[Ten key messages regarding embolic stroke of undetermined source and cryptogenic stroke]

Cryptogenic stroke is a cerebral infarction where no source of cardioembolic events, no microangiopathy with lacunar infarcts, and no macroangiopathy with high-grade stenosis of the cerebral arteries can be detected. However, cryptogenic stroke is not operationally defined. The new concept of the embolic stroke of undetermined source (ESUS) is defined as a nonlacunar stroke in cerebral imaging and exclusion of significant stenosis of the cerebral arteries by angiographic or ultrasound techniques. Cardiac embolic sources must be excluded by ECG monitoring and echocardiography. At the moment, secondary prevention in patients with ESUS is performed with acetylsalicylic acid. The question of whether non-vitamin K oral anticoagulants (NOAK) are effective in these patients for secondary prevention is currently being investigated in randomized trials. The acute treatment of cryptogenic stroke/ESUS does not differ from other stroke subtypes because the stroke etiology is often not known initially, but can be identified during the course of treatment in the stroke unit.