When an arteriovenous malformation occurs, the process in which arteries and veins transport blood between the heart and brain malfunctions, and jumbled blood vessels redirect the blood from the arteries to the veins, thereby circumventing other tissue, explains Mayo Clinic. Normally arteries carry oxygen-rich blood to the brain, while veins carry oxygen-depleted blood away from the brain, both using smaller blood vessels to slow down flow. But in an arteriovenous malformation, the smaller vessels are lacking; blood flows too fast.
During an arteriovenous malformation, the blood vessels may widen, says the American Heart Association. The scrambled network of blood vessels tends not to change too much, although some may reduce in size because of clots. Others may grow larger in order to redirect blood in surrounding vessels to the network. Symptoms accompanying an arteriovenous malformation include hemorrhaging, seizures, head pain due to greater blood flow, and problems with speech, vision and movement.
An arteriovenous malformation may bleed when fragile blood vessels burst because arteries succumb to high blood pressure, notes the American Heart Association. There is potential for brain damage and strokes, even death, accompanying a bleed. In the event of temporary or permanent damage, symptoms may result in terms of weak arms and legs, paralysis, speech difficulties, and vision or memory problems. The extent of brain damage varies due to the individual blood leakage from the arteriovenous malformation.