Abstract Background The Onodi cell is the most posterior ethmoid air cell that extends to the sphenoid sinus; its recognition is crucial prior to endoscopic sinus and skull base surgery to avoid complications. This study aims to identify the prevalence of Onodi cells and to recognize their relationship with the optic nerve and the sphenoid sinus. Methods Axial CT scan images of paranasal sinuses were taken and reviewed for 152 patients between May 2018 and March 2019. The most posterior ethmoid cells have been classified into three types based on the optic nerve relationship as follows: Type A: no contact, Type B: just contact, and Type C: wall being bulged by the optic nerve or if there is dehiscence (deh.) of the optic nerve canal. Using coronally reformatted images, the pneumatization patterns of the Onodi cell (OC) relevant to the sphenoid sinus (SS) were further classified into three patterns: superolateral, superior, and lateral. Results The prevalence of Onodi cells among patients was 18% (28/152); when examined per sphenoid side, Onodi cells were present in 11.5% (35/304) of sides. The most posterior ethmoid air cells are Types A, B, and C, which constitute 88.4%, 8.94%, and 2.64%, respectively. Onodi cell pneumatization pattern is as follows: superolateral, superior, and lateral Onodi cells were 80%, 17%, and 2.8%, respectively. Conclusion This study provides variations of the onodi cells and their relevant vital structures for both otolaryngologists and radiologists to be a guide for more accurate review during endoscopic sinus and skull base surgery.
Ibrahim et al. (Fri,) studied this question.