Vascular territory

Anatomical segments

P1: PCA from the origin to posterior communicating artery (AKA mesencephalic, precommunicating, circular, peduncular, basilar...). The long and short circumflex and thalamoperforating arteries arise from P1
P2: PCA from origin of PComA to the origin of inferior temporal arteries (AKA ambient, post-communicating, perimesencephalic), P2 traverses the ambient cistern, hippocampal, anterior temporal, peduncular perforating, and medial posterior choroidal arteries arise from P2
P3: PCA from the origin of the inferior temporal branches to the origin of the terminal branches (AKA quadrigeminal segment). P3 traverses the quadrigeminal cistern
P4: segment after the origin of the parieto-occipital and calcarine arteries, includes the cortical branches of the PCA

Segment	Description
P1	Arises from the basilar bifurcation and extends through the interpeduncular cistern to the junction with the posterior communicating artery
P2A (anterior)	Runs in the crural cistern, extending from the PComA to the lateral mesencephalic sulcus where it becomes the P2P (posterior) segment
P2P (posterior)	Runs in the ambient cistern, lateral to the midbrain
P3	Runs in the quadrigeminal cistern, separated from the P2P segment by the tectal plate
P4	Begins at the calcarine sulcus

P1 Segment	Feature
Posterior thalamoperforator arteries	From the basilar artery and P1, travels through the posterior perforated substance behind the mamillary bodies Supply: thalamus, hypothalamus, subthalamus, and midbrain (cranial nerves III and IV)
Medial posterior choroidal arteries	Travels anteromedially along the roof of the third ventricle Supply: midbrain tectum, posterior thalamus, pineal gland, and tela choroidae of the third ventricle
Meningeal branches	Supply: tentorium and the falx

P2 Segment	Feature
Lateral posterior choroidal artery	Main branch of P2, courses over the pulvinar and through the choroidal fissure Supply: posterior portion of the thalamus and choroid plexus (temporal horn and atrium)
Thalamogeniculate arteries	Medial geniculate body, lateral geniculate body, pulvinar, superior colliculus, and crus cerebri
Cortical branches	Inferior temporal artery group Supply: inferior portion of the temporal lobe

P3 Segment	Feature
Posterior temporal artery	Posterior temporal lobe, occipitotemporal and lingual gyri Anterior temporal artery branch travels to the inferior temporal lobe to supply the inferior cortex. Anastomoses with middle cerebral artery
Internal occipital artery
Parietooccipital artery	Located in the parietooccipital sulcus Supply: posterior ⅓ of the medial hemispheres, cuneus, precuneus, superior occipital gyrus, and precentral and superior parietal lobules Anastomoses with anterior cerebral artery
Calcarine artery	Located in the calcarine sulcus Supply: occipital pole and the visual cortex Anastomoses with middle cerebral artery
Posterior pericallosal artery	Supply: splenium of the corpus callosum Anastomoses with anterior cerebral artery