What vessels constitute the anterior circulation of the brain?

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Last updated: February 27, 2026 • View editorial policy

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Anterior Circulation Vessels of the Brain

The anterior circulation consists of the internal carotid arteries and their two major terminal branches—the anterior cerebral artery (ACA) and middle cerebral artery (MCA)—along with the anterior communicating artery that connects the left and right systems. 1

Primary Components

Internal Carotid Artery (ICA)

  • The internal carotid arteries provide the primary blood supply to the anterior and middle portions of the cerebral hemispheres. 1
  • The ICA enters the skull base, traverses the petrous bone, and enters the subarachnoid space near the ophthalmic artery level. 1
  • Before its terminal bifurcation, the ICA gives rise to the posterior communicating artery, which connects to the posterior cerebral artery through the circle of Willis. 1
  • The ICA then bifurcates into its two major terminal branches: the ACA and MCA. 1, 2

Anterior Cerebral Artery (ACA)

  • The ACA supplies the medial surfaces of the frontal and parietal lobes. 1
  • The left and right anterior cerebral arteries connect through the anterior communicating artery, forming the anterior portion of the circle of Willis. 1
  • Proximal ACA branches perfuse the genu and contiguous posterior limb of the internal capsule and the rostral thalamus. 3
  • Heubner's artery arises from the ACA directly opposite the anterior communicating artery to supply much of the striatum and internal capsule rostral to the anterior commissure. 3

Middle Cerebral Artery (MCA)

  • The MCA is the largest terminal branch of the internal carotid artery. 1
  • The MCA supplies the lateral surfaces of the cerebral hemispheres, including most of the frontal, parietal, and temporal lobes. 1
  • The MCA territory represents the most common site of anterior circulation stroke. 4

Anterior Communicating Artery (ACoA)

  • The anterior communicating artery connects the left and right anterior cerebral arteries. 1
  • The ACoA is the core functional anastomosis between the left and right ICA systems. 2
  • ACoA branches supply the fornix, corpus callosum, septal region, and anterior cingulum. 3

Perforating Arteries

  • Perforating arteries of the anterior circulation arise from the ICA, ACA, MCA, ACoA, and posterior communicating artery. 2
  • These perforating vessels are related to the striatum, thalamus, and basal ganglia. 2
  • Proximal 4-mm branches from the ACA supply the anterior limb of the internal capsule, the neighboring hypothalamus, anteroventral putamen, and pallidum. 3

Clinical Significance

Stroke Patterns

  • In acute ischemic stroke trials, 64% of participants had M1 occlusion alone, and an additional 27% had occlusion of M1 and the internal carotid artery. 4
  • The border zones between the ACA and MCA, between the MCA and posterior cerebral artery, and between the anterior and posterior circulations constitute watershed territories that are especially susceptible to injury during systemic hypoperfusion states. 1

Collateral Pathways

  • The circle of Willis provides crucial collateral pathways between the anterior and posterior circulations, though a complete circle exists in fewer than 50% of individuals. 1
  • External carotid to internal carotid collaterals occur via the internal maxillary and superficial temporal arteries to ophthalmic branches. 1

References

1
Guideline

Cerebral Blood Supply and Vascular Territories

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2026

4
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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