A Triple-Measure Model for Estimating Cranial-Brain Size Across Age Groups

Background: Head circumference is widely used as an indirect indicator of brain growth and cranial capacity; however, its isolated use may lead to imprecise interpretations, particularly in borderline cases of microcephaly and megalencephaly. Complementary screening approaches that remain accessible and non-invasive may therefore be useful, especially in settings with limited access to neuroimaging. Objective: To develop and evaluate an experimental, non-invasive model for estimating endocranial volume based on a combined cranial metric, termed the Triple-Measure, and to compare its performance with head circumference alone across different age ranges. Methods: One hundred forensic facial approximations with known cranial scale were analyzed. Head circumference, sagittal arc, and coronal arc were measured on three-dimensional skull models, and their sum was defined as the Triple-Measure. Endocranial volume was obtained through direct segmentation of computed tomography data or by anatomical deformation of donor models. Regression analyses and validation procedures were performed, and the results were contextualized using literature-derived datasets to assess compatibility with established population parameters. Results: The Triple-Measure showed a stronger correlation with endocranial volume (R = 0.83; R2 = 0.69) than head circumference alone (R = 0.76; R2 = 0.57), a difference confirmed by an F-test (F ~ 17.03, p < 0.001). Validation analyses performed on independent CT cases demonstrated good agreement and consistency between predicted and measured values. The sample distribution was compatible with large population datasets derived from the literature. Based on these findings, an analog lookup table and a digital calculation tool were developed to support exploratory application across adult and developmental stages, with improved sensitivity in borderline situations. Conclusions: The Triple-Measure may provide a more informative anthropometric proxy for endocranial volume than head circumference alone while remaining non-invasive and accessible. Given its exploratory nature, the method is best interpreted as a complementary screening approach intended to support clinical decision-making and to indicate when further imaging evaluation may be warranted. Additional studies with larger clinical datasets are recommended to refine its applicability across populations.