Posterior Circulation Arterial Anatomy
The posterior arterial circulation is the distal distribution of blood flow through the vertebrobasilar system and demonstrates intricate relationship between the vascular and neural structures within the posterior fossa and deep brainstem nuclei. The posterior fossa contains three sets of neurovascular complexes: upper, middle, and inferior.
These complexes correspond to the superior cerebellar artery (SCA), anterior inferior cerebellar artery (AICA), and posterior inferior cerebellar artery (PICA). Similarly these complexes encompass a corresponding perfusion zone along the midbrain, cerebellar peduncle, and cerebellum. The SCA, AICA, and PICA are divided into segments (s1 to s4, a1 to a4, and p1 to p5, respectively). This segmental division of the individual arteries permits detailed anatomical descriptions of vascular lesions arising along these arteries.
The supratentorial extent of the posterior circulation includes anastomoses with the anterior circulation via the posterior communicating arteries (PCoAs) bilaterally, to varying degrees dependent on dominance and/or atresia of these vessels. The posterior cerebral arteries (PCAs) project posteriorly, segmented into P1 to P4 running proximal to distal, and provide watershed perfusion along the ACA and MCA distributions.