Vascular Anatomy

Overview

The brain is supplied by branches of the internal carotid artery anteriorly and by branches of the vertebral artery posteriorly. It is important to understand the vascular supply of different parts of the brain.

Aortic Arch

The aortic arch gives off three great vessels: the brachiocephalic artery, the left common carotid artery and the left subclavian artery. The brachiocephalic artery subsequently divides into the right common carotid artery and right subclavian artery.

Common Carotid Artery

Within the mid portion of the neck, the common carotid artery splits into the internal carotid artery (which goes directly to the brain) and the external carotid artery (which gives off a number of branches that supply the neck and face).

Internal Carotid Artery

The internal carotid artery enters the skull base through the carotid canal within the petrous portion of the temporal bone and ascends within the cavernous sinus. Once it exits the cavernous sinus it courses intracranially over the anterior clinoid process and terminates in a T junction giving rise to the anterior cerebral artery medially and the middle cerebral artery laterally.

ACA and MCA

The Anterior Cerebral Artery (ACA) provides the blood supply to the medial part of the frontal lobes and anterior parietal lobes. The proximal ACA branches are connected by the anterior communicating artery. The Middle Cerebral Artery (MCA) supplies the lateral portion of the frontal lobes, temporal lobes and parietal lobes.

Vertebral Artery and its branches

The vertebral artery arises from the subclavian artery. The paired vessels ascend through the neck within the foramen transversarium of the cervical spine. This relationship is important to understand as patients with cervical spine trauma may have fractures that involve the foramen, putting them at risk for vertebral artery injury.

Circle of Willis

At the level of the skull base, the vertebral arteries pierce the dura and enter the posterior fossa. One of the vertebral artery's major branches is the posterior infereior cerebellar artery (PICA), which supplies the posterior inferior portion of the cerebellum. The vertebral arteries then join one another to form the basilar artery. The anterior inferior cerebellar artery (AICA) typically arises from the mid portion of the basilar artery and supplies the anterior inferior portion of the cerebellum. The basilar artery terminates into 2 paired vessels: the superior cerebellar artery (SCA) and the posterior cerebral artery (PCA). As the name implies, the superior cerebellar artery supplies the superior portion of the cerebellum. The PCA and its branches supply the occpital lobe, thalamus and inferomedial portion of the temporal lobe The posterior communicating artery is a bridge between the posterior and anterior circulations connecting the supraclinoid segment of the ICA with the PCA. The anterior communicating arter is a bridge between the anterior cerebral arteries.