Anatomical relationship between cranial surface landmarks and venous sinus in posterior cranial fossa using CT angiography.

PURPOSE

The purpose of this study was to determine the reliability of applying conventional anatomical landmarks to locate venous sinus in posterior fossa using subtraction computed tomography angiography (CTA) technique.

METHODS

We retrospectively reconstructed transverse sinus (TS), sigmoid sinus (SS), and cranial imaging from 100 patients undergoing head CTA examination. Subtraction CTA data was merged with nonenhanced data and then cranium transparency was adjusted to 50% on three-dimensional volume rendering, indicating the anatomical relationship between surface landmarks of cranium and confluens sinuum, TS, and SS.

RESULTS

CTA technique precisely displayed the anatomical relations between venous sinus in posterior fossa and cranial surface landmarks. The asterion was located directly over the transverse-sigmoid sinus junction (TSST) in 81% cases, inferior to TSST in 15%, and superior to TSST in 4%, mainly distributing on the TS side of TSST, namely the distal-end of TS. Superior nuchal line had complex relation with TS and the line drawn from the zygoma root to the inion (LZI), but failed to represent the location of TS and the trend of LZI. In proximal-end of TS, majority of LZI overlapped with TS line. However, most LZI was gradually positioned below TS line as TS moved outwards. Almost half of line drawn from the squamosal-parietomastoid suture junction to the inion and line drawn from the asterion to the inion shared the same trend with TS.

CONCLUSION

Subtraction CTA merged into nonenhanced cranial bone with 50% skull transparency provides a feasible method to identify the anatomical relation between venous sinus and surface landmarks of cranium, which is significantly varied among individuals, so it is not accurate to determine venous sinus in posterior fossa merely using surface landmarks.