Forensic Sciences, Vol. 5, Pages 78: Forensic Morphometry and Prevalence of External Occipital Protuberance Types in Northeastern Thais: CT and Dry Skull Evidence for Sex and Age Estimation

Forensic Sciences doi: 10.3390/forensicsci5040078

Authors:
Woranan Kirisattayakul
Gitsadaporn Boonruengudom
Phanusit Chalardpongpun
Suthat Duangchit
Chanasorn Poodendaen
Phatthiraporn Aorachon
Sitthichai Iamsaard

Background/Objectives: The external occipital protuberance (EOP) is an anatomical landmark with radiological and anthropological implications. Although the morphology and prevalence of EOP have been studied in many populations, data remain lacking for Northeastern Thais. Population-specific characterization of EOP variation may improve diagnostic and forensic accuracy applications. Materials and Methods: This study has investigated the prevalence and morphometry of EOPs using two primary sources: CT brain scans from 750 adult patients (375 males, 375 females) and anatomical investigations of 1060 dry skulls. EOPs were classified as Type I (flat), Type II (crest), or Type III (spur). Measurements for Type II (crest-shaped) EOPs were performed using standardized linear and angular parameters. Data differences were analyzed by sex and age group; intra- and inter-observer reliability was calculated for imaging measurements. Results: The study showed that Type II EOP was most common in both CT (56.1%) and dry skull (64.6%) samples. Type I was significantly more frequent in females (CT: 37.0%; dry skull: 32.8%), while Type III prevalence was higher in males (CT: 28.5%; dry skull: 18.4%). After age 60, the incidence of Type III declined in both datasets. Type II EOPs were significantly larger in males (mean crest length in CT: males 7.1 ± 0.1 mm, females 5.6 ± 0.1 mm; p < 0.001), with notable sex- and age-associated variation in associated angular dimensions. Conclusions: These findings established the first region-specific morphometric reference database for EOP in Northeastern Thais. The demonstrated sexual dimorphism in Type II EOP measurements provided the foundational data that may support future applications in clinical assessment, radiological interpretation, and forensic sex estimation in this population.

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Woranan Kirisattayakul www.mdpi.com