Structural variations in the jugular foramen of the human skull.

The jugular foramen was examined in 300 Anatolian skulls from the 17th and 18th centuries. In 61.6% the foramen was larger on the right and in 26% on the left, with the remainder being of almost equal size. An obvious dome caused by a superior jugular bulb was present bilaterally in 49%, on the right only in 36%, on the left only in 6%; it was absent bilaterally in 10.3%. Complete bony septation occurred in 5.6% on the right and in 4.3% on the left, partial septation was observed in 2.6% on the right and in 19.6% on the left. Another foramen which is completely separated by a spicule of bone and which transmits the inferior petrosal sinus was present in 5.6% of skulls on the right and in 4.6% on the left.