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This information material has been designed to introduce you to the category of brain problems called "aneurysms." Although some of this subject.

(A Patient Information Service)


This information material has been designed to introduce you to the category of brain problems called "aneurysms." Although some of this subject matter may appear to be detailed and technical, we have made every effort to explain (in parentheses, like this) what the terms mean. In addition, your first review of this may be a little frightening, particularly when you begin to recognize how very serious and dangerous these problems are. However, it has been our experience that patients and their families much prefer to have as much factual information as possible in order for them to make an intelligent decision about their choice of treatment. There is nothing quite as terrifying as the "unknown." Our imaginations can conjure many frightening things which usually are not at all reflective of the situation. How many times have we thought or heard the statement, "The problem must be terrible. The doctor hasn't told me anything."

Our experiences with patients and their families have taught us many things. An important lesson has been that their anxiety diminishes considerably once they are armed with enough knowledge about the particular problem, no matter how serious it is. They are also more at ease knowing that the physician will take time to explain the details to THEIR satisfaction and to answer their questions in terms they can understand.

There have been major advances in neurosciences in the past 10 years. Many of these advances have significantly contributed to a brighter outlook for the patient with an intracranial aneurysm. The newer microvascular neurosurgical techniques as well as the minimally invasive endovascular treatments have played an important role in these advances. The role of neuro-radiology in identifying, more precisely, the anatomy of the brain circulation, together with advanced intensive care unit medical management techniques for the very ill, pre-treatment aneurysm patient (or post-treatment patient), have been very helpful to improve the outcome for these patients' recovery. Advances in anesthetic techniques for the delicate micro-neurosurgical treatments have also contributed a great deal to the better results.

In this paper I will try to explain the natural history of aneurysms. That is to say: what they are, why they occur, where they occur, and what you can expect if they are left alone. I will try to review what it takes to evaluate these problems and why a combination of medical and interventional (endovascular and surgical) methods is usually recommended. I will review the treatment alternatives together with their risks and limitations. There are always choices in treatment. I grant to you that some of the treatments are poor choices and most people with any common sense will not suggest or request them; nevertheless, there are also some legitimate alternatives in some cases.

Undoubtedly this printed material will not answer every question for every patient or family member. I hope that you will accept it as general background information on the subject. Please feel free to take notes and ask whatever questions you wish. No two patients or their problems are exactly alike. It is important that you understand as much as you can. Our staff will be pleased to help you in any way that we can.

1. Natural History and Investigation Techniques

Aneurysms that occur inside the head (intracranial) are among the very serious neurological conditions which can cause severe brain injury or death as a result of hemorrhage. Aneurysms are usually described as weak places on the arteries, which supply blood to the brain. They form in a manner that looks like a blister. They are similar, in concept, to the weak spot on an inner tube of a car tire or a child's balloon that is over-inflated.

Aneurysms are present in approximately five percent (5%) of the general population. Although they can occur in children, they are more likely to make their presence known in adults between 40 and 60 years. Aneurysms form in particular areas of the cerebral (brain) arteries. These are mostly where the arteries branch. Some of us are born with a very small defect in an elastic membrane which is part of the thick, middle layer of our brain arteries. As a result of the blood pounding on the inside of the artery with each heartbeat, a small internal hernia occurs through the weak and defective elastic membrane. Over the years this internal hernia slowly enlarges to extend outside the wall of the artery and takes on the appearance of a thin-walled blister. (See Figures 1 and 2.)

The arteries of our brain have three layers. The outer layer is very thin (called the adventitia). The inner layer is also very thin (called the endothelium). The middle layer (media) is relatively thick and is made mostly of muscle. Near the center of the media is the elastic membrane (internal elastic membrane). Defects in the internal elastic membrane are more likely to occur where arteries branch. It is through this defect that the hernia of the inner wall of the artery may occur. When the hernia extends through the entire wall of the artery and forms a blister, a true aneurysm has formed. Unfortunately the aneurysm wall is made up almost entirely of the thin, inner and outer layers of the arterial wall and does not have the protection of the thick muscle or its elastic membrane to keep the blood from bursting out of the inside of the blood vessel.

Aneurysms represent one of the most serious causes of stroke. Hemorrhage from a rupture of the aneurysm is the occurrence, which we fear the most. The hemorrhage may be a small leak or a more catastrophic bleed, which severely damages or destroys brain tissue. Once a hemorrhage from an aneurysm occurs, 35% of these patients will die no matter what treatment is given. This is in addition to those patients who survive the initial hemorrhage but who have permanent brain injury as a result of the hemorrhage.

It is very important to recognize that not all patients with one or more aneurysms will have problems from the aneurysm. Aneurysms are very unpredictable peculiarities. It is generally agreed that, in any population of 100,000 patients who already have aneurysms, only about 20 of these patients will experience a hemorrhage each year. Of these 20 people, thirty-five percent will die as a consequence. In those patients who suffer a hemorrhage and survive that experience, there are certain statistical factors, which are recognized and are important to know. Although subarachnoid hemorrhage (SAH) comprises only 1% to 7% of all "strokes" (intracranial vascular accidents), the loss of years of productive life for these patients is comparable to "cerebral infarction" (death of brain tissue as a result of an obstructed blood supply, as often occurs in older people) because of the relatively younger age of the aneurysm patinet and the generally poor neurological outcome for many of these patients.

Once an aneurysm has hemorrhaged, it is likely to do so again. The patient who suffers an initial hemorrhage is at serious risk to suffer another hemorrhage within 48 hours and again at approximately two weeks after the first hemorrhage. The risk to life (mortality) is greater with each subsequent hemorrhage, as is the risk to more brain injury. In the event that the patient survives one month from the first hemorrhage without a recurrence, there is about an 80% chance they will survive to one year without treating the aneurysm.

Long-term survival of patients who have recovered from a ruptured aneurysm (that is not permanently treated) is significantly lower than that of the general population. It appears that there is a little greater than 2% risk per year that the aneurysm will re-bleed in the first 10 years after the initial hemorrhage. (Approximately 11.5% will have re-bled at five years, 21% will have re-bled at 10 years and 30% will have re-bled at 20 years after the initial hemorrhage.) There is approximately a 3 1/2% risk to death per year for those patients who survive the first hemorrhage and do not undergo surgical treatment. The bleeding episodes are reported to be fatal in 78% of patients. The overall mortality rates for patients surviving the initial hemorrhage are 18% at five years, 31% at 10 years, and 45% at 20 years. (That is to say, 18% will have died at a point five years after the initial hemorrhage; 31% will have died at 10 years and 45% at 20 years.) These deaths would be related to a recurrent hemorrhage.

Approximately 15% of aneurysm patients have two or more aneurysms inside their head. There are certain factors, which help the experienced physician determine which of the aneurysms has been the one that hemorrhaged. Sometimes this is a difficult determination to make. In any patient who has more than one aneurysm, the unruptured one still represents a significant potential threat. There is about a 10% risk to death within 10 years from the unruptured aneurysm. There are some factors, which increase the likelihood to have more than one aneurysm. Patients who are under 55 years of age and also suffer with hypertension are twice as likely to have multiple aneurysms compared to patients who have normal blood pressure. Females are more likely to have multiple aneurysms than males. Women who are over age 60 and have one aneurysm are twice as likely to have multiple aneurysms compared to men of similar age. Increasing age and hypertension are two factors in women that correlate with multiple aneurysms. There are certain locations of aneurysms, which seem to have a predilection to having a similar aneurysm on the opposite side. This is almost a mirror-like distribution. These aneurysms are relatively uncommon.

One question that is frequently asked about intracranial (inside the head) aneurysms concerns factors of heredity. The neurological and neurosurgical literature on this subject suggests that, "There are some families which have an inherited weakness of the cerebral blood vessel wall which may predispose these individuals to aneurysm formation." The occurrence has been suggested to be a strongly inherited (autosomal dominant) pattern; however, only a few families have been reported. It is suspected that the familial incidence is higher than has been reported; nevertheless, the actual likelihood of this problem occurring in your children is extremely small. Where there appears to be a family history of aneurysms screening methods are available for these other individuals.

There are certain unusual medical problems, which are closely related to the formation of an intracranial aneurysm. Fortunately these conditions are very uncommon. They are listed here only for the sake of completeness and to illustrate the rarity. For those who are interested in learning more about these conditions, further information is available. These unusual conditions are:

  1. Coarctation (narrowing) of the aorta — associated with intracranial aneurysms in younger individuals including children.

  2. Polycystic disease of kidneys — When this is associated with the adult form (bilateral disease), 16% of these patients will have an intracranial aneurysm.

  3. Fibromuscular disease of the renal and carotid arteries, Marfan's syndrome, pseudoxanthoma elasticum, Ehlers-Danlos syndrome, and Moya Moya disease are all diseases of connective tissue or blood vessels and are associated with increased risks for intracranial aneurysms.
Another question that is frequently asked relates to how a patient would know if they had an aneurysm and if there are any warning signs prior to a hemorrhage.

Almost 60% of patients will have warning signs preceding a major hemorrhage. The interval between the last warning sign and a hemorrhage averages between 6 and 17 days depending on the location of the aneurysm. The likelihood of having a warning sign varies with the location of the aneurysm in the cerebral circulation. A serious change in the pattern of headaches or the onset of persistent headaches in someone who rarely is bothered by headaches can be important. The development of any of the following problems could be warning signs of an aneurysm: drooping eyelid; double vision; unilateral (one-sided) dilated pupil; blurred or absent vision; temporary weakness (decreased motor power); impairment of peripheral vision; speech disturbance; temporary deafness; and ringing in an ear. All of these conditions could be due to the growth in size of the aneurysm, which then compresses and injures an adjacent cranial nerve or brain area. The onset of seizures (epilepsy) in someone who has not had seizures previously is very important and should be evaluated by someone knowledgeable in these matters.

There is another way that aneurysms are now coming to our attention. There is an increasing frequency of "incidental aneurysms." This term refers to the fact that the aneurysm has not yet either hemorrhaged or caused any other difficulties. The presence of the aneurysm is usually identified on one of the newer "brain scan" techniques. For example, your physician may request a CAT (computerized axial tomogram) or MRI (magnetic resonance imaging) scan either to investigate a possible blood clot after a head injury or for some other problem. These scans may "incidentally" identify an aneurysm. Scans that are being done to investigate the complaint of headaches may uncover an aneurysm, which may or may not have anything to do with the cause of headaches.

Aneurysms can only be fully evaluated by a radiological (X-ray) investigation called an angiogram or arteriogram. This test allows us to evaluate all of the arteries of the brain (as well as the blood circulation pattern of the brain including the veins). The neurosurgeon will want to see several different views of the aneurysm and its relationship to the nearby and directly adjacent vessels. This test will also help to identify if any other aneurysms or other cerebral blood vessel problems are also present. Angiograms are usually performed by a neuroradiologist. This physician has special training and competence to conduct these investigations. Although these tests carry with them some risks, they are small compared to the benefits gained for the patient. In the hands of a competent neuroradiologist, the actual risk rates are very small. The neuroradiologist will discuss these tests in considerable detail with you and answer your questions. (See Figure 6.)

A relatively new technique has emerged using Magnetic Resonance Imaging (MRI) technology called Magnetic Resonance Angiography (MRA). At the present time it may be used as a primary method for "screening" patients who are suspected of having some intracranial (inside the head) problem with the blood vessels to or of the brain. MRA is still not sufficiently accurate in clear anatomical detail for most patients to avoid cerebral angiography in those patients who are surgical candidates. The same can be said about an even newer method called "CT Angiography".

In actuality there is a team of physicians (neurosurgeons, neurologists, neuro-radiologists, neuro-ophthalmologists, intensive care specialists, etc.), surgeons and nursing staff as well as other health care professionals (such as speech therapists, physical and occupational therapists, neurophysiologists, etc.) who are involved to varying degrees in the care of aneurysm patients. Depending on the individual needs of the particular patient, these neuroscience staff personnel will contribute to that patient's treatment.

The blood supply to the brain is mainly from four (4) major arteries. The two CAROTID ARTERIES supply the front (anterior) circulation to the right and left cerebral hemispheres. (See Figures 3, 4, and 5.) The circulation to the back (posterior) of the brain is from the two VERTEBRAL ARTERIES. After the carotid artery enters the head, it branches into two (2) major divisions to supply the bulk of the arterial blood to each cerebral hemisphere. These branches are the ANTERIOR CEREBRAL (front brain) ARTERY and the MIDDLE CEREBRAL (middle brain) ARTERY. Each of these arteries begins to send off branch arteries immediately and continue to subdivide to progressively smaller arteries in order to deliver the blood to every area of the surface and interior of the brain. Each half of the brain (each hemisphere) has its own Carotid, Anterior Cerebral, and Middle Cerebral Arteries. Therefore, there are LEFT and RIGHT CAROTID, MIDDLE CEREBRAL, and ANTERIOR CEREBRAL arteries.

The back (posterior) brain circulation comes from the two VERTEBRAL arteries which join each other inside the head to form the very important BASILAR ARTERY. This vessel, in turn, sends numerous small and several important large vessels to the brain stem (medulla, pons, and midbrain) and cerebellum (the balance and motor coordination center of the brain). The BASILAR Artery ends where it forms the two (2) large POSTERIOR CEREBRAL (back of the brain) Arteries which go to the back of the left and right cerebral hemispheres. These posterior cerebral vessels supply the occipital lobes of the brain which are responsible for our sense of SIGHT. (See Figure 10 for the functional areas of the brain.)

At the base of the brain there is a remarkable interconnecting system of these major arteries which allows communication between the anterior (front) and posterior (back) circulation systems as well as the right and left hemispheres' systems. This circular interconnection of arteries is called the CIRCLE OF WILLIS. (It is named for the anatomist who described it.) The Circle of Willis is very important for a number of reasons. It allows the brain an alternative way to keep blood flowing to every area even if one or more of the major blood vessels (supplying blood to the brain) were to shut down (such as may occur in atherosclerosis — hardening of the arteries).

The Circle of Willis may be very important in planning surgery for some aneurysms since we may have to rely on it to provide a detour route for an adequate blood supply in order to eradicate some aneurysms. Unfortunately a "complete" Circle of Willis is present in only 40% of patients. In the other 60%, there is some deficiency in part of the "Circle." That does not mean that it is "BAD"; however, when the surgeon is planning the approach to "clip" the aneurysm, it is often important to know if an alternative route (detour) of blood supply is available or not. Surgery can usually be done successfully in spite of a deficiency in the "Circle"; nevertheless, it is best to have as accurate a "road map" of the cerebral circulation as possible. This information is only part of what is learned during the ANGIOGRAM (arteriogram).

Intracranial aneurysms can occur on any of the arteries of the brain. (See Figure 7.) However, there is a strong predilection to certain locations. Most aneurysms occur in association with the larger cerebral arteries and are in the region of the base (underneath) portion of the brain. Ninety percent (90%) of all intracranial aneurysms occur in the front circulation (Carotid, Anterior and Middle Cerebral Arteries) while ten percent (10%) involve the back circulation (Vertebral, Basilar, and Posterior Cerebral Arteries).

In the anterior (front) circulation approximately 25% of aneurysms involve the Internal Carotid Artery while 30% involve the Anterior Cerebral Artery and another 30% involve the Middle Cerebral Artery. The remaining 10-15% of anterior circulation aneurysms involve some of the smaller branches of each of these major vessels.

In the posterior circulation system most of the aneurysms involve the BASILAR ARTERY, usually near the area where the left and right Posterior Cerebral Arteries originate. However, aneurysms can occur anywhere along the Basilar Artery and may involve or incorporate (in the aneurysm) vital blood vessels which nourish the brain stem. (In the event that this unusual problem is encountered, it will be discussed in more detail with you.)

We hope that the foregoing gives you a little better understanding and appreciation for the requirement of a detailed "road map" which a high-quality angiogram will hopefully provide. Each aneurysm (in each patient) is unique to that patient. Each aneurysm in each location has its own particular risks and technical problems relating to surgery. High-quality, high-resolution angiography plays a vital role in identifying important anatomy so that the surgeon is given as much information as possible. While it is very uncommon for us to be surprised, it could happen. We make every effort to obtain the appropriate information so as to reduce the risks to the patient.

2. Treatment Alternatives

In medicine, there are usually some reasonable choices in the care of most diseases. Sometimes the treatments carry with them more risk than the disease itself. In diseases which themselves are very serious, the treatments are frequently also quite serious. That does not mean that the treatments cannot be or are not successful, but it does clearly mean that there are certain risks to not achieving a "perfect" result or to failure of the treatment. One must weigh all the factors involved in the particular patient such as the neurological condition, medical conditions that might interfere with successful treatment, as well as the actual disease and its risks together with the risks of the treatment, in deciding what the best treatment method is for that patient. The experience and capabilities of the physicians and surgeons in the treatment methods are also important factors. The "ideal" treatment result is the COMPLETE OBLITERATION OF THE ANEURYSM so as to prevent another haemorrhage. There are some options; however, all of these require some form of "invasive" intervention.

The "medical" management of aneurysms is an important treatment method (even for the surgical candidate) in the initial phases of therapy for the patient who has suffered a hemorrhage. Once an aneurysm ruptures, it usually causes an intense brain reaction. The brain becomes swollen, softer, and is reddened. A softened, swollen brain is at more risk to injury if it is touched than under its more normal, non-inflamed state. Many surgeons prefer to wait until the softening, swelling, and inflammation subside before operating. During this waiting period, there is a risk that the aneurysm will rupture again. It is, therefore, very important to try to reduce the risks of another hemorrhage (whether or not the patient is an operative candidate).

This initial phase of treatment requires the control of blood pressure (with appropriate medication including sedation), control of headache (which can be quite severe after the hemorrhage) together with maintaining adequate nutrition and dealing with any other medical problems that might exist are important factors with early stages of treatment. In order to prevent sudden changes (particularly elevation) in blood pressure, it is important to reduce the patient's anxiety level, pain, and sudden straining. Depending on the psychological make-up of the patient and their level of agitation (sometimes caused by the intense pain), higher levels of sedation and analgesics (pain relievers) may be necessary.

In order to reduce the chances of the patient becoming concerned with other events, we usually avoid their access to television, newspapers or the internet. (They don't need any other bad news or shocks in response to world or regional events). Patients who suffer intracranial hemorrhages are often bothered by light. We usually place them in a darkened room for this initial part of treatment (which may last up to two weeks and, under rare circumstances, as long as one month). While they are not kept entirely asleep, we strive to keep them moderately tranquil and comfortable. We ask family and friends to restrict their visits to a short time and provide loving support and encouragement while avoiding issues that may be upsetting to the patient.

There are no medications that can cure aneurysms. Additionally, there are no medications that can prevent bleeding from the aneurysm on a long-term basis. However; we have long used an anti-fibrinolytic agent, delivered intravenously, from early on once we identify that the cause of the haemorrhage has been from an aneurysm. This medication acts to prevent the clot that has formed on the outside of the aneurysm from breaking up. It is this clot that is acting to prevent another haemorrhage. Unfortunately, this medication cannot be used for extended periods of time. (Please see the last paragraph on this page for additional information about this.)

If, for some reason (which would certainly constitute a very rare circumstance), interventional therapies are not going to be done, then it is probably best to remain at bed rest with blood pressure well controlled for one month. This will allow some time for scar tissue to form over the part of the aneurysm where the leak occurred. After that, the treatment consists mostly of controlling blood pressure and avoiding sudden, severe changes in intracranial pressure (as can happen with sustained straining in a constipated individual). There are no other therapies, medications, or non-surgical procedures which are available (except as discussed in the following sections). That does not mean that all patients who have aneurysms or all patients who have had a hemorrhage from an aneurysm are doomed. We ask you to review the preceding section on the "Natural History." The discussion of the risks involved permits us to use the information as a guideline in helping to make medical management decisions. There is no way to predict with certainty what will happen to each individual patient. There is also no doubt that, once an aneurysm has hemorrhaged, the patient is under an increased risk for another hemorrhage and that the life expectancy is shortened by virtue of the definite increased death rates associated with untreated aneurysms. However, there are patients who do survive without having surgery.

A recent medical literature review regarding this aspect of treatment (ADVANCES IN SUBARACHNOID HAEMORRHAGE, Feigin, V.L. and Findlay, M.) appeared in STROKE 37: 305-308, 2006 emphasizes that : "Medical treatment of patients with aneurysmal SAH [subarachnoid haemorrhage] is directed toward the prevention and management of neurological (e.g., aneurysm rebleeding, hydrocephalus, cerebral vasospasm and ischemia [decreased blood supply] and seizures) and systemic complications (e.g., hyponatremia [low sodium], cardiac arrhythmia and myocardial damage and neurogenic pulmonary edema [lung problems].)" One factor that seems important is the early use of an agent that prevents a clot ("antifibrinolytic" agent) from breaking up. This article emphasizes that "A recent randomized trial showed that immediate administration of antifibrinolytic agent tranexamic acid (1 gram IV, followed by 1 gram every 6 hours until aneurysm repair carried out as soon as possible) reduced the rate of devastating early aneurysm rebleeding from 11% to 2.4%. Short-term antifibrinolytic treatment may protect from acute aneurysm rebleeding, but long-term antifibrinolytic treatment in patients in whom late aneurysm repair is planned does not improve overall outcome because the reduction in the rate of rebleeding before delayed surgery is offset by an increase in poor outcome secondary to cerebral ischemia."

There are some very important newer Minimally Invasive techniques for treating patients with aneurysms. These are techniques conducted by specially trained Interventional Neuroradiologists. The procedures consist of inserting a length of platinum, copper-beryllium (or other specially designed) wire via angiography into the aneurysm to try to induce clot formation. Another Endovascular angiographic technique involves the placement of a permanent balloon inside the aneurysm or the mouth of the aneurysm to try to stop blood from flowing to the aneurysm.

As these endovascular angiographic interventional methods have evolved, it has become safer and more appropriate to utilize these techniques in select circumstances. This methodology has become the most appropriate treatment for many aneurysms in recent years. Unfortunately, some aneurysms do not lend themselves to this treatment for any of several reasons but mostly related to size and configuration. Oftentimes, once an aneurysm is determined to be amenable to endovascular interventional techniques, this treatment may be done at the time of or shortly after the diagnostic angiographic procedure is done.


A recent review by the respected Cochrane Project and reported in the "Cochrane Corner" (published in STROKE 2006; 37:572-573) concludes that "for patients in good clinical condition with ruptured aneurysms of either the anterior or posterior circulation, we have firm evidence that if the aneurysm is considered suitable for surgical clipping and endovascular treatment, coiling is associated with a better outcome." Furthermore the report states: "For patients in poor clinical grades, there is no reliable randomized evidence comparing the risks and benefits of coiling versus clipping. Because coiling is less invasive than surgery, also in patients with poor clinical condition, coiling seems the preferred option. A disadvantage of coiling is that aneurysms are more often incompletely treated (90%-100%) obliteration) and carry a risk for reopening. The long-term follow-up (>1 year after SAH) of coiled patients, with regard to renewed filling of the aneurysm, is an unknown but important issue that needs further study." (Note: SAH=Subarachnoid Haemorrhage)

The technologies underlying these endovascular procedures are still evolving. Among the problematic issues for any form of aneurysm treatment are the concerns for re-bleeding. In the case of endovascular treatment, rebleeding can occur despite the apparent excellent placement of the "coils". A recent Editorial in STROKE (Gary J. Redekop, MD; 2006; 37:1252-1353) summarized an important scientific investigation regarding aneurysm treatments. "The International Subarachnoid Aneurysm Trial (ISAT) compared microsurgical clipping and endovascular coil occlusion in patients with ruptured aneurysms felt to be suitable for either technique. This study showed that the risk of late re-bleeding was low but more common after endovascular coiling than after clipping. There are concerns about the long term durability of coil occlusion as well as the need for follow-up imaging and further treatment if aneurysm recurrence is detected."

Furthermore, this editorial commented that: "The Cerebral Artery Rerupture After Treatment (CARAT) study compared rates of recurrent haemorrhage in patients with ruptured aneurysms treated initially with coil embolization or surgical clipping. Significantly more patients treated with coiling required repeat treatment during the first year and continued to require additional treatment, although infrequently, as long as 5 years after the initial procedure." This is a matter of considerable importance since "serious morbidity occurred in 11% of patients undergoing repeat coil embolization and 17% of those undergoing repeat surgery."

The durability of aneurysm coil embolization is thought to depend on the "packing density" of the coils within the aneurysm. Part of the reason for the apparent "failure" of coiling to maintain complete obliteration of an aneurysm is the entity of "compaction" of the coils over time. As the coils are pressed closer together, they no longer completely fill the aneurysm. One of the newer advances in coil technology involves the use of coils that are coated with a hydrophilic polymer causing the coil to swell when they come in contact with blood resulting in a more densely packed aneurysm. (This technology was reported in STROKE: 2006; 37:1443-1450.) The point in sharing this information with you is to demonstrate that, clearly, there are significant advances that are being made in this field to improve the safety of the procedures as well as ensure a better long term outcome for these patients.

Specific treatment strategies must be individualized, taking into account the patientís age, neurological status and other medical conditions as well as the specific anatomical characteristics of the aneurysm. These characteristics of an aneurysm that help to determine the most efficacious interventional technique include its size, location, geometry, relationship to the parent artery or other adjacent arteries, the size of the dome and shape of the aneurysm neck, presence of calcification within the wall of the aneurysm and the presence of clot (thrombus) within the aneurysm. A multi-disciplinary team that emphasizes an honest and unbiased collaboration between the surgeons and the interventionalists is critical in the decision making process for the successful treatment of these patients.

There are some circumstances that occur which will result in a recommendation for early surgical treatment. In these cases, the operation is usually carried out within the first forty-eight (48) hours after the initial hemorrhage. We are trying, in these situations, to reduce the risks to life related to repeat hemorrhage by obliterating the aneurysm before it can do harm again. However, there are some additional risks to this "early surgery". There is a significant likelihood that "vasospasm" (spasm or narrowing of the blood vessels of the brain) will occur in the "early" operations. (See Page 15, Part 2, for further discussion of vasospasm.) However, one additional major advantage to the early clipping of the aneurysm is that, in the event that vasospasm occurs, we can "artificially" raise the blood pressure with medications and try to "drive" blood through the narrowed arteries. Obviously this technique of raising blood pressure could not be used to treat vasospasm unless the aneurysm was already clipped since raised blood pressure would be expected to cause a hemorrhage from an unclipped aneurysm. Another possible technique to overcome "focal" spasm is through another angiographic maneuver called "balloon angioplasty". In this instance, a balloon catheter is used to "dilate" the segment of a vessel that is in spasm. (This can ONLY be done AFTER the aneurysm has been surgically "clipped".) This is another example of the advances available using interventional neuroradiology techniques.

For most patients with an intracranial aneurysm (most particularly those who have already suffered a hemorrhage), the treatment of choice is to obliterate or occlude the aneurysm. The goal of these interventions is to stop blood from going into the aneurysm while preserving the blood supply to the brain. The endovascular interventional techniques were described previously. The surgical method to accomplish this results in applying a specially designed metallic "aneurysm clip" in such a way that isolates the aneurysm from the artery. When blood can no longer get into the aneurysm (the weak spot), then it can no longer hemorrhage. The clip is permanent (See Figure 8). The remainder of the aneurysm wall beyond the clip shrivels up and usually scars. Occasionally we must use more than one clip to successfully occlude the aneurysm. There are some aneurysms which actually have to be cut out and the blood vessel sewn up. This is more hazardous and is rarely required. Other unusual aneurysms cannot be completely clipped (usually because to clip them entirely would result in the sacrifice or injury to another important artery and thus produce a stroke). In the event that only part of the aneurysm can be clipped, the surgeon will attempt to reinforce the remaining segment of aneurysm in some fashion (usually with a rapidly setting glue substance).

Although the ideal method (to permanently stop all blood flow to the entire aneurysm) is usually accomplished, it is not always possible to achieve the ideal. In these cases, we strive to reinforce the wall to provide a stronger wall for the part of the aneurysm that remains. In some unusual cases, surgery cannot be completely or even partially accomplished. Sometimes we find that the clipping of the aneurysm (or coating it with glue to reinforce the weak blood vessel wall) would have a high risk to produce a profound neurological injury or death. In these rare cases (and those where surgery is not being done), the patient assumes the risks of the natural history of the disease. Regrettably, physicians cannot cure everyone and even modern treatments are not always completely successful.

In some even more unusual circumstances, the only way to deal with the aneurysm is by stopping the blood flow in the major artery or arteries. Obviously this could also stop the blood supply to part of the brain. It is in these cases that the presence of the "Circle of Willis" collateral blood supply may be particularly important. These patients may require an additional operation which brings a new "bypass" artery to try to ensure and adequate blood supply. These situations are uncommon and will be discussed in more detail when the particular situation arises. There are additional medical literature references relating to this technique such as Microsurgical Cerebral Revascularization: Concepts and Practice. Surgical Neurology 1:355-359, 1973 (Lazar, M.L. and Clark, W.K.) and Selective Cerebral Revascularization as an Adjunct in the Treatment of Giant Anterior Circulation Aneurysms Neurosurgical Focus 14(3): Article 4, 2003 (Brian A. O. Shaughnessy, M.D., Sean A. Salehi, M.D., Stefan A. Mindea, M.D., H. Hunt Batjer, M.D.) among others that are more recent, all attesting to the potential usefulness of this approach.

All of the operations directed towards aneurysms require making an opening or window in the bony skull. The medical term for this operation is a "craniotomy". In most cases, the bone will be replaced, and it is held in place so that it will not move. These are almost invariably quite acceptable from a cosmetic standpoint as well. Each operation directed towards a specific aneurysm has specific risks depending upon the precise location of the aneurysm as well as the age and medical, as well as neurological, condition of the patient. In general, all operations carry with them a certain element of risk to life. These operations are conducted under general anesthesia. The anesthesiologists are experienced in these neuro-anesthetic techniques and will discuss the anesthetic aspects with you. The risk to life from the general anesthetic, is fortunately, very small. In the case of a previous hemorrhage from the aneurysm, the risk to life is generally considered to be higher compared to the surgical risk to a patient whose aneurysm has not ruptured.

The projected mortality rate for craniotomy for unruptured aneurysms is 1% or less. The mortality rates for patients with ruptured aneurysms depend on several factors which include the presence or absence of lung and heart problems (or any other major medical conditions) as well as the neurological condition of the patient. As a general rule, mortality rates are higher for patients whose neurological condition is worse. Nevertheless, the overall mortality rate for patients who have had ruptured aneurysms is still relatively small compared to the natural history of the disease. The projected mortality for many patients who have had ruptured aneurysms is between 3 and 5%. Certain aneurysms in certain locations carry with them higher risks than other locations. These will be discussed on an individual basis relating to the specific aneurysm involved in each patient.

Advances in microvascular neurosurgical technique have been of particular benefit for aneurysm patients. The risks to life and to neurological injury have significantly decreased in recent years. Nevertheless, there are some risks to injury to adjacent anatomical structures. If the aneurysm is adjacent to, pressing on, or involving any of the visual sensory apparatus (such as the optic nerve, optic chiasm, or optic tract), then there is risk to impairment or loss of vision. In the event that the aneurysm is pressing on the nerves that supply the muscles, which work the eyelid or move the eyeball, then there is a risk to injury to these nerves with the resulting drooping eyelid and/or double vision.

Aneurysms which are underneath the front portion of the brain (such as anterior communicating or anterior cerebral artery aneurysms) are directly adjacent to and frequently involve the area of brain, which controls some aspects of personality. Personality alteration can occur as a consequence of the initial rupture of these aneurysms or of the surgical procedures aimed at their repair. Fortunately, this has been uncommon in our experience.

We are confident that you are aware that the right side of the brain controls the left side of the body and that the left side of the brain controls the right side of the body. Surgery upon an intracranial aneurysm carries with it a risk to injury to the blood vessels from which they arise and to which they have an intimate relationship. Blood vessel injury could result in decreased blood flow to the brain potentially resulting in paralysis of the face, arm and leg of the opposite side. For surgical problems involving the left hemisphere (particularly for left middle cerebral artery aneurysms and less commonly left internal carotid artery aneurysms), there is the additional risk to impairment of communication skills. The left hemisphere is the dominant (by virtue of the fact that it contains the communication control centers) hemisphere in almost all right-handed people and in some left-handed people. In a similar fashion, other aneurysms in other locations have risks to injury to those particular areas of the brain. These will be discussed on an individual basis.

One of the most serious complications of a ruptured aneurysm and aneurysm surgery is the occurrence of VASOSPASM. This is a condition resulting in the contraction of the wall of the blood vessel producing a much narrower blood vessel. As a consequence, the diameter of the blood vessel, through which the blood flows to the brain, is much reduced. In some cases, it becomes so severe that the blood supply to the brain is shut down. Vasospasm is usually self-limiting and reversible; however, severe neurological injury or death can occur as a consequence of this terrible problem. Despite vigorous therapy, it is very difficult, if not impossible, to treat in some patients. (Please see the discussion of some therapeutic maneuvers for the treatment of vasospasm on Page 12 & 13.)

Brain swelling is another potential risk of brain surgery. Fortunately, this is much less common than in previous years. Hemorrhage or blood clots very rarely are encountered as complications of surgery in our experience. Infection is also a very rare occurrence.

Modern aneurysm clips are very highly refined from a metallurgical standpoint. Clip failures are exceptionally rare. In the past, there have been reports of clips slipping from the aneurysm, and at some later date postoperatively the patient is found to have reformed the aneurysm. This has been an exceptionally rare occurrence in our experience (having seen this in two patients who were referred after another surgeon had operated upon them previously). We have not had any aneurysms reform that we are aware of. Although we have had the clip progressively dislodge in some cases of very large aneurysms while the operative procedure was being carried out, we are only aware of a single instance where a clip has even slipped slightly after surgery was completed. Nevertheless, a "slipped clip" is a risk of this surgery. It is equally rare for us to carry out an operative procedure and not be able to clip the aneurysm; however, this is another serious, although fortunately rare, risk of aneurysm surgery.

Most patients who have suffered a hemorrhage from an aneurysm will already be in the Intensive Care Unit. All patients who undergo craniotomy for aneurysm repair will be in the Intensive Care Unit postoperatively for at least several days. Most patients are awake and responding immediately after surgery. Most patients are able to take some nourishment by mouth within 12 to 24 hours postoperative. Angiography is not routinely carried out on every aneurysm patient postoperatively. Nevertheless, there are some aneurysms or neurological conditions associated with their repair for which we will request postoperative angiograms.

The long-term follow-up for postoperative patients falls into two main categories. Most patients who have undergone surgery for anterior circulation (internal carotid, anterior cerebral and middle cerebral arteries or their branches) aneurysms will be taking medication to try to prevent seizures (epilepsy). This is usually taken for the first two (2) postoperative years provided there have not been any seizures. After two years, the medication is progressively discontinued. In the event that seizures occur after this then the medication will probably be required on a permanent basis. Sometimes the seizures (either pre-operatively or postoperatively) are difficult to control and may require several medications.

In the weeks following discharge from hospital, the patients are homebound. Their level of activity is, to a certain extent, governed by their medical and neurological capabilities. All postoperative patients are required to avoid bending, lifting, pushing, pulling, or straining for at least three (3) months. They are to avoid the use of aspirin-containing medications (since the aspirin interferes with platelet function of the blood and could result in bleeding) unless specifically directed to do otherwise. The same is true for most "anti-inflammatory" drugs (such as ibuprofen), which are also used by many people as a "pain reliever". Walking around the house or in the garden is all the exercise that is permitted in the first pot-operative weeks. Most patients will be seen in the office two (2) weeks after leaving the hospital. At that time further instructions for activities (based on the individual's condition) will be reviewed.

The majority of patients are required to begin walking outside the house (with an accompanying adult) on a "progressively increasing distance" schedule. As a general rule, (taking into consideration any neurological or medical conditions) patients should expect to increase the distance they walk each day or every other day. We ask most of them to set a schedule that will progressively lead them to walk a distance of one (1) mile at a point 4 to 6 weeks postoperatively and two (2) miles when they are 8 to 12 weeks postoperative. The patients should avoid becoming overheated as well as over-tired.

Headache is rarely a long-term problem. Tylenol or a similar non-narcotic agent is usually all that is required. If headaches become a problem subsequently, further tests may be required.

One of the potential long-term complications of hemorrhages from aneurysms or aneurysm-repair surgery is the development of HYDROCEPHALUS. This complication is relatively uncommon, but it is serious and may require further surgery (called a SHUNT PROCEDURE). In this condition the cerebrospinal fluid (CSF), which bathes and cushions the brain inside the skull, has developed a problem. The cerebrospinal fluid is manufactured in the interior brain cavities (called ventricles). The fluid helps to nourish the brain and makes its way through the brain in a series of channels and ventricles. Ultimately, the fluid escapes the interior of the brain and surrounds the base and then courses over the cerebral hemispheres. It is re-absorbed into the blood stream through a special vein mechanism. Blood from a ruptured aneurysm can obliterate the fluid's pathways at the base of the brain or over the surface of the brain and cause an obstruction to the flow of fluid and its absorption.

However, the brain keeps manufacturing the fluid in the ventricles. Since it can no longer be absorbed at the rate it is being produced, the pressure inside the ventricles progressively increases and the ventricles become larger. (This is HYDROCEPHALUS: Hydro = water; cephalus = brain.) The ventricles become like inflated balloons inside the brain and can injure brain function. The condition can occur acutely (soon after a hemorrhage from the aneurysm) or years later as a result of a slowly progressive scarring in the fluid absorption pathway (subarachnoid space) initiated by the presence of blood from a hemorrhage years before or from surgery. (See Figure 9.)

If hydrocephalus becomes a problem, a SHUNT PROCEDURE may be required. This operation involves placing a silicon tube (with a valve system) into the ventricle (through a small hole drilled in the skull) and diverting the cerebrospinal fluid to another area (the heart or abdominal cavity) to allow it to be absorbed. This relieves the pressure from the interior of the brain. Hydrocephalus is an INFREQUENT complication. However, it can take many years to occur. This is only one of the reasons for which patients are followed on a yearly basis after their surgery.

In the first year, routine follow-up evaluations are usually at 2 weeks postoperatively and then monthly for the first three (3) months. After this, the visits are at six (6) months and twelve (12) months postoperative. In the event that problems arise, the patient will be seen whenever necessary.

The return to daily and work activities depends on the condition of the patient and the work requirement. For most patients who have sedentary jobs, they can anticipate returning on a progressive basis (each week increasing the number of hours worked) after 1 to 3 months postoperative. For patients who do heavy work or have some neurological impairment, return to work will be delayed.

As a general rule, the brain has the capability to recover from injury. However, if brain cells have died, their functions can NEVER recover. Whatever neurological injury is present at a point one year after corrective aneurysm surgery can usually be regarded as permanent. This means, of course, that RECOVERY is possible (to some degree, if not completely) within the first year. Where necessary and appropriate, Rehabilitation and Physical Medicine Specialists will strive to achieve the maximum recovery possible for those patients who need their services.

In those patients where endovascular coiling has been utilized, follow-up cerebral angiography becomes an important part of their ongoing management. Aneurysm "reformation" is a risk that is well documented in patients having undergone endovascular coiling. The only accurate way to determine this event is through formal angiography. In those cases where the aneurysm has "reformed", additionally coiling may become appropriate. (Please review the discussion on Pages 11 & 12 of this section for more information about this.)

Follow-up cerebral angiography is rarely required in patients who have undergone successful surgical clipping of an aneurysm since most surgeons definitively "prove" that the aneurysm has been obliterated by either draining the aneurysm or removing it once it has been clipped. This is done at the time of the definitive clipping procedure in order to satisfy the surgeon that the task has been completed without any doubt. There are unusual cases where this cannot or should not be done. In those instances, follow up angiography may be important.

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This page last edited on 2/20

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Author, Martin L. Lazar, MD, FACS
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