A 43-year-old man was admitted for right upper and lower limb weakness and aphasia. He had suffered dizziness and transient blindness 6 months ago and had also been found lying in the bathroom on another occasion. Multiple cerebral infarctions were confirmed by brain CT scan and MRI. Diffuse nodes in the mediastinum and postperitoneum had been found in pulmonary CT scans and MRI scans since 1999. Pulmonary CT scan revealed multiple bilateral pneumatoceles in the lungs. Contrast CT scan showed an enlarged azygos vein on the right side of the spinal column and an enlarged azygos arch. CT scan-guided biopsy revealed a few fibers, fat, and vascular tissues in the mass. Transcranial Doppler bubble test showed gas microembolic signals in both middle cerebral arteries. Pulmonary digital subtraction angiogram confirmed an enlarged azygos vein. A fistula was found between the pulmonary and azygos veins with turbulent flow from pulmonary to azygos at rest. Cavography revealed that the pulmonary vein appeared simultaneously with the superior cava vein during Valsalva maneuver. In summary, the pathway of cerebral embolism was based on three pathologic mechanisms: (1) increased inferior vena cava pressure, (2) enlarged right azygos aneurysm, and (3) the presence of a fistula between the azygos and pulmonary veins.