1920s	Contrast angiography developed.
1940s	Indicator dilution technique used to measure brain blood flow and function.
1950s	Recognition that atherosclerosis (fatty buildups of plaque in artery walls) in carotid (neck) artery could cause stroke, often preceded by transient ischemic attack (TIA) or "mini-stroke" as a warning symptom. First carotid endarterectomy performed (surgery to clean plaque deposits out of the carotid artery). Artificial heart valves introduced for patients with rheumatic heart disease. When combined with blood thinners in most patients, they lowered risk for some kinds of stroke.
1960s	Severe hypertension (high blood pressure) identified as a treatable risk factor for stroke. Start of a decline in the number of strokes (incidence) and number of people dying from stroke (mortality). Doppler ultrasonography developed (a method for evaluating blood flow in blood vessels in the neck and elsewhere).
1970s	Demonstration that aspirin is effective in preventing stroke. Development of computerized tomography (CT) scanning that allows early separation of ischemic (clot-caused) stroke from hemorrhagic (bleeding) stroke. Recognition and management of risk factors for stroke is associated with further decline in stroke deaths. PET scanning provides important information about brain metabolism.
1980s	Demonstration that early aneurysm surgery is effective in improving outcome after subarachnoid hemorrhage (bleeding into the brain). Development of MRI further improves evaluation of persons with cerebrovascular disease. Other antiplatelet agents are shown to be effective in reducing the risk of stroke. Increased emphasis on identifying the risk factors for stroke in women and minorities begins. Cigarette smoking is established conclusively as a major risk factor for stroke; cessation produces a significant risk reduction by two years, and risk becomes equal to that of nonsmokers by five years. Demonstration that treating isolated systolic hypertension in the elderly reduces stroke risk.
1990s	Carotid endarterectomy (surgery to remove atherosclerotic plaque) is proven effective in preventing stroke among patients with severe narrowing of these neck arteries. Anticoagulants (blood thinners) and aspirin are shown to be effective in lowering the risk of stroke in people with atrial fibrillation. The FDA approves the use of tissue plasminogen activator (tPA) to treat ischemic stroke in the first three hours following the onset of symptoms. tPA is one of several drugs that can dissolve the blood clots responsible for causing many strokes. Microcoils are introduced as effective treatment for brain aneurysms.
2000s	Neurogenesis (formation of new nerve cells) is an exciting experimental approach for replenishing brain cells from internal and external sources. Regenerating affected neurons may require transplantation combined with enhancing growth factors. Transplanted cells were found to differentiate into nerve cells in laboratory animals and can be functional. Significant discoveries in genetics of cerebrovascular disease show links between people who carry certain genes and their risk for certain types of stroke.