MEDICAL ANIMATION TRANSCRIPT: Your heart pumps blood to your brain through blood vessels in your neck. These blood vessels, called arteries, branch into even smaller arteries that bring blood to your brain cells. Some of these small arteries join each other to form a loop known as the Circle of Willis. The walls of the arteries contain special muscle and elastic layers that help them adapt to the blood pulsing through them. Sometimes diseases, injuries, or birth defects can cause a weak spot in the wall of the arteries in the Circle of Willis. These weak spots usually form where arteries branch. Over time, the pressure of blood flowing through the artery stresses the weak spot further. The constant blood pressure can cause the weak spot to balloon out and form a bulge called a cerebral aneurysm. This cerebral aneurysm is the most common type called a saccular or berry aneurysm. Over time, the aneurysm may grow and push on nearby brain tissue or nerves. Blood may also leak from the aneurysm. If its wall gets too thin, the aneurysm can burst or rupture and spill high-pressure blood into the space around your brain. The blood presses on your brain tissue and can cause injury to your brain cells. Chemicals in the escaped blood can irritate other brain arteries and cause them to narrow. As a result, your brain can swell, leading to serious brain injury. Common symptoms of a ruptured cerebral aneurysm include sudden severe headache, sometimes called a thunderclap headache, problems with your vision, such as blurred or double vision, nausea, and vomiting, a stiff or painful neck or confusion. An unruptured cerebral aneurysm may not cause symptoms but large unruptured aneurysms may cause headache and pain near or behind one eye, double or blurred vision, a drooping eyelid, and numbness or weakness on one side of your face. A ruptured cerebral aneurysm is a medical emergency. If you are having symptoms, seek immediate medical attention. If you have a ruptured cerebral aneurysm, your doctor may recommend surgical clipping or endovascular coiling. In surgical clipping, your surgeon will make an opening in your skull near your aneurysm and place a small metal clip onto the stem that connects the aneurysm to your artery. The clip blocks blood flow into your aneurysm. In endovascular coiling, your doctor will put a plastic tube called a catheter into a large artery in your groin. Using a live x-ray view, your doctor will advance the catheter through your arteries until it reaches the aneurysm. Through the catheter, your doctor will insert one or more flexible wires into your aneurysm. The wires will coil up and cause a blood clot to form inside your aneurysm, which will block off the aneurysm from the rest of your artery. In a similar manner, if you have an unruptured cerebral aneurysm, your doctor may recommend surgical clipping or endovascular coiling. In addition, if your aneurysm is small and not causing pain or other symptoms, your doctor may observe your aneurysm for a period of time before performing either of these procedures.