Embolic stroke of undetermined source

Embolic Stroke of Undetermined Source (ESUS) is a type of ischemic stroke characterized by the presence of an embolus that obstructs blood flow to the brain, where the original source of the embolus remains unidentified after thorough evaluation. ESUS represents a diagnostic challenge and a distinct clinical entity within the broader category of strokes, emphasizing the need for comprehensive diagnostic strategies to identify potential sources of embolism that are not detected by standard stroke work-up procedures.

Definition

The concept of ESUS was introduced to categorize patients with ischemic strokes that are thought to be embolic in nature but lack a definitive source despite extensive investigation. This includes the absence of significant atherosclerosis in the arteries supplying the brain, no major-risk cardiac sources of embolism (such as atrial fibrillation), and no other specific causes of stroke (e.g., vasculitis, dissection, hypercoagulable states) identified.

Epidemiology

ESUS accounts for a significant proportion of ischemic strokes, with estimates suggesting that it constitutes about 17% to 30% of all cases. It tends to occur in a slightly younger population compared to other types of stroke, with a median age of onset in the late 60s. Both genders are equally affected.

Pathophysiology

The pathophysiology of ESUS is not fully understood, given its definition as a stroke of undetermined source. However, it is believed that emboli that cause ESUS may originate from subclinical cardiac sources, aortic plaques, or other unidentified factors that lead to the formation of blood clots that travel to the brain.

Clinical Presentation

Patients with ESUS present with symptoms similar to other types of ischemic stroke, which may include sudden onset of weakness or numbness on one side of the body, difficulty speaking or understanding speech, vision problems, dizziness, and imbalance. The severity and duration of symptoms can vary widely.

Diagnosis

The diagnosis of ESUS requires the exclusion of known causes of ischemic stroke. This involves a comprehensive evaluation including brain imaging (typically with MRI or CT scans), vascular imaging to assess for significant stenosis or occlusion in the arteries supplying the brain, cardiac monitoring to rule out atrial fibrillation, and other tests as indicated to exclude specific causes of stroke.

Management

Management of ESUS focuses on secondary prevention of future strokes. This may include antiplatelet therapy (e.g., aspirin) or anticoagulant therapy, depending on the patient's risk profile and the discretion of the treating physician. Lifestyle modifications and control of stroke risk factors, such as hypertension, diabetes, and hyperlipidemia, are also important.

Prognosis

The prognosis of ESUS varies, with a risk of recurrent stroke that is estimated to be about 4.5% per year. The risk of recurrence and other complications depends on the underlying risk factors and the effectiveness of secondary prevention strategies.

Research Directions

Ongoing research aims to better understand the underlying causes of ESUS and to identify more effective strategies for prevention and management. This includes the investigation of novel anticoagulants, the role of patent foramen ovale closure, and the identification of subclinical atrial fibrillation or other potential sources of embolism.