What Is It?
In a thrombotic stroke, a blood clot (thrombus) forms inside one of the brain's arteries and blocks blood flow to a part of the brain. This causes brain cells in that area to stop functioning and die quickly. Thrombotic strokes can affect large or small arteries in the brain. When a thrombotic stroke occurs in a small artery, the artery is usually one that is deep within the brain, and the stroke is more specifically named a lacunar stroke.
In a thrombotic stroke, the blood clot forms in the blood vessel in the brain. Another type of stroke -- embolic stroke -- is similar, but in an embolic stroke the blood clot forms somewhere else in the body and travels through the bloodstream to the brain artery. At first, it can be impossible for a doctor to determine which type of stroke a person is having, because the symptoms can be identical.
The blood clot that triggers a thrombotic stroke usually forms inside an artery that already has been narrowed by atherosclerosis, a condition in which fatty deposits (plaques) build up inside blood vessels. A much less common cause of thrombotic stroke is migraine headache. In especially severe cases, a migraine headache can cause a brain artery to go into spasm for a long time, which can allow a blood clot to form.
About 50% to 60% of all strokes are thrombotic strokes. The factors that increase your risk of having a thrombotic stroke are the same factors that increase your risk of atherosclerosis:
Symptoms
Because different areas of the brain are responsible for different functions (such as movement, sight, speech, balance and coordination), the symptoms of a thrombotic stroke vary, depending on which area of the brain is affected.
Symptoms can include any of the following:
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Headache
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Dizziness or confusion
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Weakness or paralysis on one side of the body
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Sudden, severe numbness in any part of the body
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Visual disturbance, including sudden loss of vision
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Difficulty walking, including staggering or veering
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Coordination problems in the arms and hands
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Slurred speech or inability to speak
If any of these symptoms appear suddenly, the person may be having a thrombotic stroke or any other kind of stroke. Symptoms, once they begin, can become worse gradually over hours or days.
Often, brief episodes of strokelike symptoms occur before a stroke. A short episode of stroke symptoms is called a transient ischemic attack (TIA). A TIA lasts less than 24 hours, usually 5 to 20 minutes. One or more of these attacks occurs before 60% of all strokes. A TIA is usually a sign that atherosclerosis has created a roughening or crack in the lining of an important artery. The cells within your blood that form clots, the platelets, respond to this rough area in the same way they would react to any wound: They form a clot. A TIA is like a "false start" by your platelets. The first small clots that your platelets form may dissolve or float downstream before they form a more permanent clot. A dissolving clot can cause the temporary symptoms of a TIA and is a clear warning that a stroke may happen soon.
Diagnosis
To diagnose a stroke, your doctor will need an image of your brain. Two different brain imaging tests can be useful, including a computed tomography (CT) scan and magnetic resonance imaging (MRI) scan. If a scan shows evidence of injured brain tissue in an area served by one artery, then you have had either a thrombotic or embolic stroke. If the scan shows bleeding in or around the brain, then you have had a hemorrhagic stroke, which has to be treated differently.
Next, your doctor will try to determine whether the stroke is thrombotic or embolic. This is important because an embolic stroke may mean that a heart problem or a problem within a blood vessel outside of the brain needs to be treated. Your doctor will do a neurological exam, take your blood pressure, and examine your heart and neck arteries. Tests that may be used to search for a source of a blood clot include an electrocardiogram (EKG), chest X-ray, Doppler ultrasound (also called carotid Doppler) and echocardiogram.
Expected Duration
If blood circulation in the brain is restored within minutes to a few hours, the person can recover rapidly, within hours to a day. For a small thrombotic stroke, symptoms may improve within a few days. When the blood supply is interrupted for longer periods, brain injury can be more severe and symptoms may last for many months. In that case, physical rehabilitation may be necessary. In some cases, permanent brain damage causes permanent disability.
Prevention
If you have had one stroke, you have a high risk of having another. You can help to prevent thrombotic strokes if you and your doctor carefully manage the factors that put you at risk of atherosclerosis. These may include high blood pressure, cholesterol problems and diabetes. You can also help to prevent stroke by eating a healthy diet, avoiding smoking and taking aspirin every day.
Treating high blood pressure with almost any medication reduces the risk of stroke, but several medicines have been shown to have an especially strong benefit. These include drugs called thiazide diuretics, such as hydrochlorothiazide (Oretic, HydroDIURIL and others) or chlorthalidone (Hygroton, Thalitone), and medicines called ACE (angiotensin-converting enzyme) inhibitors, such as enalapril (Vasotec), ramipril (Altace), captopril (Capoten) and lisinopril (Prinivil, Zestril).
If you have diabetes, you can reduce your risk of atherosclerosis and stroke by controlling your blood sugar.
If you have high cholesterol, you should take medication to reduce your cholesterol. Cholesterol-lowering medications called statins are known to prevent stroke. They include atorvastatin (Lipitor), lovastatin (Mevacor), simvastatin (Zocor), pravastatin (Pravachol) and fluvastatin (Lescol). You should have your cholesterol checked every five years, even if you have never had high cholesterol.
Diet and exercise can help to prevent stroke. You should exercise regularly and eat a healthy diet that has a lot of fruits and vegetables and is low in saturated fats, trans fats (hydrogenated or partially hydrogenated oils) and cholesterol. Recent studies have shown that eating two to four servings of fish each week may help to prevent stroke. One study showed that people who eat fish often have about half the risk of stroke compared with people who eat fish one to three times a month.
Other things you can do to prevent stroke are to avoid drinking too much alcohol and never take cocaine or amphetamines.
You should talk with your doctor about whether you should take aspirin every day. Aspirin in doses as low as 80 milligrams per day can reduce the risk of thrombotic stroke. Other medications that prevent clots also can help. These stronger medicines are sometimes recommended to people who have already experienced a stroke, to help prevent an additional stroke event. They include dipyridamole (usually as a drug combined with aspirin, Aggrenox), clopidogrel (Plavix) or ticlopidine (Ticlid).
If you have migraine headaches that are associated with neurological symptoms such as weakness, numbness or vision blackouts, it is important that you avoid taking migraine medications commonly called triptans. This class of medicines includes sumatriptan (Imitrex), rizatriptan (Maxalt) and others. Taking these medications when you have these neurologic symptoms can increase your risk of stroke.
Treatment
The most effective treatment for stroke must be given immediately, within three hours after symptoms begin. For this reason, it is important to seek emergency treatment if you have symptoms of a stroke. Do not wait to see if the symptoms go away on their own. The treatment that is used during these first hours is called tissue plasminogen activator (t-PA). It is administered through an intravenous line (IV) into a vein. This medicine can dissolve clots and restore blood flow in the brain. On average, patients who receive this medication have less long-term disability following a stroke.
Later, another type of medication, such as heparin, is given to prevent existing blood clots from getting bigger and to prevent new clots from forming.
A person who has had a significant stroke should be hospitalized so he or she can be observed in case symptoms get worse. A person who has had a severe stroke may need a mechanical ventilator to help with breathing. A stroke patient also may need help with self-care or feeding.
In the hospital, a person who has had a stroke can meet with occupational and physical therapists, who can help the person learn to work around a new disability and to regain strength. Often, a person will move from the hospital to a rehabilitation center to get intensive therapy before returning home.
When To Call a Professional
If you or someone you are with develops any of the symptoms of stroke, you should call your doctor right away or call an ambulance to be taken to an emergency room. It is important to have an evaluation even if your symptoms last only a few minutes, because a TIA can be a warning sign that you are going to have a stroke soon.
Prognosis
If the brain's blood supply is restored quickly and completely, it is possible to recover from a stroke with little or no disability. A three-year study from the U.S. National Institute of Neurological Disorders and Stroke showed that stroke patients who received the clot-dissolving drug t-PA within three hours of the start of their symptoms were 12% more likely to have little or no disability after three months compared to those who had not been treated with t-PA.
Additional Info
National Institute of Neurological Disorders and Stroke
P.O. Box 5801
Bethesda, MD 20824
Phone: 301-496-5751
Toll-Free: 1-800-352-9424
TTY: 301-468-5981
http://www.ninds.nih.gov/
National Stroke Association
9707 E. Easter Lane
Englewood, CO 80112
Phone: 303-649-9299
Toll-Free: 800-787-6537
Fax: 303-649-1328
http://www.stroke.org/
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