The Stroke CenterPreventionManaging Risky Conditions Printer Friendly Page

Abnormalities within cerebral arteries and veins include arteriovenous malformations (AVMs) and arteriovenous fistulas (AVFs). AVMs and AVFs, also called lesions, are abnormal connections between cerebral arteries (which carry blood to the brain) and veins (which take blood away from the brain).

AVMs appear to be acquired prior to birth (congenital) and tend to form near the back of the brain. Although AVFs can be congenital, more often they are caused by a trauma that damages an artery and a vein which are side by side in the brain.

These blood vessel abnormalities can cause a host of problems, but the two most common are pressure against the adjacent parts of the brain, causing neurological problems (such as seizures, paralysis or loss of speech); and, bleeding (hemorrhage) into surrounding tissues. Hemorrhage from cerebral arteriovenous abnormalities represents from 2 percent to 4 percent of all strokes.

There are three general forms of treatment for AVMs/AVFs:

• Surgery. This is the best-known and longest-standing treatment for AVMs. It involves entering the skull and tying off or clipping the arterial vessels that feed the malformation, eliminating the draining veins, and removing or obliterating the nest (nidus) of the AVM.
  
  
• Endovascular Embolization. This involves closing off the vessels of the AVM or AVF by injecting an agent into them — such as a special glue or a tiny coil or balloon — to block blood flow through the abnormal connection. Embolization is often used before surgery to minimize blood loss, making the operation safer and shorter. It can also be performed before radiosurgery to make the AVM smaller and increase the chance that radiosurgery will be successful. In some cases, endovascular embolization alone can permanently cure an AVM.
  
  

  (Left) Occipital AVM before embolization and after embolization (Right)

• Radiosurgery. Despite its name, radiosurgery does not require any surgical instruments to be placed within the head. This procedure tightly focuses beams of radiation from outside the skull onto the abnormal vessels in order to injure and clog the AVM. The vessels gradually close off and are replaced with scar tissue. The results of radiosurgery can take from weeks to years to become fully effective. A danger of radiosurgery is damage to normal brain or spinal cord tissue around the AVM. Therefore, the procedure is usually reserved for AVMs that are relatively small (less than 3 cm in diameter), are situated so deep beneath important brain tissue that the surgical approach is hazardous, or have so many feeder arteries that embolization is not feasible.

The primary risk a cerebral aneurysm poses is that it will leak or rupture, resulting in hemorrhagic stroke. Patients often experience no symptoms before a rupture occurs. In these cases, the aneurysm may be discovered incidentally, perhaps during an angiogram for carotid artery disease,

But sometimes, as an aneurysm grows, it compresses surrounding nerves and brain tissue, causing functional problems. In about 40 percent of cases, people with unruptured aneurysms experience some or all of the following symptoms:

• Peripheral vision deficits
• Thinking or processing problems
• Speech complications
• Perceptual problems
• Sudden changes in behavior
• Loss of balance and coordination
• Decreased concentration
• Short-term memory difficulty
• Fatigue

Regardless of their size or whether they are producing symptoms, all aneurysms need prompt evaluation by a neurosurgeon. Appropriate treatment depends on the size and location of the aneurysm and the patient’s medical history.

The risk of rupture increases with the size of the aneurysm and time.
New evidence suggestions that the risk of rupture for most unrepaired small aneurysms (less than 7 millimeters in size) is small.

Treatment Options

Surgery or minimally invasive endovascular therapy can be used in the treatment of brain aneurysms. The most common treatment for both unruptured and ruptured aneurysms is surgical clipping. A newer option is endovascular coiling or coil embolization.

However, not all aneurysms can or should be treated at the time of diagnosis. And not all patients are good candidates for the available treatments. Some of the factors include the patient’s health and anatomy and the size and location of the aneurysm.

Surgical Clipping. In order to clip an aneurysm, the neurosurgeon first must perform a craniotomy — an invasive procedure in which the brain and the blood vessels are accessed through an opening in the skull. The surgeon blocks the blood flow into the aneurysm by applying a metal clip to its base (neck) where it connects to the blood vessel. This redirects the blood flow along its proper route.

Aneurysm clips generally are made of titanium and come in all different shapes and sizes. The choice of a particular clip is based on the size and location of an aneurysm. The clip has a spring mechanism which allows the two "jaws" of the clip to close around either side of the aneurysm, thus separating (occluding) the aneurysm from the parent blood vessel. These clips are designed to be left in place permanently.

Endovascular Coiling. This is a newer, much less invasive technique for treating certain types of ruptured and unruptured aneurysms. The procedure can be performed under general anesthesia or light sedation either by a neurosurgeon or by an interventional neuroradiologist using real-time X-ray technology, called fluoroscopic imaging, to visualize the patient's vascular system and treat the disease from inside the blood vessel.

Angiogram picture showing placement of a coil inside an aneurysm.

Endovascular treatment of brain aneurysms involves inserting a thin plastic catheter into the femoral artery in the patient's groin and navigating it through the vascular system into the head and into the aneurysm. A tiny platinum coil is threaded through the catheter and deployed into the aneurysm, blocking blood flow into the aneurysm and preventing rupture (or re-rupture).

The coil, which is made of platinum so it can be visible via X-ray, is flexible enough to conform to the aneurysm shape. It is commonly referred to as the Guglielmi Detachable Coil (or GDC® Coil) after its inventor, Guido Guglielmi, MD, who pioneered the use of coiling technology in the brain in the late 1980s. The Food and Drug Administration approved it for use in the United States in 1995.

Coiling procedure for treating a sidewall aneurysm.

Today, more than 140 variations of the original GDC Coil design are available in a wide range of sizes in different delivery platforms to accommodate case-by-case variations.

Potential Complications of Clipping & Coiling
There are risks of complications with both clipping and coiling. When treating an unruptured aneurysm, one of the most serious problems in either procedure is rupture. Reported rupture rates range from 2 percent to 3 percent for both coiling and clipping.

Ischemic stroke is another serious complication sometimes encountered in both clipping and coiling. A clot could form and dislodge from the vessel, or a normal vessel could be blocked by the clip or coil and blood could be prevented from flowing through.

The duration of either procedure, the associated risks, projected recovery time and prognosis (anticipated outcome) depend on the location of the aneurysm, the presence and severity of hemorrhage, and the patient's underlying medical condition.

Coiling vs. Clipping
At present, there is no multi-center randomized clinical trial (considered the gold standard in study design) comparing endovascular coiling and surgical treatment of unruptured aneurysms. However, a clinical trial comparing coiling and clipping for the treatment of ruptured aneurysms so conclusively showed reduced risk of severe disability or death with coiling that the study — the International Subarachnoid Aneurysm Trial (ISAT) — was stopped early.

Retrospective analyses of cases involving treatment of unruptured aneurysms also suggest that endovascular coiling is associated with reduced risk of bad outcomes, shorter hospital stays and shorter recovery times as compared with surgical clipping.

These analyses have shown that:

• Average hospital stays are more than twice as long with surgery as compared with endovascular coiling treatment.
  
• Four times as many surgical patients as coiled patients report new symptoms or disability after treatment.
  
• There can be a dramatic difference in recovery times. One study showed that surgically treated patients had an average recovery time of one year compared with coiled patients who recovered in 27 days.

Although it gets a lot of bad press, the waxy, fatty substance called cholesterol is necessary for healthy cell membranes, among other things. We manufacture cholesterol naturally in our liver and we also get it through our diet.

There are different types of cholesterol and while our bodies use both, one — HDL (high-density lipoprotein) — is considered “good” and another — LDL (low-density lipoprotein) — "bad". Good cholesterol (HDL) carries bad cholesterol (LDL) away from the arteries. Bad cholesterol (LDL) can combine with other substances in the blood to form plaque, which can stick to the artery walls — potentially leading to clots that can result in ischemic stroke.

Some people are genetically predisposed to bad cholesterol buildup. Their liver produces too much LDL. But in most cases, people bring on the problem themselves through bad behaviors, such as smoking and lack of physical activity. A primary cause is a diet high in saturated, polyunsaturated and/or hydroginated fats and/or low in monosaturated fats, which appear to reduce bad cholesterol without affecting good cholesterol.

Modification of bad behaviors can help maintain cholesterol levels within the normal range — less than 200 mg/dL (measured in milligrams per deciliter of blood). When that is not enough, physicians also can prescribe appropriate medications to control cholesterol levels.

The most prominent cholesterol drugs are in the statin family. They work by interfering with the cholesterol-producing mechanisms of the liver and by increasing the capacity of the liver to remove cholesterol from circulating blood (by producing more HDL). They include Mevacor® (lovastatin), Lescol® (fluvastatin), Pravachol® (pravastatin), Zocor® (simvastatin), and Lipitor® (atorvastatin). [A sixth statin, Baycol® (cervastatin), is no longer available and a seventh, Crestor®, is awating approval by the Food and Drug Administration (FDA).]

People with diabetes are two to four times more likely to suffer strokes. Diabetes impedes the body’s ability to produce or properly use insulin — a hormone that allows our cells to absorb glucose, our body’s main source of fuel. Glucose is created naturally during the digestive process, and our pancreas is supposed to automatically produce the right amount of insulin to allow our bodies to use the glucose. In diabetics, the pancreas produces little or no insulin, so glucose builds up to high levels in the blood.

The disease falls into two main categories: type 1, which usually occurs during childhood or adolescence; and type 2, the most common form that generally occurs after age 45. There is also gestational diabetes, which can occur during pregnancy.

Diabetes can seriously harm blood vessels throughout the body, including those in the brain, which increases the risks of stroke. High blood glucose levels can cause hardening of the arteries (atherosclerosis), thicken capillary walls and make blood stickier — all significant risk for ischemic stroke. It can also cause small vessels to leak, reducing blood flow to the body tissue.

If blood sugar (glucose) levels are high at the time of a stroke, then brain damage can be more severe and extensive. This occurs because when the brain is deprived of oxygen, the body breaks down glucose differently. The products of this breakdown are in and around the area of dead tissue (infarction) and are, themselves, toxic to the brain tissue. If blood circulation is restored to the area, these products will break down even further and result in an increase in the size of the infarction.

Treating diabetes can delay or prevent the onset of complications that increase the risk of stroke. Healthy eating, physical activity, and insulin via injection or an insulin pump are the basic therapies for type 1 diabetes.

Healthy eating, physical activity, and blood glucose testing are the basic management tools for type 2 diabetes. In addition, many people with type 2 diabetes require oral medication, insulin injection, or both to control their blood glucose levels.

Atherosclerosis and arteriosclerosis involve the buildup of deposits on the insides of the artery walls, which causes thickening and hardening (sclerosis) of the arteries. In atherosclerosis, the deposits consist of fatty substances. In arteriosclerosis, the deposits are composed largely of calcium.

This buildup of hardened plaque results in a narrowing of the artery (stenosis), slowing and reducing blood flow. When the buildup is in an artery leading to or in the brain and becomes so extreme that no blood can pass, stroke ensues.

Atherosclerosis typically occurs in the carotid artery leading to the brain and is called carotid stenosis. This is a leading cause of ischemic stroke. Early warning signs of carotid stenosis, such as carotid bruits, can be detected by a primary care physician during a regular physical exam. Carotid bruits are the noise made by the blood flowing past the blockage. The blockage disturbs the blood flow and creates turbulence that can be heard by the physician listening to the artery with a stethoscope.

Treatment Options for Carotid Stenosis

Drug Therapy. For patients with less than 50 percent stenosis, medical therapy is often prescribed. Anticoagulant drugs (blood thinners) interfere with the formation of a blood clot. These include heparin and coumadin (also called Warfarin). Other medications called antiplatelets reduce clotting by interfering with the blood platelets. These include aspirin, Ticlopidine and Plavix.

Endarterectomy. Surgery is often recommended for patients with more than 50 percent stenosis. The plaque buildup in the artery can be removed in a procedure called carotid endarterectomy. The goal is to widen the narrowing of the artery and prevent a major stroke. Endarterectomy has been performed to prevent stroke since the late 1950s. According to statistics from the American Heart Association/American Stroke Association, approximately 140,000 of these surgical procedures are performed each year.

Two major scientific studies have proven the effectiveness of this procedure. They show that patients with more than 70 percent stenosis reduce their relative risk of stroke by 55 percent and patients with between 50 percent to 69 percent stenosis reduce their relative risk by 35 percent.

Angioplasty with Stenting: Depending on the degree and location of carotid stenosis as well as the patient’s history, angioplasty with stenting may be used instead of endarterectomy. This endovascular procedure has long been used in treating heart disease. Carotid angioplasty with stenting is less invasive than surgery, but not all patients are good candidates for the procedure and arterial catheterization brings its own risks.

(Left) Angiogram showing carotid stenosis and (Middle) the re-opening of the carotid artery after angioplasty and stent placement. (Right) Photograph of actual stent used.

In this procedure, a small, tube-like stent is affixed to the end of a thin plastic catheter, inserted in an artery (usually from the groin) and threaded up to the narrowed area of the carotid artery. The stent then is expanded to open the narrowing. When the catheter is withdrawn, the stent is left in place to maintain the opening.

During angioplasty and stenting, there is the potential for emboli (clot-producing debris) to become dislodged. The emboli are carried by the blood stream further into the brain where they can cause another blockage and stroke. Cardiologists face the same problem during cardiac angioplasty, where floating debris can be drawn into the heart, causing a heart attack. To capture the debris, they use an embolic protection device.

Leaders in stroke treatment and prevention are now applying this technique to stroke. The catheter that is used to maneuver the stent into place during angioplasty carries a filter at its tip that is deployed to catch the floating debris like a tiny fishing net. Once the angioplasty and stenting is completed, the net-like filter is retracted and removed from the body with the trapped debris inside.

Stenting vs. Endarterectomy: A comprehensive multicenter clinical trial is currently under way to compare outcomes achieved through stent-assisted angioplasty with outcomes achieved through endarterectomy for the treatment of carotid artery stenosis. The Carotid Revascularization Endarterectomy versus Stenting Trial (CREST) is comparing the methodologies for their effectiveness in preventing recurrent strokes in patients who have had a transient ischemic attack (TIA) or mild ischemic stroke. (University Hospital is a study site for this trial.)

Heart Disease (Cardiovascular Disease): One in five Americans has some form of treatable cardiovascular disease. People with coronary heart disease or heart failure have a higher risk of stroke than those with hearts that work normally. Certain types of congenital heart defects also raise the risk of stroke.

Atrial fibrillation, a heart rhythm disorder that is a common risk factor for ischemic stroke, is manageable. Anticoagulant and antiplatelet medications can be prescribed to reduce the risk of blood clot formation. Non-invasive and minimally invasive procedures, such as electrical cardioversion and ablation, can be used to terminate arrhythmias. A pacemaker can be inserted to monitor heartbeat and correct irregularities, and research is being conducted into the use of a new device, called an atrial defibrillator, as an alternative or improvement to pacemakers. There is also a surgical treatment called the Maze procedure.

High blood pressure (generally considered over 120/80 mm Hg) is the most common and most serious of all the controllable risk factors for stroke – particularly hemorrhagic stroke. Compared with people with controlled high blood pressure, people with uncontrolled high blood pressure are seven times more likely to have a stroke.

When your heart beats and pumps blood into your arteries, it creates pressure in them. The pressure causes your blood to flow to all parts of your body, transporting vital oxygen and nutrients. Arteries stretch when blood is pumped through them. How much they stretch depends on their health (the more muscular and elastic, the more they can stretch) and how much pressure the blood exerts.

High blood pressure puts excess stress on the heart (which has to pump harder) and damages blood vessels. If there is a weak spot in a blood vessel wall in the brain, high blood pressure could eventually cause it to rupture.

Sometimes high blood pressure is linked to other conditions, such as kidney disease, pregnancy or hormonal disorders, or caused by certain medications. The most common reasons for hypertension appear to be related to family history and influenced by diet (high salt intake or obesity) or habits such as smoking and drinking excessive amounts of alcohol.

It is common to have high blood pressure and not know it. The disease has no symptoms and is often called the “silent killer.” The only way to be certain is to have your pressure checked regularly by a health professional. The condition can be managed through a broad array of lifestyle changes (such as diet and exercise) and medications, of which there are more than 50 different types.

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