• Onodi cells;
  • anatomic variation;
  • endoscopic sinus surgery;
  • sphenoid sinus;
  • ethmoid sinus;
  • computed tomography;
  • trans-sphenoidal surgery;
  • endoscopic skull base surgery;
  • optic nerve;
  • parasellar anatomy;
  • Level of Evidence: 4



Onodi cells are the posterior-most ethmoid air cells that lie superior to the sphenoid sinus. Identification of these cells is essential prior to endoscopic sinus and skull base surgery due to their intricate relationship with the optic nerves and carotid arteries, which may lead to deleterious complications. In this study, high-resolution computed tomography (HRCT) scans from 170 adult-patients were analyzed by two independent observers for the presence of Onodi cells.

Study Design:

Radiographic analysis at a tertiary care medical center.


A retrospective analysis was performed on patients undergoing HRCT between July 2008 and September 2010. Incidence of Onodi cells and demographic data were collected.


The overall prevalence of Onodi cells in this cohort was 65.3%. Subgroup analysis based on ethnicity showed a rate of Onodi cells of 83.3% in Asians, 73.1% in whites, 57.0% in African Americans, and 62.7% in Hispanics. The prevalence of Onodi cells was not significantly different among the different ethnicities (P > .05). However, this was limited by a small sample size in some ethnic groups. Onodi cell prevalence was equivalent among males and females: 62.2% and 63.5% respectively (P > .05). Overall, our results show a greater prevalence of Onodi cells than previously reported.


We found a higher prevalence of Onodi cells in our cohort than previously reported in the literature. Therefore, it is important for surgeons to anticipate the presence of these cells during endoscopic sinus and skull base procedures to prevent potential complications. Laryngoscope, 2012