Anterior cerebral artery
The anterior cerebral artery along with the middle cerebral artery forms at the termination of the internal carotid artery. It is the smaller of the two, and arches anteromedially to pass anterior to the genu of the corpus callosum, dividing as it does so into its two major branches; pericallosal and callosomarginal arteries (see below).
It supplies the medial aspect of the cerebral hemispheres back to the parietal lobe.
Gross anatomy
Segments
The ACA is divided into five segments 8,9,10:
- A1 (horizontal, precommunicating): originating from the terminal bifurcation of the internal carotid artery, extending ~14 mm in length, terminating at the anterior communicating artery (ACOM)
- A2 (vertical, postcommunicating, infracallosal): originating at the ACOM, extending anterior to the lamina terminalis and along the rostrum of the corpus callosum, terminating either at the genu of the corpus callosum or at the origin of the callosomarginal artery
- A3 (precallosal): extends around the genu of the corpus callosum or distal to the origin of the callosomarginal artery, terminating where the artery turns directly posterior above the corpus callosum
- A4 (supracallosal): above the body of the corpus callosum anterior to the plane of the coronal suture
- A5 (postcallosal): above the body of the corpus callosum posterior to the plane of the coronal suture
The pericallosal artery refers either to the distal part of the ACA starting from A2 (after the origin of the ACOM) or from A3 (defined after the origin of the callosomarginal artery). In the former case, the A2, A3, and A4-5 segments refer to proximal, middle, and distal segments of the pericallosal artery, respectively 11,12.
The A4 and A5 segments predominantly run along the callosal sulcus, but in a minority of cases run above that, medial to the cingulate gyrus.
Branches
There are two main branching patterns of the ACA. In the first the A2 gives off the callosomarginal artery (which lies in the cingulate sulcus), and continues as the pericallosal artery. In this configuration, the terminal (cortical) branches are given off the callosomarginal artery.
In the second configuration, the callosomarginal is absent and the terminal branches arise directly from the pericallosal.
- A1
- A2
- A3
- pericallosal artery
- callosomarginal artery (runs in the cingulate sulcus)
Terminal (cortical) branches
Orbital branches, 2 or 3 in number, branch over the orbital surface of the frontal lobe supplying:
- olfactory cortex
- gyrus rectus
- medial orbital gyrus
They are named:
Frontal branches supply:
- corpus callosum (with the exception of the splenium)
- cingulate gyrus
- medial frontal gyrus
- paracentral lobule (as the branches reach over the vertex to supply a stip of cortex on the surface, they are responsible for supply to the lower limbs)
Parietal branches supply:
Central branches
Multiple small branches are given off proximally (A1, ACOM, proximal A2) supply:
- anterior perforated substance
- lamina terminalis
- rostrum of the corpus callosum
- septum pellucidum
- anterior part of the putamen
- head of the caudate nucleus
- anteromedial part of the anterior limb of the internal capsule
The latter two (head of caudate and adjacent part of the internal capsule) are supplied by the recurrent artery of Heubner and associated smaller perforating branches. It has its origin near the A1-ACOM-A2 junction and can arise from all three, although usually it is from the A2. It curves back on itself and is at risk from ACOM aneurysm clipping.
Variant anatomy
- ACA fenestration with a reported incidence of 0-4% of A1 segment fenestration
- azygos ACA: ACA territories supplied by a single A2 trunk; incidence of ~2% (range 0.2-4.0%)
- ACA trifurcation: three A2 segments; incidence of ~7.5% (range 2-13%)
- bihemispheric ACA: a hypoplastic A2 segment with contralateral A2 segment dominance supplying both ACA territories; incidence of ~4.5% (range 2-7%)
- A1 segment absence/hypoplasia, contralateral A1 segment dominance and supply to ipsilateral A2 segment by a large anterior communicating artery; 10% of individuals demonstrate hypoplasia of A1 segment using a diameter 1.5 mm or smaller
- Duplication of A1
- two or three AComA
- asymmetry of A1 segment which is associated with ACA aneurysm
- persistent primitive olfactory artery 6
Related Radiopaedia articles
Anatomy: Brain
-
brain
- grey matter
- white matter
-
cerebrum
-
cerebral hemisphere (telencephalon)
- cerebral lobes and gyri
- frontal lobe
- parietal lobe
-
occipital lobe
- occipital pole
- lingual gyrus
- fusiform gyrus (Brodmann area 37)
- calcarine (visual) cortex
- cuneus
- temporal lobe
- basal forebrain
- limbic system
- insula
-
cerebral sulci and fissures (A-Z)
- calcarine fissure
- callosal sulcus
- central (Rolandic) sulcus
- cingulate sulcus
- circular sulcus
- collateral sulcus
- inferior frontal sulcus
- inferior occipital sulcus
- inferior temporal sulcus
- interhemispheric fissure
- intraparietal sulcus
- lateral (Sylvian) sulcus
- lateral occipital sulcus
- marginal sulcus
- occipitotemporal sulcus
- olfactory sulcus
- paracentral sulcus
- paraolfactory sulcus
- parieto-occipital fissure
- posterior parolfactory sulcus
- precentral sulcus
- preoccipital notch
- postcentral sulcus
- rhinal sulcus
- rostral sulcus
- subparietal sulcus
- superior frontal sulcus
- superior occipital sulcus
- superior temporal sulcus
- cortical histology
- cerebral lobes and gyri
- white matter tracts
- deep grey matter
-
pituitary gland
- posterior pituitary and stalk (part of diencephalon)
- anterior pituitary
- inferior hypophyseal arterial circle
- diencephalon
-
cerebral hemisphere (telencephalon)
-
brainstem
- midbrain (mesencephalon)
- pons (part of metencephalon)
- medulla oblongata (myelencephalon)
- white matter
- grey matter (non-cranial nerve)
-
cerebellum (part of metencephalon)
- vermis
- cerebellar hemisphere
- cerebellar peduncles
- cranial meninges (meninx primitiva)
- CSF spaces
-
cranial nerves (mnemonic)
- olfactory nerve (CN I)
- optic nerve (CN II)
- oculomotor nerve (CN III)
- trochlear nerve (CN IV)
- trigeminal nerve (CN V) (mnemonic)
- abducens nerve (CN VI)
- facial nerve (CN VII) (segments mnemonic | branches mnemonic)
- vestibulocochlear nerve (CN VIII)
- glossopharyngeal nerve (CN IX)
- vagus nerve (CN X)
- spinal accessory nerve (CN XI)
- hypoglossal nerve (CN XII)
- functional neuroanatomy
- CNS development
- cerebral vascular supply
- arteries
- vascular territories
-
circle of Willis
- internal carotid artery (ICA) (segments)
- vertebral artery
-
normal variants
- intracranial arterial fenestration
- internal carotid artery (ICA)
- anterior cerebral artery (ACA)
- middle cerebral artery (MCA)
- posterior cerebral artery (PCA)
- basilar artery
- persistent carotid-vertebrobasilar artery anastomoses (mnemonic)
-
cerebral venous system
- dural venous sinuses
-
cerebral veins
-
superficial veins of the brain
- superior cerebral veins (superficial cerebral veins)
- inferior cerebral veins
- superficial middle cerebral vein
- superior anastomotic vein (of Trolard)
- inferior anastomotic vein (of Labbe)
-
superficial veins of the brain
- deep veins of the brain
- normal variants
- arteries
- glymphatic pathway