Anatomical variations of the clivus and related craniometric measurements in the adult population of Botswana: A CT-Based study

The clivus and foramen magnum are important landmarks in skull base surgeries. Incidental clival anatomical variations such as the fossa navicularis magna and canalis basilaris medianus, can mimic pathological lesions or fractures while the foramen magnum can be congenitally narrowed in conditions like achondroplasia and atlantooccipital fusion. This study investigated the morphology and morphometric dimensions of the clivus and foramen magnum in the adult population of Botswana using Computed Tomography (CT). This retrospective study analysed 86 CT images of adult patients obtained from Sir Ketumile Masire Teaching Hospital, Gaborone. Measurements of the clivus and foramen magnum were acquired from reconstructed sagittal and axial CT planes. The clivus was evaluated for anatomical variations. Statistical analysis included ANOVA, Kruskal–Wallis, and independent t -tests to determine differences by sex and age group. Effect sizes were calculated using Cohen’s d. A single case of fossa navicularis magna was observed (1.2%). Significant sex differences were identified in the clivus length (p = 0.001), foramen magnum anteroposterior diameter (p < 0.001), and transverse diameter (p = 0.001), with males exhibiting larger dimensions. No significant differences were found among age groups. Positive correlations were observed between clival and foramen magnum parameters (p < 0.01). The morphometric characteristics of the clivus and foramen magnum were stable across age groups but exhibited marked sexual dimorphism, with males showing larger measurements. These findings provide baseline data relevant to skull base surgery, radiological diagnosis, and forensic identification within the Botswana population. • Males show larger clival and foramen magnum dimensions than females • Clival dimension reach maturity at adulthood and remain fixed thereafter. • Dimensions of the clivus are strongly correlated to those of foramen magnum • 1.2% of the sample showed fossa navicularis magna variant