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Embolic Stroke of Undetermined Source (ESUS) Criteria
Diagnostic criteria for an apparently embolic ischemic stroke without an identified source.
Embolic Stroke of Undetermined Source (ESUS) Criteria
Non-lacunar infarct on CT or MRI
No extracranial or intracranial atherosclerosis causing ≥50% luminal stenosis in an artery supplying the ischemic area
No major-risk cardioembolic source identified (e.g. atrial fibrillation, mechanical valve, intracardiac thrombus, recent MI)
No other specific cause identified (e.g. arteritis, dissection, migraine/vasospasm, drug misuse)
ResultDoes not meet ESUS criteria
At least one required criterion is not satisfied; consider an alternative or identified stroke mechanism.
When to use
- Classifying a non-lacunar ischemic stroke of otherwise unclear mechanism after a standard diagnostic work-up, to define a population for secondary-prevention research and prolonged cardiac monitoring.
Formula
ESUS is diagnosed when all of the following are present: (1) non-lacunar infarct on CT/MRI, (2) absence of ≥50% stenosis in an artery supplying the ischemic territory, (3) absence of a major-risk cardioembolic source, and (4) no other specific cause identified.
Pearls and pitfalls
- ESUS is a working diagnosis of exclusion, not a confirmed mechanism — roughly half of patients later found to have an embolic source have atrial fibrillation detected only with prolonged monitoring.
- Randomized trials of routine anticoagulation (versus antiplatelet therapy) in unselected ESUS have not shown benefit; the construct is used to guide further work-up rather than blanket anticoagulation.