Anterior cerebral artery
The anterior cerebral artery is the terminal branch of the communicating segment (C7) of the internal carotid artery. Being located in the anterior and medial aspects of the interhemispheric fissure, the anterior cerebral artery supplies a large portion of the medial cerebral hemispheric surfaces namely the corpus callosum, frontal, parietal, and cingulate cortex.
Through the anterior communicating artery, it anastomoses with its contralateral counterpart. This anastomosis makes the anterior/rostral component of the circle of Willis, which is the most important anastomosis between the cerebral vessels. The other arteries that comprise the Willis' circle are the middle cerebral, posterior cerebral, anterior communicating and posterior communicating arteries.
This article will discuss the anatomy and function of the anterior cerebral artery.
|Origin||Internal carotid artery|
|Branches||Anteromedial central arteries, orbitofrontal branches, callosomarginal artery pericallosal artery|
|Supply||Frontal, parietal and cingulate cortex; corpus callosum|
- Origin and course
- Branches and supply
- Anatomical variations
- Clinical relations
Origin and course
The anterior cerebral artery, along with the middle cerebral artery, form the terminal branches of the internal carotid artery at the medial end of the lateral sulcus (Sylvian fissure). From its origin, it runs rostrally and medially towards the longitudinal cerebral fissure where it anastomoses with its contralateral counterpart via the anterior communicating artery. Furthermore, it follows the longitudinal cerebral fissure that courses around the genu of corpus callosum, and continues posteriorly along the length of its body. Around the splenium of corpus callosum, the terminal branches of the anterior cerebral artery anastomose with those of the middle and posterior cerebral arteries.
Due to the distinct features of different parts of the anterior cerebral artery, its course is divided into five segments (A1-A5). In some classical anatomical textbooks the last three segments (A3-A5) are considered as one. The five segments include:
- Precommunicating segment(A1): situated between the internal carotid bifurcation and the anterior communicating artery. It usually lies superior to the optic chiasm/optic nerves and inferior to the anterior perforated substance.
- Infracallosal (A2) segment (a.k.a. vertical/postcommunicating segment): courses around the rostrum of the corpus callosum, extending from the anterior communicating artery to the genu of corpus callosum (as far as the origin of the callosomarginal artery).
- Precallosal (A3) segment: originates at the origin of the callosomarginal artery, arching around the genu of corpus callosum. It runs posteriorly to rise above the rostral part of the body of corpus callosum.
- Supracallosal (A4) segment: runs from the body of the corpus callosum anterior to the coronal suture.
- The postcallosal (A5) segment continues its way superior to the corpus callosum after passing the plane of the coronal suture.
Branches and supply
The branches of the anterior cerebral artery can be collectively divided into two large groups: cortical and central.
The cortical branches bear the names of the corresponding areas of which they supply (orbito frontal and parietal). The orbitofrontal branches supply the olfactory cortex, gyrus rectus and medial orbital gyrus. The branches that ramify into the frontal lobe supply the corpus callosum (with the exception of the splenium), cingulate gyrus, medial frontal gyrus and paracentral lobule, while the parietal branches vascularize the precuneus. Note that several small frontal and parietal branches also cross onto the superolateral cerebral surface to supply the superior parts of the precentral and postcentral gyri. These areas are responsible for motor and sensory functions in the lower limb.
These branches arise in the proximal portion of the anterior cerebral artery, more specifically at A1 and A2 segments. They traverse the anterior perforated substance to supply deep cerebral structures. These structures include:
- Rostrum of the corpus callosum
- Septum pellucidum
- Anterior part of the putamen
- Head of the caudate nucleus
- Anteromedial aspect of the anterior limb of the internal capsule
Since the anterior cerebral artery has a broad supply territory in the brain, it gives off many branches. For a simple overview, the exact branches of each segment will be listed in the table below.
|Precommunicating part (A1)||Anteromedial central arteries
Anterior communicating artery
|Infracallosal segment (A2)||Orbitofrontal branches
Long striate/central artery (of Heubner)
Perforating branches (to hypothalamus, septum pellucidum, anterior commissure, fornix, striatum, corpus callosum)
|Precallosal part (A3)||Pericallosal artery
Medial frontal branches
|Supracallosal part (A4)||Paracentral branches
|Postcallosal part (A5)||Parietal branches
Inferior callosal branches
Learn more about the blood supply of the brain with our articles, video tutorials, quizzes and labeled diagrams.
- In up to 80% of cases, the left and right A1 segments are asymmetric, with the right example usually being longer, more narrow and tortuous than its counterpart.
- The A2 segment can be duplicated, bihemispheric (where its contralateral counterpart is hypoplastic) or alternatively present as a single, unpaired vessel formed by the joining of both A1 segments (azygos anterior cerebral artery).
- The branches of the A3 segment to the contralateral hemisphere more than 60% of cases.
ACA ischemic stroke
Ischemic stroke involving the supply territory of the anterior cerebral artery is relatively rare, accounting for only 0.5 - 4% of all ischemic brain injuries. When infarcts do occur, Ischemic injuries of this region are usually a consequence of arterosclerotic changes in the anterior cerebral artery caused by common etiological factors of cerebrovascular diseases such as: hypertension, high level of lipids in the serum (hypercholesterolemia), diabetes mellitus, smoking, etc. Occlusion can occur in the anterior cerebral artery or in its smaller branches.
Clinical presentation of ACA stroke mainly depends on the site of infarction and the supplied regions distal to it. Some of the most common symptoms of the anterior cerebral artery stroke are the motor deficits of the contralateral lower limb, contralateral face and arm paresis, urinary incontinence, sensory deficits, tremor, altered psychiatric status (e.g. memory impairments, emotional lability), etc.