Stroke is the fourth leading cause of death and the leading cause of long-term disability among adults in the United States. An estimated 7,000,000 Americans older than 20 years of age have experienced a stroke. Each year approximately 795,000 individuals experience a stroke; approximately 610,000 are first attacks and 185,000 are recurrent strokes.
Women have a lower age-adjusted stroke incidence than men. However, this is reversed in older ages; women over 85 years of age have an elevated risk compared to men. Compared to whites, African Americans have twice the risk of first-ever stroke; rates are also higher in Mexican Americans, American Indians, and Alaska Natives. he incidence of stroke increases dramatically with age, doubling in the decade after 65 years of age. Twenty-eight percent of strokes occur in individuals younger than 65 years of age. Between 5% and 14% of persons who survive an initial stroke will experience another one within 1 year; within 5 years stroke will recur in 24% of women and 42% of men. Current data reveal that stroke incidence has been declining in recent years in a largely white adult cohort. he incidence of stroke deaths is greater than 143,000 annually, and strokes account for 1 of every 18 deaths in the United States. he type of stroke is significant in determining survival. Of patients with stroke, hemorrhagic stroke accounts for the largest number of deaths, with mortality rates of 37% to 38% at 1 month, whereas ischemic strokes have a mortality rate of only 8% to 12% at 1 month. Survival rates are dramatically lessened by increased age, hypertension, heart disease, and diabetes. Loss of consciousness at stroke onset, lesion size, persistent severe hemiplegia, multiple neurological deficits, and history of previous stroke are also important predictors of mortality.1,2 Stroke is the leading cause of long-term disability in the United States. Of ischemic stroke survivors 65 or older, incidences of disabilities observed at 6 months include hemiparesis (50%), unable to walk without assistance (30%), dependent in activities of daily living (ADL) (26%), aphasia (19%), and depression (35%). Stroke survivors represent the largest group admitted to rehabilitation hospitals and about a third of patients receive outpatient rehabilitation services. Another indicator of disability is the fact that approximately 26% of patients with stroke are institutionalized in a long-term care facility. Direct and indirect costs of stroke are in the billions. Atherosclerosis is a major contributory factor in cerebrovascular disease. It is characterized by plaque formation with an accumulation of lipids, fibrin, complex carbohydrates, and calcium deposits on arterial walls that leads to progressive narrowing of blood vessels. Interruption of blood flow by atherosclerotic plaques occurs at certain sites of predilection. hese generally include bifurcations, constrictions, dilations, or angulations of arteries. he most common sites for lesions to occur are at the origin of the common carotid artery or at its transition into the middle cerebral artery, at the main bifurcation of the middle cerebral artery, and at the junction of the vertebral arteries with the basilar artery
Ischemic strokes are the result of a thrombus, embolism, or conditions that produce low systemic
perfusion pressures. The resulting lack of cerebral blood flow (CBF) deprives the brain of needed oxygen and glucose, disrupts cellular metabolism, and leads to injury and death of tissues. A thrombus
results from platelet adhesion and aggregation on plaques. Cerebral thrombosis refers to the formation
or development of a blood clot within the cerebral arteries or their branches. It should be noted that
lesions of extracranial vessels (carotid or vertebral arteries) can also produce symptoms of stroke. Thrombi lead to ischemia, or occlusion of an artery with resulting cerebral infarction or tissue death (atherothrombotic brain infarction [ABI]). Thrombi can also become dislodged and travel to a more distal site in the form of an intra-artery embolus. Cerebral embolus (CE) is composed of bits of matter (blood clot, plaque) formed elsewhere and released into the bloodstream, traveling to the cerebral arteries where they lodge in a vessel, producing occlusion and infarction. The most common source of CE is disease of the cardiovascular system. Occasionally systemic disorders may produce septic, fat, or air emboli that affect the cerebral circulation. Ischemic strokes may also result from low systemic perfusion, the result of cardiac failure or significant blood loss with resulting systemic hypotension. The neurological deficits produced with systemic failure are global in nature with bilateral neurological deficits. Hemorrhagic strokes, with abnormal bleeding into the extravascular areas of the brain, are the result of rupture of a cerebral vessel or trauma. Hemorrhage results in increased intracranial pressures with injury to brain tissues and restriction of distal blood flow. Intracerebral hemorrhage (IH) is caused by rupture of a cerebral vessel with subsequent bleeding into the brain. Primary cerebral hemorrhage (nontraumatic spontaneous hemorrhage) typically occurs in small blood vessels weakened by atherosclerosis producing an aneurysm. Subarachnoid hemorrhage (SH) occurs from bleeding into the subarachnoid space typically from a saccular or berry aneurysm affecting primarily large blood vessels. Congenital defects that produce weakness in the blood vessel wall are major contributing factors to the formation of an aneurysm. Hemorrhage is closely linked to chronic hypertension. Arteriovenous malformation (AVM) is another congenital defect that can result in stroke. AVM is characterized by a tortuous tangle of arteries and veins with agenesis of an interposing capillary system. he abnormal vessels undergo progressive dilation with age and eventually bleed in about 50% of cases. Sudden and severe cerebral bleeding can result in death within hours, because intracranial pressures rise rapidly and adjacent cortical tissues are compressed or displaced as in brainstem herniation.
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