Brain-to-Brain Paradoxical Embolism through Patent Foramen Ovale after Cerebral Vein Thrombosis

agulation factors were found; in particular, we searched for MTHFR mutation, prothrombin G20210A mutation and factor V Leyden mutation, and none was found. He was treated with intravenous heparin (5,000 IU bolus, followed by continuous infusion of 1,000 IU/h), with complete resolution of symptoms. Color-coded duplex sonography of the cervical arteries showed no carotid or vertebral disease, and arterial transcranial Doppler ultrasound was unremarkable. A venous color-Doppler of the legs did not show the presence of venous thrombosis, yet it cannot completely exclude this condition. A second cerebral MRI and MRA examination showed partial recanalization of transverse and sigmoid sinuses, and the persistence of thrombosis of sagittal sinus. Then the patient was discharged with oral anticoagulants (warfarin) with a suggested International Normalized Ratio interval of 2–3. After 10 months, warfarin was stopped and replaced with aspirin, 100 mg, because of the occurrence of bilateral spontaneous subdural hematoma. Two months later he was admitted again to our Stroke Unit for sudden onset of vertigo, nausea, vomiting and cerebellar ataxia. Neurological examination showed horizontal nystagmus and dysmetria of the right limbs. The acute cerebral CT scan was normal, while a CT scan, performed after 48 h, showed a right cerebellar infarction with mass effect. MRI confirmed the presence of the recent right cerebellar ischemic infarction, associated with other recent bilateral temporal and occipital small Dear Sir, Patients with right-to-left shunt due to patent foramen ovale (PFO), especially if associated to atrial septal aneurysm, are at increased risk of stroke [1–5] . Although there are many possible mechanisms of stroke in these subjects (in situ formation of thrombus, atrial vulnerability, other comorbidities), paradoxical embolism is thought to be one of the most important causes of stroke, yet difficult to be proven [6–8] . Ultrasonographic examination of the venous system as well as CT or MRA studies can identify a venous source in no more than 20% of subjects with cryptogenic stroke [7–10] . We report a case of stroke in a young man with a large PFO, in which the only source of paradoxical embolism was the presence of a recent cerebral venous thrombosis.