Dipal Krishna Adhikary

A Giant Arteriovenous Malformation Involving Tongue, Neck and Face

Vascular malformations result from abnormal-sized vascular structures or an abnormal number of vascular structures. Vascular anomalies are a diffuse collection of vascular abnormalities that are present at birth or soon after. Historically the terminology has been complicated, descriptive, difficult to understand and a barrier to communication between specialties. The International Society for the Study of Vascular Anomalies (ISSVA) was founded after 16 years of biennial meetings with the primary goal of improving the understanding of these abnormalities. ISSVA adopted the biological classification system developed by Mulliken & Glowacki published in 1982.1 This classification differentiated vascular anomalies due to their endothelial cell characteristics and clinical behaviour. It simply distinguished two main types of vascular anomalies: vascular tumours (grow by cellular mainly endothelial hyperplasia) and vascular malformations (localised defects in vascular morphogenesis caused by dysfunction in embryogenesis and vasculogenesis). All AVMs are present at birth, but they are not always clinically evident. Although the pathogenetic mechanisms of AVMs are not completely understood, the hemodynamic alterations that lead to the clinical manifestations of AVMs have been described well. An abnormal communication causes shunting of blood from the high-pressure arterial side to the low-pressure venous side. This creates an abnormal low-resistance circuit that steals from the high-resistance normal capillary bed.