The challenge of mixed cerebrovascular disease.

Stroke in general, and ischemic stroke in particular, are routinely defined using clinical criteria. Incorporating brain imaging and neuropathological findings into an expanded conceptual definition of stroke will result in a vastly increased prevalence of the disease. The resultant category of mixed cerebrovascular disease thus may include subclinical infarct, cerebral white matter disease, and cerebral microbleeds. Subclinical brain infarcts occur five times more frequently than does clinical ischemic stroke. Abnormalities of cerebral white matter are present in more than 95% of the population over the age of 65 years, and magnetic resonance imaging evidence of cerebral microbleeds is found in at least 18% of the population, beginning at the age of 60 years. Pathologic evidence supports at least a partial microvascular origin for cerebral white matter disease and cerebral microbleeds. Emphasizing mixed cerebrovascular disease as a conceptual framework allows for a focus on common underlying mechanisms and new therapeutic strategies.