The relationship between optic nerve and Onodi cells on CT scan

The Onodi cells, also known as sphenoethmoidal air cells, are a variant of the most posterior ethmoid cells and are closely related to the optic canal. The presence of Onodi cells may increase the risk of optic nerve injury and result in confusion with sphenoid sinuses during endoscopic sinus surgery, leading to the oversight of sphenoid sinus pathology. The aim of the study was to examine the characteristics of Onodi cells and their relationship with the optic nerve on CT scans. A cross-sectional study was conducted, analyzing CT scans of paranasal sinuses in 196 posterior ethmoid air cells from 98 patients (30 males and 68 females) aged 18 or older, without abnormalities in the paranasal sinuses and optic nerve anatomy. The prevalence of Onodi cells was 38.78%, with 26.32% on the left, 44.74% on the right, and 28.94% bilaterally. Onodi cell pneumatization was observed in the order of Type I > Type II > Type III on both sides. The most common relationship between Onodi cells and the optic nerve was Type A on both sides. The incidence of the optic nerve bulging into Onodi cells was 50%, and the exposure of the optic nerve into Onodi cells was 7.89%. The study investigated the prevalence and relationship between Onodi cells and the optic nerve. CT scans proved to be a crucial diagnostic tool in providing essential information about Onodi cells before surgery.