The Vertebrobasilar SystemThevertebral arteriesoriginate from thesubclavian artery,and ascend through the transverseforamen of the upper six cervicalvertebra. At the upper margin of the Axis(C2) it moves outward and upward to thetransverse foramen of the Atlas (C1). Itthen moves backwards along the articularprocess of atlas into a deep groove, passesbeneath the atlanto-occipital ligament andenters theforamen magnum. The arteries then runforward and unite at the caudal border ofthe pons to form thebasilar artery.
Blood Supply to the Spinal Cordand BrainstemTheSpinal Cord receives its blood supply from two major sources;1. Branches of thevertebral arteries, the major source of blood supply,via theanterior spinalandposterior spinal arteries.2. Multipleradicular arteries, derives sporadically fromsegmentalarteriesThe Medulla, Pons and Midbrain areas receive their major sources of bloodsupply from several important branches of theBasilar artery
Branches of the Vertebral Artery1.Posterior Inferior Cerebellar Artery(PICA),the largest branch of thevertebral, arises at the caudal end of themedulla on each side.Runs a course winding between themedulla and cerebellumDistribution:a. posterior part of cerebellar hemisphereb. inferior vermisc. central nuclei of cerebellumd. choroid plexus of 4th ventriclee.