Pneumatization patterns of onodi cell on multidetector computed tomography

Background: Onodi cell is the most common anatomical variant of posterior ethmoidal air cells. Pneumatization patterns of Onodi cell are important clinically due to its proximity to optic nerve and internal carotid artery canal. Multidetector computed tomography (MDCT) provides the best imaging modality for identification and pneumatization pattern of Onodi cell. Objectives: The present study is done to know the patterns of pneumatization of Onodi cell by 128 slice MDCT. Materials and Methods: This was a retrospective analysis of paranasal sinuses in 1080 cases by MDCT in adults. Axial images of paranasal sinuses were taken by 128 MDCT with further multiplanar reconstruction to identify Onodi cell and their pneumatization patterns. Statistical analysis was done using SPSS version 20, and 95% confidence interval (CI) values were calculated using a confidence Interval calculator for proportional values. Results: A total of 260 cases (24.07%, CI - 21.52%–26.62%) showed Onodi cell among the total 1080 cases included in this study. Males formed more cases than females with 62.69% and 37.31%, respectively, Type II was the most common pattern of pneumatization with 56.55% (CI - 50.12–62.18), followed by Type I with 41.53% (CI - 35.54–47.52) and Type III with 1.92% (CI - 0.25–3.59) of cases. Conclusion: Onodi cell is the most common anatomical variation of ethmoidal sinuses with higher prevalence among Asian populations. Their patterns of pneumatization are important clinically to avoid surgical damage to optic nerve and internal carotid artery canals. Onodi cell is better detected with MDCT and helpful for sinonasal surgeons for a better surgical outcome.