Remember as a child sneaking up on your friends with a loaded water balloon and blasting them? Some say that no experience matches that childhood satisfaction. But of course, on rare occasion the water balloon would surprise you before you could throw it, bursting prematurely and drenching you instead of your target—major bummer! Now imagine if that unpredictable weapon were actually inside your body. That’s essentially what happens if you have a not uncommon, but sometimes dangerous condition called an aneurysm.
WHAT IS AN ANEURYSM?
Aneurysms, in general, are weaknesses in the sides of arteries, the tubes of muscle that carry blood from the heart to the rest of the body. For some unknown reason, the muscle on one side of an artery is sometimes thinned, causing it to expand with time, like inflating a balloon. Because the blood flowing through the artery is under pressure, the wall of the artery billows out, forming a blister or bleb. If we harken back to childhood, we may recall a worn bicycle tire through which the innertube has protruded.
Aneurysms infrequently cause problems—or even symptoms—while they are bulging (although they can occasionally cause trouble by pressing on surrounding tissues). The real danger is that without warning the aneurysm wall can become weak and burst, causing sudden bleeding (hemorrhage).
WHERE DO ANEURYSMS OCCUR?
Although aneurysms can occur on arteries anywhere in the body, among the most common and most dangerous are those that crop up on arteries in the brain. When a brain aneurysm bursts, the brain experiences a sudden blast of pressure and blood spills into the surrounding spinal fluid. (This process is referred to as subarachnoid hemorrhage.) This blast of pressure has the same effect as hitting one’s head on the windshield in a high-speed car accident. Needless to say, the fragile brain tissue can be severely injured. Of all of our body tissue, the brain’s has the least ability to recover from such an injury.
Because of the sudden and severe damage it causes, the rupture of a brain aneurysm is often thought of as a brain attack. It is also a form of stroke (though not the most common form). About half of the people who have a brain aneurysm that ruptures die immediately, similar to the mortality from a heart attack. Most of the rest don’t live long enough to leave the hospital, despite the best available treatment, as is the case with most severe brain injuries. Some persist in a coma before passing away from complications weeks or months later. Nevertheless, some people with ruptured aneurysms survive with the aid of modern treatment and return to live in the community. Unfortunately, only a handful of these patients achieve recovery similar to their condition before the aneurysm burst.
HOW COMMON ARE ANEURYSMS?
It turns out that brain aneurysms (also called cerebral aneurysms) are relatively rare, and those that burst are even more rare; however, estimates are that if you’re at a party with 100 people, there’s a good chance that one of you has an aneurysm in your brain. Fortunately, not all aneurysms rupture, and many people die of other causes before their aneurysm ever has a chance to burst (and often without ever knowing they have one).
To get technical, if you are that one person at the party with the aneurysm, the statistical chance that it will rupture before something else gets you depends on how many more years you are expected to live (given your age and state of health). It is possible for the aneurysm to burst any time, though, and without much warning.
Nevertheless, this does not mean that we should all run to our doctors to get tests to see if we have an aneurysm. First, the tests are not hazard-free, and second, the risk of aneurysm is still relatively small— about equal to the risk of being killed today in a car accident. It is much more likely for each of us to face other varieties of vascular illness, such as a heart attack or other types of stroke.
HOW ARE ANEURYSMS TREATED?
When an aneurysm bursts and the person survives long enough to get to a hospital, doctors are faced with two problems that could result in the patient’s death or severe disability: 1) the aneurysm could burst again at any moment, making the brain injury worse; and 2) the brain tissues—through a complex response to blood within the brain—can close off further blood supply, causing the brain to die from lack of oxygen.
Unfortunately, despite considerable progress in recent years, treatment is often less successful than one would hope. The principle member of the treatment team is a neurosurgeon (a surgeon trained especially in the treatment of diseases of the brain and spine), with important input from neurologists (physicians who specialize in the non-surgical treatment of the brain and spine), and many highly skilled doctors and nurses in the emergency department, intensive care unit (ICU), radiology department and operating room.
The initial and most important objective is to prevent re-rupture of the aneurysm, which would virtually assure coma or death. Until recently, this goal could be achieved only by having the neurosurgeon perform an operation on the brain to place a metal clip on the aneurysm. Now, it is increasingly possible to have a specially trained radiologist (called a neuro-interventional radiologist) place a small tube through an artery in the leg, guide it to the arteries in the brain, deposit small metal coils from the inside, and block off the blister so it cannot burst again. Neither treatment is successful 100 percent of the time and neither is without significant risks, although the procedure performed by the radiologist (called coil embolization) is less invasive. But that does not mean it’s not dangerous or that it’s always the best choice for treatment. The neurosurgeon and the neuro-interventional radiologist must collectively decide the best recommendation for each particular case.
Once the aneurysm is treated to prevent it from bursting again, the treatment team then faces the big killer for those who survive the initial rupture and treatment— vasospasm (literally squeezing vessels). This is a lessthan-well-understood phenomenon whereby the blood spilled around the rupture causes the arteries in the brain to tighten or constrict abnormally. This response does not occur universally, and when it does, it may occur Cutaway-view of the head showing the view of an artery of the brain with an aneurysm. Aneurysms are typically about the size of the fingernail on your small finger. several days after the rupture, when the patient has been initially stabilized in the ICU. If the arteries suddenly begin to constrict, inadequate amounts of blood reach the cells of the brain, causing them to die and ushering in a new danger.
The brain is particularly vulnerable when it receives inadequate blood supply, especially if it has already been injured by the bursting of an aneurysm. Unfortunately, treatment for vasospasm is not very successful. Most of it occurs in the ICU under the direction of the neurosurgeon, who is assisted by other physician consultants. Intravenous fluids and medications are administered and many sophisticated monitors are used, but frequently vasospasm causes the patient’s death or severe disability. Occasionally, the neuro-interventional radiologist can place a tube through the artery in the leg, reach the arteries in the brain from the inside, and open the constriction with a small inflatable balloon on the end of the tube. However, this treatment is not only risky, but is also frequently only temporary, and constriction of the arteries generally recurs.
The outcome of any burst aneurysm is largely determined by the condition the patient is in when he or she arrives at the hospital. If the person is in a deep coma, a successful recovery is much less likely. On the other hand, if the person arrives in good shape, there are no guarantees, but chances are better.
by E. Thomas Chappell, MD
Dr. Chappell is a neurosurgeon with 20 years serving primarily underserved populations throughout California. He has been a professor of neurosurgery at the Universities of California at Sacramento, San Diego and Irvine.