The basilar artery arises from the confluence of the two vertebral arteries at the junction between the medulla oblongata and the pons between the VIth cranial nerves.
It ascends superiorly in the basilar sulcus ventral to the pons and divides at the ponto-mesencephalic junction into the paired posterior cerebral arteries close to the pituitary stalk.
Its branches can be divided into two groups:
- Paramedian perforating arteries arising either directly from the dorsal surface or from short circumferential arteries running around and into the pons supplying the corticospinal tracts and vital deep nuclei.
- Two or three paired long circumferential branches:
- the internal auditory or labyrinthine artery, which may arise directly from the basilar artery in about 15% of people, but more commonly as a branch from the:
- the anterior inferior cerebellar artery (supplying the inferior and middle cerebellar peduncles of the cerebellum) and the adjacent hemisphere).
- the superior cerebellar artery.