Stroke (Brain Attack)
A stroke is a sudden event affecting the brain's blood supply. In an ischemic stroke, a blood vessel that supplies the brain becomes blocked. In a hemorrhagic stroke, a blood vessel in the brain bursts.
The tem "brain attack" is sometimes used to describe a stroke because it is similar to how the heart muscle is suddenly deprived of blood during a "heart attack".
The symptoms of a stroke depend on where in the brain the blood vessels have been blocked or have ruptured.
|Call 911 immediately if you suspect you or someone you know is experiencing any of the symptoms of a stroke. Do not wait. There are now effective therapies for stroke that must be administered at a hospital, but they lose their effectiveness if not given within the first 3 hours after stroke symptoms appear. Every minute counts! (See Stroke Warning Signs)|
Brain cells die when they no longer receive oxygen from the blood or when they are damaged by sudden bleeding into the nearby brain tissue. Ischemia describes the loss of oxygen and nutrients for brain cells when there is not enough blood flow. Ischemia of the brain cells lead to their death (infarct).
When blood flow to the brain is interrupted, some brain cells die immediately, while others remain at risk for death. These damaged cells create a region in the brain called the "ischemic penumbra" that can linger in a compromised state for several hours before either recovering or dying. These damaged nerve cells can often be saved with immediate treatment.
Although stroke is most common in older people, it can occur in individuals of any age, including young adults and children. About 1 in 6 Americans will experience a stroke at some point after age 65. Stroke is fatal in about 10-20% of cases and, among survivors, it can cause a host of disabilities, including loss of mobility, impaired speech, and cognitive problems. This makes stroke the 3rd leading cause of death in the U.S. (behind heart disease and cancer) and a major cause of disability.
The long-term outcomes after a stroke vary considerably and depend partly on the type of stroke and the age of the affected person. Although most stroke survivors regain their functional independence, 15-30% will have a permanent physical disability. Some will experience a permanent decline in cognitive function known as post-stroke or vascular dementia.
Unfortunately, many stroke survivors face a danger of recurrent stroke in the future. About 20% of people who experience a first-ever stroke between ages 40 and 69 will have another stroke within five years.
An ischemic stroke occurs when an artery supplying the brain with blood becomes blocked, suddenly decreasing or stopping blood flow and ultimately causing a brain infarction.
This type of stroke accounts for approximately 80% of all strokes. Blood clots are the most common cause of artery blockage and brain infarction. The process of clotting is necessary and beneficial throughout the body because it stops bleeding and allows repair of damaged areas of arteries or veins. However, when blood clots develop in the wrong place within an artery they can cause devastating injury by interfering with the normal flow of blood. Problems with clotting become more frequent as people age.
Blood clots can cause ischemia and infarction in two ways. A clot that forms in a part of the body other than the brain can travel through blood vessels and become wedged in a brain artery. This free-roaming clot is called an embolus and often forms in the heart. A stroke caused by an embolus is called an embolic stroke. The second kind of ischemic stroke, called a thrombotic stroke, is caused by thrombosis, the formation of a blood clot in one of the cerebral arteries that stays attached to the artery wall until it grows large enough to block blood flow.
Ischemic strokes can also be caused by stenosis, or a narrowing of the artery due to the buildup of plaque (a mixture of fatty substances, including cholesterol and other lipids) and blood clots along the artery wall. Stenosis can occur in large arteries and small arteries and is therefore called large vessel disease or small vessel disease, respectively. When a stroke occurs due to small vessel disease, a very small infarction results, sometimes called a lacunar infarction, from the French word "lacune" meaning "gap" or "cavity."
The most common blood vessel disease that causes stenosis is atherosclerosis. In atherosclerosis, deposits of plaque build up along the inner walls of large and medium-sized arteries, causing thickening, hardening, and loss of elasticity of artery walls and decreased blood flow. Elevated of cholesterol levels and blood lipids plays a role in increasing a person's risk of developing atherosclerosis and stroke.
In a healthy, functioning brain, neurons do not come into direct contact with blood. The vital oxygen and nutrients the neurons need from the blood come to the neurons across the thin walls of the cerebral capillaries. The glia (nervous system cells that support and protect neurons) form a blood-brain barrier, an elaborate meshwork that surrounds blood vessels and capillaries and regulates which elements of the blood can pass through to the neurons.
When an artery in the brain bursts, blood spews out into the surrounding tissue and upsets not only the blood supply but the delicate chemical balance neurons require to function. This type of stroke is called a hemorrhagic stroke and accounts for approximately 20% of all strokes.
Hemorrhage in the braine can occur in several ways. One common cause is a bleeding aneurysm, a weak or thin spot on an artery wall. Over time, these weak spots stretch or balloon out under high arterial pressure. The thin walls of these ballooning aneurysms can rupture and spill blood into the space surrounding brain cells.
Hemorrhage also occurs when arterial walls break open. Plaque-encrusted artery walls eventually lose their elasticity and become brittle and thin, prone to cracking. Hypertension, or high blood pressure, increases the risk that a brittle artery wall will give way and release blood into the surrounding brain tissue.
A person with an arteriovenous malformation (AVM) also has an increased risk of hemorrhagic stroke. AVMs are a tangle of defective blood vessels and capillaries within the brain that have thin walls and can therefore rupture.
Bleeding from ruptured brain arteries can either go into the substance of the brain or into the various spaces surrounding the brain. Intracerebral hemorrhage occurs when a vessel within the brain leaks blood into the brain itself. Subarachnoid hemorrhage is bleeding under the meninges, or outer membranes, of the brain into the thin fluid-filled space that surrounds the brain.
The subarachnoid space separates the arachnoid membrane from the underlying pia mater membrane. It contains a clear fluid (cerebrospinal fluid or CSF) as well as the small blood vessels that supply the outer surface of the brain. In a subarachnoid hemorrhage, one of the small arteries within the subarachnoid space bursts, flooding the area with blood and contaminating the cerebrospinal fluid. Since the CSF flows throughout the cranium, within the spaces of the brain, subarachnoid hemorrhage can lead to extensive damage throughout the brain. In fact, subarachnoid hemorrhage is the most deadly of all strokes.
Transient ischemic attacks
A transient ischemic attack (TIA), sometimes called a mini-stroke, starts just like a stroke but then resolves leaving no noticeable symptoms or deficits. The average duration of a TIA is a few minutes. For almost all TIAs, the symptoms go away within an hour.
Someone who has had a TIA is at risk for a more serious and debilitating stroke. Of the approximately 50,000 Americans who have a TIA each year, about 1/3 will have an acute stroke sometime in the future. The addition of other risk factors compounds a person's risk for a recurrent stroke.
There is no way to tell whether symptoms will be just a TIA or persist and lead to death or disability. The patient should assume that all stroke symptoms signal an emergency and should not wait to see if they go away.
About 25% of people who recover from their first stroke will have another stroke within 5 years. Recurrent stroke is a major contributor to stroke disability and death, with the risk of severe disability or death from stroke increasing with each stroke recurrence.
The risk of a recurrent stroke is greatest right after a stroke, with the risk decreasing with time. About 3% of stroke patients will have another stroke within 30 days of their first stroke and 1/3 of recurrent strokes take place within 2 years of the first stroke.
Diagnosing Stroke and Determining Its Cause
There are several diagnostic tools that can quickly and accurately diagnose stroke and its causes. The first step is a short neurological examination to determine the region of the brain that has been affected.
Blood tests, an electrocardiogram of the heart, and a head CT, or head MRI will often be ordered.
CT Scans, MRI Scans and other Imaging Studies
The most widely used imaging test for acute stroke is the computed tomography (CT) scan. CT creates a series of cross-sectional images of the head and brain. A Head CT will quickly rule out a hemorrhage (bleeding), can occasionally show a tumor that might mimic a stroke, and may even show evidence of early infarction. Infarctions generally show up on a CT scan about 6-8 hours after the start of stroke symptoms.
If a stroke is caused by hemorrhage, a CT can show evidence of bleeding into the brain almost immediately after stroke symptoms appear. Hemorrhage is the primary reason for avoiding certain drug treatments for stroke, such as thrombolytic therapy, the only proven acute stroke therapy for ischemic stroke. Thrombolytic therapy cannot be used until the doctor can can be reassured that there is no bleeding in the brain because this treatment can increase bleeding and could make a hemorrhagic stroke worse.
Magnetic resonance imaging (MRI) scan of the head is also frequently performed to diagnose and manage stroke. MRI uses magnetic fields to detect subtle changes in brain tissue content. One effect of stroke is the slowing of water movement, called diffusion, through the damaged brain tissue. MRI can show this type of damage within the first hour after the stroke symptoms start. The benefit of MRI over a CT scan is more accurate and earlier diagnosis of infarction, especially for smaller strokes. It is also accurate in determining if hemorrhage (bleeding) is present. MRI is more sensitive than CT for other types of brain disease, such as brain tumor, that might mimic a stroke. MRI cannot be performed in patients with certain types of metallic or electronic implants, such as pacemakers for the heart.
Although increasingly used in the emergency diagnosis of stroke, MRI is not immediately available at all hours in most hospitals, where CT is used for acute stroke diagnosis. Also, MRI takes longer to perform than CT, and may not be performed if it would significantly delay treatment.
Magnetic Resonance Angiography (MRA) and Functional Magnetic Resonance Imaging (fMRI) are other forms of MRI tests that may be used to diagnose problems with blood flow to the brain that predict the risk of stroke. Neurosurgeons use MRA to detect stenosis (blockage) of the brain arteries inside the skull by mapping flowing blood. Functional MRI uses a magnet to pick up signals from oxygenated blood and can show brain activity through increases in local blood flow.
Duplex Doppler ultrasound and arteriography are two diagnostic imaging techniques used to decide if an individual would benefit from a surgical procedure called carotid endarterectomy. This surgery is used to remove fatty deposits from the carotid arteries and can help prevent stroke.
Ultrasound of the carotid is a painless, noninvasive test in which ultrasound waves are sent into the neck. Echoes bounce off the moving blood and the tissue in the artery and can be formed into an image. Ultrasound is fast, painless, risk-free, and relatively inexpensive compared to MRA and arteriography, but it is not considered to be as accurate as arteriography.
Arteriography is an X-ray of the carotid artery taken when a special dye is injected into the artery. The procedure carries its own small risk of causing a stroke and is costly to perform. The benefits of arteriography over MR techniques and ultrasound are that it is extremely reliable and still the best way to measure stenosis of the carotid arteries. Even so, significant advances are being made every day involving noninvasive imaging techniques such as fMRI.
Treatments for Stroke
There are a wide range of treatments for people who have suffered a stroke. The recommended treatment is based on several variables, including the type of stroke, the stage of disease, and the presence of other medical conditions.
Generally there are three treatment stages for stroke:
- stroke prevention
- stroke treatment immediately after stroke
- post-stroke rehabilitation.
Treatments to prevent a first or recurrent stroke are based on treating an individual's underlying risk factors for stroke, such as hypertension, atrial fibrillation, and diabetes, or preventing the widespread formation of blood clots that can cause ischemic stroke in everyone, whether or not risk factors are present.
Treatments immediately after a stroke try to stop a stroke while it is happening by quickly dissolving a blood clot causing the stroke or by stopping the bleeding of a hemorrhagic stroke.
The purpose of post-stroke rehabilitation is to overcome disabilities that result from stroke damage.
Medications for Stroke Treatment and Prevention
Medications the most common treatment for stroke. The most popular classes of drugs used to prevent or treat stroke are the following:
- Antithrombotics that prevent the formation of blood clots that can become lodged in a cerebral artery and cause strokes. Antiplatelet agents and anticoagulants are forms of antithrombotics.
- Thrombolytics agents treat an ongoing, acute ischemic stroke caused by an artery blockage. These drugs halt the stroke by dissolving the blood clot that is blocking blood flow to the brain.
Antiplatelet drugs prevent clotting by decreasing the activity of platelets, blood cells that contribute to the clotting property of blood. These drugs reduce the risk of blood-clot formation, thus reducing the risk of ischemic stroke. Antiplatelet drugs are prescribed mainly to prevent stroke. The most widely known and used antiplatelet drug is aspirin. Other antiplatelet drugs include clopidogrel (Plavix), ticlopidine (Ticlid), dipyridamole, and dipyridamole and aspirin (Aggrenox).
Anticoagulants reduce stroke risk by reducing the clotting property of the blood. The most commonly used anticoagulants include warfarin (Coumadin®), heparin, and enoxaparin (Lovenox®).
Thrombolytic agents dissolve the blood clot that is blocking blood flow to the brain. Recombinant tissue plasminogen activator (rt-PA) is a genetically engineered form of t-PA, a thombolytic substance made naturally by the body. It can be effective if given intravenously within 3 hours of stroke symptom onset, but it should be used only after a physician has confirmed that the patient has suffered an ischemic stroke. Thrombolytic agents can increase bleeding and therefore must be used only after careful patient screening.
Surgery for Stroke
Surgery can be used to prevent stroke, to treat acute stroke, or to repair vascular damage or malformations in and around the brain. There are two prominent types of surgery for stroke prevention and treatment:
- carotid endarterectomy
- extracranial/intracranial (EC/IC) bypass.
Carotid endarterectomy is a surgical procedure in which a doctor removes fatty deposits (plaque) from the inside of one of the carotid arteries, which are located in the neck and are the main suppliers of blood to the brain. As mentioned earlier, the disease atherosclerosis is characterized by the buildup of plaque on the inside of large arteries, and the blockage of an artery by this fatty material is called stenosis.
EC/IC bypass surgery is a procedure that restores blood flow to a blood-deprived area of brain tissue by rerouting a healthy artery in the scalp to the area of brain tissue affected by a blocked artery.
One useful surgical procedure for treatment of brain aneurysms that cause subarachnoid hemorrhage is a technique called "clipping." Clipping involves clamping off the aneurysm from the blood vessel, which reduces the chance that it will burst and bleed.
A new therapy that is gaining wide attention is the detachable coil technique for the treatment of high-risk intracranial aneurysms. A small platinum coil is inserted through an artery in the thigh and threaded through the arteries to the site of the aneurysm. The coil is then released into the aneurysm, where it evokes an immune response from the body. The body produces a blood clot inside the aneurysm, strengthening the artery walls and reducing the risk of rupture. Once the aneurysm is stabilized, a neurosurgeon can clip the aneurysm with less risk of hemorrhage and death to the patient.
The disabilities that can result from stroke can be devastating to the stroke patient and family, but stroke rehabilitation can minimize the impact of stroke.
For most stroke patients, physical therapy (PT) is the cornerstone of the rehabilitation process. A physical therapist uses training, exercises, and physical manipulation of the stroke patient's body with the intent of restoring movement, balance, and coordination. The aim of PT is to have the stroke patient relearn simple motor activities such as walking, sitting, standing, lying down, and the process of switching from one type of movement to another.
Another type of therapy involving relearning daily activities is occupational therapy (OT). OT also involves exercise and training to help the stroke patient relearn everyday activities such as eating, drinking, dressing, bathing, cooking, reading and writing, and toileting. The goal of OT is to help the patient become independent or semi-independent.
Speech and language problems arise when brain damage occurs in the language centers of the brain. Due to the brain's great ability to learn and change (called brain plasticity), other areas can adapt to take over some of the lost functions. Speech language pathologists help stroke patients relearn language and speaking skills, including swallowing, or learn other forms of communication. Speech therapy is appropriate for any patients with problems understanding speech or written words, or problems forming speech. A speech therapist helps stroke patients help themselves by working to improve language skills, develop alternative ways of communicating, and develop coping skills to deal with the frustration of not being able to communicate fully. With time and patience, a stroke survivor should be able to regain some, and sometimes all, language and speaking abilities.
Many stroke patients require psychological or psychiatric help after a stroke. Psychological problems, such as depression, anxiety, frustration, and anger, are common post-stroke disabilities. Talk therapy, along with appropriate medication, can help alleviate some of the mental and emotional problems that result from stroke. Sometimes it is also beneficial for family members of the stroke patient to seek psychological help as well.
© 2010 Vivacare. Last updated January 16, 2012.
Reference: The National Institute of Neurological Disorder and Stroke.
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Hemorrhagic Strokes and Their Causes (link to ASA)
Ischemic Strokes and Their Causes (link to ASA)
Recognize a Stroke (link to ASA)
Stroke Tests Overview (link to ASA)
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Clot-busting Therapy Helps Stroke Victims - But Only If They Get Treatment In Time (link to Neurology Journal)
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Even a Minor Stroke Might Lead to Stress and Anxiety (link to Neurology Journal)
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National Stroke Association (link to )
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