Computed Tomography Analysis of the Prevalence of Onodi Cells

Background: Onodi cells are the posterior-most ethmoid air cells that lie superior to the sphenoid sinus. It is essential to recognize the presence of these cells prior to endoscopic sinus and skull base surgery as these cells are intimately related to the optic nerve and may lead to unwanted complications. In this study, CT scans from 175 patients (age range, 19–81 years) with no posterior ethmoid or sphenoid sinus fractures or associated masses were analyzed by two independent observers for the presence of Onodi cells.

Methods: A retrospective radiographic analysis was performed.

Results: The overall prevalence of Onodi cells in this cohort was 62.9–69.7%. Further subgroup analysis based on ethnicity (Asian, African American, Hispanic, and White) showed a greater prevalence in the Asian population and an equivalent prevalence among the other groups—70%, 45%, 58%, and 41%, respectively. The prevalence was equivalent among men and women, 48% and 44.5%, respectively. These figures show a greater prevalence of Onodi cells than previously reported.

Conclusions: Although studies of the Asian population are consistent with these data, it shows an increased prevalence in the other populations studied. It is therefore important for surgeons to anticipate and look for the presence of these cells when undertaking endoscopic sinus and skull base procedures.