Computed tomography assessment of neurocranial structures for sexual dimorphism identification: a meta-analysis

The human neurocranium exhibits significant sexual dimorphism, making it a valuable resource for anthropological studies. This systematic review aggregated and analyzed data from literature on sex differences in neurocranial dimensions as measured by computed tomography (CT). Following registration of the review protocol with PROSPERO (#CRD 42023442451), comprehensive searches were conducted in six databases and gray literature. From an initial pool of 1,499 articles, 14 met the inclusion criteria and were analyzed for data extraction, meta-analysis of linear measurements, risk of bias (RoB), and certainty of evidence (GRADE) evaluation. In the meta-analysis (Sample size- 1726 female and 1837 male), the inverse variance method and a random-effects model were employed using Review Manager (version 5.4.1). Statistical heterogeneity was quantified using the I² coefficient. The studies primarily involved linear measurements between specific cranial landmarks, manually delineated using imaging software. Measurements analyzed included Maximum Cranial Length (G-Op), Cranial Base Length (N-Ba and N-Pfm), Cranial Height (Ba-Br), Frontal Chord (N-Br), Maximum Cranial Breadth (Eu-Eu), Minimum Frontal Breadth (Ft-Ft), Upper Facial Breadth (Fmt-Fmt), and Bimastoid Breadth (Ms-Ms). Results indicated that the mean values were significantly lower in females (p < 0.001), with no differences between the subgroups of dry skulls and living patients. The largest differences between sexes were observed in G-Op [-8.64 (-9.69, -7.59) mm] and N-Pfm [-8.83 mm (-12.75, -4.91)]. Our meta-analysis showed a low risk of bias, and measurements of N-Ba, Ba-Br, N-Br, and Ms-Ms demonstrated high certainty of evidence according to the GRADE approach. This research underscores the reliability of specific neurocranial measurements for sex differentiation in CT scans, with smaller dimensions consistently found in females.