Overview
The dural venous sinuses are clinically important, because you want to AVOID hitting them as they can become a massive source of haemorrhage. Yes you can control the bleeding which may eventually cause thrombosis, however the risk of life threatening air embolus is the main problem.
The large vessel running in the falx cerebri is the superior saggital sinus and ends at the confluence of sinuses this is called the TORCULA. The occipital protuberance marks the torcula. This is the confluence of the straight, transverse, superior saggital and occipital sinus.
Within the supergior saggital sinus are the arachnoid granulation, through which CSF is absorbed. Disruption to the arachnoid granulations leads to a communicating hydrocephalus.
The inferior saggital sinus runs on the inferior border of the falx cerebri and joins with the Great Cerebral Vein of Galen to form the straight sinus.
The transverse sinuses run along the postero-lateral aspect of the tentorium and than become the sigmoid sinus at the posterior petrous temporal bone.
The sigmoid sinus like the sigmoid colon is S shaped and forms the IJV for which the outflow of the brain. Clinically raising the head 30 degrees increases venous outflow and reduces intra-cranial pressure.
The occipital sinus lies in the falx cerebelli and runs superiorly to meet at the Torcula.
The Cavernous Sinus
The Cavernous Sinus is an important exam question because of its anatomy. At whatever stage of your medical training it important to understand the anatomy. This question gets asked from year 1 medical school all the way through to MRCS.
The cavernous sinus is a large venous plexus located on either side of the sella turcica. It runs from the superior orbital fissure to the petrous temporal bone.
It receives blood from the superior and inferior opthalmic veins, facial veins, spheno-parietal sinus and superficial middle cerebral vein. The cavernous sinus communicate with each other by the inter-cavernous sinus.
The cavernous sinus drains inferiorly via the superior and inferior petrosal sinus, emissary veins to the basilar and ptyregoid plexus.
Inside each cavernous sinus lies the Internal Carotid Artery (carotid plexus), Abducens Nerve. In the lateral wall of the sinus lies 111,1V, V1,V2. The superior petrosal sinus drains blood to the transverse sinus. The inferior petrosal sinus drains blood directly to the sigmoid sinus.
The emissary veins connect veins from the scalp to the dural venous sinuses, these open up a significant route by which infection may spread.
