Blood Supply To The Brain Jake Turner
Learning Objectives • Understand the basic blood supply of the brain • Understand how to localise blockages of arteries based on symptoms • Understand how to work out which parts of the brain will be based on where a blockage is. • Have a brief understanding of the venous drainage of the brain.
Why is it important? • Strokes! • Locating the point of blockage of the blood supply based on clinical signs and symptoms.
What will be the effect of a blockage? • Stroke • TIA • Ischaemia • Death • Seizures • Sensory hallucination
Anterior Cerebral Artery • The anterior cerebral artery extends upward and forward from the internal carotid artery. • It supplies the frontal lobes, the parts of the brain that control logical thought, personality, and voluntary movement, especially of the legs. • Stroke in the anterior cerebral artery results in opposite leg weakness. If both anterior cerebral territories are affected, profound mental symptoms may result (akineticmutism).
Middle Cerebral Artery • The middle cerebral artery is the largest branch of the internal carotid. • The artery supplies a portion of the frontal lobe and the lateral surface of the temporal and parietal lobes. • This includes the primary motor and sensory areas of the face, throat, hand and arm, and in the dominant hemisphere, the areas for speech. • The middle cerebral artery is the artery most often occluded in stroke.
Posterior Cerebral Artery • The posterior cerebral arteries stem in most individuals from the basilar artery but sometimes originate from the ipsilateral internal carotid artery. • The posterior arteries supply the temporal and occipital lobes of the left cerebral hemisphere and the right hemisphere. • Blockages of the posterior cerebral artery are usually secondary to embolism from lower segments of the vertebral basilar system or heart.
Lenticulostriate Arteries • Small, deep penetrating arteries known as the lenticulostriate arteries branch from the middle cerebral artery. • These supply deep structures in the cerebrum including the internal capsuleand reticular formation. Strokes in these vessels are common and can cause a lot of damage as emboli are carried up into the MCA. • About 20% of all stokes are lacunar.
Venous Drainage of the brain • The main drainage of the brain is via the superior sagittal sinus and the inferior sagittal sinus. These then form the two transverse sinuses, which travel laterally and inferiorly to form the sigmoid sinuses. • The sigmoid sinuses then form the jugular veins and descend through the neck into the superior vena cava. • The superior sagittal sinus runs across the top of the skull in the midline, while the inferior sagittal sinus runs through the middle of the brain between the two hemispheres.
Deep Venous Drainage • Composed of traditional veins inside the deep structures of the brain • These join behind the midbrain to form the vein of Galen, which merges with the inferior vein of Galen. • This vein merges with the inferior sagittal sinus to form the straight sinus which then joins the confluence of sinuses.