Background Functional endoscopic sinus surgery is a common surgery done in otorhinolaryngology, but it is also riddled with complications. The most dangerous complication is the injury to the skull base leading to cerebrospinal fluid leak, meningitis or damage to intracerebral vessels. Lateral lamella of the cribriform plate is the most common site of injury. Keros described the depth of the olfactory fossa in detail and divided them into three types. This study aims to assess the anatomical variations of type of ethmoid roof and depth of olfactory fossa as per Keros classification Methods Descriptive study where CT scans were evaluated from the radiology department from 29 September 2018 to 20 May 2020. All the CT films were assessed according to the observation checklist. Results Our study included 256 patients. Males constituted 54.3% of patients, and 45.7% of patients were females. Type 2 Keros was the most common followed by type 1 and type 3. Type 3 was seen more in males, and it was statistically significant too. Conclusion The study evaluated the depth categorization of the ethmoid roof and its variations on the basis of age and gender. In our study, the most common type was Keros type 2, but there was a noteworthy difference between the two sides in the same individual. Therefore, extra care must be taken during surgery to note the type of Keros on each side.

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