The treatment of stroke

Summarized by Robert W. Griffith, MD
October 17, 2000 (Reviewed: February 1, 2003)

Most strokes are what is called 'ischemic', which means there is an interruption of the blood flow to brain tissue, due to a clot forming in a brain artery, or being carried there from a more distant site (e.g. the wall of the heart or another blood vessel). The other type of stroke is termed 'hemorrhagic' (this involves bleeding into the brain tissue). Ischemic strokes are responsible for a third of all deaths in the USA. They are also the leading cause of disability. Once the blood supply to an area of the brain is blocked, there is a series of events over time that leads to the death of brain tissue. The aim of treatment is to prevent or slow this cascade of events, and to restore normal blood flow as quickly as possible. There are several ways to do this, which depend on the circumstances of the case. Two experts in the field have recently reviewed the main choices open to physicians today.

The first step is to evaluate the airway, breathing and circulation of the patient, and deal with any immediate problems affecting them. Then a full account of the symptoms and their development should be obtained, and a complete physical exam done, including an extensive examination of the nervous system. A battery of laboratory tests, an ECG and a chest x-ray are done next. Normally, computerized tomography (CT) of the head will be used to make sure that it is indeed an ischemic rather than a hemorrhagic stroke.

Treatment depends, in part, on where the blockage has occurred and it's likely cause. To help determine this, further investigations - magnetic resonance imaging (MRI), cerebral angiography, ultrasound, and various refinements of CT - may be ordered.

Quite often, there is a severe increase in blood pressure following a stroke. Lowering the blood pressure rapidly may cause a reduction in the amount of blood getting to the already partially damaged tissues, and in fact there is no evidence to show that lowering blood pressure in such cases is actually helpful. Of course, there may be additional conditions that make it necessary to reduce the blood pressure - dissection (or splitting of the wall) of the aorta, a heart attack, or heart failure. If the blood pressure is to be reduced using medication, it should be lowered slowly.

Nowadays most people are aware of the need to get likely stroke victims to a hospital as soon as possible. Within three hours of the onset of symptoms, a drug to dissolve the clot blocking a brain artery can be used effectively. This is called tissue plasminogen activator (t-PA), which is given intravenously. In clinical trials, t-PA leads to complete or near-complete recovery in 31-50% of stroke patients, as compared with 20-38% of those given a dummy injection. The overall death rate in these studies was not affected by the t-PA, as the improvement in recovery was counterbalanced by an increase in the occurrence of brain hemorrhage. The authors of this review lay down strict guidelines for selecting patients for t-PA treatment, and how the drug should be dosed, in order to ensure the best outcome.

Occasionally, if the main brain artery (the middle cerebral artery) is blocked, t-PA or another drug that dissolves clots (pro-urokinase) can be given directly into the artery, using a very small catheter threaded up from the neck (the carotid artery). Using this route up to six hours after the first stroke symptoms, 40% of patients have a complete, and 35% have a partial recanalization of the blocked artery. The results are clearly better than those obtained by giving t-PA in to a vein. However, so far there is only convincing evidence of these benefits in people with blockage of the middle cerebral artery.

Sometimes ischemic stroke is due to a blood clot breaking off from the wall of the heart or another blood vessel and lodging in an artery in the brain (an 'embolism'). In such cases, anticoagulant therapy is often given. Usually this consists of heparin by injection and warfarin by mouth. In fact, a large study (almost 20,000 patients) showed there were no differences between the major outcome results in people treated with low or high doses of heparin, or those given aspirin as well. Only a low dose of heparin showed some slight benefits, any advantages of high doses being counterbalanced by an increased risk of bleeding.

Other studies have shown that low doses of aspirin (160-325 mg daily) can prevent vascular events like stroke or a heart attack. However, aspirin doesn't seem to have any benefit in the treatment of an acute stroke. A more promising drug is called ancrod, which decreases the fibrinogen in the blood (a protein necessary for clot formation). If this is given within three hours of the onset of a stroke, it can produce 43% total or near-total recovery, compared with 34% in patients given a dummy injection.

When they reach hospital, acute stroke patients are usually put in a general medical unit, intensive care, or a stroke unit. If they are going to have medication to dissolve the clot, they should be in intensive care or a special stroke unit. Once hospitalized, there must be a concerted effort to prevent any of the medical or neurological complications that are responsible for a poor outcome. These include deep vein thrombosis (clot in a leg vein), pneumonia, infection of the urinary tract, and swelling of the brain (cerebral edema). In the latter, repeated CT scan may be necessary, together with intravenous drugs to reduce the swelling; in extreme cases, surgery may be required to relieve the pressure.

The short- and long-term death rates are lower, hospitalization is shorter, and the chances of returning home are greater for people treated in special stroke units. Over half of those who get over the initial period will retain their independence, and three-quarters of these will be able to walk. However, these results cannot be achieved without intensive efforts on the part of the patient, physicians, nurses, and rehabilitation therapists. Not surprisingly, stroke victims may develop severe depression, which, provided it is recognized, can be treated successfully.

New medications and treatment regimens for stroke are being developed in clinical studies all the time, and the outlook for acute stroke victims should improve at the same rate. The most important step that family or friends of the stroke sufferer can take is to ensure speedy hospitalization.

Source

• Treatment of acute ischemic stroke. T. Brott, J. Bogousslavsky, N Eng J Med, 2000, vol. 343, pp. 710--722

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