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Ischemic Stroke

Ischemic Stroke, Ischemic Infarct and Ischemic Treatment

Ischemic Stroke – Causes, Symptoms, Diagnosis, Treatment

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Brain tissue dies in an ischemic stroke (brain infarction) because the brain is not sufficiently supplied with blood and oxygen due to a blocked artery.

  • An ischemic stroke is usually caused by a blockage in an artery to the brain, often caused by a blood clot or a fat deposit due to arteriosclerosis.
  • The symptoms are sudden and can include muscle weakness, paralysis, unusual sensations or loss of sensation on one side of the body, language difficulties, confusion, vision problems, dizziness and loss of balance and coordination.
  • The diagnosis is usually based on the symptoms and results of the physical examination and the brain imaging examinations.
  • To determine the cause of the stroke, further imaging procedures and blood tests can be carried out.
  • The treatment may include the administration of medication that dissolves blood clots or makes blood clotting less likely, as well as surgery for the physical removal of blood clots with subsequent rehabilitation.
  • Preventive measures include the control of risk factors, the use of drugs that reduce blood clotting tendency, and sometimes surgery or angioplasty to open blocked arteries.
  • Approximately one third of patients recover all or most of their normal functions after an ischemic stroke.

Causes

An ischemic stroke is usually caused by a blockage of an artery that supplies the brain, usually a branch of the inner carotid arteries (“blood supply to the brain”).

Common causes

Blockages are usually caused by blood clots (thrombi) or pieces of fat deposits (atheromas or plaques) due to arteriosclerosis. Such blockages often occur as follows:

  • By forming and blocking an artery: An atheroma in the wall of an artery can accumulate enough fatty material and become large enough to clog the artery. Even if the artery is not completely closed, the atheroma narrows it so that blood flow slows down, similar to the flow of water in a blocked tube. Blood clots tend to form in slow flowing blood. A large blood clot can reduce the blood flow through the narrowed artery sufficiently to cause the brain cells supplied by this artery to die. Or a blood clot can form and clog the artery if an atheroma tears (“How atherosclerosis develops”).
  • By migrating from another artery to an artery in the brain: Can a piece of an atheroma or a blood clot in the wall of an artery detach itself and migrate through the bloodstream (and become an embolus). The embolus can then settle in an artery that supplies the brain and blocks blood flow. (Embolism refers to a blockage of arteries by materials that move through the Ischemic Stroke   Causes, Symptoms, Diagnosis, Treatmentbloodstream to other parts of the body. Such blockages are more likely where the arteries are already constricted by fat deposits.
  • Migration from the heart to the brain: Blood clots can form in the heart or on a heart valve, especially on artificial valves and valves that have been damaged by an infection of the inner heart membrane (endocarditis). Strokes due to such blood clots occur particularly frequently after heart operations before and after a heart attack or in the case of cardiac valve diseases or cardiac arrhythmias (arrhythmia), especially after a fast, irregular heart rhythm, the so-called atrial fibrillation.

Apart from the fact that an atheroma can tear, various situations can trigger or promote the formation of blood clots and increase the risk of blockage by a blood clot. These include the following:

  • Blood diseases: In certain disorders, such as an excess of red blood cells (polycythemia), antiphospholipid syndrome and high blood homocysteine levels (hyperhomocysteinemia), the likelihood of blood clot formation is increased. In children, sickle cell anemia can cause ischemic stroke.
  • Oral contraceptives: Oral contraceptives, especially those containing a high dose of estrogen, increase the risk of blood clots.

Blood clots in a brain artery don’t always cause a stroke. If the clot dissolves spontaneously in less than 15 to 30 minutes, no brain cells die and the symptoms of the affected patients recede. In such cases, it is called a transient ischaemic attack (TIA – transient ischaemic attack).

When an artery becomes constricted over a long period of time, other arteries (collateral arteries – the blood supply of the brain) sometimes dilate to ensure blood supply to the parts of the brain normally supplied by the congested artery. If a clot develops in an artery that has formed collateral arteries, no symptoms may develop.

Constipation and clots: causes of ischemic stroke

If an artery that transports blood to the brain is blocked or blocked, an ischemic stroke may occur. The arteries can be blocked by fat deposits (atheromas or plaques) due to arteriosclerosis. Carotid arteries, especially the internal carotid arteries, are frequent sites for atheromas.

Arteries can also be blocked by a blood clot (thrombus). Blood clots can form on an atheroma in an artery. Blood clots can also form in the heart of people with heart disease. Part of the clot could loosen and migrate through the bloodstream (it could become an embolus). It can then block an artery that supplies the brain with blood, like one of the cerebral arteries.

Other causes

Another common cause of ischaemic strokes is a lacunal infarction. In a lacunar infarct, one of the small arteries is blocked deep in the brain by breaking down part of its wall and replacing it with a mixture of fat and connective tissue (lipohyalinosis). Lipohyalinosis differs from arteriosclerosis, but both disorders can lead to blockage of the arteries. Lacunar infarctions are more likely to occur in elderly people with diabetes or poorly adjusted hypertension. In a lacunar infarct, only a small part of the brain is damaged, so the prognosis is usually good. However, many small lacunar infarctions can develop over time.

An ischemic stroke can also be caused by a disorder that reduces blood supply to the brain. Stroke can also occur if an inflammation of the blood vessels (vasculitis) or an infection (such as herpes simplex) narrows the blood vessels leading to the brain. Migraine headaches or medications such as cocaine and amphetamines can cause arterial spasms that constrict blood vessels to the brain long enough to cause a stroke. A stroke rarely develops as a result of a general reduction in blood flow, e. g. after a high loss of blood or at very low blood pressure.

Occasionally, an ischaemic stroke also occurs if the brain has a normal blood supply but the blood does not contain enough oxygen. Disorders affecting the oxygen content of the blood include a severe lack of red blood cells (anemia), asphyxiation and carbon monoxide poisoning. In such cases, brain damage is usually widespread (diffuse) and a coma occurs.

Sometimes blood clots are released from a leg vein (deep venous thrombosis) or rarely small pieces of fat from the bone marrow into the blood after a fracture of the leg. These blood clots and fat particles usually migrate into the heart and block an artery in the lungs (lung embolism). Sometimes people have a different opening (a so-called open foramen oval) between the right and left upper ventricle (the atria). In these people, blood clots and fat particles can pass through the opening, bypassing the lungs and migrating into the aorta (the largest artery in the body). If they get into brain arteries, a stroke can occur.

Risk factors

The main risk factors for an ischemic stroke are:

  • Arteriosclerosis (narrowing or blocking of the arteries due to fat deposits in the arterial walls)
  • High cholesterol levels
  • hypertension
  • diabetes
  • smoking

Other risk factors include

  • Relatives who had a stroke
  • excessive drinking
  • Use of cocaine or amphetamines
  • An abnormal heart rhythm, also known as atrial fibrillation
  • Presence of another heart disease, such as a heart attack or infectious endocarditis (infection of the inner heart skin)
  • Inflammated blood vessels (vasculitis)
  • Obesity is also a factor, especially when fat is concentrated in the abdominal region
  • Too little physical exercise
  • Unhealthy diet (many saturated fats, trans fats and calories)
  • an existing blood clotting disorder

Symptoms

Usually the symptoms appear suddenly and are most severe a few minutes after their onset, as most ischaemic strokes occur suddenly, develop rapidly and cause brain tissue to die within minutes to hours. Then most strokes stabilize and hardly cause any further damage. Strokes that remain stable for 2 to 3 days are complete strokes. For this type of stroke, sudden blocking by an embolus is the most likely cause.

Symptoms develop more rarely slowly. They result from strokes that worsen over several hours or one to two days, while more and more brain tissue dies. Such strokes are called developing strokes. The progression of symptoms and damage is then usually interrupted by more or less stable phases in which the affected area temporarily does not enlarge or some improvements occur. Such strokes are usually caused by the formation of blood clots in a narrowed artery.

Many different symptoms can occur, depending on which artery is blocked and which part of the brain is not supplied with blood and oxygen due to it (brain damage according to brain region). When arteries branching off from the carotid artery (transporting blood along the front of the neck to the brain) are affected, the following symptoms often occur:

  • blindness in one eye
  • Inability to look at the same side with both eyes
  • unusual sensations, weakness or paralysis in an arm or leg or on one side of the body

When arteries branching off from the vertebral arteries (transporting blood along the back of the neck to the brain) are affected, the following symptoms often occur:

  • Vertigo and vertigo
  • double vision
  • General weakness on both sides of the body

Many other symptoms, such as language difficulties (e. g. sluggish speech), impaired consciousness (e. g. confusion), loss of coordination and urinary incontinence can occur.

Severe strokes can lead to stupor or coma. In addition, even lighter strokes can make you feel depressed or unable to control your emotions. For example, those affected could cry or laugh for no reason.

Some patients have a seizure at the beginning of the stroke. Even months to years later, seizures can occur. Such late seizures are the result of scarring or material from the blood that is deposited in the damaged brain tissue.

Sometimes there is a fever. This can be caused by the stroke or other illness.

If the symptoms, especially the impairment of consciousness, worsen during the first two to three days, the cause is often swelling due to excess fluid (edema) in the brain. The symptoms usually subside within a few days when the fluid is absorbed. Such a swelling is particularly dangerous because the top of the skull does not yield. The resulting increase in pressure can cause a shift of the brain and worsen brain function, although the area damaged by the stroke does not spread any further. If the pressure is very high, the brain in the skull can be pushed down by the rigid structures that divide the brain into compartments. The resulting disorder is called brain hernia (stress: the brain under pressure).

Strokes can lead to other problems. Patients with difficulty swallowing may not be able to eat enough and be undernourished. Food, saliva or vomit could be inhaled (aspirated) into the lungs and lead to aspiration pneumonia. Lying too long in a certain position without moving can cause pressure sores and muscle atrophy. As these patients are unable to move their legs, blood clots can form in the deep veins of the legs and inguinal veins (deep venous thrombosis). The blood clots can loosen, migrate through the bloodstream and block an artery leading to the lungs (there is pulmonary embolism). Those affected could have difficulty sleeping. The losses and problems caused by a stroke can lead to depression in many people.

Diagnosis

The physician can usually diagnose an ischemic stroke on the basis of the procedure and the results of a physical examination. Usually, the blocked artery in the brain can be identified by symptoms (damage to certain regions of the brain and their consequences). For example, if the left leg is weakened or paralyzed, this indicates that an artery blockage is present in the area on the right side of the brain that controls the muscle movements of the left leg.

Computed tomography (CT) is usually performed first. A CT helps to distinguish an ischemic stroke from a hemorrhagic stroke, a brain tumor, abscess and other structural anomalies. Blood glucose levels are also measured to rule out low blood sugar levels (hypoglycaemia) which can cause similar symptoms. If available, diffusion magnetic resonance tomography (MRI) could be performed next to detect ischemic strokes within minutes of their onset.

It is important to find out the exact cause of the stroke. If a blood clot is the cause, another stroke may occur if the underlying problem is not resolved. If blood clots are caused by an abnormal heart rhythm, for example, treatment of this disorder can prevent the formation of new blood clots and the onset of another stroke.

The following tests can be performed to determine the cause:

  • Electrocardiography (ECG) to check for irregularities in the heartbeat.
  • Continuous ECG monitoring (at home or in the hospital – Further examinations for cardiovascular diseases and blood vessels: long-term electrocardiography) to continuously record heart rate and rhythm over 24 hours (or more) to detect abnormal heart rhythms that occur unpredictably or for a short period of time.
  • Echocardiography to check the heart for blood clots, pump or structural abnormalities and valve diseases
  • Imaging tests – colour Doppler ultrasonography, magnetic resonance angiography, CT angiography or cerebral angiography (standard) – to determine whether arteries, especially the internal carotid arteries, are blocked or constricted
  • Blood tests for anemia, polycythemia, blood clotting disorders, vasculitis and some infections (such as heart valve infections and syphilis) as well as risk factors such as high cholesterol levels and diabetes

Imaging tests allow doctors to determine how much the carotid arteries are narrowed and thus assess the risk of another stroke or TIA. This information can be used to determine which treatments are required.

In cerebral angiography, a thin, flexible tube (catheter) is inserted into an artery, usually in the groin, and pushed through the aorta into an artery of the neck (angiography). Then a contrast agent is injected to represent the artery. This test is therefore more invasive than other tests that provide images of blood supply to the brain. However, it provides more information. Cerebral angiography can be performed prior to surgical removal of atheromas or if vasculitis is suspected.

In rare cases, a spinal puncture (lumbar puncture) is carried out after a CT, for example, if the doctors still have to determine whether the stroke-like symptoms are due to an infection or whether there is subarachnoid haemorrhage (subarachnoid haemorrhage). This procedure is only carried out if the doctors believe that there is no excessive pressure in the brain (which is usually detected by CT or MRI).

Forecast

Approximately 10 percent of patients suffering an ischemic stroke recover almost all of their normal function, and approximately 25 percent regain most of their function. Approximately 40 percent of patients have moderate to severe disabilities requiring special care, and approximately 10 percent need to be cared for in a nursing home or long-term care facility. Some patients are physically and mentally destroyed and cannot move, speak or eat normally. Approximately 20 percent of stroke patients die in the hospital. This percentage is higher for older people. Approximately 25 percent of patients recovering from a stroke suffer another stroke within 5 years. Subsequent strokes cause a further impairment of the functionality.

In the first few days after an ischemic stroke, it is generally impossible to predict whether a patient will experience an improvement or an aggravation. The likelihood of a complete recovery is greater in younger patients and in patients with rapid improvement. About half of the patients with one-sided paralysis and most patients with less severe symptoms have recovered some of the failed functions at the time of discharge from the hospital and are able to take care of themselves to a large extent. They are able to think clearly and can move reasonably well, even if they can only use the affected arm or leg to a limited extent. In most cases, the use of an arm is more restricted than that of a leg. Most of the handicaps that are still present after 12 months are permanent.

Treatment

People with symptoms that suggest an ischemic stroke should receive immediate emergency care. The earlier the treatment starts, the better the chances of recovery.

The first priority is to normalize breathing, heart rate, blood pressure (if low) and patient’s temperature. If necessary, an intravenous approach is used to supply medication and liquids if required. A fever could be reduced with acetaminophen, ibuprofen or a chilled blanket, as the brain damage is stronger at elevated body temperature. In general, high blood pressure is not treated immediately unless it is extremely high (over 220/120 mmHg) as the blood pressure must be higher than normal when the arteries are narrowed in order to carry enough blood through these arteries to the brain. However, a very high blood pressure can lead to damage to the heart, kidneys and eyes and must be lowered.

In the case of a very severe stroke, medications such as mannitol could be administered to reduce the swelling and increased pressure in the brain. Some patients may need a breathing apparatus to breathe properly.

Special treatments for stroke include blood clot dissolution (thrombolytics), anticoagulant drugs (blood clot inhibitors and anticoagulants), followed by rehabilitation. In some specialized centers, blood clots are physically removed from arteries (mechanical thrombectomy).

Preventive measures include the control of risk factors (e. g. hypertension, diabetes and high cholesterol), the use of drugs that reduce blood clotting, sometimes surgery or angioplasty to open blocked arteries.

Thrombolytic (fibrinolytic) drugs

Under certain circumstances, a drug called plasminogen activator (tPA) is administered intravenously to dissolve blood clots and restore blood flow to the brain. Since tPA can cause bleeding in the brain and elsewhere, it should not be used in certain circumstances:

  • Former hemorrhagic stroke, bulge (aneurysm) in an artery to the brain, other structural abnormalities of the brain or brain tumor
  • Brain haemorrhages detected with CT
  • seizure at the onset of stroke
  • bleeding propensity
  • Recent major surgery
  • Recent haemorrhage (hemorrhagia) in the gastrointestinal or urinary tract
  • Recent head injury or other serious injury
  • Very high or very low blood sugar level
  • heart infection
  • Current use of anticoagulants such as warfarin or heparin, depending on their effect on blood coagulation.
  • Major ischemic stroke
  • Blood pressure that remains high after treatment with antihypertensive drugs
  • Symptoms that quickly subside

Before the administration of tPA, a CT scan is performed to rule out cerebral haemorrhage. In order to be effective and safe, intravenous administration of tPA must be initiated within three hours after the onset of an ischemic stroke. Some experts recommend the use of tPA up to 4.5 hours after the onset of an ischemic stroke. However, some circumstances prohibit the use of tPA in the time window between 3 and 4.5 hours. These include, for example, an age over 80 years, a severe stroke and a stroke as well as diabetes mellitus in the medical history. After 4.5 hours, most of the damage to the brain cannot be reversed and the risk of bleeding outweighs the potential benefits of tPA.

However, it is sometimes difficult to say when the stroke started. The doctors therefore assume that the stroke started when the person appeared healthy for the last time. For example, if a person wakes up with symptoms of stroke, doctors assume that the stroke started when the person was last seen awake and healthy. Therefore, tPA can only be used in a small number of patients after a stroke.

If the patient comes to hospital 3 to 6 hours (sometimes up to 18 hours) after the onset of the stroke, he or she could receive tPA or other thrombolytic medication. However, the drug must then be administered directly into the blocked artery via a catheter and not intravenously. For this treatment (in-situ thrombolysis), a small incision is made in the skin, usually in the groin, and a catheter is inserted into an artery. The catheter is then advanced through the aorta and other arteries to the blood clot. The clot is partially broken apart by the catheter wire and then injected with tPA. This treatment is usually only available at special stroke centres.

Mechanical thrombectomy

This method physically removes blood clots. It is usually performed when a severe stroke has occurred and treatment with tPA, intravenous or catheter treatment has been ineffective, but must take place within 8 hours of onset of symptoms. You can use different tools. For example, a small corkscrew-shaped device is attached to a catheter and pushed forward to the blood clot through a cut, usually in the groin. The blood clot is then pulled out through the catheter. Mechanical thrombectomy is suitable for people who cannot be given tPA but is still considered experimental.

Blood clotting inhibitors and anticoagulants

When thrombolytic drugs cannot be used, most patients receive aspirin (a blood clotting inhibitor) as soon as they come to the hospital. When symptoms worsen, anticoagulants such as heparin are occasionally used. However, their effectiveness has not been proven. Blood clotting inhibitors cause the platelets to become less likely to clot and form blood clots. (platelets are tiny cell-like particles in the blood, which support clotting if the blood vessels are damaged. Anticoagulants inhibit proteins in the blood that support its coagulation (coagulation factors).

Regardless of the initial treatment, long-term treatment usually consists of aspirin and other anticoagulants to reduce the risk of blood clots and other strokes resulting from them (overview of stroke: prevention). Patients with atrial fibrillation or cardiac valve disease receive anticoagulants (such as warfarin) instead of anticoagulants that do not appear to prevent the formation of blood clots in the heart. Occasionally, the new blood clotting inhibitors dabigatran, apixaban and rivaroxaban are used instead of warfarin. Occasionally, patients at high risk for another stroke receive aspirin and a blood clotting inhibitor.

After the administration of a thrombolytic, physicians usually wait at least 24 hours before anticoagulants or blood clotting inhibitors are administered, as these drugs already contribute to an increased risk of cerebral haemorrhage. Patients with uncontrolled high blood pressure or patients who have suffered a hemorrhagic stroke are not treated with anticoagulants.

Surgical intervention

After an ischemic stroke has ended, surgical removal of the atheromas or blood clots (endarteriectomy) in an internal carotid artery could be performed. A carotid endarterectomy can help in the following circumstances:

  • Stroke was the result of a narrowing of the carotid artery by more than 70 percent (more than 60 percent in patients with transient ischemic attack).
  • Brain tissue supplied by the affected artery is still functional after the stroke.
  • The life expectancy of the patient is at least 5 years.

In such patients, a carotid endarterectomy could reduce the risk of further strokes. It also restores the blood supply to the affected area, but cannot restore functional loss because some brain tissue has died off.

A carotid endarterectomy is performed under general anaesthesia. The surgeon makes an incision in the neck area of the artery containing the blockage and an incision in the artery. The blockage is removed and the cuts are closed. The throat could hurt for a few days and swallowing could be difficult. Most patients stay in hospital for 1 or 2 days. Do not lift heavy objects for about 3 weeks. After a few weeks, patients can resume their normal activities.

A carotid endarteriectomy can cause a stroke because the operation can lead to blood clots or other materials that then enter the bloodstream and clog an artery. However, after an operation, the risk of stroke is lower for several years after surgery than when treated with medication.

In other narrowed arteries, such as the vertebral arteries, an endarterectomy is usually not possible because surgery is more risky there than in the internal carotid arteries.

Patients should find a surgeon who has experience with this operation and a low rate of serious complications after surgery (such as heart attack, stroke and death). If no suitable surgeon can be found, the risks of endarterectomy outweigh the expected benefits.

Stents

If an endarterectomy is too dangerous, a less invasive procedure can be performed: A wire mesh tube (stent) with a screen filter can be placed in the carotid artery. This stent keeps the artery open and the filter catches blood clots and prevents them from entering the brain causing a stroke. The filter is comparable to the filter to avoid pulmonary embolism (shields: a way of preventing pulmonary embolism). After the administration of a local anaesthetic, a catheter is inserted into the groin or arm by a small incision in a large artery and pushed forward to the inner carotid artery. A contrast medium that is visible on X-ray images is injected and X-rays are taken so that the narrowed area can be located. After the stent and filter have been placed, the catheter is removed. Patients usually stay awake for 1 to 2 hours during this procedure. The procedure seems to be as safe as an endarterectomy and almost as effective in preventing strokes and death.

Statins

Statins are medications that lower the level of cholesterol and other fats (lipids). They are often administered when a stroke is due to the accumulation of fat particles in an artery. Such a therapy can help to prevent a stroke.

Treatment of stroke-related problems

Measures to prevent aspiration pneumonia (aspiration pneumonia and chemical pneumonitis) and pressure ulcers (pressure sores: prevention) are introduced at an early stage. Heparin injected under the skin can be administered to prevent deep vein thrombosis (deep vein thrombosis: prevention). Patients are carefully monitored to determine whether the esophagus, bladder and intestine work. Other diseases such as heart failure, abnormal heart rhythms and lung infections often need to be treated. High blood pressure is often not treated until the stroke has stabilized.

Since a stroke often causes mood changes, especially depression, relatives or friends should inform the doctor if the patient appears depressed. Depression can be treated with medication and psychotherapy.

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