations in the anatomical relations of the optic nerve with the sphenoid sinus. Proper understanding of these variations is clinically important to minimize injuries associated with surgical procedures that involve the sphenoid sinus. CT scans of paranasal sinuses obtained prior to any endoscopic surgery in the sphenoid sinus area is useful for designing operative strategies. Ethnic variations in sinonasal anatomy have been documented. The objective was to study the pattern of relationship between optic nerve and the sphenoid sinus using computerized tomographic imaging in a north Indian population, to compare our findings with previous studies in different ethnic groups and find out if ethnic variations in such a relationship matter. A prospective study was conducted on 300 patients who underwent computed tomography of the paranasal sinuses from Sept 2020 to June 2021. Relationship of optic nerves to the sphenoid sinuses was categorized according to DeLano classification. Pneumatization of the anterior clinoid process and bony dehiscence of optic nerve was also observed. Type 1 position of optic nerve was seen in 69.3%, Type 2 in 20.9%, Type 3 in 3% and Type 4 in 6.8% of sinuses. The pneumatization of anterior clinoid process (ACP) was observed in 10.5% and the bony dehiscence of optic nerve was noted in 6.5% sinuses. Bony dehiscence of optic canal had associated ACP pneumatization in 64.1% sinuses.The variability of the relation of optic nerve to the sphenoid sinus even in the persons of same ethnicity precludes a definite role of ethnicity in these variations. Other factors possibly contributing to such a relationship have been discussed.