Anterior cerebral artery (ACA)

A1 - Precommunicating segment

Extends from the origin of ACA to the anterior communicating artery (ACom).


Branches:

  1. Medial lenticulostriate arteries
    • Supply:
      • Anterior hypothalamus
      • Head of caudate nucleus
      • Anterior part of putamen
      • Anterior limb of internal capsule

  1. Recurrent artery of Heubner
    • Arises in A1 or proximal A2 segment or rarely might arise from ACom or have a common origin with orbitofrontal or frontopolar arteries.
    • Supplies:
      • Head of the caudate nucleus (inferior part)
      • Anterior limb of internal capsule (inferior part)
      • Anteromedial parts of globus pallidus and putamen
      • Anterior part of hypothalamus (septal area)

  1. Anterior perforating arteries
    • Supply:
      • Optic chiasm
      • Optic tract
      • Hypothalamus

Anatomic variants:

  • Hypoplastic or absent A1
  • Fenestrated A1
  • Bihemispheric ACA: the distal ACA branches supply part of the contralateral ACA territory
  • Azygous ACA: single ACA trunk, absent ACom
  • Infraoptic ACA: A1 passes under optic nerve

Anterior communicating artery (ACom)

Short artery connecting the A1 segments, part of the circle of Willis. Does not have any major branches but may give off small perforators:


  1. Anteromedial perforating arteries to
    • Preoptic area
    • Anterior hypothalamus
    • Lamina terminalis
    • Optic chiasm
    • Suprachiasmatic nucleus

  1. Median artery of the corpus callosum (inconstant) to genu of corpus callosum and rostrum

  1. Accessory ACA branches (inconstant) contributing to medial frontal lobes

A2 - Infracallosal segment

Runs into the interhemispheric fissure anterior to the rostrum of corpus callosum from immediately distal to the ACom to the origin of the callosomarginal artery.


Branches:

  1. Medial orbitofrontal (medial frontobasal) artery
    • Usually arises from the proximal part of A2.
    • Supplies:
      • Gyrus rectus
      • Orbital gyri
      • Olfactory bulb and tract

  1. Frontopolar artery
    • Usually arises from the middle part of A2.
    • Supplies:
      • Frontal pole
      • Medial superior frontal gyrus

  1. Callosomarginal artery
    • The smaller of the two distal ACA branches. Runs posteriorly above the cingulate gyrus.
    • Supplies:
      • Medial superior frontal gyrus
      • Anterior cingulate gyrus
      • Superior part of precentral and postcentral gyri
      • Paracentral lobule
      • Parts of supplementary motor area
      • Corpus callosum (indirectly, via anastomoses)

A3 - Precallosal segment

Curves around the genu of corpus callosum and continues into the pericallosal artery.


There is a subtle variation in the nomenclature of A2 and A3. Anatomic texts consider the A3 to be the continuation of the ACA along the corpus callosum distal to the origin of the callosomarginal artery, essentially, the pericallosal artery. Surgical texs consider the A3 to be the precallosal curve of the ACA around the genu of the corpus callosum.

Branches:

  1. Pericallosal artery
    • The largest of the two distal ACA branches, essentially the continuation of A3. Runs posteriorly, above the corpus callosum, below cingulate gyrus.
    • Supplies:
      • Cingulate gyrus
      • Precuneus
      • Paracentral lobule
      • Medial parts of parietal lobe
      • Posterior medial parts of frontal lobe
      • Corpus callosum (genu, body, splenium)

  1. Perforating branches to corpus callosum
    • Arise in the proximal part of A3 and supply the anterior part of the genu of corpus callosum.