An enormous number of blood vessel disorders regularly occur in the brain. Just as the heart and coronary blood flow may be adversely affected by the nature of the walls of the blood vessels, so the brain may be similarly affected. However, the cardiac picture is repeated and extended in the brain, for the circumstances are somewhat different.
Almost all cases of serious brain damage (many of which lead to sudden death) are associated with damage to the blood vessel walls, and nearly always there is associated elevated blood pressure. Sudden disasters affecting the brain are usually referred to as “cerebrovascular accidents” (CVA for short). This means accidents in the blood-vessel system of the brain.
These often involve a series of events, which may be separate or occur in combination. Nearly always the vessel walls are adversely affected by atheroma. With the increased content of blood fats (essentially cholesterol and triglycerides), this material is laid down in the walls of the vessels. This leads to their thickening and hardening. Other elements are also laid down, and together these produce atheroma, or hardening of the walls. Collectively this is called arteriosclerosis, or atherosclerosis. It can occur slowly, over a period of many years, and gradually affect the blood vessel system throughout the whole body. But the vessels of the heart and the brain seem to be particularly susceptible to these pathological changes.
As this advances, and it is very common in the second half of life when the risks increase with advancing years, the blood flow through the cerebral system is impeded. The vessel becomes narrowed as its walls thicken. Certain parts may become narrower than others, impeding still further blood supplies (and food and iffproxygenation) to particular areas, ultimately causing damage there.
Atheromatous plaques form on the walls, and these may become craggy outposts in the central vessel bloodstream. Blood clots may commence at these points. Later on, part of the clot, or the entire mass, may break off and become part of the cerebral circulation. Suddenly, this may block a major or minor vessel, and an abrupt cessation of blood to a given area will ensue. Depending on the area this nerve centre supplies, symptoms will follow. Embolus formation, as it is called, and its subsequent blocking of a vital area is common.
Smaller arteries may steadily narrow, and these may gradually become filled with clot. This is termed a thrombosis. Again, brain areas affected by clot formation may soften and undergo liquidation. Often the vessels around them are weakened by atheroma. If the patient also suffers from an increased blood pressure, the combination may lead to a sudden breakdown in the arterial walls. Blood spurts out into the surrounding tissues. As it enters the vascular brain substance, inevitably more and more vessels are exposed and broken, so that a small rupture may become a major one. Of course, it may be a large vessel that originally ruptures, destroying a large area of brain tissue.
Brain hemorrhages of this nature are usually of major impact. Often death occurs, usually not instantly (as with the dramatic heart attacks), but generally within hours. The cerebral hemorrhage is often referred to as an “apoplexy of sudden onset,” and usually the outlook in these cases is grave. The brain is a very vascular organ. If smaller vessels are interfered with over a period of time, blood will be channeled from other areas through the so called “collateral circulation” to provide nutritional elements to the part involved.
In recent years, with more investigation of the brain possible with newer forms of scrutiny (particularly with angiography, cerebral scans and more recently with the computerized tomogram, MRI and PET), information is accumulating about these forms of brain disorder. Although certain disorders occur in the brain itself, others may be located in the blood vessels supplying it. For example, they may have become pathologically narrowed by disease, preventing adequate blood from reaching the nerve cells. In some cases, this may be helped by surgery.
The symptoms of a stroke (as these conditions are collectively referred to) vary with the site of the lesion. A common outcome is for one half of the body to be involved. A paralysis of that half can occur rapidly. This is called Hemiplegia. There may also be loss of speech. The essential feature is weakness and complete looseness of the muscles on the affected side of the body.
Hemiplegia is the most common sequel to vascular accidents of the brain. After the initial cerebral ischemic (lack of blood to the part) attacks, if death does not follow (and this may take anything from hours to days following the stroke), then restoration of function may take place. If this does occur, it is usually in a particular fashion. The deviation of the tongue to one side and the lack of facial symmetry clear up first. Then the lower limb begins to recover. Finally (and often very incompletely) the upper limb movements improves. The joints recover first proximally (i.e. the ones closest to the trunk). The result is that the patient can often stand after a period, but is not able to walk properly, for the feet may not be able to function adequately.
However, often the patient suddenly develops a coma with a CVA. If this is deep, with the patient showing no response to stimulation, and with respiratory irregularity, the outlook is increasingly poor. Often a sudden rise in temperature will herald death.
Almost invariably the patient has other underlying disorders precipitating the onset of the CVA. However, there has often been no treatment beforehand, and the patient merely presents in a coma, the accident already having taken place. Treatment is minimal at this stage, and supportive therapy in hospital is all that can be given in the hope that the patient will regain consciousness and be amenable to recovery to some degree.
If a patient is seen for the first time in a coma, the best form of therapy that can be instituted by an onlooker is to place the patient in a supine position (on the back) and endeavor to make certain the airway is clear, then check for cardiac and respiratory function. If these are not present, artificial respiration (mouth to mouth resuscitation) and external cardiac massage may assist in restoring these vital functions until either expert medical attention arrives or the patient can be transported to the emergency unit of a hospital.
Anticoagulants have been tried by doctors, but this is currently not favored as being helpful in these cases. If the patient shows signs of improving, the doctors might carry out investigations (e.g. angiography, CT scan, MRI) to see if the patient is a suitable candidate for neurosurgery. Sometimes narrowing is discovered in the arteries in the neck or thorax that may be assisted by surgery. Whatever line of action is taken, often the hemiplegia is not greatly assisted by such measures. Many patients do not improve significantly.
The best advice that can be given for preventing heart attacks include the regular check ups. There are devices that can show if the blood-vessel system is likely to be affected by disease. Elevated blood fat levels (cholesterol and triglycerides) are a measurable entity. If they are raised, efforts to reduce them must be made as early as practical. This has been clearly outlined in the section on the heart, and reference to this is recommended. If the blood pressure is raised, this too must be reduced to acceptable levels. Cigarette smoking and alcohol intake must be curtailed or stopped. Taking sensible measures before it is too late is the wisest approach to what may be a sudden and lethal disease.