- 1 Overview of Dural Venous System
- 2 Unpaired Sinuses
- 3 Paired Sinuses
- 4 Basilar Venous Plexus
- 5 Clinical Relevance – Cavernous Sinus Thrombosis
The dural venous sinuses refer to multiple venous channels within the cranial cavity, which are sandwiched between the two layers of the dura mater (the outermost layer of the meninges).
This venous system represents the main pathway of returning venous blood from the brain into the circulation via the internal jugular vein.
In this article, we shall look at the anatomy of the dural venous sinuses – their structure, location, and clinical correlations.
Note: This article specifically discusses the dural venous sinuses. For a more general overview of venous drainage of the central nervous system, please see here.
Overview of Dural Venous System
The dural venous sinuses receive blood from the veins associated with the cerebrum, cerebellum and brainstem. They also receive contributions from the diploic and emissary veins (draining the cranium and the scalp, respectively).
Venous blood then flows through the dural venous sinus system – which consists of a series of paired and unpaired sinuses. They eventually empty into the internal jugular vein, where deoxygenated blood is returned to the systemic circulation.
There are five main unpaired dural venous sinuses. These typically lie along the sagittal midline of the brain.
Superior Sagittal Sinus
The superior sagittal sinus is the largest dural venous sinus. It receives venous blood from many tributaries of the cerebral hemispheres and superficial cortical veins.
It extends from the frontal crest (of the frontal bone) to the internal occipital protuberance (of the occipital bone). Here, it combines with the straight and occipital sinuses to form the confluence of sinuses.
This venous sinus lies within the superior border of the falx cerebri.
Inferior Sagittal Sinus
The inferior sagittal sinus is smaller than its superior counterpart and lies within the inferior margin of the falx cerebri.
It receives venous drainage from the falx cerebri itself, and numerous small venous veins which drain the medial surface of the cerebral hemispheres.
Posteriorly, it combines with the great cerebral vein to form the straight sinus.
The straight sinus forms from the convergence of the inferior sagittal sinus with the great cerebral vein.
It is located where the falx cerebri meets the tentorium cerebelli.
As it courses posteriorly, it receives venous tributaries from superior cerebellar veins before joining the confluence of sinuses.
The occipital sinus is the smallest of the venous sinuses and is situated on the inner surface of the occipital bone within the falx cerebri.
It is formed at the edge of the foramen magnum and empties into the confluence of sinuses at the internal occipital protuberance.
The intercavernous sinuses provide a connection between the right and left paired cavernous sinuses.
They are variable in position and number, but usually consist of anterior and posterior channels – which lie either side of the pituitary stalk.
There are five main paired dural venous sinuses, located on the left and right side of the cranial cavity.
The right and left transverse sinuses (also known as lateral sinuses) are formed at the confluence of sinuses by the convergence of the superior sagittal, straight and occipital sinuses.
They pass along the posterolateral border of the tentorium cerebelli, along the internal surface of the occipital bone.
As they approach the petrous part of the temporal bone, the transverse sinuses become the sigmoid sinuses.
The sigmoid sinuses are a continuation of the transverse sinuses at the internal surface of the petrous part of the temporal bone.
They take an ‘S’ shaped course along the temporal and occipital bones.
When they pass through the jugular foramen to leave the cranial cavity, the right and left sigmoid sinuses become the internal jugular veins.
The cavernous sinuses are located within the sphenoid bone of the skull base. They receive drainage from the ophthalmic vein, superficial middle cerebral vein and sphenoparietal sinus.
They are interconnected by the intercavernous sinuse and drained by the superior and inferior petrosal sinuses.
For more information regarding the cavernous sinuses, please see our dedicated article here.
Superior Petrosal Sinuses
The superior petrosal sinuses drain the cavernous sinuses into the transverse sinuses.
They begin at the posterior border of the cavernous sinus and pass along the internal surface of the petrous part of the temporal bone. They empty into the transverse sinus.
In addition to draining the cavernous sinus, they also receive tributaries from inferior cerebral veins, cerebellar veins, and the labyrinth vein.
Inferior Petrosal Sinuses
The inferior petrosal sinuses assist in the drainage of the cavernous sinuses.
They also begin at the posterior border of the cavernous sinus. They pass between the petrous part of the temporal bone and the basal part of the occipital bone – emptying into the internal jugular vein at the jugular foramen.
The left and right sinuses are interconnected by the basilar venous plexus.
Basilar Venous Plexus
The basilar venous plexus is located on the internal surface of the skull floor, posterior to the sella turcica of the sphenoid bone.
It interconnects the inferior petrosal sinuses and also communicates inferiorly with the vertebral venous plexus.
Clinical Relevance – Cavernous Sinus Thrombosis
Cavernous sinus thrombosis (CST) refers to the formation of a clot within the cavernous sinus.
This most common cause of CST is infection, which typically spreads from an extracranial location such as the orbit, paranasal sinuses, or the ‘danger zone’ of the face. Infection is able to spread in this manner due to the anastomosis between the facial vein and superior ophthalmic veins.
Common clinical features include headache, unilateral periorbital oedema, proptosis (eye bulging), photophobia and cranial nerve palsies. The abducens nerve (CN VI) is most commonly affected.
Treatment is typically with antibiotic therapy. Where the cause is infection, thrombosis of the cavernous sinus can rapidly progress to meningitis.