An asymptomatic stroke is a stroke that is asymptomatic or with symptoms that are mild enough to attract the patient’s attention. Many physicians often find some old cerebral infarct foci during CT examination of acute stroke cases, but some symptoms associated with stroke have not been present when the medical history is taken. Asymptomatic stroke is not completely asymptomatic, but should be renamed as “subclinical stroke”. Clinical manifestations: There are three types of stroke: (1) completely asymptomatic, with occasional intracerebral lesions on imaging; (2) some patients have dizziness, headache, mild limb numbness, weakness, etc.; (3) some patients have cortical damage and emotional changes, such as memory loss, inattention, cognitive decline, and even depression and anxiety. Morbidity: The incidence of subclinical stroke is 5 times higher than that of stroke. A statistic in the United States shows that one in 10 people aged 62 years or so without a history of stroke has a subclinical stroke. In China, the incidence is about 1 in 10 people over 45 years of age. Subclinical stroke is mainly caused by hypertension, diabetes, atherosclerosis and, in a few cases, chronic atrial fibrillation. Because the lesions are small and located in relatively unimportant areas of brain function, they do not present with symptoms such as hemiparesis or aphasia. However, subclinical strokes can develop into “major strokes” or symptomatic strokes if the infarcts increase in size and scope and affect important functional areas of the brain. In addition to cognitive and emotional impairment, physical dysfunction may also occur, which is tantamount to “adding insult to injury” and indeed causing great problems to the family and society. Therefore, the theme of World Stroke Day 2008 is “Small Stroke, Big Trouble” (small stroke means subclinical stroke), which aims to warn the society that prevention is the key to cerebrovascular disease and that it is important to plan ahead. Subclinical strokes share a common pathophysiological basis with most cerebrovascular diseases, so the prevention and treatment measures are basically the same as those for ischemic strokes.