Review began 12/07/2021 Review ended 02/14/2022 Published 02/19/2022 © Copyright 2022 Almushayti et al. This is an open access article distributed under the terms of the Creative Commons Attribution License CC- BY 4.0., which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Evaluation of the Keros Classification of Olfactory Fossa by CT Scan in Qassim Region Ziyad A. Almushayti , Abdulhakeem N. Almutairi , Mohammed A. Almushayti , Haytham S. Alzeadi , Emad A. Alfadhel , Abdullah N. AlSamani 1. Department of Radiology, Qassim University, Buraydah, SAU 2. Department of Otolaryngology, Head and Neck Surgery, Qassim University, Buraydah, SAU 3. Department of Dentistry, Qassim University, Buraydah, SAU 4. College of Medicine, Qassim University, Buraydah, SAU Corresponding author: Ziyad A. Almushayti, ziyadalmushayti@qu.edu.sa Abstract Objective Endoscopic sinus surgery (ESS) is now the most often utilized surgical procedure for treating chronic sinonasal disorders. Therefore, anatomical knowledge of its variations is required to avoid serious postoperative complications. Thus, careful preoperative examination for patients with a paranasal sinus CT scan is necessary. Our study aims to evaluate Keros types and their incidence by evaluating the olfactory fossa (OF) depth according to the Keros classification on paranasal sinus CT scans in the Qassim region. Methods A cross-sectional study was conducted between January 2018 and January 2021 on 148 patients with an average age of 32.59 ± 6.1 who had a non-enhanced paranasal sinus CT scan evaluated by a consultant radiologist using the PACS (picture archiving and communication system) software. Statistical analysis was performed using the statistical software package SPSS version 25 (IBM Corp., Armonk, NY). The chi-square test was used to analyze the relationship between findings and patient characteristics. Also, a p-value of < 0.05 was kept in mind to indicate statistical significance. Results The average depth of the right olfactory fossa (OF) was 5.1 mm with a standard deviation of 1.756 while it was 5.28 on the left side with a standard deviation of 1.66. According to the Keros classification, out of a total of 296 OF, type 1 was found in 84 (28.4%), type 2 in 188 (63.5%), and type 3 in 24 (8.1%). Consequently, the majority of cases were of type 2. Also, we found that type 2 was the most common on both sides in males, whereas, in females, type 2 was the most common on the left side and type 1 on the right side. Conclusion The study of the Keros classification is significantly important to evaluate the anatomy of the anterior skull base and give the surgeon knowledge about the depth of the olfactory fossa. Thus, a preoperative CT scan of the paranasal sinus is critical to ensure that the surgical approach is properly planned and possible surgical complications related to the anatomy of this area can be prevented. Our study showed that Keros type II is the most common, followed by type I and then type III. Categories: Otolaryngology, Radiology, Other Keywords: endoscopic sinus surgery, computed tomography, paranasal sinus, olfactory fossa, keros classification Introduction In otolaryngology, chronic sinonasal diseases are one of the most common diseases requiring surgical attention [1]. Currently, endoscopic sinus surgery (ESS) is the most used surgical approach for treatment [2- 3]. Therefore, to prevent serious postoperative complications, anatomical knowledge of its variations is mandatory. Thus, every patient should be examined carefully prior to the surgery [4]. The ethmoid bone is open superiorly; the roof is closed by the orbital plate of the frontal bone. Ethmoidal air cells indent this plate; each one is a fovea ethmoidalis. The thin, lateral cribriform lamella (one of the thinnest parts of the cranial base) forms the medial wall of the roof, extending from the middle turbinate to the cribriform plate, and the lateral wall of the olfactory fossa or niche. The olfactory fossa varies in depth and is frequently asymmetrical; it is at risk during sinus surgery [5]. The anterior ethmoidal artery may pass via the ethmoid sinus within the skull base, in the inferior surface of the skull base, or freely hang in a mesentery inferior to the skull base. Because the risk of damaging the artery during surgery is increased when it lies freely below the skull base, this relationship between the 1 2 3 4 4 4 Open Access Original Article DOI: 10.7759/cureus.22378 How to cite this article Almushayti Z A, Almutairi A N, Almushayti M A, et al. (February 19, 2022) Evaluation of the Keros Classification of Olfactory Fossa by CT Scan in Qassim Region. Cureus 14(2): e22378. DOI 10.7759/cureus.22378