This study seeks to determine the clinical characteristics of young ESUS patients using diagnostic criteria of the Cryptogenic Stroke / ESUS International Working Group, and to determine the rates of stroke recurrence, death, and hospital readmission in a contemporary cohort of young ESUS patients during follow-up of up to 18 months.

Inclusion Criteria:

1. Embolic stroke of undetermined source (ESUS) within 60 days, defined as:

   1. Recent ESUS (including transient ischemic attack with positive neuroimaging) visualized by brain computed tomography (CT) or magnetic resonance imaging (MRI) that is not lacunar (i.e., lacunar infarcts are subcortical infarcts ≤ 1.5 cm in the territory of middle cerebral artery or pons; infarcts involving the cerebellum or lateral medulla are not considered as lacunar infarcts). Patients with multiple simultaneous acute lacunar infarcts on diffusion weighted imaging may be included. In case of embolic large artery occlusions clearly documented on angiography who undergo successful recanalization, visualization of infarct on neuroimaging is not mandated, and
   2. Absence of cervical carotid atherosclerotic stenosis (or vertebral and basilar atherosclerotic stenosis in case of posterior circulation stroke), that is >50%, or occlusion in arteries supplying the area of ischemia, (unless deemed embolic) in CT or magnetic resonance (MR) angiography or conventional angiography or ultrasound, and
   3. No history of atrial fibrillation (AF), no documented AF on 12-lead electrocardiogram or episode of AF lasting 6 minutes or longer detected after ≥ 24-hour cardiac rhythm monitoring (Holter or telemetry; at least 20 hours acceptable), and
   4. No intra-cardiac thrombus on either transesophageal or transthoracic echocardiography, and
   5. No other specific cause of stroke identified by routine clinical care (e.g., arteritis, dissection, migraine/vasospasm, drug abuse)

2. Age ≥ 21 to ≤ 50 years

3. Written informed consent with local regulations governing research in human subjects

Exclusion Criteria:

1. Close affiliation with the investigational site; e.g. a close relative of the investigator, dependent person (e.g., employee or student of the investigational site)
2. Enrollment in an investigational study on ESUS
3. If imaging of intracranial arteries are performed by CT or MR angiography, digital subtraction angiography or transcranial Doppler: >50% luminal stenosis or occlusion in arteries supplying the area of ischemia (unless deemed embolic)

Patients presenting to hospital-based stroke unit with an ESUS Stroke