Morphological and Morphometric Study of Variations in the Shape and Size of the Foramen Magnum of Human Skulls

Abstract

Introduction: The shape of the Foramen Magnum (FM) is variable and the incidence of the variants in shape vary in different ethnic groups. Such morphological and morphometic measurements of the FM are of forensic and anthropological importance. Aim: The present study was aimed at documenting frequency of the various shapes of FM, and to calculate the FM Index (FMI) and the surface area of FM using the sagittal and transverse diameters of FM, in male and female skulls of South Indian origin and finally to look for correlation between the cephalic index, the FMI and its surface area. Materials and Methods: One hundred skulls (81 male and 19 female) of South Indian origin were studied for the variation in shape of the FM. In all the skulls cephalic index, surface area of FM and FMI was calculated. Results: An irregularly shaped FM was found to be of maximum in occurrence (32%). The mean sagittal diameters in males and females were 37±0.3 mm and 35±0.23 mm respectively. The mean transverse diameters in males and females were 33±0.35 mm and 32±0.43 mm respectively. The mean surface area ranged from 788- 1113 mm2 . The mean FMI of male and female skull was 1.13±0.11 and 1.09±0.15 respectively. The cephalic index did not show any significant correlation with the surface area of the FM and the FMI. Conclusion: The FM, plays an important role as a landmark because of its close relationship to key structures such as the brain stem and the spinal cord. FM The sagittal and transverse diameters have been reported to be larger in male skulls than in female Size of the FM cannot be a completely reliable indicator of sex; however, it can be used as a supplement for preliminary identification

Keywords

• anthropometry
• cervicomedullary junction
• transcondylar approach