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

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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 Asterion Cranial morphology Wormian bones Meta-analyses Pooled Prevalence Predictive value Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 1. Introduction The asterion is an important cranial landmark located at the junction of the lambdoid, parietomastoid, and occipitomastoid sutures. Owing to its close relationship with the transverse and sigmoid venous sinuses, the asterion has considerable relevance in neurosurgical approaches to the posterior cranial fossa, as well as in forensic anthropology and cranial morphometry [ 1 – 3 ]. Morphologically, the asterion demonstrates notable variability in its sutural configuration. The most commonly described patterns are type I, characterized by the presence of a sutural (Wormian) bone at the asterion, and type II, in which no sutural bone is present [ 4 ]. These morphological variations are of practical importance, as the presence of sutural bones may obscure surface landmarks and alter the reliability of the asterion as a guide during surgical procedures [ 1 ]. Wormian bones is a small accessory bone that develops in sutures. It commonly develops in the lambdoid suture, coronal suture, asterion, and parieto-mastoid suture [ 5 ]. It is used as a marker for the diagnosis of autosomal dominant genetic disorders like craniosynostosis and osteogenesis imperfecta [ 6 ]. Less commonly, asterion is categorized based on the presence or absence of sutures; type I asterion, with all three sutures (occipito mastoid, parieto mastoid, lambdoid sutures), which is the dominant type 88.46% and type II asterion, which lacks at least one suture, accounting for 11.54% asterion [ 7 ]. Previous anatomical studies have reported wide variation in the prevalence of asterion types across different populations. Such variability has been attributed to genetic factors, developmental influences, and population-specific cranial growth patterns, as well as environmental and evolutionary determinants [ 6 , 8 – 10 ]. However, most available studies are limited by relatively small sample sizes and are often restricted to single geographic or ethnic populations, limiting the generalizability of their findings. In addition, inconsistencies exist in the literature regarding sex and side-based differences in the presence of Wormian bones. Side and sex based dimorphism was reported by some studies, while others stated no sex and side-based significant different [ 4 , 11 – 13 ]. To date, no comprehensive meta-analysis has systematically quantified the prevalence of type I and type II asterion morphology, or evaluated the influence of sex and side on their distribution across populations. Therefore, the present study aimed to systematically review the literature and perform a meta-analysis to estimate the pooled prevalence value for asterion morphological types. 2. Method 2.1. Study design and reporting protocol This study was conducted as a systematic review and meta-analysis of published literature that reported the morphology of the asterion. The methodology followed established principles for meta-analysis of prevalence data and was prepared in accordance with the preferred reporting item for systematic review and meta-analysis (PRISMA) guidelines [ 14 ]. 2.2. Information source A comprehensive literature search was performed in the following electronic databases: PubMed, PubMed Central (PMC), Scopus, Science Direct, and Google Scholar, from database inception to December 2025. Reference lists of relevant articles were manually screened to identify additional eligible studies that may not have been captured through the electronic database searches. 2.3. Search strategy We performed a complete search of electronic databases, such as PubMed, PubMed Central (PMC), Scopus, Science Direct and Google Scholar, to find relevant articles to the topic of interest. Reference from retrieved articles were also used to manually search for additional relevant articles if they were missed. The search terms were derived from the following keywords: asterion, morphology, morphometry, craniometric points, skull anatomy, variation, cranium, imaging, and cadaver. A search strategy was developed based on these terms, linking them with appropriate Boolean operators "AND" and "OR." The details of the search strategy are provided in (S1 Search Strategy). 2.4. Selection process The retrieved studies were imported to Rayyan screening tool, and duplicates were removed. Two independent reviewers screened all the articles for eligibility criteria. Reviewers began by screening the abstracts and titles, followed by full-text screening. Any disagreement between the two reviewers were resolved through discussion until consensus was reached. No automation was used during the study selection process. The overall study selection process is summarized in the PRISMA 2020 flow diagram (S2). 2.5. Eligibility criteria The inclusion criteria for this systematic review and meta-analysis were studies that reported original data on asterion morphology in human skulls and classified asterion morphology into type I and type II based on the presence or absence of Wormian bones. Only studies conducted on adult human skulls were included. To be eligible, studies were required to report sample size and frequency data sufficient for the calculation of prevalence estimates. There were no restrictions based on geographic location. Studies were excluded if they were reported in foreign language other than English, if they are review articles, case reports, conference abstracts, or editorial materials. Reports lacking extractable prevalence data, studies conducted on pathological or syndromic skull, and investigations involving duplicated or overlapping samples were also excluded. where ambiguity regarding sample overlap or classification criteria existed such studies were excluded to avoid potential bias. 2.6. Study risk of bias assessment We adopted the modified Newcastle-Ottawa Scale adapted for cross-sectional studies, and two reviewers independently assessed the methodological quality of the included studies [ 15 ]. The studies were evaluated for specimen selection, outcome measurement, and statistical analyses. The adopted Newcastle Ottawa scale for anatomical study is illustrated on supplementary file (S3 modified Newcastle Ottawa scale). Specimen selection was assessed based on representativeness, sample size adequacy, and completeness of data. The sample size adequacy was evaluated high if the study included at least ten adult human skulls for morphological description with at least five skulls for each sex group, if it intends to describe sex based difference [ 16 ]. Outcome assessment focused on the clarity of asterion definition, appropriateness of asterion classification. Statistical analyses were evaluated for appropriateness and clarity of reported methods. As most studies were descriptive, the comparability domain of the original Newcastle Ottawa scale was considered not applicable and was assessed only when formal sex or side-based or subgroup comparisons were performed. Individual items were rated as high, moderate, low, or unclear quality, and overall study quality was judged based on key methodological items and the presence of serious flaws rather than the summation of scores. Any disagreements were resolved through discussion. No study was excluded based on quality assessment. 2.7. Data collection process and data items Data were extracted from all eligible studies using a standardized extraction format prepared in Microsoft Excel by two independent reviewers. The format included: first author, publication year, country or population studied, methods, study design, sample size, number of type I and type II asterion, and sex and side-specific frequencies. Any discrepancies or uncertainties encountered during data extraction were resolved through careful re-examination of the original articles and discussion to ensure consistency and accuracy. No automated tool was used to extract data. 2.8. Outcome measures The primary outcome was the prevalence of type I and type II asterion morphology. Secondary outcomes included sex- and side-based differences in prevalence. 2.9. Statistical analysis A meta-analysis of prevalence was conducted using the meta package in R version 4.3.3. A random-intercept logistic regression model was used to pool prevalence estimates, acknowledging expected inter-study variability. Prevalence proportions were logit-transformed before pooling, and pooled estimates were back-transformed for presentation. Between-study variance was estimated using the maximum-likelihood method τ 2 . Statistical heterogeneity was assessed using Cochran’s Q and quantified with I 2 statistic, with values greater than 75% considered indicative of considerable heterogeneity [ 17 ]. Confidence intervals for individual study prevalence estimates were calculated using the Clopper-Pearson exact method. Leave-one-out sensitivity analyses were conducted to evaluate the influence of individual studies on pooled estimates. In addition, subgroup analyses were performed based on sex (male Vs female) and side (right Vs left) to assess the consistency of the pooled result. To account for heterogeneity and to estimate the expected range of prevalence in future studies, 95% predictive intervals were calculated for both type I and type II asterion prevalence. A Funnel plot is used to visually assess the publication bias. 3. Result 3.1. Study selection A total of 944 studies were identified through database searching, including PubMed (n = 46), PubMed Central (n = 164), Scopus (n = 142), Science Direct (n = 423), and Google Scholar (n = 200). After removing 175 duplicate records, 800 records remained for title and abstract screening. During the screening phase, 759 records were excluded based on irrelevance to the study objectives. The full texts of 41 studies were sought for retrieval, of which 5 studies could not be retrieved. Consequently, 36 full-text articles were assessed for eligibility. Of these, 23 studies were excluded for the following reasons: A different way of asterion types classification (n = 1), wrong outcome (15), unclear denominator (n = 5), and unclear standard deviation or insufficient quantitative data (n = 2). Ultimately, 13 studies met the inclusion criteria and were included in the systematic review and meta-analysis. The study selection process is summarized in the PRISMA 2020 flow diagram (S2). 3.2. Study characteristics A total of 13 studies were included in the final analysis. Among these, five studies were from India, two were from Thailand, and one each was from Serbia, Turkey, South Africa, Ethiopia, and Iran. collectively reported data from 824 skulls, corresponding to 1605 asterions, which were analyzed in the present review. Table 1 explains the included studies. Table 1 Characteristics of included studies: the articles are listed in ascending order of publication year Authors Publication Year Country TypeI% Type II% Sample size Seema_Depak et.al [ 18 ] 2015 India 27.00 73.00 100 Vivaan Dutta et.al [ 9 ] 2017 India 13.46 86.54 156 Umesh_P Modaysiya et.al [ 19 ] 2018 India 8.18 91.82 220 Serdar Babacan et.al [ 20 ] 2019 Turkey 31.82 68.18 22 Abebe_Muche [ 10 ] 2021 Ethiopia 14.75 85.25 122 Hossein Jafari et.al [ 21 ] 2021 Iran 13.81 86.19 210 Wimon Wirakiat et.al [ 4 ] 2021 Thailand 38.75 61.25 80 Sadhana Karuna et.al [ 22 ] 2021 India 15.00 85.00 40 Krstonosic Bojana et.al [ 12 ] 2023 Serbia 34.88 65.12 43 Soniya_ArunKumar et.al [ 23 ] 2023 India 15.00 85.00 60 Yasmin_Khan et.al [ 24 ] 2023 South Africa 25.00 75.00 72 Rahul Sharma et.al [ 25 ] 2024 India 17.50 82.50 80 Tanat Tabtieang et.al [ 26 ] 2024 Thailand 4.00 96.00 400 3.3. Overall pooled prevalence of Type I and Type II Asterion The pooled prevalence of type I asterion was 17% (95% CI: 12%-24%) under a random effects model. Considerable heterogeneity was observed among studies (I 2 = 88.1%, T 2 = 0.4720, p < 0.0001). The 95% predictive interval for type I asterion prevalence ranged from 4.2% to 49.7%, indicating substantial variability in the expected prevalence across future population-based studies. In contrast, type II asterion represented the predominant morphological pattern with a pooled prevalence of 83% (95% CI: 76%-88%). Similar to type I, considerable heterogeneity was present (I 2 = 88.1%, T 2 = 0.4720, p < 0.0001). The 95% predictive interval for type II asterion prevalence ranged from 50.3% to 95.9%, reflecting marked inter-population variability while confirming its predominance. Taken together, these findings indicate that type I and type II asterion morphologies are complementary and mutually exclusive, with type II accounting for the majority of cases across populations. 3.4. Sex based subgroup analysis The pooled prevalence of type I asterion was 18% (95% CI: 11%-28%) in males and 15% (95% :6%-31%) in females. The test for subgroup differences was not statistically significant (X 2 = 0.36, df = 1, p = 0.5487). consistent with these findings, sex based subgroup analysis for type II asterion revealed a pooled prevalence of 82% (95% CI: 72%-89%) in males and 85% (95% CI: 69%-94%) in females. Considerable heterogeneity persisted within both male (I 2 = 89.8% ) and female (I 2 = 83.1% ) subgroups. The test for subgroup difference was not statistically significant (X 2 = 0.36, df = 1, p = 0.5487). Which indicates no evidence of sexual dimorphism in asterion morphology for either type I or type II. 3.5. Side based subgroup analysis The pooled prevalence of type I asterion was 21% (95% CI: 16%-27%) on the right side and 19% (95% CI: 12% − 30%)on the left side, with no statistically significant difference between sides. Similarly, the pooled prevalence of type II asterion was 79% − 81% across sides, with overlapping confidence intervals and no statistically significant side difference. Substantial heterogeneity was observed with both right and left side subgroups. Implying bilateral symmetry in asterion morphology at population. 3.6. Sensitivity analysis Leave-one-out sensitivity analyses for both type I and type II asterion demonstrated that omission of any individual study did not materially alter pooled prevalence estimates. For type II asterion, pooled prevalence estimates ranged from 81% to 84% following omission of single studies, with heterogeneity remaining consistently high (I 2 range: 81.1% − 89.1%). These results confirm the robustness of the pooled estimates. 3.7. Risk of publication bias Visual inspection of funnel plots for both Type I and Type II asterion revealed some asymmetry. Given the high heterogeneity and the descriptive nature of anatomical prevalence studiesm this asymmetry is most plausibly attributed to true population-level anatomical variation and sampling variability, rather than publication bias. 4. Discussion The primary objective of this meta-analysis was to assess the pooled prevalence of type I (has Wormian bones) and type II (with no Wormian bones) asterion in various populations and observe its distribution based on sex and side-based subgroups. Our findings demonstrate that type II asterion is the dominant morphological type, accounting for approximately four-fifth of cases, whereas type I asterion, which has Wormian bones, occurs in roughly one-sixth of skulls. Despite wide inter-study variability, the complementary distribution of these two morphological types was consistent across analyses and robust to leave-one-out sensitivity testing. Given that asterion is an important landmark as an initial burr hole site when performing basal suboccipital craniotomy to expose the lower portion of the cerebellopontine angle(CPA) and in temporo parietal craniotomy to access the floor of the middle cranial fossa [ 27 , 28 ], type I asterion is clinically significant. The presence of Wormian bones may cause complications during craniotomy [ 29 ]. Moreover, it may affecte measurement of asterion from surface landmarks, which affects its localization during craniotomy[ 23 ]. Wormian boness may also be confused for fracture in radiographs [ 29 , 30 ]. This implies that type I asterion should be sought carefully. Considerable heterogeneity was observed for both morphological types of asterion. High I 2 values are common in meta-analysis of prevalence and should be interpreted with caution, as the I 2 statistic reflects the proportion of total variability attributable to between-study differences rather than the absolute magnitude or clinical relevance of that variability. In prevalence meta-analysis, I 2 values are influenced by the number of included studies and by extreme pooled prevalence estimates, and therefore, high I 2 is not necessarily synonymous with excessive or problematic heterogeneity In the present study, the high I 2 value likely reflects a genuine anatomical variation across populations in asterion morphology rather than methodological inconsistency alone. The variation is likely influenced by MSX2 gene, a transcription factor linked to suture of craniofacial morphogenesis [ 31 ]. In addition to genetic determination, Wormian bones are thought to form in connection with increased dural strain from mechanical force as well as increased sutural width like in hydrocephalus, or iatrogenic mechanical stress due to intentional deformation like that is practiced in ancient culture [ 6 ]. We also reported wide predictive intervals observed for both type I and type II asterion, that further emphasize the presence of genuine population-level anatomical variation. While pooled prevalence estimates represent average values, the predictive intervals demonstrate that prevalence in individual populations may deviate substantially from these averages. This finding underscores the importance of population-specific anatomical data and cautions against overgeneralization of pooled estimates. Importantly, neither sex nor side emerged as a significant moderator of asterion morphology, indicating that these traits are largely independent of sexual dimorphism and lateralization. Studies has showed that bilaterally symmetric asterion types are predominant as compared to asymmetric asterion types. Umesh et al reported 92 (83.63%) of skull had symmetrical type II and no type I bilateral asterion [ 19 ]. Similarly, Serdar et. al demonstrated 10 (90.11%) of skull had bilateral asterion type 7 (63.3%) type II and 3 (27.27%) type I astrion [ 20 ]. Which could explain the non-significant side-based variation reported in this meta-analysis. Overall, the predominance of type II asterion underscores the importance of population-specific anatomical knowledge when using the asterion as a surgical landmark. The absence of consistent sex or side related differences suggests that morphological expectations should not be adjusted solely on these factors. 5. Strengths and Limitations of the study The strength of this study is that it provides comprehensive information on the prevalence of type I and type II asterion and its distribution based on side and sex in human adult skull following PRISMA guideline. We also rigorously searched the literature using different databases and identified eligible studies. Although the meta-analytic technique we used was robust, we were unable to compute inter-population subgroup analysis due to a lack of sufficient studies. Nevertheless, asterion morphology is reported to be dependent on genetic factors and varies across populations. 6. Conclusion Overall, the pooled prevalence of type II asteron was predominant. Though the presence of Wormian bones is clinically significant, we have observed considerable morphological variation across populations. This underscores caution against overgeneralization of pooled prevalence estimates in clinical and anthropological applications. Declarations Author Contribution T.A.- Conceptualization, Write the main manuscriptH.W. - Data extractionH.E. - MethodologyB.D. - Data extractionS.M. - Review the manuscriptA.M. - Conceptualization Acknowledgment We pass our sincere gratitude to all the researchers whose studies were included in this study. References Day JD, Tschabitscher M (1998) Anatomic position of the asterion. Neurosurgery 42(1):198–199 Lang J (1983) Clinical anatomy of the head: neurocranium, orbit, craniocervical region. Springer-, Berlin Grays's Anatomy (2016) The Anatomical Basis of Clinical Practice, 41st edn. Elsevier, London Wirakiat W, Kaewborisutsakul A, Kaewborisutsakul WK (2021) Anatomic Position of the Asterion and Implication for Neurosurgical Procedure. Int J Morphology. ;39(5) Natsis K, Piagkou M, Lazaridis N, Anastasopoulos N, Nousios G, Piagkos G et al (2019) Incidence, number and topography of Wormian bones in Greek adult dry skulls. 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J Neurosurg 106(3):449–454 B S. Multiple Wormian bones at the lambdoid suture in an Indian skull. Neuroanatomy. (2008) Cirpan S, Aksu F, Mas N (2015) The Incidence and Topographic Distribution of Sutures Including Wormian Bones in Human Skulls. J Craniofac Surg 26(5):1687–1690 Liu YH, Tang Z, Kundu RK, Wu L, Luo W, Zhu D et al (1999) Msx2 gene dosage influences the number of proliferative osteogenic cells in growth centers of the developing murine skull: a possible mechanism for MSX2-mediated craniosynostosis in humans. Dev Biol 205(2):260–274 Additional Declarations No competing interests reported. Supplementary Files S1Searchstrategy.docx S2PRISMA2020flowdiagramnewSRsv1.docx S3NOS.docx Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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I asterion based on random effect meta-analysis\u003c/p\u003e","description":"","filename":"Picture1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8817841/v1/ab5ac507f8309830a5934a85.jpg"},{"id":103234011,"identity":"321748fc-a958-407e-9555-c9dbe01eda29","added_by":"auto","created_at":"2026-02-23 12:50:18","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1079946,"visible":true,"origin":"","legend":"\u003cp\u003eForest plot of pooled prevalence of type II asterion based on random effect meta-analysis\u003c/p\u003e","description":"","filename":"Picture2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8817841/v1/44f3daeb66f50b74865f1740.jpg"},{"id":103234012,"identity":"7011cb1d-0bd5-4e0c-87cc-dc0e4c7588e5","added_by":"auto","created_at":"2026-02-23 12:50:18","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1155942,"visible":true,"origin":"","legend":"\u003cp\u003eForest plot of sex based subgroup analysis for prevalence of type I asterion\u003c/p\u003e","description":"","filename":"Picture3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8817841/v1/9da46372ad92423d58f13e80.jpg"},{"id":103234022,"identity":"4b02bedb-ffe1-481b-bc5a-d139d8c76ac7","added_by":"auto","created_at":"2026-02-23 12:50:18","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":1204035,"visible":true,"origin":"","legend":"\u003cp\u003eForest plot of sex based subgroup analysis for the prevalence of type II asterion\u003c/p\u003e","description":"","filename":"Picture4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8817841/v1/55d809aecace46765ab618a4.jpg"},{"id":103505528,"identity":"a321bcd4-351a-4939-9453-99409236098d","added_by":"auto","created_at":"2026-02-26 13:31:37","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":1526254,"visible":true,"origin":"","legend":"\u003cp\u003eForest plot of side-based subgroup analysis for the prevalence of type II asterion\u003c/p\u003e","description":"","filename":"Picture5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8817841/v1/fdf0125819372f444790a742.jpg"},{"id":103234016,"identity":"819435e7-8bfb-4e8f-aa29-158ea0957381","added_by":"auto","created_at":"2026-02-23 12:50:18","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":1485118,"visible":true,"origin":"","legend":"\u003cp\u003eForest plot of side-based subgroup analysis for the prevalence of type I asterion\u003c/p\u003e","description":"","filename":"Picture6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8817841/v1/92832dc8caf52f52a29bdf17.jpg"},{"id":103234017,"identity":"7ec278d3-18e2-41d6-b1b7-dd38d1c422e1","added_by":"auto","created_at":"2026-02-23 12:50:18","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":1101076,"visible":true,"origin":"","legend":"\u003cp\u003eLeave one out sensitivity analysis forest plot for the pooled prevalence of type II asterion.\u003c/p\u003e","description":"","filename":"Picture7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8817841/v1/cc46ffef4ebfd7edb43a9764.jpg"},{"id":103505048,"identity":"1281a7cd-9af8-4377-984a-b0a0122251f7","added_by":"auto","created_at":"2026-02-26 13:22:39","extension":"jpg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":1128308,"visible":true,"origin":"","legend":"\u003cp\u003eLeave one out sensitivity analysis forest plot for the pooled prevalence of type I asterion.\u003c/p\u003e","description":"","filename":"Picture8.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8817841/v1/82497faecb699794b9e88102.jpg"},{"id":103234023,"identity":"041deb49-14ef-4660-ba07-209af1613bac","added_by":"auto","created_at":"2026-02-23 12:50:18","extension":"jpg","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":304901,"visible":true,"origin":"","legend":"\u003cp\u003eFunnel plot for assessment of publication bias in studies reporting the prevalence of type II asterion\u003c/p\u003e","description":"","filename":"Picture9.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8817841/v1/afd1c886655337bbffb92cdd.jpg"},{"id":103234018,"identity":"0a2d3f85-fedc-49fc-b096-7b038e1f3905","added_by":"auto","created_at":"2026-02-23 12:50:18","extension":"jpg","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":266811,"visible":true,"origin":"","legend":"\u003cp\u003eFunnel plot for assessment of publication bias in studies reporting prevalence of type I asterion.\u003c/p\u003e","description":"","filename":"Picture10.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8817841/v1/73950ad00368fdc8cc6b8dfd.jpg"},{"id":104404216,"identity":"242471c7-e252-4449-8f98-df77f2fb9d87","added_by":"auto","created_at":"2026-03-11 12:19:52","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":11196930,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8817841/v1/d985b997-3fcc-4224-9275-965650fd940d.pdf"},{"id":103234014,"identity":"75c9d6fb-60cd-425d-8a6f-9ba97abd0f76","added_by":"auto","created_at":"2026-02-23 12:50:18","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":13148,"visible":true,"origin":"","legend":"","description":"","filename":"S1Searchstrategy.docx","url":"https://assets-eu.researchsquare.com/files/rs-8817841/v1/e6e3f20ff46d3124f1806e85.docx"},{"id":103234020,"identity":"2e442271-eb33-42e5-8d99-dfeec9bcf2b6","added_by":"auto","created_at":"2026-02-23 12:50:18","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":50632,"visible":true,"origin":"","legend":"","description":"","filename":"S2PRISMA2020flowdiagramnewSRsv1.docx","url":"https://assets-eu.researchsquare.com/files/rs-8817841/v1/a20e7396a862822f3e5dcf58.docx"},{"id":103505499,"identity":"7233bc34-8b71-4efe-83f4-3b673ed968eb","added_by":"auto","created_at":"2026-02-26 13:31:31","extension":"docx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":14630,"visible":true,"origin":"","legend":"","description":"","filename":"S3NOS.docx","url":"https://assets-eu.researchsquare.com/files/rs-8817841/v1/9112702175532b1872d440e8.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Morphology of the Asterion: A Systematic Review and Meta-analysis","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe asterion is an important cranial landmark located at the junction of the lambdoid, parietomastoid, and occipitomastoid sutures. Owing to its close relationship with the transverse and sigmoid venous sinuses, the asterion has considerable relevance in neurosurgical approaches to the posterior cranial fossa, as well as in forensic anthropology and cranial morphometry [\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eMorphologically, the asterion demonstrates notable variability in its sutural configuration. The most commonly described patterns are type I, characterized by the presence of a sutural (Wormian) bone at the asterion, and type II, in which no sutural bone is present [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. These morphological variations are of practical importance, as the presence of sutural bones may obscure surface landmarks and alter the reliability of the asterion as a guide during surgical procedures [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Wormian bones is a small accessory bone that develops in sutures. It commonly develops in the lambdoid suture, coronal suture, asterion, and parieto-mastoid suture [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. It is used as a marker for the diagnosis of autosomal dominant genetic disorders like craniosynostosis and osteogenesis imperfecta [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eLess commonly, asterion is categorized based on the presence or absence of sutures; type I asterion, with all three sutures (occipito mastoid, parieto mastoid, lambdoid sutures), which is the dominant type 88.46% and type II asterion, which lacks at least one suture, accounting for 11.54% asterion [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e].\u003c/p\u003e \u003cp\u003ePrevious anatomical studies have reported wide variation in the prevalence of asterion types across different populations. Such variability has been attributed to genetic factors, developmental influences, and population-specific cranial growth patterns, as well as environmental and evolutionary determinants [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan additionalcitationids=\"CR9\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. However, most available studies are limited by relatively small sample sizes and are often restricted to single geographic or ethnic populations, limiting the generalizability of their findings.\u003c/p\u003e \u003cp\u003eIn addition, inconsistencies exist in the literature regarding sex and side-based differences in the presence of Wormian bones. Side and sex based dimorphism was reported by some studies, while others stated no sex and side-based significant different [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan additionalcitationids=\"CR12\" citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eTo date, no comprehensive meta-analysis has systematically quantified the prevalence of type I and type II asterion morphology, or evaluated the influence of sex and side on their distribution across populations. Therefore, the present study aimed to systematically review the literature and perform a meta-analysis to estimate the pooled prevalence value for asterion morphological types.\u003c/p\u003e"},{"header":"2. Method","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Study design and reporting protocol\u003c/h2\u003e \u003cp\u003eThis study was conducted as a systematic review and meta-analysis of published literature that reported the morphology of the asterion. The methodology followed established principles for meta-analysis of prevalence data and was prepared in accordance with the preferred reporting item for systematic review and meta-analysis (PRISMA) guidelines [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Information source\u003c/h2\u003e \u003cp\u003eA comprehensive literature search was performed in the following electronic databases: PubMed, PubMed Central (PMC), Scopus, Science Direct, and Google Scholar, from database inception to December 2025. Reference lists of relevant articles were manually screened to identify additional eligible studies that may not have been captured through the electronic database searches.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Search strategy\u003c/h2\u003e \u003cp\u003eWe performed a complete search of electronic databases, such as PubMed, PubMed Central (PMC), Scopus, Science Direct and Google Scholar, to find relevant articles to the topic of interest. Reference from retrieved articles were also used to manually search for additional relevant articles if they were missed. The search terms were derived from the following keywords: asterion, morphology, morphometry, craniometric points, skull anatomy, variation, cranium, imaging, and cadaver. A search strategy was developed based on these terms, linking them with appropriate Boolean operators \"AND\" and \"OR.\" The details of the search strategy are provided in (S1 Search Strategy).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4. Selection process\u003c/h2\u003e \u003cp\u003eThe retrieved studies were imported to Rayyan screening tool, and duplicates were removed. Two independent reviewers screened all the articles for eligibility criteria. Reviewers began by screening the abstracts and titles, followed by full-text screening. Any disagreement between the two reviewers were resolved through discussion until consensus was reached. No automation was used during the study selection process. The overall study selection process is summarized in the PRISMA 2020 flow diagram (S2).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.5. Eligibility criteria\u003c/h2\u003e \u003cp\u003eThe inclusion criteria for this systematic review and meta-analysis were studies that reported original data on asterion morphology in human skulls and classified asterion morphology into type I and type II based on the presence or absence of Wormian bones. Only studies conducted on adult human skulls were included. To be eligible, studies were required to report sample size and frequency data sufficient for the calculation of prevalence estimates. There were no restrictions based on geographic location.\u003c/p\u003e \u003cp\u003eStudies were excluded if they were reported in foreign language other than English, if they are review articles, case reports, conference abstracts, or editorial materials. Reports lacking extractable prevalence data, studies conducted on pathological or syndromic skull, and investigations involving duplicated or overlapping samples were also excluded. where ambiguity regarding sample overlap or classification criteria existed such studies were excluded to avoid potential bias.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e2.6. Study risk of bias assessment\u003c/h2\u003e \u003cp\u003eWe adopted the modified Newcastle-Ottawa Scale adapted for cross-sectional studies, and two reviewers independently assessed the methodological quality of the included studies [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. The studies were evaluated for specimen selection, outcome measurement, and statistical analyses. The adopted Newcastle Ottawa scale for anatomical study is illustrated on supplementary file (S3 modified Newcastle Ottawa scale).\u003c/p\u003e \u003cp\u003eSpecimen selection was assessed based on representativeness, sample size adequacy, and completeness of data. The sample size adequacy was evaluated high if the study included at least ten adult human skulls for morphological description with at least five skulls for each sex group, if it intends to describe sex based difference [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Outcome assessment focused on the clarity of asterion definition, appropriateness of asterion classification. Statistical analyses were evaluated for appropriateness and clarity of reported methods.\u003c/p\u003e \u003cp\u003eAs most studies were descriptive, the comparability domain of the original Newcastle Ottawa scale was considered not applicable and was assessed only when formal sex or side-based or subgroup comparisons were performed. Individual items were rated as high, moderate, low, or unclear quality, and overall study quality was judged based on key methodological items and the presence of serious flaws rather than the summation of scores. Any disagreements were resolved through discussion. No study was excluded based on quality assessment.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e2.7. Data collection process and data items\u003c/h2\u003e \u003cp\u003eData were extracted from all eligible studies using a standardized extraction format prepared in Microsoft Excel by two independent reviewers. The format included: first author, publication year, country or population studied, methods, study design, sample size, number of type I and type II asterion, and sex and side-specific frequencies. Any discrepancies or uncertainties encountered during data extraction were resolved through careful re-examination of the original articles and discussion to ensure consistency and accuracy. No automated tool was used to extract data.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e2.8. Outcome measures\u003c/h2\u003e \u003cp\u003eThe primary outcome was the prevalence of type I and type II asterion morphology. Secondary outcomes included sex- and side-based differences in prevalence.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e2.9. Statistical analysis\u003c/h2\u003e \u003cp\u003eA meta-analysis of prevalence was conducted using the meta package in R version 4.3.3. A random-intercept logistic regression model was used to pool prevalence estimates, acknowledging expected inter-study variability. Prevalence proportions were logit-transformed before pooling, and pooled estimates were back-transformed for presentation.\u003c/p\u003e \u003cp\u003eBetween-study variance was estimated using the maximum-likelihood method τ\u003csup\u003e2\u003c/sup\u003e. Statistical heterogeneity was assessed using Cochran\u0026rsquo;s Q and quantified with I\u003csup\u003e2\u003c/sup\u003e statistic, with values greater than 75% considered indicative of considerable heterogeneity [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eConfidence intervals for individual study prevalence estimates were calculated using the Clopper-Pearson exact method. Leave-one-out sensitivity analyses were conducted to evaluate the influence of individual studies on pooled estimates. In addition, subgroup analyses were performed based on sex (male Vs female) and side (right Vs left) to assess the consistency of the pooled result.\u003c/p\u003e \u003cp\u003eTo account for heterogeneity and to estimate the expected range of prevalence in future studies, 95% predictive intervals were calculated for both type I and type II asterion prevalence. A Funnel plot is used to visually assess the publication bias.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Result","content":"\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e3.1. Study selection\u003c/h2\u003e \u003cp\u003eA total of 944 studies were identified through database searching, including PubMed (n\u0026thinsp;=\u0026thinsp;46), PubMed Central (n\u0026thinsp;=\u0026thinsp;164), Scopus (n\u0026thinsp;=\u0026thinsp;142), Science Direct (n\u0026thinsp;=\u0026thinsp;423), and Google Scholar (n\u0026thinsp;=\u0026thinsp;200). After removing 175 duplicate records, 800 records remained for title and abstract screening.\u003c/p\u003e \u003cp\u003eDuring the screening phase, 759 records were excluded based on irrelevance to the study objectives. The full texts of 41 studies were sought for retrieval, of which 5 studies could not be retrieved. Consequently, 36 full-text articles were assessed for eligibility. Of these, 23 studies were excluded for the following reasons: A different way of asterion types classification (n\u0026thinsp;=\u0026thinsp;1), wrong outcome (15), unclear denominator (n\u0026thinsp;=\u0026thinsp;5), and unclear standard deviation or insufficient quantitative data (n\u0026thinsp;=\u0026thinsp;2). Ultimately, 13 studies met the inclusion criteria and were included in the systematic review and meta-analysis. The study selection process is summarized in the PRISMA 2020 flow diagram (S2).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003e3.2. Study characteristics\u003c/h2\u003e \u003cp\u003eA total of 13 studies were included in the final analysis. Among these, five studies were from India, two were from Thailand, and one each was from Serbia, Turkey, South Africa, Ethiopia, and Iran. collectively reported data from 824 skulls, corresponding to 1605 asterions, which were analyzed in the present review. Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e explains the included studies.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCharacteristics of included studies: the articles are listed in ascending order of publication year\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAuthors\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePublication Year\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCountry\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eTypeI%\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eType II%\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eSample size\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSeema_Depak et.al\u003c/b\u003e [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2015\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eIndia\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e27.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e73.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eVivaan Dutta et.al\u003c/b\u003e [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2017\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eIndia\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e13.46\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e86.54\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e156\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eUmesh_P Modaysiya et.al\u003c/b\u003e [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2018\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eIndia\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e8.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e91.82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e220\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSerdar Babacan et.al\u003c/b\u003e [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2019\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eTurkey\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e31.82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e68.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e22\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAbebe_Muche\u003c/b\u003e [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2021\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eEthiopia\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e14.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e85.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e122\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eHossein Jafari et.al\u003c/b\u003e [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2021\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eIran\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e13.81\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e86.19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e210\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eWimon Wirakiat et.al\u003c/b\u003e [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2021\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eThailand\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e38.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e61.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e80\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSadhana Karuna et.al\u003c/b\u003e [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2021\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eIndia\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e15.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e85.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eKrstonosic Bojana et.al\u003c/b\u003e [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2023\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSerbia\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e34.88\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e65.12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e43\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSoniya_ArunKumar et.al\u003c/b\u003e [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2023\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eIndia\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e15.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e85.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e60\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eYasmin_Khan et.al\u003c/b\u003e [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2023\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSouth Africa\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e25.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e75.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e72\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eRahul Sharma et.al\u003c/b\u003e [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2024\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eIndia\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e17.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e82.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e80\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eTanat Tabtieang et.al\u003c/b\u003e [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2024\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eThailand\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e96.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e400\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003e3.3. Overall pooled prevalence of Type I and Type II Asterion\u003c/h2\u003e \u003cp\u003eThe pooled prevalence of type I asterion was 17% (95% CI: 12%-24%) under a random effects model. Considerable heterogeneity was observed among studies (I\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;88.1%, T\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.4720, p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001). The 95% predictive interval for type I asterion prevalence ranged from 4.2% to 49.7%, indicating substantial variability in the expected prevalence across future population-based studies. In contrast, type II asterion represented the predominant morphological pattern with a pooled prevalence of 83% (95% CI: 76%-88%). Similar to type I, considerable heterogeneity was present (I\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;88.1%, T\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.4720, p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001). The 95% predictive interval for type II asterion prevalence ranged from 50.3% to 95.9%, reflecting marked inter-population variability while confirming its predominance. Taken together, these findings indicate that type I and type II asterion morphologies are complementary and mutually exclusive, with type II accounting for the majority of cases across populations.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003e3.4. Sex based subgroup analysis\u003c/h2\u003e \u003cp\u003eThe pooled prevalence of type I asterion was 18% (95% CI: 11%-28%) in males and 15% (95% :6%-31%) in females. The test for subgroup differences was not statistically significant (X\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.36, df\u0026thinsp;=\u0026thinsp;1, p\u0026thinsp;=\u0026thinsp;0.5487). consistent with these findings, sex based subgroup analysis for type II asterion revealed a pooled prevalence of 82% (95% CI: 72%-89%) in males and 85% (95% CI: 69%-94%) in females. Considerable heterogeneity persisted within both male (I\u003csup\u003e2 =\u003c/sup\u003e 89.8% ) and female (I\u003csup\u003e2 =\u003c/sup\u003e 83.1% ) subgroups. The test for subgroup difference was not statistically significant (X\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.36, df\u0026thinsp;=\u0026thinsp;1, p\u0026thinsp;=\u0026thinsp;0.5487). Which indicates no evidence of sexual dimorphism in asterion morphology for either type I or type II.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003e3.5. Side based subgroup analysis\u003c/h2\u003e \u003cp\u003eThe pooled prevalence of type I asterion was 21% (95% CI: 16%-27%) on the right side and 19% (95% CI: 12% \u0026minus;\u0026thinsp;30%)on the left side, with no statistically significant difference between sides. Similarly, the pooled prevalence of type II asterion was 79% \u0026minus;\u0026thinsp;81% across sides, with overlapping confidence intervals and no statistically significant side difference. Substantial heterogeneity was observed with both right and left side subgroups. Implying bilateral symmetry in asterion morphology at population.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec18\" class=\"Section2\"\u003e \u003ch2\u003e3.6. Sensitivity analysis\u003c/h2\u003e \u003cp\u003eLeave-one-out sensitivity analyses for both type I and type II asterion demonstrated that omission of any individual study did not materially alter pooled prevalence estimates. For type II asterion, pooled prevalence estimates ranged from 81% to 84% following omission of single studies, with heterogeneity remaining consistently high (I\u003csup\u003e2\u003c/sup\u003e range: 81.1% \u0026minus;\u0026thinsp;89.1%). These results confirm the robustness of the pooled estimates.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec19\" class=\"Section2\"\u003e \u003ch2\u003e3.7. Risk of publication bias\u003c/h2\u003e \u003cp\u003eVisual inspection of funnel plots for both Type I and Type II asterion revealed some asymmetry. Given the high heterogeneity and the descriptive nature of anatomical prevalence studiesm this asymmetry is most plausibly attributed to true population-level anatomical variation and sampling variability, rather than publication bias.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cp\u003eThe primary objective of this meta-analysis was to assess the pooled prevalence of type I (has Wormian bones) and type II (with no Wormian bones) asterion in various populations and observe its distribution based on sex and side-based subgroups.\u003c/p\u003e \u003cp\u003eOur findings demonstrate that type II asterion is the dominant morphological type, accounting for approximately four-fifth of cases, whereas type I asterion, which has Wormian bones, occurs in roughly one-sixth of skulls. Despite wide inter-study variability, the complementary distribution of these two morphological types was consistent across analyses and robust to leave-one-out sensitivity testing. Given that asterion is an important landmark as an initial burr hole site when performing basal suboccipital craniotomy to expose the lower portion of the cerebellopontine angle(CPA) and in temporo parietal craniotomy to access the floor of the middle cranial fossa [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e], type I asterion is clinically significant. The presence of Wormian bones may cause complications during craniotomy [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. Moreover, it may affecte measurement of asterion from surface landmarks, which affects its localization during craniotomy[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. Wormian boness may also be confused for fracture in radiographs [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. This implies that type I asterion should be sought carefully.\u003c/p\u003e \u003cp\u003eConsiderable heterogeneity was observed for both morphological types of asterion. High I\u003csup\u003e2\u003c/sup\u003e values are common in meta-analysis of prevalence and should be interpreted with caution, as the I\u003csup\u003e2\u003c/sup\u003e statistic reflects the proportion of total variability attributable to between-study differences rather than the absolute magnitude or clinical relevance of that variability. In prevalence meta-analysis, I\u003csup\u003e2\u003c/sup\u003e values are influenced by the number of included studies and by extreme pooled prevalence estimates, and therefore, high I\u003csup\u003e2\u003c/sup\u003e is not necessarily synonymous with excessive or problematic heterogeneity\u003c/p\u003e \u003cp\u003eIn the present study, the high I\u003csup\u003e2\u003c/sup\u003e value likely reflects a genuine anatomical variation across populations in asterion morphology rather than methodological inconsistency alone. The variation is likely influenced by MSX2 gene, a transcription factor linked to suture of craniofacial morphogenesis [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. In addition to genetic determination, Wormian bones are thought to form in connection with increased dural strain from mechanical force as well as increased sutural width like in hydrocephalus, or iatrogenic mechanical stress due to intentional deformation like that is practiced in ancient culture [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eWe also reported wide predictive intervals observed for both type I and type II asterion, that further emphasize the presence of genuine population-level anatomical variation. While pooled prevalence estimates represent average values, the predictive intervals demonstrate that prevalence in individual populations may deviate substantially from these averages. This finding underscores the importance of population-specific anatomical data and cautions against overgeneralization of pooled estimates.\u003c/p\u003e \u003cp\u003eImportantly, neither sex nor side emerged as a significant moderator of asterion morphology, indicating that these traits are largely independent of sexual dimorphism and lateralization. Studies has showed that bilaterally symmetric asterion types are predominant as compared to asymmetric asterion types. Umesh et al reported 92 (83.63%) of skull had symmetrical type II and no type I bilateral asterion [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Similarly, Serdar et. al demonstrated 10 (90.11%) of skull had bilateral asterion type 7 (63.3%) type II and 3 (27.27%) type I astrion [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Which could explain the non-significant side-based variation reported in this meta-analysis.\u003c/p\u003e \u003cp\u003eOverall, the predominance of type II asterion underscores the importance of population-specific anatomical knowledge when using the asterion as a surgical landmark. The absence of consistent sex or side related differences suggests that morphological expectations should not be adjusted solely on these factors.\u003c/p\u003e"},{"header":"5. Strengths and Limitations of the study","content":"\u003cp\u003eThe strength of this study is that it provides comprehensive information on the prevalence of type I and type II asterion and its distribution based on side and sex in human adult skull following PRISMA guideline. We also rigorously searched the literature using different databases and identified eligible studies.\u003c/p\u003e \u003cp\u003eAlthough the meta-analytic technique we used was robust, we were unable to compute inter-population subgroup analysis due to a lack of sufficient studies. Nevertheless, asterion morphology is reported to be dependent on genetic factors and varies across populations.\u003c/p\u003e"},{"header":"6. Conclusion","content":"\u003cp\u003eOverall, the pooled prevalence of type II asteron was predominant. Though the presence of Wormian bones is clinically significant, we have observed considerable morphological variation across populations. This underscores caution against overgeneralization of pooled prevalence estimates in clinical and anthropological applications.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eT.A.- Conceptualization, Write the main manuscriptH.W. - Data extractionH.E. - MethodologyB.D. - Data extractionS.M. - Review the manuscriptA.M. - Conceptualization\u003c/p\u003e\u003ch2\u003eAcknowledgment\u003c/h2\u003e \u003cp\u003eWe pass our sincere gratitude to all the researchers whose studies were included in this study.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eDay JD, Tschabitscher M (1998) Anatomic position of the asterion. Neurosurgery 42(1):198\u0026ndash;199\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLang J (1983) Clinical anatomy of the head: neurocranium, orbit, craniocervical region. Springer-, Berlin\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGrays's Anatomy (2016) The Anatomical Basis of Clinical Practice, 41st edn. Elsevier, London\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWirakiat W, Kaewborisutsakul A, Kaewborisutsakul WK (2021) Anatomic Position of the Asterion and Implication for Neurosurgical Procedure. Int J Morphology. ;39(5)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNatsis K, Piagkou M, Lazaridis N, Anastasopoulos N, Nousios G, Piagkos G et al (2019) Incidence, number and topography of Wormian bones in Greek adult dry skulls. Folia Morphol 78(2):359\u0026ndash;370\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBellary SS, Steinberg A, Mirzayan N, Shirak M, Tubbs RS, Cohen-Gadol AA et al (2013) Wormian bones: a review. Clinical anatomy (New York, NY). ;26(8):922-7\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKhan G (2022) Morphometric Study on Types of Asterion in Dry Human Skull of Nepalese Origin. Med Phoenix 7:31\u0026ndash;35\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHardy E, Fernandez-Patron C (2020) Destroy to Rebuild: The Connection Between Bone Tissue Remodeling and Matrix Metalloproteinases. Front Physiol 11:47\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDutt V, Shankar VV, Shetty S (2017) Morphometric study of pterion and asterion in adult human skulls of Indian origin. Int J Anat Res 5(22):3837\u0026ndash;3842\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMuche A (2021) Morphometry of Asterion and its Proximity to Dural Venous Sinuses in Northwest Ethiopian Adult Skulls. J Craniofac Surg 32(3):1171\u0026ndash;1173\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePatil M, Sheelavant S (2012) Sexual Dimorphism among the Wormian Bones In Adult Human Skulls. J Indian Acad Forensic Med 34:124\u0026ndash;127\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKrstonosic B, Stipic N, Turanjanin D, Babovic-S S (2023) An\u0026aacute;lisis de la Morfolog\u0026iacute;a del Asterion en Relaci\u0026oacute;n con su Importancia Cl\u0026iacute;nica. Int J Morphology 41(6):1744\u0026ndash;1750\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHassanali J, Mwachaka P, Odula P. Sutural morphology of the pterion and asterion among adult Kenyans., Mwachaka PM, Hassanali J, Odula P (2009) Brazilian Journal of Morphological Sciences 26:4\u0026ndash;7 Brazilian Journal of Morphology. 2009;26:4\u0026ndash;7\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePage MJ, McKenzie JE, Bossuyt PM, Boutron I, Hoffmann TC, Mulrow CD et al (2021) The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. BMJ 372:n71\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBlanchard L, Ray S (2024) The effectiveness, cost-effectiveness and policy processes of regulatory, voluntary and partnership policies to improve food environments: an evidence synthesis. 12(8):1\u0026ndash;173\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eIwanaga J, Obata K, Kato T, Samrid R, Lesser E, Cardona JJ et al (2025) What Is the Appropriate Sample Size in Human Cadaveric Studies? A Quantitative Review of 770 Articles. Clin Anat 39:14\u0026ndash;19\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCochrane (2026) Cochrane Handbook for systematic reviews of interventions. Cochrane, London\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDeepak S, Dakshayani K (2015) Morphometric features of asterion in adult human skulls\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eModasiya UP, Kanani SD (2018) Study of pterion and asterion in adult human skulls of north Gujarat region. Ind J Clin Anat Physiol 5(3):353\u0026ndash;356\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFang B, Chen G, Wang L, Zhu X, Hu Q, Zhang J (2016) Skull anatomic landmarks for retrosigmoid craniotomy in a Chinese cohort: a 3D-computed tomography study in vivo. Turk Neurosurg 26(4):564\u0026ndash;567\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGharehdaghi J, Jafari-Marandi H, Faress F, Zeinali M, Safari H (2020) Morphology of asterion and its proximity to deep vein sinuses in Iranian adult skull. Br J Neurosurg 34(1):55\u0026ndash;58\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKarunakaran S, Mohanraj KG (2021) Morphometric Analysis and Variation of Pterion, Asterion and Lambda in Dry Human skulls and its sexual dimorphism. J Pharm Res Int 33(60B):1218\u0026ndash;1226\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGupta SA, Goyal N, Kaul N, MORPHOLOGICAL, STUDY OF POSTEROLATERAL CRANIUM\u0026amp; ITS IMPORTANCE IN LOCALIZING THE SAFE AREA IN NEUROSURGICAL PROCEDURES (2023) Int J Acad Med Pharm 5(5):1589\u0026ndash;1594\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKhan Y, Ishwarkumar S, Pillay P (2023) Morphology and Morphometry of the Asterion in the South African sample within KwaZulu-Natal. Translational Res Anat. ;32\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSharma R, Vaibhav V, Meshram R, Khorwal G, Singh B, Bhardwaj Y (2024) Morphometric Evaluation of Sutural Patterns at the Pterion and Asterion in Dry Indian Skulls: Surgical Relevance. Cureus. ;16(2)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTabtieang T, Dokthien S, Amorntodsapornpong P, Huanmanop T, Agthong S, Chentanez V (2025) Localisation of asterion and its relationship to transverse and sigmoid venous sinuses. Folia Morphologica (Poland) 84(2):371\u0026ndash;377\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRibas GC, Rhoton AL Jr., Cruz OR, Peace D (2005) Suboccipital burr holes and craniectomies. NeuroSurg Focus 19(2):E1\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRibas GC, Rodrigues AJ (2007) The suprapetrosal craniotomy. J Neurosurg 106(3):449\u0026ndash;454\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eB S. Multiple Wormian bones at the lambdoid suture in an Indian skull. Neuroanatomy. (2008)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCirpan S, Aksu F, Mas N (2015) The Incidence and Topographic Distribution of Sutures Including Wormian Bones in Human Skulls. J Craniofac Surg 26(5):1687\u0026ndash;1690\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLiu YH, Tang Z, Kundu RK, Wu L, Luo W, Zhu D et al (1999) Msx2 gene dosage influences the number of proliferative osteogenic cells in growth centers of the developing murine skull: a possible mechanism for MSX2-mediated craniosynostosis in humans. Dev Biol 205(2):260\u0026ndash;274\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Asterion, Cranial morphology, Wormian bones, Meta-analyses, Pooled Prevalence, Predictive value","lastPublishedDoi":"10.21203/rs.3.rs-8817841/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8817841/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eIntroduction:\u003c/h2\u003e \u003cp\u003eThe 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.\u003c/p\u003e\u003ch2\u003eAim of the study:\u003c/h2\u003e \u003cp\u003eTo assess the pooled prevalence of type I and type II morphology and observe its distribution based on sex and side subgroups.\u003c/p\u003e\u003ch2\u003eMethod\u003c/h2\u003e \u003cp\u003eA 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\u003csup\u003e2\u003c/sup\u003e. Heterogeneity was assessed using the I\u003csup\u003e2\u003c/sup\u003e 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.\u003c/p\u003e\u003ch2\u003eResult\u003c/h2\u003e \u003cp\u003eA total of thirteen studies encompassing 1605 asterions were assessed in this study. We reported a pooled prevalence of 17% (95% CI: 12\u0026ndash;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\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;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.\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e \u003cp\u003eOverall, 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.\u003c/p\u003e\u003ch2\u003eSystematic review registration number:\u003c/h2\u003e \u003cp\u003ePROSPERO \u003cspan type=\"Underline\" class=\"Underline\" name=\"Emphasis\"\u003eCRD420251267482\u003c/span\u003e\u003c/p\u003e","manuscriptTitle":"Morphology of the Asterion: A Systematic Review and Meta-analysis","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-02-23 12:50:09","doi":"10.21203/rs.3.rs-8817841/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"0d5fea70-31ac-4341-ba54-1ab89640ba17","owner":[],"postedDate":"February 23rd, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-03-09T07:12:16+00:00","versionOfRecord":[],"versionCreatedAt":"2026-02-23 12:50:09","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8817841","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8817841","identity":"rs-8817841","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}