Treatment of Aneurysms
Unruptured Aneurysm Embolization
What is an aneurysm?
Aneurysms are areas of a blood vessel where the wall has bulged out. Some aneurysms are smooth dilatations of the full circumference of the blood vessel (fusiform aneurysms, see Figure 1) while other aneurysms bulge outward in one direction from the blood vessel (saccular or berry aneurysms, see Figure 2). Aneurysms can occur in blood vessels supplying any part of the body. When an aneurysm affects a blood vessel supplying the brain, it can cause a stroke. Most of these aneurysms are located inside the skull (intracranial, or cerebral aneurysms) but occasionally aneurysms of blood vessels supplying the brain can form where the blood vessel is still in the chest, or neck, or at the floor of the skull. Intracranial aneurysms are more common than most people realize. Different studies have differed in their conclusions regarding incidence in the general population but many doctors believe that approximately 2% of the general population will develop a cerebral aneurysm at some point in there life.
How can aneurysms cause problems?
Not all aneurysms cause problems - many people die of other natural causes without ever even suspecting they have a brain aneurysm. Some aneurysms, however, do cause problems. The most severe problem is bleeding of the aneurysm, usually into the space surrounding the brain – the subarachnoid space. This is called subarachnoid hemorrhage, or SAH (see Figure 3). Some patients, however, learn that they have a cerebral aneurysm without the aneurysm having ever bled. Sometimes this is because the aneurysm is causing problems by pressing on a nerve or brain tissue 
so that the nerve or brain tissue does not function right. Double vision caused by an aneurysm pressing on one of the nerves controlling eye movement is one example. Unruptured aneurysms can also cause problems by causing pain, or rarely aneurysms can allow blood clots to form which then go downstream and block off small branches supplying the eye or part of the brain, causing a stroke or a mini-stroke. Finally, many patients learn they have a cerebral aneurysm after they have an imaging study such as CT or MRI for a completely different reason. These unsuspected aneurysms, which are not causing any symptoms are called asymptomatic or incidental aneurysms.
Treatment Options
Treatment options for aneurysms can include open surgery, a less invasive endovascular approach such as embolization, or sometimes simply observation. In general aneurysms that have caused symptoms are usually treated either with surgery or embolization. Asymptomatic or incidental aneurysms are sometimes treated with surgery, sometimes with embolization and also sometimes simply observed. The decision of whether to treat any particular asymptomatic aneurysm is a very complex issue because there is not good agreement on the risk of leaving asymptomatic aneurysms untreated. One study trying to address this is the International Study of Unruptured Intracranial Aneurysms (ISUIA). Any study which measures the risk of treatment – or the risk of nontreatment – of cerebral aneurysms must have a large enough series of patients, long enough follow-up and complete enough follow-up to capture all complications and management failures of either treatment or nontreatment. Many doctors believe we simply do not yet have a definitive study that answers these questions and this is one reason why there is such disagreement within the field. Still, the data that we do have suggests that the risk of leaving unruptured asymptomatic aneurysms untreated appears to be dependent on many factors, such as patient age and health, aneurysm size and shape and location, and whether the patient has had bleeding from a different aneurysm. It is also believed that tobacco smoking is a risk factor for aneurysm development and rupture and therefore most doctors will recommend that stopping smoking is particularly important for patients found to have cerebral aneurysms.
What is embolization?
If your doctor recommends treating your unruptured aneurysm, he or she may recommend an endovascular approach, most commonly “embolization” of the aneurysm with coils. Embolization is a medical term meaning to block off a blood vessel or abnormal part of a blood vessel. Embolization of different problems of the blood vessels including severe epistaxis (nosebleeds), bleeding from trauma, bleeding from tumors, aneurysms, and vascular malformations. For each of these problems an endovascular procedure can be performed, steering a catheter through the blood vessels to the abnormality and introducing materials through the catheter into the abnormality to block it off. Different blood vessel problems are blocked off with different materials; for cerebral aneurysms soft detachable coils made of platinum are most commonly used. Treatment of cerebral aneurysms with detachable coils is often described as a recent development in medicine but in fact detachable coil technology has been available (approved by the FDA) for more than 10 years. In the United States in 2006, more aneurysms are treated with coil embolization than with open surgery and clipping1.
When an aneurysm has the right size and shape for embolization, the data suggests that this less-invasive form of treatment is safer than open surgery. But not all aneurysms have the right size or shape for coiling. In general, aneurysms larger than 20 mm diameter and aneurysms with wide necks or branches arising from the aneurysm may be more safely and effectively treated with open surgery. There have been technological advances in the endovascular treatment of aneurysms, which have expanded the number of aneurysms which can safely, effectively and durably treated with coil embolization. It is important to discuss the treatment of your aneurysm with a team which performs both procedures and is most familiar with the abilities and limitations of each treatment strategy.
The embolization procedure itself is similar in some respects to the diagnostic angiogram. A catheter is placed through the skin into a blood vessel and the x-ray camera is again used to visualize the catheter as it is steered gently through the blood vessels to the neck. A tiny second catheter – a microcatheter – is then advanced through the first catheter and then the tip of the microcatheter is gently placed in the aneurysm sac. A series of soft metal coils are then placed through the microcatheter one after another into the aneurysm sac until the aneurysm is packed with coils. The catheter is then removed and the coils stay in place in the aneurysm, generally for the remainder of the patient’s life. The small amount of blood between the coils in the aneurysm turns first to clot and then with time undergoes a process of maturation and organization of the clot, usually eventually turning into scar tissue. Because the aneurysm no longer fills with blood, it is protected from bleeding. Some aneurysms are treated with more complicated coiling strategies such as the use of stents or balloons, and some aneurysms are treated by blocking off the entire blood vessel at the site of the aneurysm. Your doctor may discuss these additional strategies with you if your aneurysm size/shape makes these necessary.
Coil embolization of aneurysms is usually – but not always – performed with general anesthesia. The procedure can last less than an hour or most of a day. After the procedure your doctor may want you to remain in the hospital for one or two days, occasionally more. Your doctor may place limitations on your activity following the procedure, including time off from work. It is important to discuss these issues with your doctor before your procedure.
For more information about brain aneurysms and treatment options please click on any of the following links:
1. Boston Scientific Neurovascular: Analysis of U.S. Medicare and HCUP Data from 2001-2004.
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