The anterior cerebral artery is divided into 5 segments. Its smaller branches: the callosal (supracallosal) arteries are considered to be the
A4 and
A5 segments. •
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 irrigates the
caudate nucleus and the anterior limb of the
internal capsule •
A2 extends from the AComm to the bifurcation forming the
pericallosal and
callosomarginal arteries. The
recurrent artery of Heubner (distal medial striate artery), which irrigates 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, also termed the
pericallosal artery, is 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. Angiography studies cite that the vessel can be seen 67% of the time.
Development The anterior cerebral artery develops from a primitive anterior division of the
internal carotid artery that initially supplies the optic and olfactory regions. This anterior division, which appears at the twenty-eighth day of development, also forms the
middle cerebral artery and the
anterior choroidal artery. The anterior cerebral arteries grow toward each other and form the
anterior communicating artery at the 21–24 mm stage of the
embryo.
Variation The anterior cerebral artery shows considerable variation. In a study made using
MRA, the most common variation was an underdeveloped A1 segment (5.6%), followed by the presence of an extra A2 segment (3%). In 2% of cases there was only one A2 segment. ==Function==