Medial occipital artery; P4 segment

Medial occipital artery; P4 segment: medial terminal branch of the posterior cerebra artery passing to the medial surface of the occipital lobe.

Note that this term ("medial occipital artery") and definition for P4 segment is not used routinely and differs from microsurgical and angiographic approach where the P4 segment is defined as: 

The P4 segment corresponds to the parts (cortical branches) of the PCA that run along or inside both the parieto-occipital sulcus and the distal part of the calcarine fissure. It includes the two main division of the distal PCA, the calcarine artery and parieto-occipital artery.