Figure 5. Components of the pathogenic mechanism of paradoxical brain embolism.

Two major conduits allow venous-originated emboli to reach the cerebral circulation: cardiac and transpulmonary. The source of embolism, on the other hand, can be located anywhere in the venous structures of the pelvis and lower extremities. In this regard, the gray circle points to the typical location of May-Thurner iliac arteriovenous anomalies, an important risk factor for thromboembolism. See text for expanded discussion. AVMs, arteriovenous malformations; IVC, inferior vena cava; R -> L, right-to-left.