Posterior cerebral artery (PCA)

The posterior cerebral arteries stem in most individuals from the basilar artery but sometimes originate from the ipsilateral internal carotid artery. 1).

They supply the temporal lobe and occipital lobes of the left cerebral hemisphere and the right hemisphere. When infarction occurs in the territory of the posterior cerebral artery, it is usually secondary to embolism from lower segments of the vertebrobasilar system or heart.

Clinical symptoms associated with occlusion of the posterior cerebral artery depend on the location of the occlusion and may include thalamic syndrome, thalamic perforate syndrome, Weber’s syndrome, contralateral hemplegia, hemianopsia and a variety of other symptoms, including including color blindness, failure to see to-and-fro movements, verbal dyslexia, and hallucinations. The most common finding is occipital lobe infarction leading to an opposite visual field defect.

The PCA is divided into four segments:

P1 segment

P2 segment

P3 segment

P4: cortical segment (e.g. calcarine artery, within the calcarine fissure).

The anterior choroidal artery (AChA) gives off an anterior uncal artery that irrigates the semilunar gyrus and an uncohippocampal artery that irrigates the uncinate gyrus and band of Giacomini and penetrates the uncal sulcus to vascularize the extraventricular hippocampal head. The internal carotid artery (ICA) gives off an anterior uncal artery that supplies the semilunar gyrus. This branch usually is present when the anterior uncal artery of the AChA is absent. An anterior uncal artery also arises from the M1 segment of the middle cerebral artery (MCA) and supplies the ambient gyrus. An uncoparahippocampal artery arises from the temporopolar artery and irrigates both the ambient gyrus and the anterior parahippocampal area. Branches from the P2a segment of the PCA irrigate the anterior parahippocampal region (anterior parahippocampal artery) or both the anterior parahippocampal gyrus and hippocampal head (anterior hippocampal-parahippocampal artery). (b) The medial surface of the anterior segment of the left MTR. The white arrow points the posterior end of the uncal notch. The anterior part of this segment is irrigated by middle cerebral branches (orange shaded area), the posterosuperior part is supplied by anterior choroidal branches (blue shaded area), and the posteroinferior part is vascularized by posterior cerebral branches (yellow shaded area). The ICA typically supplies the area supplied by the AChA and the MCA if their branches are absent. The branches of the MCA are the anterior uncal artery superiorly and the unco-parahippocampal artery inferiorly.

The branches of the AChA are the anterior uncal artery anteriorly, the posterior uncal artery posteriorly, and the unco-hippocampal artery posteroinferiorly.

The branches of the PCA are the anterior hippocampal-parahippocampal artery medially and the anterior parahippocampal artery laterally. Areas of vascular anastomosis are typically found at the confluence of vascular territories (curved arrows).

© The same view of (a) in a silicon injected anatomic specimen.

(d) Inferior view of the anterior segment of the left MTR.

The inferior lip of the posterior uncal segment has been removed to expose the extraventricular hippocampal head. The semilunar gyrus has been retracted to expose the branches of the AChA.

Two anterior uncal arteries arise from the first one-third of the AChA and irrigate the semilunar gyrus. A posterior uncal artery from the AChA penetrates the uncal sulcus and irrigates the extraventricular hippocampal head. An anterior hippocampal-parahippocampal artery arising from the anteroinferior temporal branch of the PCA gives rise to an anterior hippocampal branch that supplies the extraventricular hippocampal head and anastomoses with the unco-hippocampal branch of the AChA (green arrow).

(e) Lower surface of the anterior segment of the right MTR. The entorhinal area is irrigated medially by the parahippocampal branch of the anterior hippocampal-parahippocampal artery that arises from the P2a, and laterally by a large anterior parahippocampal artery that originates from the anterior inferior temporal artery.

A.: artery; A.C.A.: anterior cerebral artery;

A.Ch.A.: anterior choroidal artery;

Amb.: ambient; Ant.: anterior;

Car.: carotid;

Chor.: choroidal;

Dent.: dentate;

Entorhin.: entorhinal;

Giac.: Giacomini;

Hippo.: hippocampus;

ICA: internal carotid artery;

Inf.: inferior;

Intralimb.: intralimbic;

Lent.: lenticulo;

M.C.A.: middle cerebral artery;

M1.: M1 segment of middle cerebral artery;

Parahippo.: parahippocampal;

P.C.A.: posterior cerebral artery;

P2A.: anterior part of the P2 segment of posterior cerebral artery;

P2P.: posterior part of the P2 segment of posterior cerebral artery;

P.Co.A.: posterior communicating artery;

Ped.: peduncle;

Pol.: polar;

Semianul.: semiannular;

Semilun.: semilunar;

Str.: striate;

Sulc.: sulcus;

Temp.: temporal;

Tr.: tract;

Unc.: uncal;

Uncin.: uncinate;

V.: vein.

The branches of the posterior cerebral artery are divided into two sets, ganglionic and cortical:

Central branches

See also: Artery of Percheron

Also known as the perforating branches:

Thalamoperforating and thalamogeniculate or postero-medial ganglionic branches: a group of small arteries which arise at the commencement of the posterior cerebral artery: these, with similar branches from the posterior communicating, pierce the posterior perforated substance, and supply the medial surfaces of the thalami and the walls of the third ventricle. Peduncular perforating or postero-lateral ganglionic branches: small arteries which arise from the posterior cerebral artery after it has turned around the cerebral peduncle; they supply a considerable portion of the thalamus.

Posterior cerebral artery

Choroidal branches See also: Anterior choroidal artery Medial posterior choroidal branches: run forward beneath the splenium of the corpus callosum, and supply the tela chorioidea of the third ventricle and the choroid plexus. Lateral posterior choroidal branches: small branches to the cerebral peduncle, fornix, thalamus, and the caudate nucleus.

Cortical branches The cortical branches are:

Anterior temporal, distributed to the uncus and the anterior part of the fusiform gyrus Posterior temporal, to the fusiform and the inferior temporal gyri Lateral occipital, which branches into the anterior, middle and posterior inferior temporal arteries Medial occipital, which branches into the: Calcarine, to the cuneus and gyrus lingualis and the back part of the convex surface of the occipital lobe Parieto-occipital, to the cuneus and the precuneus Splenial, or the posterior pericallosal branch, sometimes anastamoses with the anterior cerebral artery (ACA), and may not be present if the ACA wraps around the corpus callosum.

Garcia JH et al., In Barnett HJM at al (eds) Stroke Pathophysiology, Diagnosis, and Management New York Churchill Livingstone 1992 125
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