Brain embolism is a dynamic process with variable characteristics.

Abstract

Embolism is recognized today as one of the main mechanisms causing ischemic brain injury. Emboli arise from many sources and in different circumstances such as atherosclerosis of the cervicocranial arteries, fat embolism syndrome, and coronary artery bypass graft surgery. Despite its importance and frequent clinical recognition, embolism remains relatively poorly understood, and its characteristics and effects on brain perfusion often are unknown. In addition, the intravascular process in brain embolism remains poorly imaged. The main historical reason for this relative paucity of knowledge was the lack of technologies that enabled detection of emboli in vivo, and assessment of their effects on the brain. This review focuses on the intravascular process of brain embolism rather than its effects on brain tissue. Based on data from selected techniques and clinical observations, it presents evidence that brain embolism is a dynamic process with some characteristics that can be assessed. Clinical experience often leaves physicians with the impression that brain embolism is a one-time event. If a patient presents to the emergency room with a sudden and focal neurologic deficit and atrial fibrillation, “embolus to the middle cerebral artery stem” is often diagnosed and is supported by neuroimaging data. Although a one-time event may very well be the pattern of embolism underlying a specific brain ischemic incident, symptomatic events may represent only the “tip of the iceberg.” Asymptomatic embolism occurs frequently between symptomatic events and often does not lead to clinically recognized or silent brain ischemia. Data from several fields of cerebrovascular research support the concept that embolism is a dynamic process with asymptomatic and symptomatic events. ### Asymptomatic retinal embolism. Asymptomatic embolism is often detected in arteries of the retinal circulation during routine funduscopic examination. Emboli composed of cholesterol, platelet-fibrin, calcium and other materials can be seen on funduscopic examination in 1.4% of the general population.1 …