Brain Blood Supply

The entire arterial supply ^[41] of the brain is derived from two arterial systems: the two internal carotid arteries ^{[85, 86]} anteriorly, and the two vertebral arteries ^{[86, 87]} (or the vertebrobasilar system ^{[88, 89, 90]}) posteriorly.

These four major axes are interconnected at several levels, most notably at the base of the brain by the Circle of Willis ^{[86, 91]}. This anastomotic circle functions as a safety system; if one of the axes becomes deficient, the blood supply from the others compensates for the deficit.

From this anastomotic circle arise the main cerebral arteries.

The internal carotids give off two essential branches: the anterior cerebral artery ^[2] , which supplies the medial part of the cerebral hemisphere, and the middle cerebral artery ^[2] , which supplies the lateral surface of the hemisphere.

The two vertebral arteries merge to form a common trunk (the basilar artery ^[2] ), which gives off branches to the brainstem and the cerebellum. It subsequently divides to form the two posterior cerebral arteries ^[51] , destined for the occipital lobe and the ventral part of the temporal lobe.