Variations in the structure of the jugular foramen of the human skull.

The jugular foramina were examined in 156 skulls. In 69% of cases the right was larger than the left and in 23% the left was larger, with the remainder being of equal size. An obvious dome caused by a superior jugular bulb was present bilaterally in 54%, on the right only in 30%, on the left only in 6% and was absent bilaterally in 10%. Of the 312 jugular foramina examined there was no evidence of an enlargement due to a superior jugular bulb in 28%.