SummaryParadoxical embolism is a possible cause of ischemic stroke, particularly in younger patients without any other cause, i.e. cryptogenic stroke, and a patent foramen ovale is the most frequently assumed cause. The contrast transcranial Doppler monitoring mode has a sensitivity that is comparable to contrast transesophageal echocardiography for detection of a right-to-left shunt, however, the contrast transesophageal echocardiography remains the “golden standard” for the detection of a patent foramen ovale. Diagnostic studies that can identify a patent foramen ovale may be considered for prognostic purposes. In most cases, however, it is difficult to establish a firm etiological association and the debate about medical or interventional management is ongoing. Other possible causes of right-to-left shunting leading to cerebral complications like pulmonary arteriovenous malformations have also been noted but are rarely discussed.