Morphology of the Asterion: A Systematic Review and Meta-analysis

Abstract Introduction: The asterion is an important landmark in neurosurgical approaches to the posterior cranial fossa. Morphologically, the asterion is commonly categorized as type I, characterized by the presence of a sutural (Wormian) bone, and type II, in which no sutural bone is present. Previous anatomical studies have reported wide variation in the prevalence of asterion types across different populations. However, no comprehensive meta-analysis has systematically quantified the prevalence of type I and type II asterion morphology, nor evaluated the influence of sex and side on their distribution across populations. Aim of the study: To assess the pooled prevalence of type I and type II morphology and observe its distribution based on sex and side subgroups. Method A systematic review and meta-analysis of prevalence studies was conducted following PRISMA guidelines. Eligible studies on asterion morphology in adult human skulls with extractable frequency data were included. Random-effects meta-analyses were performed using a random intercept logistic regression model with logit transformation of proportions. Between-study variance was estimated using maximum likelihood τ 2 . Heterogeneity was assessed using the I 2 statistic, and 95% predictive intervals were calculated to estimate the expected range of prevalence in future studies. Sex and side-based subgroup analyses were conducted. Publication bias was assessed using funnel plots. Result A total of thirteen studies encompassing 1605 asterions were assessed in this study. We reported a pooled prevalence of 17% (95% CI: 12–24%) of type I asterion, while type II asterion accounted for 83% (95% CI: 76%-88%). Considerable heterogeneity was observed for both types of asterion (I 2  = 88.1%). The 95% predictive interval ranged from 4.2% to 49.7% for type I and from 50.3% to 95.9% for type II asterion, indicating substantial inter-population variability. Subgroup analyses by sex and side did not reveal consistent sources of heterogeneity. Leave-one-out sensitivity analyses demonstrated stability of the pooled estimates. Conclusion Overall, the pooled prevalence of type II asterion was predominant. However, the presence of Wormian bones is clinically significant, and we have observed that considerable morphological variation exists across populations. This underscores caution against overgeneralization of pooled prevalence estimates in clinical and anthropological applications. Systematic review registration number: PROSPERO CRD420251267482