The transverse sinuses are paired dural venous sinuses that drain the confluence of sinuses (a meeting place of the superior sagittal, straight, occipital, and transverse sinuses), where they begin, and run along the occipital attachment of the tentorium cerebelli to terminate in the sigmoid sinus. There are several venous sinuses of the dura mater, including the:
- superior sagittal
- inferior sagittal
- superior petrosal
- inferior petrosal
The dural venous sinuses are endothelium-lined spaces between the periosteal and meningeal layers of the dura mater. They form where the dural septa attach along the free edge of the falx cerebri and in relations to formations of the cranial floor. Large veins from the surface of the brain empty into these sinuses and most of the blood from the brain ultimately drains through them into the internal jugular veins (IJVs).
The transverse sinuses (also called left and right lateral sinuses of the dura mater) are two cavities beneath the brain which allow blood to drain from the back of the head. They run laterally in a groove along the interior surface of the occipital bone, and drain from the confluence of sinuses (by the internal occipital protuberance) to the sigmoid sinuses, which ultimately connect to the internal jugular vein.
The transverse sinuses are of large size and begin at the internal occipital protuberance; one being the direct continuation of the superior sagittal sinus, the other of the straight sinus. The transverse sinuses are frequently of unequal size, with the one formed by the superior sagittal sinus being the larger (this is the right transverse sinus, it is dominant and drains more blood). They increase in size as they proceed, from posterior to centre. On a transverse section, the horizontal portion exhibits a prismatic form while the curved portion has a semi-cylindrical form.
Each transverse sinus passes laterally and forward, describing a slight curve with its convexity upward relative to the base of the petrous portion of the temporal bone. In this part of its course each one lies in the attached margin of the tentorium cerebelli. It then leaves the tentorium and curves downward and medial-ward forming the sigmoid sinus, finally reaching the jugular foramen where it ends in the internal jugular vein.
In addition, the two transverse sinuses communicate at their commencement at the internal occipital protuberance (confluence of sinuses). Each receives tributaries from the nearby surfaces of cerebral and cerebellar hemispheres and, at its termination at the commencement of the sigmoid sinus, the superior petrosal sinus enters.
The transverse sinuses receive the blood from the superior petrosal sinuses at the base of the petrous portion of the temporal bone. They communicate with the veins of the peri-cranium by means of the mastoid and condyloid emissary veins, and receive some of the inferior cerebral and inferior cerebellar veins. They also drain the superior sagittal sinus, the occipital sinus and the straight sinus.
In the end they empty into the sigmoid sinus, which in turn reaches the jugular bulb.