MR imaging of vascular malformations

Arteriovenous malformations (AVMs) are a congenital abnormality in which the arteries and veins on the surface of the brain or in the parenchyma connect directly without capillary vessels. The lesions comprise three components - feeding arteries, a nidus, which replaces the normal arterioles and capillaries with a low resistance high flow vascular bed, and draining veins. Histologically, the veins usually have thickened collagenous walls and appear arterialized. The pathological blood vessels are separated by brain parenchyma that often shows gliosis, hemosiderin deposition, and foci of calcification [11, 22].