Figure 1.

Classification of AVM angioarchitecture as proposed by Yakes et al. [17]; A = arterial vasculature (red), V = venous vasculature (blue); Type I: direct arteriovenous fistula. Type II: multiple inflow arteries into a nidus pattern with direct artery/arteriolar to vein/venular structures that may, or may not, be aneurysmal. Type IIIa: multiple arteries/arterioles into an enlarged aneurysmal vein with an enlarged outflow vein. Type IIIb: multiple arteries/arterioles into an enlarged aneurysmal vein with multiple dilated outflow veins. Type IV: innumerable micro-AV connections infiltrating an entire tissue.