Stroke is a syndrome characterized by the acute onset of a neurologic deficit that persists for at least 24 hours, reflects focal involvement of the central nervous system, and is the result of a disturbance of the cerebral circulation. Stroke is the third most common cause of death in the United States and the most common disabling neurologic disorder.

Stroke incidence is defined by the number of first cases of stroke over a defined time interval in a defined population, whereas stroke prevalence measures the total number of cases, new and old, at a particular time also in a defined population. Stroke incidence estimations depend on whether the data are gathered clinically, by CT, or at autopsy and whether the study is hospital or population based.

Stroke accounts for about 10% of all deaths in most industrialized countries, and most of these deaths are among persons over the age of 65. The average age-adjusted stroke mortality in the United States is 50 to 100 per 100,000 population per year. About 750,000 new strokes occur and about 150,000 people die from stroke in the United states each year.

The strongest determinant of stroke is age. Stroke is less common before age 40, but stroke in young adults is of growing concern because of the impact of early disability. About two-thirds of all strokes occurring in those over age 65 years, and is somewhat higher in men than in women and in African-Americans than in whites. A vascular etiology may be inferred from the acute onset of symptoms and often from the patient's age, the presence of risk factors for stroke, and the occurrence of symptoms and signs referable to the territory of a particular cerebral blood vessel. When this is confirmed by imaging studies, further investigations can be undertaken to identify a specific cause