Foramen Magnum: Morphometric Analysis in Dry Adult Human Skulls

Abstract

Background: Foramen magnum (FM) is a crucial aperture situated in the occipital bone and connects the brain to the spinal cord. Its size and dimensions are crucial in understanding a range of disorders, with implications for clinical, surgical, radiological, and forensic fields. We undertook the present study to analyze the morphometry of FM in detail and to compare this data with other similar studies. Methodology: This study analyzed 51 dry human skulls from Northern India of unspecified gender. Morphometric assessments of the FM were conducted, encompassing measurements of its shape, anteroposterior diameter (APD), transverse diameter (TD), FM index (FMI), size, and surface area using digital Vernier calipers. Minimum, maximum, and mean values and standard deviations (SDs) were calculated for each parameter. A comparison with previous studies was conducted. Results: The study established that the most common shape of FM as calculated by the ratio of AP diameter to TD was round (58.8% of specimens) and the majority of FM (41.1%) were narrow according to Martin and Saller classification. Mean APD was 33.71 ± 2.53, and TD was 27.88 ± 1.92; AP diameter was significantly greater than TD (P < 0.05). FMI ranged from 70.54 to 93.55 (mean: 82.92 and SD: 5.63). The mean surface area as calculated by Teixeira’s method was higher compared to Radinsky’s formula; 747.51 ± 96.25 mm2 and 739.93 ± 94.85 mm2, respectively. This difference was not statistically significant (P = 0.68). Conclusion: This study furnishes data on detailed morphometry of FM, a complete knowledge of which is essential for planning surgical procedures for optimal preoperative and postoperative results. It provides an objective definition of the FM’s morphology and highlights the ambiguous role of visual assessment which needs to be reconsidered. The comparison of present morphometric data with other national and international studies further highlights the ethnic and genetic variation of FM.

Keywords

• foramen magnum index
• medulla oblongata
• morphology
• occipital bone
• posterior cranial fossa