C H A P T E R 4

Blood Supply

Objectives

1.List the major branches of the vertebral and internal carotid arteries and indicate the regions/ structures that each artery supplies.

2.Describe the cerebral arterial circle (of Willis).

3.List the major deep cerebral veins.

4.Explain and identify the dural venous sinuses and include a description of their drainage patterns and location of each sinus.

5.Describe the various types of intracranial hemorrhage.

IThe Spinal Cord and Caudal Brainstem are supplied with blood

through the anterior spinal artery (Figure 4-1).

A.The anterior spinal artery supplies the anterior two-thirds of the spinal cord.

B.In the medulla, the anterior spinal artery supplies the pyramid, medial lemniscus, and root fibers of cranial nerve (CN XII).

II The Internal Carotid System (see Figure 4-1) consists of the internal

carotid artery and its branches:

A.Ophthalmic Artery enters the orbit with the optic nerve (CN II). The central artery of the retina is a branch of the ophthalmic artery. Occlusion results in blindness.

B.Posterior Communicating Artery irrigates the hypothalamus and ventral thalamus. An aneurysm of this artery is the second most common aneurysm of the cerebral arterial circle and commonly results in third-nerve palsy.

C.Anterior Choroidal Artery arises from the internal carotid artery. It perfuses the lateral geniculate body, globus pallidus, and posterior limb of the internal capsule.

D.Anterior Cerebral Artery (Figure 4-2) supplies the medial surface of the cerebral hemisphere from the frontal pole to the parieto-occipital sulcus.

1.The anterior cerebral artery irrigates the paracentral lobule, which contains the leg-foot area of the motor and sensory cortices.

2.The anterior communicating artery connects the two anterior cerebral arteries. It is the most common site of aneurysm of the cerebral arterial circle, which may cause bitemporal lower quadrantanopia.

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Figure 4-1 Arterial supply to the brain as seen from the undersurface of the brainstem.

A B

Figure 4-2 Areas of the cerebrum supplied by each of the three main cerebral arteries.

Figure 4-3 Coronal section through the cerebral hemisphere at the level of the internal capsule and thalamus, showing the major vascular territories.

3.The medial striate arteries (see Figure 4-1) are the penetrating arteries of the anterior cerebral artery. They supply the anterior portion of the putamen and caudate nucleus and the anteroinferior part of the internal capsule.

E.Middle Cerebral Artery (Figure 4-2)

1.Supplies the lateral convexity of the hemisphere, including:

a.Broca and Wernicke speech areas.

b.The face and arm areas of the motor and sensory cortices.

c.The frontal eye field.

2.Lateral striate arteries (Figure 4-3)—penetrating branches of the middle cerebral artery. They are the arteries of stroke, and they supply the internal capsule, caudate nucleus, putamen, and globus pallidus.

IIIThe Vertebrobasilar System. See Figure 4-1.

A.Vertebral Artery—a branch of the subclavian artery. Gives rise to the anterior spinal artery (see section I) and the posterior inferior cerebellar artery (PICA), which supplies the dorsolateral quadrant of the medulla. This quadrant includes the nucleus ambiguus (CNs IX and X) and the inferior surface of the cerebellum.