Arteriovenous malformation

An arteriovenous malformation, or AVM, is an abnormal tangle of blood vessels in which arteries connect directly to veins without passing through a capillary bed. Removing the capillaries' resistance lets blood flow at unusually high pressure and speed, which strains the vessel walls and disrupts normal circulation nearby. AVMs are usually present from birth and most often affect the brain, though they can form in the spinal cord, lungs, kidneys, liver, or limbs. Many people carry one without symptoms, but when an AVM presses on surrounding tissue or ruptures it can cause headaches, seizures, weakness, speech trouble, numbness, or dangerous bleeding. The physicians Hubert von Luschka and Rudolf Virchow gave the first descriptions of the condition in the mid nineteenth century. Some AVMs arise alongside inherited disorders such as hereditary hemorrhagic telangiectasia, and researchers have linked certain cases to mutations in the PTEN gene. Neurosurgeons and interventional radiologists treat AVMs with surgery, embolization, or targeted radiation, chosen according to the malformation's size and location.