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Ischemic Stroke
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The term stroke refers to any new neurological symptoms with a sudden onset. While the term is sometimes used to refer to other sudden neurological events, such as subarachnoid hemorrhage or spontaneous hypertensive hemorrhage, it is most commonly used to refer to ischemic stroke.
If ischemic (decreased blood flow) is severe enough and/or prolonged enough it causes death of the part of brain which is involved. This is also termed cerebral infarction. While lower levels of ischemia may cause symptoms, they can be reversible if reversed before a full infarction occurs.
Ischemic stroke and cerebral infarction occurs when something obstructs the normal flow of blood to a part of the brain. Most commonly this is due to a blood clot which forms in an artery and then lodges into an artery that supplies the brain. Blood clots can form in many areas and from many causes but one of the most common causes of cerebral infarction is carotid stenosis. The carotid artery is a large artery which supplies the head and neck. It is prone to the development of atherosclerosis and the resultant narrowing of the artery, particularly in patients with high blood pressure, high cholesterol levels, and diabetes mellitus. Smoking, obesity and a sedentary lifestyle also contribute highly to the development of atherosclerosis. The narrowing of the carotid and the atherosclerotic plaque in the artery can lead to clot formation. Often, these clots break free and travel downstream, lodging into a smaller artery in the head. If this blockage is severe and is not quickly reversed, permanent damage to the brain supplied by that artery will occur.
Because the risk factors for these types of brain infarction are identical to the risks for coronary artery disease and other blood vessel diseases, patients most at risk for ischemic stroke are often the same patients who have heart disease or other peripheral vascular disease.
Other causes of ischemic stroke are less common. Blood clots from aneurysms, from heart conditions (such as atrial fibrillation, septal defects or valve disease) and other sources are less common but do occur in some patients.
Occasionally, small blockages of an artery can be resolved quickly on their own. If the blockage is reversed soon enough, in these cases the new neurological symptoms may reverse completely. These temporary neuro symptoms are often referred to as transient ischemic attacks (TIAs). While they do not lead to permanent disability on their own, they usually occur in patients at high risk for stroke and often predict further ischemic injuries including full cerebral infarction.
What Types of Symptoms Are Typical?
The symptoms caused by a stroke are extremely variable depending on which brain arteries are involved, the severity of ischemia and ultimately the areas of brain which are damaged. Almost any neurological symptom can occur. However, one of the most common sites involved is the middle cerebral artery. Ischemic stroke in the region of the middle cerebral artery typically causes weakness of the opposite side of the body (hemiparesis). If the ischemia involves the dominant hemisphere (usually the left side) then language can be affected as well. In the case of very large infarctions of the middle cerebral artery territory the brain can swell significantly, leading to increased intracranial pressure which can lead to coma or death.Ischemia can involve many other blood flow territories, creating different symptoms. Infarction of the brain stem for example can cause coma and death because the brain stem is important for normal respiration and for normal alertness and level of consciousness.
How Is The Diagnosis Typically Made?
When a patient presents with the sudden onset of new neurological symptoms consistent with ischemic stroke, their work-up typcially includes a full neurological assessment. This usually includes a CT scan (to rule out hemorrhage) and an MRI scan, which can often demonstrate ischemia in the brain very early after the onset of symptoms.In some patients, a cerebral angiogram is performed to identify the site of obstruction of the blood vessels, particularly if that patient is being considered for an endovascular procedure for treatment (see below).
What Are Some Common Treatments?
The treatment of ischemic stroke is highly individualized and varies from patient to patient considerably. In general, patients are generally observed with general supportive measures in the hospital and are often given medications which help prevent further clotting of the blood to prevent further ischemic events.For patients who present early enough after the onset of symptoms, some form of medication or procedure to open the blocked blood vessel is often attempted. If a patient does not know the exact time of onset of symptoms (such as if they wake up with the symptoms) or if too much time has elapsed, most of these treatments are not attempted because of the risk of hemorrhage if blood supply is reinstated too long after the onset of ischemia. Some of the most common treatment options are explained here:
- Intravenous tPA: tPA (tissue plasminogen activator) is a compound made by the body which can be used as a drug to help reverse blood vessel obstruction by a blood clot. The drug activates the body's ability to break down blood clots. In this case the drug is given by a standard intravenous catheter (IV). At the site of the clot, the clot is dissolved, hopefully re-opening the artery and improving the blood flow to the ischemic brain. Because it is given peripherally, a larger dose of tPA is required and therefore it is felt that the risk for bleeding is greater with this treatment. Therefore it is only used if the patient gets to medical attention very early after the onset of neurological symptoms.
- Intra-arterial tPA: Another option for tPA is to give it at the site of action, in the artery at the site of the blood clot. In this procedure, a small catheter is maneuvered through the artery (usually from the femoral artery in the leg) to the site of the blockage. A small amount of tPA is then given at this site to help break up and dissolve the clot.
- Clot Retrieval Devices: The newest of these treatments, clot retrieval devices are also used through a small catheter in the artery. However, rather than using a drug to dissolve the clot these devices attempt to "grab" the clot and pull it out of the artery. Experience is early with these devices but they appear to have effectiveness which is similar to the use of tPA.
These more aggressive treatments can have dramatic effects, often reversing some or all of the patient's neurological symptoms and preventing permanent disability. However, they are not effective in all patients and in patients who present too late after the onset of symptoms their use is dangerous. In these cases they are not used and treatment is simply focused on supporting the patient, preventing further clotting and later on rehabilitation to help the patient live with their neurological disabilities.
The treatment and outcome of patients suffering from ischemic stroke is highly variable and thus each patient should discuss their appropriate treatment options and outcome with their treating physicians.
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Important Note: This site is not intended to offer medical advice. Every patient is different, and only your personal physician can help to counsel you about what is best for your situation. What we offer is general reference information about various disorders and treatments for your education.
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