ABSTRACT
Nidus is a crucial issue for diagnostic assessment of arteriovenous malformations (AVMs). This chapter supports the fact that nidus is not an angiographic terminology used only by radiologists and interventionalists but also by pathologists, geneticists, and perigenetic and biotechnology scientists. AVM is a devastating vascular malformation characterized by direct connections of dilated arteries and veins and a lack of the normal capillary system. Feeding artery, draining vein, and nidus are the three parts of the AVM lesion. Mechanisms in the formation of AVM are not yet clear. Recent studies showed that multiple pathways are involved in AVM pathogenesis rather than a single pathway. Vascular malformations could occur when there is a defect in either the early or the late phase of vascular development. This may be caused by various regulatory signaling molecules that are involved. There is a coexpression of both artery-specific genes HEY2, DLL4, and EFNB2, and vein-specific gene COUP-TFII in the endothelial cells. Simultaneous expression of these genes in the endothelial cells of the nidus could be a cause for the deregulation of artery-vein developmental determination in AVM.
