section_path: Causes/Embolic stroke
section_name: Embolic stroke
paragraph_text: Embolic stroke
  
  An embolic stroke refers to an arterial embolism (a blockage of an artery) by an embolus, a traveling particle or debris in the arterial bloodstream originating from elsewhere. An embolus is most frequently a thrombus, but it can also be a number of other substances including fat (e.g., from bone marrow in a broken bone), air, cancer cells or clumps of bacteria (usually from infectious endocarditis).
  
  Because an embolus arises from elsewhere, local therapy solves the problem only temporarily. Thus, the source of the embolus must be identified. Because the embolic blockage is sudden in onset, symptoms are usually maximal at the start. Also, symptoms may be transient as the embolus is partially resorbed and moves to a different location or dissipates altogether.
  
  Emboli most commonly arise from the heart (especially in atrial fibrillation) but may originate from elsewhere in the arterial tree. In paradoxical embolism, a deep vein thrombosis embolizes through an atrial or ventricular septal defect in the heart into the brain.
  
  Causes of stroke related to the heart can be distinguished between high- and low-risk:
  
  Among those who have a complete blockage of one of the carotid arteries, the risk of stroke on that side is about one percent per year.
  
  A special form of embolic stroke is the embolic stroke of undetermined source (ESUS). This subset of cryptogenic stroke is defined as a non-lacunar brain infarct without proximal arterial stenosis or cardioembolic sources. About one out of six cases of ischemic stroke could be classified as ESUS.