Cerebrovascular system


The cerebrovascular system comprises the vessels that transport blood to and from the brain. The brain's arterial supply is provided by a pair of internal carotid arteries and a pair of vertebral arteries, the latter of which unite to form the basilar artery. The anterior cerebral artery, a branch of the internal carotid artery, perfuses the anteromedial cerebral cortex; the middle cerebral artery, also a branch of the internal carotid artery, perfuses the lateral cerebral cortex; and the posterior cerebral artery, a branch of the basilar artery, perfuses the medial and lateral portions of the posterior cerebral cortex. The internal carotid arteries, the anterior cerebral arteries, and the posterior cerebral arteries anastomose through the anterior and posterior communicating arteries to form the circle of Willis, a vascular circuit surrounding the optic chiasm and pituitary stalk. The circle of Willis provides an alternative channel for blood flow in case of vascular occlusion and equalizes blood flow between the cerebral hemispheres. The cerebral hemispheres are drained by superficial cerebral veins (superior cerebral veins, middle cerebral veins, inferior cerebral veins) and deep cerebral veins (great cerebral vein, basal vein), which empty into the dural venous sinuses. Brain perfusion is regulated by the partial pressure of carbon dioxide (PaCO2). The interruption of perfusion due to occlusion or hemorrhage of the cerebral vessels results in a stroke, which manifests with focal neurologic deficits in the body parts controlled by the affected brain territory.

Arterial supply

The arterial supply of the brain is provided by the internal carotid arteries and the vertebral arteries, which are derivatives of the branches of the aortic arch.

Internal carotid arteries (ICA) [1][2]

Vertebral arteries

Circle of Willis

Most saccular cerebral aneurysms, also known as berry aneurysms, occur in the anterior circulation of the brain, usually at the junction of the anterior cerebral artery and the anterior communicating artery in the circle of Willis. They are the most common cause of nontraumatic subarachnoid hemorrhage.

Cerebral arterial territories

Overview of cerebral arterial territories [4][5]
Artery Arterial territory Main branches Features of stroke

Anterior circulation

Branches of the internal carotid artery

Anterior cerebral artery


Middle cerebral artery


Anterior choroidal artery

Posterior circulation

Branch of the basilar artery

Posterior cerebral artery


Venous drainage

The cerebral hemispheres are drained by superficial and deep cerebral veins, which empty into the dural venous sinuses.

Superficial cerebral veins [8][9]

Superficial veins
Drain the white matter

Bridging vein

Draining venous sinus

Superior cerebral veins

Superior anastomotic vein Superiorsagittal sinus
Middle cerebral veins Inferior anastomotic vein Cavernous sinus
Inferior cerebral veins Cavernous and transverse venous sinuses

Deep cerebral veins [10]

Deep cerebral veins drain the cerebral medulla and drain into the straight sinus.

Dural venous sinuses [8][9]

Venous sinus Characteristics
Superior sagittal sinus
  • Located at the midline
  • Terminates at the confluence of sinuses
  • Becomes the right transverse sinus
  • Drains blood from cortical veins of the cerebral hemispheres
  • Main location of cerebral fluid return via arachnoid granulations
Inferior sagittal sinus
  • Located at the midline
  • Joined by the great cerebral vein of Galen before draining into the straight sinus
  • Drains blood from the medial surface of the cerebral hemispheres
Straight sinus
Occipital sinus
Confluence of sinuses

Superior petrosal sinus


Transverse sinus


Inferior petrosal sinus


Sigmoid sinus


Sphenoparietal sinus


Cavernous sinus


Basilar venous plexus


  • Lies over the basilar part of the occipital bone (the clivus)
  • Connected with the cavernous and petrosal sinuses and the internal vertebral (epidural) venous plexus. [11]

Brain veins run in the subarachnoid space, have no valves to allow bidirectional blood flow, and have no muscular layer in the vessel wall!


Clinical significance