 It passes posteriorly to descend the medulla passing in front of the posterior roots of the spinal nerves.Along its course it is reinforced by a succession of segmental or radiculopial branches, which enter the vertebral canal through the intervertebral foramina, forming a plexus called the vasocorona with the anterior vertebral arteries.Below the medulla spinalis and upper cervical spine, the posterior spinal arteries are rather discontinuous; unlike the anterior spinal artery, which can be traced as a distinct channel throughout its course, the posterior spinal arteries are seen as somewhat larger longitudinal channels of an extensive pial arterial meshwork.