Stroke
Stroke |
|
When circulation to a part of the brain is interrupted for more than a few minutes, the brain cells in that region may die or malfunction and the patient will demonstrate loss of some bodily function such as vision, speech, movement of a body part or sensation. When the underlying disease process is temporary, the symptoms may be similarly temporary and the episode is known as a "transient ischemic attack" or TIA. Some people also refer to these as "mini-strokes." When the underlying blockage is fixed, the loss of function may be permanent and the patient will have a "stroke" or CVA (cerebrovascular accident). Although brain cells do not regenerate once they have died, surrounding areas of brain can assume some of the functions performed by the dead cells and thus, the patient can recover lost function following a stroke. If the doctors suspect that a patient has suffered a stroke, they may order a computerized tomogram, or CT scan, or a magnet resonance image, or MRI, to confirm the diagnosis and to measure the extent of damage. Strokes can result from many causes and surgical correction of a lesion in the carotid artery will be necessary in only a small percentage of patients.
There are four principal arteries, two on each side, that supply blood to the brain. The left and right carotid arteries which lie on either side of the neck carry more than 80% of the flow. When atherosclerosis, or hardening of the arteries, develops in one of these vessels, small pieces of this plaque can break loose, go to the brain where they obstruct circulation to a small region of the brain and cause a temporary, or permanent, loss of function known as a stroke. Studies have shown that the risk of stroke appears to be directly related to the severity of the narrowing. When more than 70% of one carotid artery is narrowed by atherosclerosis, the likelihood that the patient will have a stroke within the next several years on that side is greater than the danger of an operation to remove the blockage. In such patients, it may be necessary to consider a procedure to prevent stroke, even if the patient is having NO symptoms! Since it is difficult to restore function once a stroke has occurred, it is important to detect threatening lesions before they cause trouble. Patients who have evidence of atherosclerosis elsewhere in their body or who are experiencing brief episodes of numbness, paralysis, loss of speech or vision, etc. should undergo careful ultrasound examination of their carotid arteries. Ultrasound scanning can accurately measure blood flow in the carotid arteries and identify significant degrees of narrowing which increase the patient's risk of stroke. Because the margin for error is so small, it is important that any surgery on the carotid artery only be performed by surgeons who have been specifically trained to do this procedure safely. The best results often are achieved by surgeons who perform this operation frequently and prospective patients should not be afraid to ask their surgeon how often he/she has performed the operation and what his stroke and death rates are following it. Depending on the patient's condition and the reasons for the surgery, the combined risk of stroke and death after this procedure should range between 3 and 10%. Recently, some physicians have begun treating narrowing of the carotid arteries using balloon dilation with/without the addition of metal stents to keep the dilated segment open. This has the advantage of avoiding open surgery but appears to be associated with an increased risk of stroke. Currently, there are clinical trials comparing this treatment with conventional surgery in equally matched patients. Until the results of these trials is available, this method of treating carotid disease must be considered experimental, despite the claims of its proponents.