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, running close to the edge of the tentorium cerebelli. Topographically, it lies parallel to and slightly superior to the superior cerebellar artery.
Blood flows into the artery not only from the basilar artery but also from the internal carotid artery (ICA) system via the posterior communicating artery (a. communicans posterior), which joins it approximately 10 mm distal to the bifurcation. In early ontogenesis, the posterior cerebral artery develops precisely as a branch of the ICA.
Fisher segments
The anatomical landmark for dividing the artery into segments is the entry point of the posterior communicating artery:
- P1 segment (precommunicating part / pars precommunicalis) — the proximal section of the artery located proximal to the entry point of the posterior communicating artery.
- P2 segment (postcommunicating part / pars postcommunicalis) — the section located distal to this anastomosis.
- Terminal part (pars corticalis) — the distal cortical sections of the vessel.
Branches and areas of blood supply
The branches of the posterior cerebral artery supply extensive areas of the cortex and deep brain structures. Both arteries give off penetrating branches to the midbrain and thalamus.
- Branches of the precommunicating part: gives off aa. centrales posteromediales (to the ventrolateral nuclei of the thalamus) and the posterior thalamoperforating artery (supplies the basal and medial parts of the thalamus, pulvinar).
- Branches of the postcommunicating part: includes aa. centrales posterolaterales, rr. thalamici, and rr. pedunculares. The thalamogeniculate artery (to the lateral part of the thalamus) and the medial/lateral posterior choroidal arteries (rr. choroidei posteriores mediales/laterales), which nourish the geniculate bodies, thalamic nuclei, and choroid plexus, also arise here.
- Cortical branches (arising in the ambient cistern): the calcarine artery, parieto-occipital artery, temporal branches, and the lateral and medial occipital arteries (a. occipitalis lateralis et medialis). They supply 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 stenoses and occlusions. Saccular aneurysms in this territory are relatively rare (about 2% of cases).
Percheron artery is an important clinical and anatomical anatomical variant in which the right and left posterior thalamoperforating arteries arise from a common trunk. This variant is often combined with unilateral hypoplasia of the P1 segment and a fetal configuration 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 part of the basilar artery from the P1 segment may be observed. A "filling defect" may also be visualized in the posterior cerebral artery — a phenomenon of contrast "washout" by blood flowing from the carotid system via the posterior communicating artery.
Class and exam questions
How is the posterior cerebral artery connected to the internal carotid artery?
They are connected via the posterior communicating artery (a. communicans posterior). Moreover, in early ontogenesis, the posterior cerebral artery is initially a branch of the internal carotid artery.
What is the Percheron artery?
This is an anatomical variant in which the posterior thalamoperforating arteries on both sides arise from a single common trunk. This variant is often accompanied by a fetal vessel configuration and unilateral hypoplasia of the P1 segment.
Why might a "filling defect" be visible in the posterior cerebral artery on an angiogram?
This hemodynamic phenomenon is associated with the "washout" of the contrast medium. Unenhanced blood flows into the artery from the carotid basin via the posterior communicating artery, creating the appearance of a defect.
What else to study on this topic
- Basilar artery (a. basilaris)
- Posterior communicating artery (a. communicans posterior)
- Circle of Willis (circulus arteriosus cerebri)
- Blood supply to the thalamus
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