The dural venous sinuses are spaces between the endosteal and meningeal layers of the dura. They contain venous blood that originates for the most part from the brain or cranial cavity. The sinuses contain an endothelial lining that is continuous into the veins that are connected to them. They are no valves in the sinuses or in the veins that are connected to the sinuses. The vast majority of the venous blood in the sinus drains from the cranium via the internal jugular vein. A beginning student may be confused in comparing the dural venous sinus with the paranasal sinus. The paranasal sinuses (e.g., sphenoid sinus) are spaces that are continuous with the nasal cavity and are embedded in the bones of the skull. They contain air and have a mucous lining that is continuous into the nasal mucosa. Thus, the dural venous sinuses contain blood and the paranasal sinus contain air.
The various dural venous sinus are now described. The superior sagittal sinus is found in the upper border of the falx cerebri and begins at the crista galli. The superior sagittal sinus is fed by blood from the superior cerebrals vein and ends at the confluence of sinuses near the internal occipital protuberance. The inferior sagittal sinus is located in the lower free border of the falx cerebri between the two cerebral hemispheres. It begins anteriorly and ends with its junction with straight sinus. The straight sinus originates with the union of the great cerebral vein and inferior sagittal sinus. It runs posteriorly in the junction between the falx cerebelli and tentorium cerebelli to become continuous with one of the transverse sinuses (most commonly the left). The cavernous sinuses are found on either side of the body of the sphenoid bone in middle cranial fossae. They receive blood from the sphenoparietal sinuses which are located underneath the free edges of the lesser wings of the sphenoid bone. Blood also drains into the cavernous sinuses via the superior and inferior ophthalmic veins. The intercavernous sinuses provide a communication between the cavernous sinuses. They are located in the diaphragma sellae which covers the hypophyseal fossa and surrounds the hypophyseal stalk. The internal carotid artery, sympathetic nerve plexus and the abducens nerve are inside the cavernous sinuses. In the wall of the cavernous sinuses are the oculomotor, trochlear, ophthalmic and maxillary nerves. The cavernous sinuses drain posteriorly through the superior and inferior petrosal sinuses and inferiorly through the pterygoid plexus of veins. The superior petrosal sinuses are located in the edge of the tentorium cerebelli on the ridge of petrous part of the temporal bone. They drains into the transverse sinuses. The inferior petrosal sinuses are found at the base of the petrous part of the temporal bone in the posterior cranial fossae where they empty into the internal jugular vein. The basilar sinus interconnects with inferior petrosal sinuses and the internal vertebral plexus. The transverse sinuses extend laterally from the confluence of sinuses in the tentorium cerebelli. The transverse sinuses travel ventrally to become the sigmoid sinuses of each side. The sigmoid sinuses bend into an S-shaped curve and continue into the internal jugular vein through the jugular foramen. The occipital sinus is located in the posterior attached border of the falx cerebelli. It communicates superiorly with confluence of sinuses and inferiorly with the internal vertebral plexus.