Cerebrovascular system

Last updated: April 12, 2023

Summarytoggle arrow icon

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, 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 equalizes the blood flow between the cerebral hemispheres and provides anastomotic circulation, connecting the anterior and posterior cerebral circulations and, thereby, permitting continued perfusion of the brain in the event of carotid occlusion. 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 drain 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 supplytoggle arrow icon

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

Internal carotid arteries (ICA)

Vertebral arteries

Basilar artery

Circle of Willistoggle arrow icon

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 territoriestoggle arrow icon

Overview of cerebral arterial territories [1]
Artery Arterial territory Main branches Features of ischemia/hemorrhage
Anterior circulation (branches of the internal carotid artery)

Anterior cerebral artery


Middle cerebral artery


  • Lenticulostriate arteries

Anterior choroidal artery [2]

  • N/A
Posterior circulation (branch of the basilar artery)

Posterior cerebral artery


Venous drainagetoggle arrow icon

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

Superficial cerebral veins

Overview of superficial cerebral veins
Superficial veins
Drain the white matter

Bridging vein

Draining venous sinus

Superior cerebral veins

Superior anastomotic vein Superior sagittal sinus
Middle cerebral veins Inferior anastomotic vein Cavernous sinus
Inferior cerebral veins N/A Cavernous and transverse venous sinuses

Deep cerebral veins

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

Dural venous sinuses

Venous sinus
Location Characteristics
Superior sagittal sinus
  • At the midline
Inferior sagittal sinus
  • At the midline
Straight sinus
  • At the midline
Occipital sinus
  • Posteriorly
Confluence of sinuses
  • Posteriorly

Superior petrosal sinus


  • Laterally

Transverse sinus


  • Drains into the sigmoid sinus

Inferior petrosal sinus


  • Laterally

Sigmoid sinus


  • Laterally

Sphenoparietal sinus


  • Anteriorly

Cavernous sinus


Basilar venous plexus


  • Connected with the cavernous and petrosal sinuses and the internal vertebral (epidural) venous plexus. [3]

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

Cerebral blood flow regulationtoggle arrow icon

  • Neurometabolic coupling: enables adequate delivery of nutrients or substrates to areas with increased neural activity
  • Neurovascular coupling (functional hyperemia): enables adequate delivery of oxygen through constriction or dilation of microvessels to areas with increased neural activity

Therapeutic hyperventilation reduces pCO2 ↓ cerebral blood flow → ↓ intracranial pressure (e.g., used when patients with acute cerebral edema are unresponsive to other treatments).

Referencestoggle arrow icon

  1. CT Brain Anatomy - Cerebral Vascular Territories. . Accessed: December 16, 2018.
  2. Clinical Findings in Anterior Choroidal Artery Infarction. Updated: November 4, 2008. Accessed: December 16, 2018.
  3. Dural Venous Sinuses. Updated: January 1, 2018. Accessed: December 16, 2018.
  4. Mangla R, Kolar B, Almast J, Ekholm SE. Border zone infarcts: Pathophysiologic and imaging characteristics. Radiographics. 2011; 31 (5): p.1201-1214.doi: 10.1148/rg.315105014 . | Open in Read by QxMD

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