Anatomic variations of venous sinuses in the region of the torcular Herophili.

In this study of 110 cranial cavities from adult cadavers, the superior sagittal sinus was found to divide into two channels. In most cases, the division was associated with a dural partition. Essentially, the variations as observed in this study could be grouped into three types: Type 1 includes those specimens in which the sagittal sinus drains into one lateral sinus and the straight sinus into the other, with no connection between the two. Type 2 includes those specimens in which the superior sagittal sinuses and the straight sinus fork, and the forks from both sinuses join to form the lateral sinuses. Type 3 includes those specimens in which a confluence of sinuses exists, varying from a common pool to merely a potential confluence, depending upon the presence of pads, incomplete partitions, and complete partitions of dura mater. Rare findings previously not reported consist of double straight sinuses draining into one transverse sinus; the superior sagittal sinus dividing into three channels with two transverse sinuses on one side; a transverse sinus originating from a tentorial vein; and drainage of a tentorial vein into the confluence of sinuses.