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A cerebral aneurysm is a weak spot on the wall of an artery in the brain that can balloon out and burst. Most aneurysms are silent until they begin to bleed - causing a stroke - or grow to a size that pushes on a nerve or the surrounding brain.
Bleeding from a brain aneurysm is a life-threatening emergency, requiring complex medical and surgical skills to increase the chances of recovery.
About 10 million people have a brain aneurysm in the United States each year and about 15,000 people die from their aneurysms. Neurosurgeons (physicians who specialize in surgery of the nervous system) at the Institute are specialists in the surgical treatment of aneurysms. Visit Frequently Asked Questions about Brain Aneurysms for more information.
The longer an aneurysm goes without treatment, the more likely it is to rupture. If it bursts, blood will spread over the brain, causing potentially life-threatening damage. Nearly 40% of the people who have a ruptured brain aneurysm die. An aneurysm is an emergency that should be treated within 24 hours if possible. If an aneurysm begins to bleed once, it is likely to start bleeding again - there's a 20% chance that it will do so within two weeks.
There are two basic approaches to treating an aneurysm:
- The traditional approach, which involves making a window in the skull to repair the aneurysm by surgically clipping it
- Coil embolization, which is threading a small tube into the aneurysm through an artery in the brain and packing the aneurysm with platinum coils.
Traditional Surgical Treatment for a Cerebral Aneurysm
With this approach, surgery is done to clip the aneurysm. First a window is made in the skull. This is called a craniotomy. This allows the surgeon to get inside the skull to find the aneurysm. Aneurysms usually occur just under the brain or between the lobes of the brain. It isn't usually necessary to cut into the brain to remove the aneurysm.
Once the aneurysm is exposed and dissected, a small, hinged aneurysm clip is placed on the neck of the aneurysm to seal off the weakened part of the artery.
For small aneurysms, this surgery can be done safely with a relatively low risk (about 5%) of complications. The risks are greater - 30% or more - for aneurysms that are complex, an inch or larger or located in the back part of the brain.
Sometimes more complex surgery, such as cerebral artery bypass or deliberate cardiac standstill are needed for more complex aneurysms.
Coil Embolization to Treat Cerebral Aneurysms
With this approach, small platinum coils are placed into the bulge of the aneurysm to seal it off while preserving the normal blood flow of the artery.
This procedure does not require a craniotomy or any incision on the head. The procedure is done in a radiology suite where angiograms are done. It is done under general anesthesia.
During the procedure, a small tube is placed through an artery in the groin. The tube is advanced up to the arteries in the neck. Another smaller tube is threaded through the first one. Small platinum coils are delivered to the aneurysm through the second tube. They block off the ballooned part of the artery. The normal opening of the artery is left clear.
Although this treatment may successfully cure the aneurysm, there are, as in surgery risks to the procedure including risks of complications such as stroke or aneurysm rupture. The overall risk of any complication occurring with this procedure for small aneurysms with a small neck is typically less than 5%. However, the aneurysm's size, location and shape and complexity all affect the risks. It's important to discuss these factors with your surgeon.
Some aneurysms that have a wide neck may need a stent to help keep the coils in the aneurysm
Life After Treatment of an Aneurysm
If an aneurysm has ruptured, there are other risks even after treatment. The bleeding in the brain may set off a chain reaction that can cause complications. These include:
- Fluid build up in the brain (hydrocephalus)
This happens when the bleeding irritates the arteries of the brain, causing them to tighten or go into spasm.
The spasm makes the artery narrower. This means less blood can get through to nourish the brain. This may cause a stroke or seriously lessen the amount of blood getting to the brain cells.
Once vasospasm has been diagnosed, it may be treated. This is usually done in the intensive care unit. A large amount of intravenous fluids are given. This increases the blood volume and the blood pressure. As a result, it holds the walls of the arteries open. Likewise, the patient's blood pressure may be deliberately raised with medication to increase the blood flow to the brain.
If the vasospasm is severe, it may be necessary to do angioplasty. This is a procedure in which a balloon is used to open up the narrowed artery.
Fluid Build-Up in the Brain (Hydrocephalus)
This is a condition in which too much fluid builds up in the brain after a brain aneurysm has been bleeding.
Normally the brain makes about 500 cubic centimeters (or a little more than two cups) of cerebral spinal fluid every day. The brain absorbs that much fluid every day.
If there is bleeding from an aneurysm, however, the pathways through which the spinal fluid drains can become blocked. Less spinal fluid is absorbed. More collects in the brain.
This is usually treated by placing a tube- a ventriculostomy - inside the skull to drain off the excess fluid. If the condition doesn't get better, a permanent tube (called a shunt) is put in place that allows the fluid to drain from the brain, under the skin into the abdomen.
Blood leaking over brain tissues also increases the risk of seizures. Most patients who have ruptured aneurysms in the cerebrum (the main part of the brain) are given medicines to prevent seizures after bleeding has happened. If an aneurysm hemorrhage happens in the bottom part of the brain, below the tentorium, this may not be needed.