Rationale and Objectives: The torcular herophili, or " confluence of the sinuses," shows various configurations with other venous sinuses, as revealed by angiography. The aims of this study were to evaluate anatomic variations of this confluence and to assess their clinical relevance using three-dimensional (3D) computed tomographic (CT) venography. Materials and Methods: The torcular herophili and its relevant venous sinuses were analyzed using 3D CT venography in 120 adults, consisting of 76 patients who were proven to have aneurysms and 44 patients who were proven to have no vascular malformations or aneurysms after the examinations. Three-dimensional CT venography was performed following the arterial phase of 3D CT angiography without any additional injection of contrast material. Three-dimensional volume-rendered venous images were reconstructed on a workstation and reviewed. Results: The superior sagittal sinus (SSS) drained into the transverse sinus (TS) in four patterns: the SSS reached the centrally located confluence, where it divided into the bilateral TS (20.0%); the SSS was prematurely duplicated into the right and left limbs and drained into the same side TS (26.7%); the SSS drained exclusively into the right TS (44.2%); or the SSS drained exclusively into the left TS (9.2%). The draining pattern of the straight sinus was also classified into four types. The right TS was larger than the left TS. The right TS were higher compared to the left TS. Persistent occipital sinuses were recognized in 57.5% of the subjects. Finally, persistent falcial sinuses were seen in 2.5% of the subjects. A septum in the SSS and complicated venous channels in the confluence were each seen in only one case. Conclusion: Three-dimensional CT venography is useful as a noninvasive method to evaluate the confluence and its relevant dural sinuses and can provide useful information for surgical intervention.
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