Onodi Cell Prevalence and Their Most Common Types in Kurdistan Region of Iraq

Background The Onodi cell is the most posterior ethmoid air cells that extend to the sphenoid sinus; its recognition is crucial prior to endoscopic sinus and skull base surgery to avoid complications. The aim of this study is 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 for 152 patients between May 2018 and March 2019 have been reviewed. 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; Type C: wall being bulged by the optic nerve or if there is dehiscence (deh.) of 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 cell was 18%. The most posterior ethmoid air cells are Type A, B, and C, which constitute 88.4%, 8.94%, and 2.64% respectively. Onodi cell pneumatization pattern 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.