MANILA, Philippines - During ischemia, tissues do not get enough oxygen because blood flow through vessels that supply those tissues is impeded. An ischemic attack in the brain resembles a stroke resulting from a cerebral embolism, but a transient ischemic attack differs in that the symptoms last less than 24 hours.
A sudden onset of weakness and numbness down one side of the body, for example, may last a few minutes or hours and then disappear, but the symptoms of a stroke last more than 24 hours. It is important to understand this difference. But transient ischemic attacks are often signals of impending stroke. Therefore, it should be quickly evaluated by a physician to attempt to avoid a stroke that may occur later and cause more serious and lasting damage.
The narrowing or obstruction of arteries to the brain can be caused by several factors. Most often, however, an ischemic attack occurs because a small clot or a piece of plaque (atherosclerosis) breaks away from the wall of an artery or heart halve and is carried into the brain. As the fragment of clot or plaque (called an embolus) passes through blood vessels in the brain, it temporarily impedes the flow to an area of brain tissue and causes stroke-like symptoms. The exact symptoms will vary, depending primarily on the portion of the brain affected. Circulation may soon be restored, however, and the temporarily deprived tissues recover. The block is therefore transient, or short-lived. But the problem is likely to occur.
What are the symptoms?
The symptoms are like those of a stroke, but they do not last long. They may include headaches, dizziness, tingling, numbness, blurred vision, confusion, or loss of the use of part or one side of the body. If the embolus makes its way into an artery that supplies the eye, there may be temporary blindness in that eye.
What are the risks?
Recurring transient ischemic attacks often warn of an impending stroke. Nearly half of those who have transient ischemic attacks are apt to have a stroke within 5 years after they have their first attack.
What should be done?
If you have had stroke-like symptoms or sudden loss of vision in one eye, do not delay in consulting your physician, who will examine you and who may refer you to a neurologist. The first diagnostic step will be to try to identify the source of a possible embolus. A likely source of emboli is one of the two carotid arteries in your neck. To search for signs of narrowing of the carotid arteries, your physician may listen with a stethoscope to various places in your neck. Your physician may also listen with a stethoscope placed on your chest to pick up any sounds of an abnormal heart valve or irregularity in heartbeat rhythm. You may then need to have a portable electrocardiogram (Holter monitor) and also tests of neck arteries and heart (when rhythm changes exist) using ultrasound techniques. If these tests suggest that one of your carotid arteries is narrowed or blocked, and surgery is recommended, more tests may be done using X-rays and a dye injected into the circulatory system. These arteriograms give accurate pictures of the blood vessels that may be the source of the problem.
What is the treatment?
The purpose of treatment is to try to prevent a future stroke. The preventive measures used depend mainly on your age and general state of health. Medical treatment may consist simply of an aspirin tablet once a day for the rest of your life. Aspirin is a good weapon against recurrent attacks, since it acts as an anticoagulant, reducing the likelihood of blood clot formation. More powerful anticoagulant drugs have reduced the number of strokes in people with abnormal heart rhythms. In some cases surgery may be recommended to remove the fatty material that is the cause of the narrowing.