Blood supply of the brain

5 Blood supply of the brain

Arterial Supply of the Forebrain

The blood supply to the forebrain is derived from the two internal carotid arteries and from the basilar artery (Figure 5.1).

Each internal carotid artery enters the subarachnoid space by piercing the roof of the cavernous sinus. In the subarachnoid space, it gives off ophthalmic, posterior communicating, and anterior choroidal arteries before dividing into the anterior and middle cerebral arteries.

The basilar artery divides at the upper border of the pons into the two posterior cerebral arteries. The cerebral arterial circle (circle of Willis) is completed by a linkage of the posterior communicating artery with the posterior cerebral on each side, and by linkage of the two anterior cerebrals by the anterior communicating artery.

The choroid plexus of the lateral ventricle is supplied from the anterior choroidal branch of the internal carotid artery and by the posterior choroidal branch from the posterior cerebral artery.

Dozens of fine central (perforating) branches are given off by the constituent arteries of the circle of Willis. They enter the brain through the anterior perforated substance beside the optic chiasm and through the posterior perforated substance behind the mammillary bodies. They have been classified in various ways but can be conveniently grouped into short and long branches. Short central branches arise from all the constituent arteries and from the two choroidal arteries. They supply the optic nerve, chiasm, and tract, and the hypothalamus. Long central branches arise from the three cerebral arteries. They supply the thalamus, corpus striatum, and internal capsule. They include the striate branches of the anterior and middle cerebral arteries.

Middle cerebral artery (Figure 5.3)

The middle cerebral artery is the main continuation of the internal carotid, receiving 60–80% of the carotid blood flow. It immediately gives off important central branches, then passes along the depth of the lateral fissure to reach the surface of the insula. There it usually breaks into upper and lower divisions. The upper division supplies the frontal lobe, the lower division supplies the parietal and temporal lobes and the midregion of the optic radiation. Named branches and their territories are listed in Table 5.2. Overall, the middle cerebral supplies two-thirds of the lateral surface of the brain.

Table 5.2 Cortical branches of the middle cerebral artery

Origin Branch(es) Territory
Stem Frontobasal Orbital surface of frontal lobe
Anterior temporal Anterior temporal cortex
Upper division Prefrontal Prefrontal cortex
Precentral Premotor areas
Central Pre- and postcentral gyri
Postcentral Postcentral and anterior parietal cortex
Parietal Posterior parietal cortex
Lower division Middle temporal Midtemporal cortex
Temporooccipital Temporal and occipital cortex
Angular Angular and neighboring gyri

The central branches of the middle cerebral include the lateral striate arteries (Figure 5.4). These arteries supply the corpus striatum, internal capsule, and thalamus. Occlusion of one of the lateral striate arteries is the chief cause of classic stroke, where damage to the pyramidal tract in the posterior limb of the internal capsule causes hemiplegia, a term denoting paralysis of the contralateral arm, leg, and lower part of face.

Note: Additional information on the blood supply of the internal capsule is provided in Chapter 35.

Posterior cerebral artery (Figures 5.2 and 5.5)

The two posterior cerebral arteries are the terminal branches of the basilar. However, in embryonic life they arise from the internal carotid, and in about 25% of individuals the internal carotid persists as the primary source of blood on one or both sides, by way of a large posterior communicating artery.

Close to its origin, each posterior cerebral artery gives branches to the midbrain and a posterior choroidal artery to the choroid plexus of the lateral ventricle. Additional, central branches are sent into the posterior perforated substance (Figure 5.1). The main artery winds around the midbrain in company with the optic tract. It supplies the splenium of the corpus callosum and the cortex of the occipital and temporal lobes. Named cortical branches and their territories are given in Table 5.3.

Table 5.3 Named cortical branches of the posterior cerebral artery

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Jun 10, 2016 | Posted by in NEUROLOGY | Comments Off on Blood supply of the brain
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Branch Artery