Target CT images of 147 patients and digital subtraction angiography (DSA) images of 15 patients were examined to assess the relation between jugular bulb position and intracranial veins.
First, relation of jugular bulb position to venous volume was examined from CT. The height of the jugular bulb was measured from the lower margin of the tympanic annulus to the apex of the jugular bulb by counting CT slices individually on the both side. The heights of the right and left jugular bulbs were 4.0+/-3.9mm and 2.0+/-3.9mm respectively, indicating that the right jugular bulb was higher than the left, consistent with previous reports. The depth of the sigmoid sinus sulcus, which may reflect the venous volume, was measured on the slice showing the internal auditory canal. The right side was 6.7+/-2.2mm deep, while the left side was 5.3+/-2.0mm in depth. These measurement also showed that the height of jugular bulb and depth of the sulcus of the sigmoid sinus were closely related. The jugular bulb was higher on the side with the deeper sigmoid sinus sulcus (correlation coefficient r=0.73).
Frontal head and neck angiography were performed after bolus injection of contrast medium. Angiographic images were modified and examined by means of a digital subtraction process. A result from angiography was consistent with the measurement of CT. The side with greater venous flow has the higher jugular bulb. And such difference in right and left venous flows was observed at and proximately to the transverse sinuses.
The position of the jugular bulb and sigmoid sinus are important during ear surgery. Our date shows that the position of the venous system is influenced by the laterality in venous blood flow. From the embryological aspect, cases of high jugular bulb are due to a large difference between right and left venous return. And the right sided dominance of the height of the jugular bulb and sigmoid sinus sulcus are attributable to the variable development of the fetal venous system.