Variations in the shape of foramen magnum at the base of human skulls among Indians in Rajasthan.

Variations in the shape of foramen magnum can affect the normal anatomy of vital structures passing through it. Therefore, it is of interest to evaluate the various shapes of foramen magnum by using CT scans performed in patients of Indian population to establish clinical correlation. A total of 314 CT images of human skull base obtained from the Department of Radio-diagnosis, Geetanjali Medical College and Hospital, Udaipur, Rajasthan were used in the present study. All the patients' CT scans were observed to determine the shape of foramen magnum. They were classified into one of the following shapes: Oval, round, tetragonal, egg shaped, hexagonal, pentagonal and irregular. The shapes of the foramen magnum in CT scans were oval in 39.09%, round in 22.61%, tetragonal in 12.10%, hexagonal in 10.51%, irregular in 7.96%, pentagonal in 5.41% and egg shaped in 1.59% CT images. Data shows that it is easy to operate at the base of skull in case of round, oval and hexagonal shape foramen magnum, as the working space is more in these shapes.