Introduction: Posterior ethmoid cells may pneumatize the sphenoid bone posteriorly to give rise to a cell, which extends superolateral to the sphenoid sinus for a much longer distance which is known as the Onodi cell. Onodi cell may complicate the outcome of functional endoscopic sinus surgery (FESS) as it may be confused with the sphenoid sinus. The present study was undertaken to determine the prevalence of Onodi cells on CT scan in patients having sinonasal complaints.

Materials & Methods: This was a descriptive observational study carried out on 150 patients who presented with various sino-nasal complaints and underwent CT Scan in the Department of Radiodiagnosis, Bangur Institute of Neurosciences, Kolkata. Their CT scans were studied retrospectively for the presence of Onodi cells. Radiological variations data were summarized by routine descriptive statistics namely counts and percentages for categorical variables. Fisher’s Exact Tests and were applied to calculate the ‘p’ value to find out any statistically significant difference between males and females.

Results: Onodi cells were found in 6.6% (10 cases) in the present study, 4.6% in males and 2% in females. ‘p’ value in this case was 0.334 on applying Fisher’s Exact test.

Conclusion: Onodi cell being in the close vicinity of sphenoid sinus is a very important variation which should be looked for by the surgeon before planning any endoscopic surgery. This study tried to find out the prevalence of the Onodi cells in Eastern India to help the FESS surgeons and improve its outcomes.

Keywords: posterior ethmoid cell, functional endoscopic sinus surgery, optic nerve.

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Md. Jawed Akhtar

Assistant Professor, Department of Anatomy, Indira Gandhi Institute of Medical Sciences, Patna (Bihar)