Knife After Death

Anterior Cerebral Artery & the Circle of Willis

The Circle of Willis is a network of arteries that supplies blood to the brain, and the anterior cerebral artery is one of these vessels.

The Circle provides a continuous flow of blood to all areas of the brain. The anterior cerebral artery delivers oxygen-rich blood from the heart to an area called the Anterior Communicating Artery, which then divides into two branches: internal carotid arteries and vertebral arteries. These branches deliver oxygen-poor blood to other parts of your body.

What is the anterior cerebral artery?

The anterior cerebral artery (ACA) is a large vessel in the front portion of the human brain. It’s primary function is to supply blood to the frontal lobe of the brain. The ACA is one of two terminal branches of the internal carotid artery, which arises from the common carotid artery. It arises from the front (anterior) part of the Circle of Willis, a ringed structure of blood vessels at the base of the brain.

What is the Circle of Willis?

The Circle of Willis (CoW) is a ring-shaped anastomosis formed by the union of the four major cerebral arteries in the brain: the two internal carotid arteries and the two vertebral arteries. This allows blood to be distributed evenly around the brain.

What are the branches of anterior cerebral arteries?

The anterior cerebral arteries are as follows:

A1 Cerebral Artery

A1 originates from the internal carotid artery and extends to the anterior communicating artery (AComm). The anteromedial central (medial lenticulostriate) arteries arise from this segment as well as the AComm, which supplies blood to the caudate nucleus and the anterior limb of the internal capsule

A2 Cerebral Artery

A2 Extends from the AComm to the bifurcation forming the pericallosal and callosomarginal arteries. The recurrent artery of Heubner (distal medial striate artery), which supplies blood the internal capsule, usually arises at the beginning of this segment near the AComm. Two branches arise from this segment:

Orbitofrontal artery (medial frontal basal)

Arises a small distance away from the AComm

Frontopolar artery (polar frontal)

Arises after the orbitofrontal, close to the curvature of A2 over the corpus callosum. It can also originate from the callosal marginal.

A3 pericallosal artery

One of the (or the only) main terminal branches of the ACA, which extends posteriorly in the pericallosal sulcus to form the internal parietal arteries (superior, inferior) and the precuneal artery. This artery may form an anastomosis with the posterior cerebral artery.

Callosal marginal artery

A commonly present terminal branch of the ACA, which bifurcates from the pericallosal artery. This artery in turn branches into the medial frontal arteries (anterior, intermediate, posterior), and the paracentral artery, with the cingulate branches arising throughout its length.

Depending on anatomical variation, the callosal marginal artery may be none discrete or not be visible. In the latter case, the branches mentioned will originate from the pericallosal artery. In a study of 76 hemispheres, the artery was present in only 60% of the cases.[3] Angiography studies cite that the vessel can be seen 67% [1] or 50%[4] of the time.

Anterior Cerebral Artery and the arteries of the brain. Wikimedia Commons
Arteries of the brain – Photo credit Wikimedia

What happens when the anterior cerebral artery is blocked?

When the artery is blocked the front of the brain doesn’t get enough blood. These include the areas of the inferior, middle and medial frontal lobes. This can result in a stroke, which can lead to problems with movement, speech, and understanding. 

Because the frontal lobe includes an area for speech known as Broca’s area (named after Pierre Paul Broca), a common symptom of ACA stroke is difficulty with speech. The anterior cerebral artery (ACA) is one of two terminal branches of the internal carotid artery, which arises from the common carotid artery.  The internal carotid artery is one of the main arteries that feeds the Circle of Willis.

What does an ACA stroke look like to the pathologist?

When a blockage of the anterior cerebral artery (ACA) occurs, after a few minutes the brain tissue that is normally nourished by the artery starts to die. This is called necrosis, and is irreversible if blood flow is not restored. When brain tissue dies it undergoes what is called ‘liquefactive necrosis’, which manifests as a marked softening of the brain tissue.

As the term ‘liquefactive’ implies, the affected areas become more like liquid. If a few days or weeks passes a stroke can appear like a cavity within the brain. 

Summary of the anterior cerebral artery

The anterior cerebral artery is one of two terminal branches of the internal carotid artery, which arises from the common carotid artery. It supplies oxygenated blood to the front of the brain—the inferior, middle and medial frontal lobes, including Broca’s area. The first symptoms of an ACA stroke are indistinguishable from those of a large MCA infarction (eg hemiplegia, aphasia, abulia).

An anterior cerebral artery stroke is a type of stroke that happens when the anterior cerebral artery is blocked. This can lead to problems with movement, speech, and understanding. The Circle of Willis (CoW) is a ring-shaped anastomosis formed by the union of the four major anterior cerebral arteries in the brain: the two internal carotid arteries and the two vertebral arteries. This allows blood to be distributed evenly around the brain.