The normal function of the brains control centers depends on the adequate supply of oxygen and nutrients through a dense network of blood vessels. Blood is supplied to the brain, face, and scalp through two major sets of vessels: the left and right common carotid arteries and the left and right vertebral arteries. The common carotid arteries have two divisions. The external carotid arteries supply the face and scalp with blood. The internal carotid arteries supply blood to the majority of the anterior portion of the cerebrum. The vertebrobasilar arteries supply the posterior two-fifths of the cerebrum, part of the cerebellum, and the brain stem.
Any decrease in the blood flow through one of the internal carotid arteries brings about some impairment in the function of the frontal lobes. This impairment might result in numbness, weakness, or paralysis on the side of the body opposite to the obstruction of the artery. Occlusion of one of the vertebral arteries can cause many serious implications, which range from blindness to paralysis. Circle of Willis – In the base of the brain, the carotid, and vertebrobasilar arteries form a circle of communicating arteries known as the Circle of Willis. From this circle, other arteries anterior cerebral artery, the middle cerebral artery, the posterior cerebral artery arise and travel to all portions of the brain.
Posterior Inferior Cerebellar Arteries, which branch from the vertebral arteries, aren’t shown. Since the carotid and vertebrobasilar arteries form a circle, if one of the main arteries is occluded, the distal smaller arteries that it supplies can receive blood from the other arteries. Anterior Cerebral Artery – The anterior cerebral artery extends upward and forwards from the internal carotid artery. Stroke in the anterior cerebral artery results in opposite leg weakness. The artery supplies a part of the frontal lobe and the lateral surface of the temporal and parietal lobes, including the primary motor and sensory regions of the face, throat, hand, and arm, and in the dominant hemisphere, the areas for speech.
The middle cerebral artery is the artery most frequently occluded in stroke. Posterior Cerebral Artery – The posterior cerebral arteries stem in most people from the basilar artery, but sometimes originate from the homolateral internal carotid artery. The posterior arteries supply the temporal and occipital lobes of the left cerebral hemisphere and the right hemisphere. When infarction occurs in the territory of the posterior cerebral artery, it’s usually secondary to embolism from lower segments of the vertebral-basilar system or heart. Clinical symptoms associated with occlusion of the posterior cerebral artery depend on the position of the occlusion and might include thalamic syndrome, thalamic perforate syndrome, Weber’s syndrome, contralateral hemiplegia, hemianopsia and a wide range of other symptoms, including color blindness, failure to see to fro movements, verbal dyslexia, and hallucinations.