Origin and Course
The posterior cerebral artery originates from the bifurcation of the basilar artery (a. basilaris) at the level of the pons. From its origin, it winds around the midbrain and enters the ambient cistern, traveling near the margin of the tentorium cerebelli. Topographically, it runs parallel and slightly superior to the superior cerebellar artery.
Blood flow to the artery is supplied not only by the basilar artery but also by the internal carotid artery (ICA) system via the posterior communicating artery (a. communicans posterior), which joins it approximately 10 mm distal to the bifurcation. During early ontogeny, the posterior cerebral artery initially forms as a branch of the ICA.
Segments (Fisher Classification)
The entry point of the posterior communicating artery serves as the anatomical landmark for dividing the artery into segments:
- P1 segment (precommunicating part / pars precommunicalis) — the proximal segment of the artery located prior to the junction with the posterior communicating artery.
- P2 segment (postcommunicating part / pars postcommunicalis) — the segment located distal to this anastomosis.
- Cortical part (pars corticalis) — the distal cortical branches of the vessel.
Branches and Supplied Territories
The branches of the posterior cerebral artery supply extensive areas of the cerebral cortex and deep brain structures. Both arteries give off penetrating branches to the midbrain and thalamus.
- Branches of the precommunicating part: gives rise to aa. centrales posteromediales (to the ventrolateral thalamic nuclei) and the posterior thalamoperforating artery (supplying the basal and medial parts of the thalamus, and the pulvinar).
- Branches of the postcommunicating part: includes aa. centrales posterolaterales, rr. thalamici, and rr. pedunculares. This segment also gives off the thalamogeniculate artery (to the lateral thalamus) and the medial/lateral posterior choroidal arteries (rr. choroidei posteriores mediales/laterales), which supply the geniculate bodies, thalamic nuclei, and choroid plexuses.
- Cortical branches (given off within the ambient cistern): the calcarine artery, occipitotemporal artery, temporal branches, and the lateral and medial occipital arteries (a. occipitalis lateralis et medialis). They provide blood to the occipital lobe and the mediobasal regions of the temporal lobe.
Clinical Significance and Hemodynamics
The posterior cerebral artery is a common site for atherosclerotic stenosis and occlusion. Saccular aneurysms in this territory are relatively rare (about 2% of cases).
Artery of Percheron: An important clinical and anatomical variant where the right and left posterior thalamoperforating arteries arise from a common single trunk. This variant is frequently associated with unilateral hypoplasia of the P1 segment and a fetal origin of the posterior cerebral artery.
Angiographic Phenomena: During digital subtraction angiography (DSA) with contrast injection into the internal carotid artery, retrograde filling of the upper basilar artery from the P1 segment may be observed. Additionally, a "filling defect" may be visualized in the posterior cerebral artery — a wash-out phenomenon caused by non-contrast blood flowing into the artery from the carotid system via the posterior communicating artery.