Cerebrovascular System

Blood supply to the brain can be divided into an anterior and a posterior circulation, which interconnect to form the circle of Willis. The anterior circulation is derived from the internal carotid arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries and consists mainly of the anterior and middle cerebral arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries. The posterior circulation is derived from the vertebral arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries and consists primarily of the cerebellar and posterior cerebral arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries. The primary venous drainage of the brain occurs via the internal jugular vein.

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Arterial Supply

Arterial origin

The arterial supply of the brain is derived from 2 arterial systems:

  • Internal carotid arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries (anterior circulation):
    • Bifurcates from common carotid artery at the level of C4
    • Continues into brain and becomes the middle cerebral artery
    • Anterior cerebral artery branches off middle cerebral artery.
  • Vertebrobasilar system (posterior circulation):
    • Vertebral arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries arise from the subclavian arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries.
    • Vertebral arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries join to become the basilar artery.
    • Basilar artery bifurcates to become the posterior cerebral arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries.
    • Cerebellar arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries arise from the vertebral and basilar arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries.
2 sources of blood supply to the brain

Blood supply to the brain is derived from 2 sources—the internal carotid arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries and the vertebrobasilar system.

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Cerebral blood supply

  • Anterior cerebral artery:
    • Origin: smaller terminal branch of the internal carotid artery
    • Course: occupies the longitudinal fissure and travels posteriorly, ultimately anastomosing with the posterior cerebral arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries
    • Divisions: distributes numerous anteromedial central branches
    • Supplies:
      • Medial frontal and parietal lobes
      • Anterior limb of internal capsule
      • Most of corpus callosum
  • Middle cerebral artery:
    • Origin: larger terminal branch of the internal carotid artery
    • Course: runs through lateral fissure and posterosuperiorly on insula
    • Divisions: cortical and central branches
    • Supplies:
      • Lateral frontal and parietal lobes
      • Portion of temporal lobes
      • Genu and posterior limb of internal capsule
      • Most of basal ganglia Basal Ganglia Basal ganglia are a group of subcortical nuclear agglomerations involved in movement, and are located deep to the cerebral hemispheres. Basal ganglia include the striatum (caudate nucleus and putamen), globus pallidus, substantia nigra, and subthalamic nucleus. Basal Ganglia
  • Posterior cerebral artery:
    • Origin: arises as terminal branches of basilar arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries
    • Course:
      • Travels parallel to superior cerebellar artery
      • Receives the posterior communicating artery as it runs laterally
    • Supplies:
      • Occipital lobe
      • Posteromedial temporal lobes
      • Midbrain

Cerebellar blood supply

The cerebellum Cerebellum The cerebellum, Latin for "little brain," is located in the posterior cranial fossa, dorsal to the pons and midbrain, and its principal role is in the coordination of movements. The cerebellum consists of 3 lobes on either side of its 2 hemispheres and is connected in the middle by the vermis. Cerebellum is supplied by branches of the vertebral and basilar arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries.

  • Superior cerebellar artery:
    • Origin: arises from distal aspect of the basilar artery
    • Supplies: 
      • Superior cerebellum Cerebellum The cerebellum, Latin for "little brain," is located in the posterior cranial fossa, dorsal to the pons and midbrain, and its principal role is in the coordination of movements. The cerebellum consists of 3 lobes on either side of its 2 hemispheres and is connected in the middle by the vermis. Cerebellum
      • Pineal body
  • Anterior inferior cerebellar artery:
    • Origin: arises from proximal aspect of the basilar artery
    • Supplies:
      • Anterior inferior surface of cerebellum Cerebellum The cerebellum, Latin for "little brain," is located in the posterior cranial fossa, dorsal to the pons and midbrain, and its principal role is in the coordination of movements. The cerebellum consists of 3 lobes on either side of its 2 hemispheres and is connected in the middle by the vermis. Cerebellum
      • Inferolateral aspect of the pons
  • Posterior inferior cerebellar artery:
    • Origin: arises from vertebral artery
    • Supplies:
      • Posterior inferior surface of cerebellum Cerebellum The cerebellum, Latin for "little brain," is located in the posterior cranial fossa, dorsal to the pons and midbrain, and its principal role is in the coordination of movements. The cerebellum consists of 3 lobes on either side of its 2 hemispheres and is connected in the middle by the vermis. Cerebellum
      • Choroid plexus of 4th ventricle

Circle of Willis

The circle of Willis is an interconnected network of arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries within the brain. The circle of Willis represents the collateral pathways of arterial blood, and it has many anatomical variants. The circle is formed via anastomoses between the anterior and posterior arterial systems that supply blood to the brain. This duality provides a safety net if 1 of the systems fails via occlusion, trauma, or a neoplastic process. Vessels comprising the circle of Willis include:

  • Components of anterior circulation: 
    • Left and right internal carotid arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries 
    • Horizontal segments of the left and right anterior cerebral arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries
    • Single anterior communicating artery
  • Posterior circulation: 
    • Left and right posterior communicating arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries
    • Horizontal segments of the left and right posterior cerebral arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries, arising from the single basilar artery

Venous Drainage

Venous drainage of the brain occurs via the cerebral veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins, which ultimately drain into the straight sinus, transverse sinus, and finally the sagittal sinus before reaching the internal jugular vein and traveling back to the heart. 

  • Venous drainage of the brain occurs via the superficial and deep venous systems:
    • The 2 systems are connected via anastomoses and drain via the dural venous sinuses and, ultimately, to the internal jugular vein.
    • Unlike all other veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins of the body, cerebral veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins do not have valves.
  • Superficial venous system:
    • Composed of cortical veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins
    • Drains the cerebral cortex Cerebral cortex The cerebral cortex is the largest and most developed part of the human brain and CNS. Occupying the upper part of the cranial cavity, the cerebral cortex has 4 lobes and is divided into 2 hemispheres that are joined centrally by the corpus callosum. Cerebral Cortex
  • Deep venous system:
    • Divisions:
      • Deep cerebral veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins
      • Straight sinus
      • Transverse sinus
      • Sagittal sinuses
    • Drains the deep brain structures
  • Dural venous sinuses:
    • Drain blood from the cerebral veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins, orbits, and skull Skull The skull (cranium) is the skeletal structure of the head supporting the face and forming a protective cavity for the brain. The skull consists of 22 bones divided into the viscerocranium (facial skeleton) and the neurocranium. Skull 
    • Empty into the internal jugular veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins

Clinical Relevance

  • Intracranial aneurysms: A cerebral, or intracranial, aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms is an abnormal dilation of a local area of the artery wall in the CNS. These aneurysms most often occur at junction points of the major arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries of the brain, usually around the circle of Willis. They can either compress adjacent structures or rupture and cause a hemorrhagic stroke.
  • Arterial dissections: The vertebral and carotid arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries are vital components of the blood supply to the brain. Arterial dissections occur when the integrity of the arterial wall structure fails, usually abruptly, resulting in an intramural hematoma formation and a false lumen between the tunica media and adventitial layers. This process may result in aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms, stenosis, or occlusion. Presentation is typically with unilateral head or neck pain Neck Pain Neck pain is one of the most common complaints in the general population. Depending on symptom duration, it can be acute, subacute, or chronic. There are many causes of neck pain, including degenerative disease, trauma, rheumatologic disease, and infections. Neck Pain and/or stroke-like symptoms.
  • Subclavian steal syndrome Subclavian steal syndrome Subclavian steal syndrome occurs when narrowing/occlusion of the subclavian artery proximal to the origin of the vertebral artery causes a reversal of blood flow in the ipsilateral vertebral artery to continue perfusing the ipsilateral arm. The most common cause is atherosclerosis. Subclavian Steal Syndrome: occurs when narrowing/occlusion of the subclavian artery proximal to the origin of the vertebral artery causes a reversal of blood flow in the ipsilateral vertebral artery to continue perfusing the ipsilateral arm Arm The arm, or "upper arm" in common usage, is the region of the upper limb that extends from the shoulder to the elbow joint and connects inferiorly to the forearm through the cubital fossa. It is divided into 2 fascial compartments (anterior and posterior). Arm. The most common cause of subclavian steal syndrome is atherosclerosis Atherosclerosis Atherosclerosis is a common form of arterial disease in which lipid deposition forms a plaque in the blood vessel walls. Atherosclerosis is an incurable disease, for which there are clearly defined risk factors that often can be reduced through a change in lifestyle and behavior of the patient. Atherosclerosis. Symptoms are rare, but when they occur, they are usually triggered by physical exertion of the arm Arm The arm, or "upper arm" in common usage, is the region of the upper limb that extends from the shoulder to the elbow joint and connects inferiorly to the forearm through the cubital fossa. It is divided into 2 fascial compartments (anterior and posterior). Arm and subsequent hypoperfusion of the arm Arm The arm, or "upper arm" in common usage, is the region of the upper limb that extends from the shoulder to the elbow joint and connects inferiorly to the forearm through the cubital fossa. It is divided into 2 fascial compartments (anterior and posterior). Arm or brain.
  • Stroke: The 2 types of stroke are ischemic and hemorrhagic. Risk factors include hypertension Hypertension Hypertension, or high blood pressure, is a common disease that manifests as elevated systemic arterial pressures. Hypertension is most often asymptomatic and is found incidentally as part of a routine physical examination or during triage for an unrelated medical encounter. Hypertension, cerebral amyloid angiopathy, neoplastic diseases, and cerebral aneurysms. Strokes can be diagnosed with brain CT or MRI, and treatment is geared toward reperfusing the ischemic area or stopping the brain hemorrhage.

References

  1. Barshes, N. R. (2019). Overview of upper extremity peripheral artery disease. UpToDate. Retrieved February 15, 2021, from https://www.uptodate.com/contents/overview-of-upper-extremity-peripheral-artery-disease
  2. Spittell, P. C. (2019). Subclavian steal syndrome. UpToDate. Retrieved February 15, 2021, from https://www.uptodate.com/contents/subclavian-steal-syndrome
  3. Edwardson, M. A. (2021). Overview of ischemic stroke prognosis in adults. UpToDate. Retrieved August 5, 2021, from https://www.uptodate.com/contents/overview-of-ischemic-stroke-prognosis-in-adults
  4. Oliveira-Filho, J., Mullen, M. T. (2021). Initial assessment and management of acute stroke. UpToDate. Retrieved August 1, 2021, from https://www.uptodate.com/contents/initial-assessment-and-management-of-acute-stroke

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