an abnormal cluster of blood vessels in the brain that we call an AV malformation certain drugs like cocaine or amphetamine can cause blood vessels on the brain to rupture but hypertension is the one that that we could really make a huge difference if we controlled it so the aneurysm which you guys mentioned causes what's known as a subarachnoid hemorrhage so the aneurysms sit actually on the surface of the brain they sit in an area called the Circle of Willis that we're going to talk about in just a few minutes and when they bleed