Petrosal sinuses

The petrosal sinuses are two paired dural venous sinuses that participate in draining the cranial cavity. There is a superior and an inferior petrosal sinus (Latin: sinus petrosus superior, sinus petrosus inferior) located on the petrous part of the temporal bone on each side.

The superior petrosal sinus arises from the cavernous sinus. It runs posterolaterally in the attached margin of the tentorium cerebelli. Further, it passes in a groove on the superior margin of the temporal bone's petrous part. This groove is called the superior petrosal sulcus. Finally, the superior petrosal sinus drains into the transverse sinus. The superior petrosal sinus collects venous blood from the superior petrosal vein, and, occasionally, from the inferior cerebral and tympanic veins.

The inferior petrosal sinus also arises from the cavernous sinus, but passes posteriorly in the petroclival or petro-occipital fissure. This fissure is formed by the articulation between the posterior and medial surfaces of the petrous apex of the temporal bone and the lateral surface of the basiocciput (basilar part of the occipital bone). Further, the inferior petrosal sinus runs through the jugular foramen and drains into the jugular bulb, which continues as the internal jugular vein. The inferior petrosal sinus collects blood from the labyrinthine veins, and small veins from the medulla oblongata, pons, as well as the inferior cerebellar surface.