Impaired Cerebral Blood Flow Disorders CEREBRAL BLOOD FLOW Impaired cerebral blood flow disorders are extremely common, and factors such as the site of the lesion, existing collaterals, and the amount of tissue affected determine the actual neurological deficit that results. The alteration of blood flow can have various causes. Things like changes in blood pressure, changes in the arterial walls, and occlusions of the arterial lumen are some of the most important causes. The brain is supplied with blood by two internal carotid arteries and two vertebral arteries. These arteries form the anastomosis known as the Circle of Willis. In 1951, two researchers, McDonald and Potter, demonstrated that "the blood supply to one half of the brain is provided by the internal carotid artery and the vertebral artery of that side, and that their respective flows join in the posterior communicating artery in a point where the pressure of the two is equal and they do not mix." (Snell, p514). This is important to keep in mind when considering how significant collateral circulation really is. “If, however, the internal carotid or vertebral artery is occluded, blood passes forward or backward through that point to compensate for the reduction in blood flow. The arterial circulation also allows blood to flow across the midline, as shown when the internal artery the carotid or vertebral artery on one side is occluded." This provides some relief for occlusions in the main vascular supply. Another important finding was that the blood flowing from the two vertebral arteries remains on the same side of the lumen and does not mix as it passes through the basilar artery. These are important elements for the primary vascular supply, however, once… half of the article… the physician's focus in treating a stroke patient must be the individual patient and their underlying lesion. Cerebral blood flow deficit is not limited to the scope of patients it can afflict. The care of stroke patients is changing, and optimal management of a patient's condition requires careful consultation with a knowledgeable medical team. Works Cited: Auer, L.M. & Ladurner, G. “Alterations of the Cerebral Blood Volume,” pp 233 -38.Snell, R.S. “The Blood Supply to the Brain,” Clinical Neuroanatomy for Medical Students. Little, Brown and Co., Boston/Toronto, pp 507-24.Stern, B.J. "Cerebrovascular disease and neurological disorders of pregnancy." pp 32-34.Walton, John. "Cerebral circulation disorders", Brain diseases of the central nervous system. Oxford University Press, New York; page. 219.