1) What is a brain aneurysm?
Aneurysms are a localized swelling or bulging in the wall of an artery. If an aneurysm develops inside the brain compartment, it's called a brain aneurysm.
2) What is an artery? How is it different from a vein?
Arteries are high pressure blood vessels that transmit oxygen and nutrient- rich blood away from your heart and lungs to the body tissues. When your doctor measures your blood pressure, she or he is measuring the pressure in your arteries. Veins, on the other hand are low pressure vessels that carry oxygen and nutrient-poor blood back to your heart and lungs. The pressure in veins is very low. Almost zero, in fact.
3) Why do aneurysms develop?
Aneurysms develop in arteries because of weak zones that are present within the artery wall.
4) Where else can aneurysms develop?
Although brain aneurysms are more common, aneurysms also occur in other parts of the body. The most likely site outside of the brain is in the large artery in the abdomen called the aorta. Although simplistically they are the same thing, they cause very different problems and are handled in an entirely different way. This site does not address these types of aneurysms. Aneurysms occurring elsewhere are very rare.
5) What types of brain aneurysms are there?
There are 2 common types of brain aneurysms. The first and most common is called a saccular aneurysm. These are the result of a very small zone of weakness in the artery wall and develop into a sac-like structure with a narrow, well defined neck. For unclear reasons these are much more common. They are also the type that typically leak or rupture and cause a sub- arachnoid hemorrhage or bleeding in the brain.
The second much less common type of brain aneurysm is called a fusiform aneurysm. These are the result of weakness involving the entire circumference of the artery wall, causing a circumferential enlargement or bulging. These types of aneurysms are less likely to leak, and more typically cause problems by enlargement and compression of adjacent brain structures.
Saccular aneurysms are the type generally treated with detachable coils. Fusiform aneurysms are much more difficult to treat.
6) Where do brain aneurysms typically occur?
Saccular aneurysms typically occur at branching points of arteries called bifurcations. There are roughly 5 so called bifurcation sites in the brain arteries where most aneurysms occur. These are
- near the ophthalmic artery
- near the posterior communicating artery
- in the middle cerebral artery bifurcation at the termination of the internal carotid artery, and
- at the basilar artery apex or tip.
It's important to remember however that every brain aneurysm is uniquely different and can occur anywhere in the brain. These are just some of the more typical locations.
7) How did I get a brain aneurysm?
No one knows for sure. Arteries are high pressure vessels. In order to contain this high pressure, artery walls are made up of muscular tissue containing smooth muscle cells. It is theorized that some individuals are born with an abscence or deficiency of these smooth muscle cells at certain predictable branch points in the brain arteries. It likely takes several decades before the accumulated pressure on the artery wall causes it to bulge and develop into an aneurysm. This is why aneurysms rarely occur in children. It is also likely why individuals who have high blood pressure or chronically smoke are more likely to develop aneurysms.
8) How common are brain aneurysms?
The incidence of brain aneurysms is roughly 1-2%. That is, if you test 100 individuals for a brain aneurysms, 1 or 2 of them will be found to have one. This rate is remarkably constant across all cultures and regions of the world.
9) How commonly do aneurysms leak or rupture?
Aneurysms leak or rupture at the rate of 1-2% per year. That is, if you identify 100 individuals with brain aneurysms and follow them over a year, 1 or 2 of them will suffer a leak. This effect is cumulative. That is, if someone has a known brain aneurysm, and they wait say 10 years, they will have exposed themselves to a 10-20 percent chance of suffering a leak. This fact is very useful in helping patients decide whether or not to have their aneurysms repaired.
10) Why are brain aneurysms dangerouss?
Because the artery wall in an aneurysm is stretched or thinned, it can break, causing leakage of blood into the brain compartment. This is called a sub-arachnoid hemmorhage. When blood spills into the general brain compartment, it can cause many problems and even death. Patients who suffer a sub-arachnoid hemorrhage can become very sick and require repair of the aneurysm if possible, as well as long periods of time in the hospital to recover
11) How dangerous is it when an aneurysms leaks?
Very dangerous. Nearly one third of all patients who suffer a sub-arachnoid hemorrhage die. About the same amount suffer some form of long term brain damage, such that they cannot return to the previous type of work and may need help to perform their normal daily activities. Another third are fortunate to survive and are able to function at the same level as they did before the hemorrhage.
12) What determines how badly or how well patients do after an aneurysm leak?
Basically it's the amount of blood leakage that happens. Generally speaking, the more blood that spills into the brain compartment, the more dangerous it is. Physicians grade so called sub-arachnoid hemorrhages into various levels. They use 2 different ways to grade the amount of bleeding. The first is called the Hunt+Hess scale and is based upon the level of consciousness that a patient exhibits after a leak. Grade 1 is a very mild leak. Grade 5 is a very severe leak. This is more commonly used since it is more accurate and does not depend on any fancy tests, just a thourogh physical exam.
The second is called the Fisher scale and is based on the appearance of the head CAT scan performed at time of leak and how much blood can be seen. This is less commonly used.
Physicians use these scales to predict how well or how poorly patients will do.
Generally speaking patients with a grade 1 or 2 Hunt Hess SAH are very likely to survive their hemorrhage with little or no long term brain damage. Patients with a grade 4 or 5 are very likely to die or suffer more severe long term brain damage. Patients with a grade 3 hemorrhage have a variable outcome
13) How are brain aneurysms diagnosed?
Prior to the development of sophisticated non-invasive brain imaging techniques such as CT and MRI, the only way to diagnose a brain aneurysm was with a catheter angiogram or arteriogram (these are 2 words for the same thing). This still remains the "gold standard" or best way to make the diagnosis. Since the early 1990's however, both MR and CT techniques have advanced enough so that they can produce angiogram-type images non- invasively. Both of these techniques can now diagnose brain aneurysms fairly accurately, if done well, but still not as accurately as a catheter angiogram. This is why catheter angiograms are commonly done if a CT or MR indicates the presence of a brain aneurysm.
CT or MRI are now the most common way brain aneurysms are diagnosed. In fact, because so many patients are undergoing MRs and CTs, brain aneurysms are being found more frequently than before the development of these machines.
14) What is involved in a catheter angiogram?
As noted above, these are "invasive" tests, which means they have higher risks than the non-invasive MR or CT and are typically done in a hospital by an interventional neuroradiologist. They involve inserting a catheter through the skin, into the groin artery, while the patient is awake, but mildly sedated. This is the same approach as many other types of angiograms, such as a cardiac catheterization or a "heart cath".
The catheter is advanced under flouroscopic guidance (x-ray) up the large garden hose sized artery in the abdomen and chest called the aorta. This only takes a few seconds and is painless. Once in the chest, the interventional neuroradiologist uses a mild curve on the end of the catheter to advance the tip of the catheter into one of the 4 large arteries supplying the brain. Again, this is painless because the arteries have no nerves on the inside of them.
Once the catheter is positioned in the neck of one of these 4 large brain arteries, radio-opaque contrast material is injected and rapid sequence xrays are taken of the brain for about 10 seconds, giving very high resolution pictures of the brain arteries. Because these are 2 dimensional images of a very complex structure (the brain), the interventional neuroradiologist will frequently do several different injections to map out all the arteries.
After all four brain arteries are studied, the catheter is removed. Because the catheter has made a small hole in the artery, the patient must remain flat in bed with the leg straight for several hours under observation in the hospital before being discharged home.
15) What types of activities make brain aneurysms more likely to develop? To leak?
The only 2 (controllable) factors that have been shown to increase the incidence of brain aneurysms is high blood pressure and smoking. Females are slightly more likely to develop brain aneurysms than males. Nothing else has been shown to promote or reduce the likelihood of developing a brain aneurysm.
Similarly, elevated blood pressure and smoking have both been shown to make brain aneurysms more likely to leak. Patients who smoke or have high blood pressure and suffer a leak are more likely to suffer a more severe leak than those with normal blood pressure or who do not smoke.
Strenuous activity has been linked to leakage of aneurysms, but it is poorly understood and most physicians don't feel that avoiding strenuous activity has much impact on aneurysm rupture rate. Some aneurysms do rupture during strenuous activity, but most leak during non-strenuous periods.
16) If I am found to have a brain aneurysm, what are my choices?
Essentially, you have 3 choices.
First, some individuals, because of age or other health problems choose not to have their brain aneurysm treated. This can be an entirely reasonable decision given the relatively low likelihood of aneurysm leakage (1-2% per year). Very rarely, brain aneurysms are in such a location or of such a shape that they cannot be treated safely. In others, the decision to treat is based upon a number of factors including risk of treatment, age of patient and presence of other more life threatening health problems.
Second, some individuals have their brain aneurysms treated with surgical clipping. This is the oldest, most conventional and most proven method of treating brain aneurysms. Neurosurgeons have been treating brain aneurysms in this way for nearly one hundred years. Over that time period, tremendous advances in the technique of surgical aneurysm treatment have been made so that it is now a very safe and effective method. It still remains a reasonable approach, especially for brain aneurysms that cannot be treated by the non-surgical (endovascular) method described below.
Surgical clipping involves surgical opening of the brain cavity, retraction of the brain and placing a spring loaded clip on the aneurysm across the neck.
Thirdly, brain aneurysms can be treated non-surgically by endovascular means. Endovascular means literally "from within the blood vessel". First developed by a neurosurgeon named Guido Guglielmi, endovascular treatment
17) What does endovascular mean?
Endovascular literally means "from the inside of the blood vessel". It is a generic term that refers to any type of minimally invasive procedure that involves the use of small catheters to treat blood vessel problems without surgery. In the specific case of brain aneurysms, we use it to describe the method of treating them with microcatheters and coils..
18) What is a catheter?
A long thin hollow plastic tube. The types of catheters used for endovascular treatments inside the brain are typically extremely thin and flexible.
19) Do brain aneurysms cause symptoms?
Generally speaking, no. Unless they rupture and cause a sub-arachnoid hemorrhage (SAH), in which case the symptoms can range from severe headache, drowsiness and loss of consciousness.
But regarding non-ruptured aneurysms, most specialists agree that they don't cause symptoms, unless they reach a very large size of 10 mm or greater. Then they can cause symptoms simply because of the pressure they exert on adjacent brain structures. We call this "mass effect".
Remember that most aneurysms are now discovered when patients undergo a brain MRI, which is typically done for a common neurological complaint, like headaches. Typically successful treatment of the aneurysm does not have any impact on the patients headaches, for which they underwent the MRI in the first place.
20) How long is the hospitalization required for endovascular repair of a brain aneurysm?
The vast majority of cases require a hospitalization of roughly 24 hours. Usually, the patient is admitted early the morning of the procedure, which is done under general anesthesia and typically takes 1-3 hours. Following recovery from anesthesia, the patient is admitted to the hospital for observation, during which he or she can eat, relax and watch TV. Typically discharge home is first thing the next morning.
21) How long does it take to fully recover from endovascular aneurysm repair? Is there much pain involved?
Because endovascular aneurysm repair does not involve surgery, there is very little recovery time involved after repair of unruptured aneurysms. Most individuals experience a mild to moderate headache for 3-4 days after repair. This is related to inflammation caused by the coils, which usually self resolves in a few days to a week. Most people don't feel like doing much during this time. Otherwise, that's it. Most folks are encouraged to return to their full activity level as soon as they feel up to it. For most patients, that means less than a week.
22) Are there any restrictions on my activity once my brain aneurysm is repaired?
None. You can return to whatever you did before the repair, though if you smoke your doctor will strongly advise you to quit.
23) Can I safely undergo an MR or CT or other medical test with coils in place?
Yes. The coils are made of platinum and completely inert. Undergoing an MRI is entirely safe. You should be aware however that because the platinum coils do not generate an MR signal like the rest of the brain tissue, if you undergo a brain MR examination after the coil repair, the area of the brain that contains the coils will not produce a signal and therefore will show up as a "black hole" on the MR image.
24) Why do I have to be put asleep for endovascular aneurysm repair?
First, this is the way we do it at Swedish Medical Center. Some institutions and practitioners may choose to do it differently.
We perform nearly all aneurysm repair procedures under general anesthesia because people cannot hold their head perfectly still for the length of time it requires to perform the repair (usually 1-3 hours). In order to repair it safely, the treating physician must be able to maintain a constant viewing angle of the aneurysm and its relationship to the other arteries of the brain. General anesthesia is the best way to ensure this.
25) Is endovascular repair of a brain aneurysm permanent?
Generally speaking, yes. Since 1994, over 100,000 patients have undergone non-surgical repair. The vast majority of them are permanently cured of their aneurysm.
26) Are there some patients in whom endovascular repair is not permanent?
Yes. This is because of the problem of coil compaction and recurrence of the aneurysm. Occasionally, especially in larger aneurysms treated with coils, the pulsatile blood flow in the arteries slowly compacts some of the coils. This compaction causes the coil nest to be smaller in size. Since this smaller size no longer fills the entire aneurysm, a portion of the aneurysm sac fills with flowing blood again. (shown here). This recurrent aneurysm is at risk for leakage or rupture (albeit at a very very low rate).
This is why we ask that all aneurysm patients who have undergone successful endovascular repair to return in 6 months for a repeat catheter angiogram. Greater than 95% of aneurysms repaired with coils do not need additional coils placed. A small percentage do need more coils, which can be placed very safely.
This is why your treating physician attempts to place as many coils into the aneurysm as safely possible during the original treatment.
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27) Can't a CT or MR be done 6 months after repair instead of a catheter angiogram?
No. The platinum coils produce different types of artifact on both CT and MR, making it impossible to determine if the aneurysm has remained fully treated. Only a catheter angiogram can provide that information.
28) What is an aneurysm remnant?
An aneurysm remnant is the residual aneurysm left after surgical or endovascular repair. No matter how carefully the aneurysm is surgically clipped or packed with coils, a small number are left with a small remnant (shown here). Remnants are more common after endovascular repair than with surgical clipping, but are an issue with both forms of treatment.
Fortunately, extensive studies have shown that the risk of these aneurysm remnants rupturing or leaking, causing a sub-arachnoid hemorrhage, is extremely low.
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29) If I have a brain aneurysm, am I likely to have another?
15% of patients with a brain aneurysm are discovered to have a second, or even third. This is why the diagnostic catheter angiogram involves studying all of the arterial supply to the brain.
30) Once my brain aneurysm is repaired, will I develop another one?
It is felt that aneurysms take several decades to develop. Therefore, if no aneurysms are found at the time of your diagnostic catheter angiogram, it will likely be many years before you're at risk for developing another. A surveillance brain MRA every 5 years is probably a reasonable way to screen for new aneurysms in patients who have undergone repair.
31) Do brain aneurysms run in families?
Originally it was felt the vast majority of brain aneurysms were spontaneous and did not have a tendency to occur in families. This is now undergoing intensive study with some research suggesting there is more of a familial pattern than originally thought. It is still believed however that most brain aneurysms are non-familial or spontaneous. Certain medical conditions like polycystic kidney disease and bicuspid aortic valves do predispose people to brain aneurysms.
32) Should my family undergo testing if I have one?
No one knows for sure and different doctors recommend different approaches. We suggest that once a member is found to have a brain aneurysm, immediate family members be screened. We also recommend screening family members for aneurysms if a member has been found to have polycystic kidney disease or a bicuspid aortic valve.
33) What types of testing are there?
MR angiography is currently the best method and is the one we suggest. CT angiography is also very good and is probably equivalent, assuming it's done properly. Everyone should understand that these non-invasive tests are not perfect and small aneurysms may be missed by them. The gold standard in detecting brain aneurysms remains the catheter angiogram.
34) What if I'm allergic to iodinated contrast material?
Very dangerous. Nearly one third of all patients who suffer a sub-arachnoid hemorrhage die. About the same amount suffer some form of long term brain damage, such that they cannot return to the previous type of work and may need help to perform their normal daily activities. Another third are fortunate to survive and are able to function at the same level as they did before the hemorrhage.
35) Are people allergic to the coils?
No. Platinum is biologically inert.
36) How dangerous is it when an aneurysms leaks?
Very dangerous. Nearly one third of all patients who suffer a sub-arachnoid hemorrhage die. About the same amount suffer some form of long term brain damage, such that they cannot return to the previous type of work and may need help to perform their normal daily activities. Another third are fortunate to survive and are able to function at the same level as they did before the hemorrhage.
37) Which is better: Surgery or coils?
There is no right answer to this question. No two aneurysms are exactly alike, nor are any two patients exactly alike. Each patient and their aneurysm has their own unique set of characteristics and features that must be carefully analyzed before making a final decision. An 85 year old patient with a history of heart problems or cancer may choose to have their aneurysm treated differently than a healthy 40 year old. This is why we suggest patients discuss treatment of their unruptured aneurysms with at least 2 different practitioners. One who is trained, performs and is fully knowlegable in endovascular repair with coils, as well as one fully trained in surgical clipping. This is the only way patients can make a fully informed decision regarding their care.
38) What are the risks of endovascular repair of brain aneurysms??
Everyone must understand that treatment of brain aneursysms is inherently risky and must be performed only by individuals thoroughly trained and experienced in the technique. The risks attendant to this repair are varied and not easily predicted. Nonetheless, there are several broad categories of technical problems that may occur during endovascular repair.
First, like any foreign body that is placed inside the blood stream, the catheter, coils and other devices used in this technique can cause blood clots to form on their surfaces, which can break off, migrate downstream into the brain and lodge in a branch vessel, causing a stroke. The size and severity of the stroke depends on how large the blood clot is. This risk is present even during a diagnostic catheter angiogram, although it is extremely unlikely during that type of procedure. Doctors keep this risk to a minimum by administering blood thinning agents such as heparin during the repair procedure. Additionally, if such a clot occurs, doctors can quickly dissolve the clot by injecting blood clot dissolving agents, such as TPA, into the clot.
Secondly, coils placed in the aneurysm can migrate out (typically during placement of subsequent coils), float downstream and lodge in a branch vessel, causing a stroke. This is rare because the doctor can "test" the coil by placing it in the aneurysm but not initially detaching it with the electrical current. Based upon it's behavior while non-detached, your doctor can make a very accurate prediction of how "stable" that coil will be once it's detached. Also, placement of additional coils causes them to "inter-lock", making migration much less likely. In the rare event of a coil migration during the procedure, a micro-catheter snare device is available that can allow safe removal of the migrated coil. Lastly the Neuroform stent (shown here) can be placed to pin the coil harmlessly against the vessel wall and prevent migration further downstream.
Thirdly, coils can perforate the sac of the aneurysm, causing bleeding (sub-arachnoid hemorrhage) to occur. This is a rare event, but is more likely to occur when treating an aneurysm that has recently leaked. Fortunately the treatment is to continue placing additional coils until the leak is sealed. Most cases of perforation are quickly sealed again by additional coils and cause no permanent harm.
Finally, it should be noted that any form of aneurysm treatment is risky and can result in major stroke or death.
39) Once coils are placed, can they be removed?
Not really. Although unanticipated coil migration can be addressed by using a microcatheter snare, this is reserved only for emergency situations. Generally speaking, once a coil is placed by detachment, it cannot or should not be removed.
40) What is a Neuroform stent?
The ability to place coils within an aneursym sac safely depends on the shape of the aneurysm, specifically the size of the aneurysm neck. That is, the size of the opening in the artery wall that allows the aneurysm to form. A narrow necked aneurysm (shown here), will contain coils easily since the narrow neck forms a barrier to keep them inside the aneurysm.
A broad necked aneurysm (shown here) has no such barrier to migration, so coils placed within it will easily migrate out, possibly into the parent artery (shown here).
The Neuroform stent (shown here) was developed as a remedy to this problem. Unlike stents used to open clogged arteries in the heart and elsewhere, the Neuroform stent has very thin struts and relatively wide openings between struts. This allows it to be very trackable and navigate the very tortuous blood vessels in the brain. Once placed across a wide necked aneurysm, the treating physician can then advance a micro-catheter through the stent side wall and into the aneurysm. With the stent in place, coils can be placed in the aneurysm can be placed much more safely and are much less likely to migrate, allowing a tighter coil packing.
41) Can ruptured aneursyms be repaired by endovascular means?
Yes. In fact there is some data to suggest that endovascular repair of brain aneurysms that have leaked or ruptured is superior to surgical clipping, since the brain swelling caused by sub-arachnoid hemorrhage makes surgery on the brain compartment more difficult and dangerous. Such brain swelling does not make endovascular repair any more difficult.
Overall, surgical or endovascular treatment of non-ruptured aneurysms is much safer than treating aneurysms that have leaked or ruptured. This is why individuals usually decide to have their aneurysm repaired before it leaks or causes other problems.
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