Introduction:The Foramen Magnum (FM) lies in an anteromedian position and leads into the posterior cranial fossa. It is oval and wider behind, with its greatest diameter being anteroposterior. It contains the lower end of the medulla oblongata, meninges, vertebral arteries and spinal accessory nerve. The apical ligament of dens and the tectorial membrane pass through it, to attach to the basiocciput. Anteriorly the margin of foramen magnum is slightly overlapped by the occipital condyles. Transcondylar, supracondylar, and other lateral surgical approaches provide access to various foramina on the base of skull and prevent broad retraction of the neural structures passing through them Morphometric analysis of foramen magnum plays important role in transcondylar approach. Aim: The study was designed to measure the diameters and shape of foramen Magnum and correlates the measurements with clinical importance, as its shape and variation in diameters will be of great help to operating surgeon during surgical procedures. Materials and Methods: Forty dry human skulls were studied during this research work. Skulls were taken from the department of anatomy, dayanand medical college and hospital, Ludhiana and other medical college. Results: During this study the mean MAPD was 35.42mm, the MTD found to be 27.90mm The Foramen magnum Index found to be 17.20mm. The shape of foramen magnum found mostly was oval in 60% cases. The anterior inter condylar distance found to be 18.01 to 20.00mm. Whereas middle intercondylar distance is 20.1 to 22mm and posterior was 30.01 to 32.00mm. Conclusion:The present study had observed the variation in the measurements of skull base foramen magnum which were different from observations by the western studies because of difference of race and geographical areas.

The study was designed to measure the diameters of jugular foramen and correlates the measurements with clinical importance. The bony bridging of the jugular foramen is established by the contact of the intrajugular process of the temporal bone with the bony process of the occipital bone projecting either from just above the hypoglossal canal or from posterior to the hypoglossal canal. If both the processes of the occipital bone reach the intrajugular process of the temporal bone simultaneously, it is divided into three compartments. As observed during the study, a lot of variation in measurements of jugular foramen was seen. Even among Indians there was difference noted, so the operating surgeon should keep in mind the differences in measurements.