Corpus: Posterior cerebral artery
1. Definition
The posterior cerebral artery, or PCA for short, is a branch of the basilar artery and is one of the three primary arteries supplying the brain.
2. Anatomy
The paired posterior cerebral arteries arise from the bifurcation of the unpaired basilar artery within the cerebral arterial circle (Circle of Willis). Each PCA connects to the middle cerebral artery via the posterior communicating artery, forming an arterioarterial anastomosis. The PCA then wraps around the cerebral peduncles, travels through the cisterna ambiens, and continues through the tentorial notch to supply the caudal surface of the temporal lobe and the occipital lobe along the parahippocampal gyrus.
2.1. Segments
The posterior cerebral artery is divided into four segments, with the P1 segment separated from the P2 segment by the junction of the posterior communicating artery. These segments are often referred to as pre-communicating and post-communicating:
- P1: Pre-communicating segment: Runs through the interpeduncular cistern
- P2: Post-communicating segment: Runs through the cisterna ambiens
- P3: Quadrigeminal segment: Passes through the quadrigeminal cistern
- P4: Terminal segment
In some literature, the P3 segment is associated with the lateral occipital artery, and the P4 segment with the medial occipital artery.
2.2. Topography
The posterior cerebral artery is anatomically close to the cerebral peduncles of the midbrain and the oculomotor nerve.
2.3. Branches
The posterior cerebral artery gives rise to various central, choroidal, and cortical branches. The individual anatomy of these branches can vary.
2.4. Central Branches
- Thalamic perforating artery (P1)
- Collicular artery (P1)
- Short circumferential arteries (P1)
- Posteromedial central arteries (P1)
- Posterolateral central arteries (P2)
- Thalamogeniculate branch (P2)
- Peduncular branches (P2)
2.5. Choroidal Branches
The medial and lateral posterior choroidal branches can also arise from a common trunk as the posterior choroidal artery.
2.6. Cortical Branches
- Anterior temporal branches (P3)
- Posterior temporal branches (P3)
- Lateral occipital artery (P3)
- Medial occipital artery (P4)
- Calcarine branch
- Parieto-occipital branch
- Posterior pericallosal artery
2.7. Supply area
The posterior cerebral artery supplies the occipital lobe, the basal surface of the temporal lobe, the hippocampus, the thalamus, and the posterior sections of the hypothalamus. It also sends branches to the choroid plexus of the lateral ventricles.
2.8. Norm variant
The fetal posterior cerebral artery is a common anatomical variant, occurring in 20 to 30 % of individuals. In this variant, the PCA is primarily supplied by the internal carotid artery rather than the basilar artery.
3. Clinic
Occlusion of the posterior cerebral artery can result in posterior infarction. A unilateral occlusion typically causes visual field loss on the opposite side (homonymous hemianopsia). In rare cases, bilateral occlusion may lead to cortical blindness. Occlusion of specific branches can cause distinct neurological syndromes, such as thalamic syndrome if the central branches are affected.