Estimation of Cranial Capacity Using Retrospective Three-Dimensional Brain Computed Tomography Scans: A Sex-Comparative Study in Abuja Municipal Area Council, Nigeria

Abstract

Background: Cranial capacity is a widely used anthropometric and clinical index of intracranial volume, with applications ranging from neurosurgical planning to forensic identification and evolutionary anthropology. Three-dimensional computed tomography (3D CT) offers a non-invasive, reproducible alternative to traditional cadaveric and anthropometric techniques, yet population-specific reference data remain scarce for Nigeria and sub-Saharan Africa more broadly.

Objective: To estimate cranial capacity in adult males and females using retrospective 3D brain CT scans obtained in Abuja Municipal Area Council, to characterise its relationship with gender and cranial dimensions, and to compare directly measured (observed) volumes with age-based predicted values.

Methods: A retrospective cross-sectional study was conducted on 100 3D brain CT scans (52 males, 48 females; mean age 49.78 ± 1.25 years) drawn from certified imaging centres within the Abuja metropolis over a five-year period. Cranial length, height, and width were measured on reconstructed volumes, and cranial volume and cephalic index were computed for each subject. Data were analysed in SPSS v20.0 using means, standard errors, one-way ANOVA, Pearson correlation, and linear regression, with statistical significance set at p < 0.05.

Results: Males had significantly greater cranial length, height, and width than females (all p = 0.001). Observed mean cranial volume was significantly higher in males (1225.16 ± 8.95 cm³) than females (1153.62 ± 5.84 cm³; p = 0.001), whereas age-predicted volumes did not differ significantly by sex (1169.62 ± 1.66 vs 1167.33 ± 1.33 cm³; p = 0.291). Cranial volume correlated strongly with height (r = 0.835), width (r = 0.829), and length (r = 0.825; all p < 0.001). An age-based regression equation (cranial volume = 1211.133 − 0.856 × age) produced predicted values that did not differ significantly from observed values (p = 0.998). Using the cephalic index, the population was predominantly mesocephalic (54%), with males showing greater morphological variability than females, including rare ultrabrachycephalic skulls (3.8%).

Conclusion: 3D CT-derived cranial volumetry is a reliable, non-invasive method for cranial capacity estimation and confirms clear sexual dimorphism in this Nigerian adult sample. The derived age-based regression equation performed well against observed values and, together with the cephalic index distribution, contributes reference anthropometric data of value to clinical, forensic, and anthropological practice in the sub-Saharan African context.