The patent foramen ovale is a permanent aperture, similar to a floating membrane, remainder from fetal circulation. It can be easily diagnosed by transesophageal echocardiography and/or transcraneal Doppler with contrast. It is being described an increasing number of pathologies, where the presence of a patent foramen ovale can have pathologic significance. The paradoxical embolism considered a rare clinic curiosity, can be an underestimated cause of ischemic stroke. Patients with obstructive sleep apnea present a major prevalence of patent foramen ovale than normal population. In these patients can easily concur, at least theoretically, the basic criteria for paradoxical embolism. In this study, we revised the pathologic implications that can derive from this association.