I. Introductory Concepts
Disorders resulting from impairment in brain circulation are the greatest single cause of neurological disability in the adult population and the third leading cause of death. "Strokes", which may be classified as ischemic or hemorrhagic, are the most common of the cerebrovascular lesions. The three major pathogenesis categories of thrombosis, embolism and hemorrhage are important because management of patients differs for each group.
Cerebrovascular disease is less prevalent in children, since atherosclerosis, hypertension and diabetes mellitus, major determinants of such disease in adults, are rare in children. A number of conditions in which stroke occurs are inherited in a classical mendelian pattern; usually stroke is only part of the phenotype. The cause of most common strokes is multifactorial and involves both genetic variants and environmental factors.
Due to its very high metabolic demands, the brain depends on a constant supply of glucose and oxygen from the circulation, and on the removal of metabolic waste, primarily in the form of carbon dioxide. Homeostatic mechanisms provide for the maintenance of adequate cerebral blood flow in the event of systemic changes in perfusion pressure, although pathological changes in the vasculature may impair these mechanisms.