Although there has been increasing interest in the association between cancer and cerebrovascular disease, the underlying pathophysiology of stroke in cancer patients is still not fully understood. The aim of this study is to investigate the stroke mechanisms in patients with cancer-associated stroke.

Patients with cryptogenic embolic stroke will be prospectively enrolled and categorized into two groups according to the presence of active cancer: cryptogenic embolic stroke with active cancer (cancer-associated stroke) vs. without active cancer (cryptogenic embolic stroke). All patients will undergo brain MRI/MRA, 12-lead electrocardiography, transthoracic and transesophageal echocardiography with injection of agitated saline, and 24-hour Holter and/or telemonitoring. Duplex ultrasonography to detect venous thrombosis of the lower extremity will also be performed in patients with a positive right-to-left shunt on echocardiography.

Inclusion Criteria:

• Subjects with acute ischemic stroke who presented within 7 days from symptom onset
• Subjects who had embolic infarction outside the perforator territory revealed by diffusion-weighted imaging
• Subjects with undetermined cause of stroke despite of initial evaluation including electrocardiogram and brain imaging upon admission
• Subjects who performed brain magnetic resonance image (MRI) and MR angiography (MRA), cardiac work-ups (12-lead electrocardiography, transthoracic and/or transesophageal echocardiography with injection of agitated saline (or agitated saline transcranial Doppler monitoring), and 24-hour Holter and/or telemonitoring)
• Subjects with informed consent

Exclusion Criteria:

• Subjects with single subcortical infarction
• Subjects with primary brain tumor
• Inability to perform comprehensive studies
• Refusal or withdrawal of the consent

Embolic stroke of undetermined source with or without cancer, admitted to Samsung Medical Center (tertiary hospital with comprehensive stroke and cancer center)