Anatomical variants of surgically important landmarks in the sphenoid sinus: a radiologic study in Southeast Asian patients.

Abstract

Failure of a surgeon to understand the local variations of the anatomical landmarks of the sphenoid sinus is a potential risk factor to cause damage to the optic nerve (ON) or internal carotid artery (ICA) that lies on the walls of the sphenoid sinus. The aim of this study was to identify the anatomical variants of the sphenoid sinus and its related surrounding structures among the Southeast Asian (SEA) population, based on computed tomography (CT) scans. This cross-sectional study analyzed 300 CT scans of the brain, paranasal sinuses (PNS), and head and neck (H&N) at a tertiary referral centre in Malaysia utilizing the Osirix software. The images were reconstructed into 1 mm cuts on bone window. Demographic details and scan findings were documented in a standardized data collection sheet. The rates of ON dehiscence, ICA dehiscence and ICA protrusion in the SEA population were 7.0, 3.0 and 10.0 %, respectively. The rate of ON protrusion was 2.3 %. There was no statistically significant relationship (p > 0.05) noted on Chi-square test, between anterior clinoid process (ACP) pneumatization and ON protrusion. The rate of Onodi cells in our population was 14.3 %. The average vertical distance of the ostia from the roof of the posterior choanae was 1.42 cm (±0.32). The horizontal distance of the ostia from the anterior end of the superior turbinate was 1.58 cm (±0.41) and the oblique distance of the ostia from the anterior nasal spine was 5.35 cm (±0.48). Independent t tests showed that there is a statistically significant difference between the means of each of these parameters (p < 0.001) and their international averages. The rate of ON protrusion is lower in the SEA population, whereas the rates of ON dehiscence, ICA dehiscence and ICA protrusion fall within the range of international averages. In our population, ACP pneumatization is not related to ON protrusion. The distance of the ostia from given landmarks was significantly shorter than in other studies.