Olfactory fossa depth: CT analysis of 1200 patients

Abstract

Background:Olfactory fossa (OF) is a depression in anterior cranial cavity whose floor is formed by cribriform plate of ethmoid. Lateral lamella, which forms its lateral boundary, is a thin plate of bone and is at risk of injury during functional endoscopic sinus surgery, especially when fossa is deep/asymmetric.Aims:To measure the variations in the depth of OF and categorize Kerala population as per Keros classification using computed tomography (CT).Settings and Design:This study was conducted in our institution from January 2016 to August 2017. Patients >16 years of age undergoing CT scan of paranasal sinuses (PNS) were included.Materials and Methods:Coronal PNS CT scan studies of 1200 patients were reviewed. The depth of OF was measured from vertical height of lateral lamella.Statistical Methods:Results were analyzed according to gender and laterality using independent sample t-test and Chi-square test.Results:The mean depth of OF was 5.26 ± 1.69 mm. Statistically significant difference was seen in the mean depth of OF between males and females but not between right and left sides. Keros type I was found on 420 sides (17.5%), type II in 1790 (74.6%), and type III on 190 sides (7.9%). Type III Keros was more on the right (9%) than left (6.8%) side, more in males (9.5%) than females (5.9%), and more among males on the right side (11.4%). Asymmetry in OF depth between two sides was seen in 75% of subjects.Conclusion:Prevalence of the dangerous type III OF, even though low, is significant especially among males and on the right side. Therefore, preoperative assessment of OF depth must be done to reduce iatrogenic complications.

Evaluation of olfactory fossa anatomy by computed tomography and the place of Keros classification in functional endoscopic sinus surgery

“…Again, this study has one of the largest case series in the literature. [9] Souza et al used the coronal plan on CT images in their study; the most common type 2 olfactory fossa (73.3%) was observed with the Keros classification in their cases, and similar to our study, they found the least type 3 olfactory fossa (0.5%). Also, a remarkable asymmetry has been achieved in the ethmoid roof height and contour.…”

“…In Babu et al study, a statistically significant relationship was found between Keros type and gender, especially on the right side. [9] Although the rate of asymmetry in our study group was quite high (97.1%) compared to other studies, asymmetry was >1 mm in only 2.9% of cases. Finally, only seven subjects (1.3%) had different Keros type OFs on both sides, which was higher in Babu et al and Pawar et al [9,24] In the study conducted by Babu et al, the mean OF depth was 5.26±1.69 mm, which was slightly higher than in our study.…”

“…[9] Although the rate of asymmetry in our study group was quite high (97.1%) compared to other studies, asymmetry was >1 mm in only 2.9% of cases. Finally, only seven subjects (1.3%) had different Keros type OFs on both sides, which was higher in Babu et al and Pawar et al [9,24] In the study conducted by Babu et al, the mean OF depth was 5.26±1.69 mm, which was slightly higher than in our study. Similarly, although there was a statistically significant difference in mean OF depth between males and females, no difference was observed between the right and left sides.…”

“…[21][22][23] A statistically significant difference was found between males and females in mean OF depth, similar to some previous studies. [6,9] Also, we did not find a significant difference in mean OF depth between the right and left sides. In Babu et al study, a statistically significant relationship was found between Keros type and gender, especially on the right side.…”

“…[8] After the Keros classification, several studies have been conducted on the ethmoid roof and OF based on Keros classification in various populations over the years. [8][9][10][11][12] Contrary to the Keros types and classification, there is also the Yenigun classification based on the anterior ethmoidal artery and ethmoid roof and evaluating the olfactory fossa as transverse. [13] According to this classifi-cation, as the length of the canal of the anterior ethmoidal artery and the incidence of the artery increases, the risk of injury increases.…”