The purpose of this study was to evaluate the prevalence and characteristics of 3 anatomical variations of the clivus: fossa navicularis magna (FNM), canalis basilaris medianus (CBM), and craniopharyngeal canal (CPC). Findings were correlated with sex, age, and facial skeletal pattern. A total of 602 cone beam computed tomography scans of Brazilian adults were retrospectively evaluated by 2 independent examiners. The presence of an FNM, CBM, or CPC was recorded, and length, depth, and width were measured. The CBM was classified according to type (3 complete and 3 incomplete varieties). All data were correlated with sex, age, and facial skeletal pattern. Results were tested using chi-square, Mann-Whitney U, and Kruskal-Wallis tests (P < 0.05). The prevalence rates for FNM, CBM, and CPC were 15.78% (n = 95), 6.64% (n = 40), and 0.17% (n = 1), respectively. No significant differences in the prevalence of the variations were found based on sex or facial skeletal patterns (P > 0.05). The median length, depth, and width of FNM were 5.55, 1.83, and 4.81 mm, respectively, with no significant differences (P > 0.05) between the variables. The prevalence of FNM was significantly higher in patients aged 18 to 33 years than in those aged 34 and older (P < 0.001). An incomplete variant of the CBM, presenting as an inferior recess, was more common (32.5%). The FNM is the most prevalent anatomical variation of the clivus, especially in young adults. The sex and facial skeletal pattern of the individual do not affect the frequency of FNM, CBM, or CPC. Because of their clinical relevance, recognition of these anatomical variations is essential, as they can be misdiagnosed as pathologies.
Keywords: anatomical variation; cone beam computed tomography; posterior cranial fossa; skull base.