Anatomic imaging: Angiography.

This chapter reviews the vascular anatomy of the brainstem and posterior circulation with emphasis on clinical neurology and angiographic interpretation. Using a caudal-to-cranial approach, we describe the vertebral artery at the craniocervical junction and its key branches, including meningeal, medullary, spinal, and posterior inferior cerebellar arteries (PICA), highlighting common variants and clinically important anastamoses. We then outline basilar artery segments, pontine perforator patterns, and vertebrobasilar perforator groups, linking lesion location to characteristic neurologic syndromes. The cerebellar arteries (PICA, AICA, and superior cerebellar artery) are discussed with attention to variant origins, shared trunks, and collateral pathways that influence infarct topography. Finally, we summarize basilar tip and posterior cerebral artery (PCA) anatomy, including fetal PCA configurations, and thalamoperforator variants, such as the artery of Percheron.