The underlying cause of nearly 60% of migraine patients is foramen ovale. The foramen ovale is an important passage between the right and left ventricles during fetal life and gradually closes after birth as the pressure between the right and left ventricles changes. If it does not close after one year of age, it is called foramen ovale. A shunt from the left atrium to the right atrium can occur. Most patients with migraine are born with a dislodged lower extremity vein thrombus that enters the right atrium with the blood flow, and the embolus passes through the foramen ovale into the left atrium and then into the left ventricle-aorta-intracranial vessels. This tiny embolus is the main cause of headache. Therefore, patients with headache should be carefully monitored for the presence of an unclosed disorganized foramen ovale. Transesophageal ultrasound can be performed in cases where transthoracic ultrasound does not show well.