What is a stroke?
A stroke or stroke is a failure of the blood circulation that affects a more or less important area of the brain. It occurs as a result of obstruction or rupture of a blood vessel and causes the death of nerve cells, which are deprived of oxygen and nutrients essential to their functions. In the majority of people, there is no warning sign of a crisis. However, several risk factors can be monitored.
Strokes have very different consequences. More than half of the people have sequelae. About 1 in 10 people recover completely.
The severity of the sequelae depends on the region of the brain affected and the functions it controls. The larger the area without oxygen, the more likely the sequelae will be. Following a stroke, some people will have difficulty speaking or writing (aphasia) and memory problems. They may also be suffering from more or less significant paralysis of the body.
The signs of stroke, a medical emergency
When the nerve cells are deprived of oxygen, if only for a few minutes, they die; they will not regenerate. Also, the shorter the time between stroke and medical management, the lower the risk of serious sequelae.
Whatever the damage caused by oxygen deprivation, the brain has some adaptability. Healthy nerve cells sometimes succeed in taking over dead cells if they are stimulated by various exercises.
Causes of Stroke
Atherosclerosis, that is the formation of lipid plaques on the wall of blood vessels, is one of the main causes of stroke. High blood pressure is also a significant risk factor. Over time, the abnormal pressure exerted by the blood on the wall of the blood vessels can cause them to rupture. The rupture of an artery of the brain can be facilitated by the presence of an aneurysm. The aneurysm is a swelling of a small section of an artery, due to a weakness of the wall.
It is not always possible to determine the exact cause of a stroke. It is important, however, that physicians seek it through various tests to reduce the risk of re-offending.
Prevalence of Stroke
With advances in prevention, the prevalence of stroke has declined significantly in recent decades. Since the 1990s, however, it seems to have stabilized.
Even today, more than 50,000 people in Canada suffer from stroke each year and about 14,000 dies from it. While stroke is rarer than a heart attack, it is still the third leading cause of death in the country and is a major contributor to disability.
Three-quarters of strokes occur in people aged 65 and over. In Canada and North America, in general, they affect women more than men. Young children may also suffer, but this rarely happens.
Types of Stroke
There are 3 types of cerebrovascular accidents: the first 2 are caused by the blockage of a cerebral artery ( ischemic stroke ). They are the most common and account for about 80% of strokes. The third is caused by a brain hemorrhage ( hemorrhagic stroke ):
- Cerebral thrombosis It accounts for 40% to 50% of cases. It occurs when a blood clot forms in a cerebral artery, on a lipid plaque (atherosclerosis);
- Cerebral embolism It accounts for about 30% of cases. As in the case of thrombosis, a cerebral artery is blocked. However, here the clot that blocks the artery has formed elsewhere and has been transported by the bloodstream. It often comes from the heart or carotid artery (in the neck);
- Cerebral hemorrhage. It accounts for about 20% of cases, but it is the most serious form of stroke. Often caused by long-standing hypertension, it can also result from the rupture of an artery in the brain, where an aneurysm is located.
In addition to depriving a part of the brain of oxygen, hemorrhage destroys other cells by exerting pressure on the tissues. It can occur in the center or periphery of the brain, just below the cranial envelope.
Other rare causes of cerebral hemorrhage include hypertension, hemorrhage in a brain tumor, and blood clotting problems.
It can happen that the obstruction of a cerebral artery is only temporary and that it resorbs naturally, without leaving any sequelae. This phenomenon is called a transient ischemic attack (TIA) or mini-stroke. The diagnosis is confirmed by MRI. The symptoms are the same as those of a “true” stroke but they disappear in less than an hour. A mini-stroke is a warning signal to be taken seriously: it can be followed by a stroke sometimes more serious during the next 48 hours. It is therefore important to consult a doctor as soon as possible.
Stroke can cause paralysis or loss of consciousness. Sometimes it is detected by one or other of the following signs:
- dizziness and sudden loss of balance
- sudden numbness, loss of tenderness or paralysis of the face, arm, leg or side of the body;
- confusion, sudden difficulty in expressing oneself or understanding;
- Sudden loss of vision or blurred vision in one eye
- a sudden headache, of exceptional intensity, sometimes accompanied by vomiting.
- In all cases, emergency services should be contacted as soon as possible.
People at risk of a stroke
- People who have had a transient ischemic attack (mini-stroke) or stroke;
- People with a heart condition ( heart valve abnormality, heart failure or cardiac arrhythmia) and those who have recently had a myocardial infarction. Atrial fibrillation, a form of cardiac arrhythmia, is particularly dangerous because it causes the blood to stagnate in the heart; this leads to the formation of blood clots. If these clots circulate to the arteries of the brain, they can cause a stroke;
- People with diabetes. Diabetes contributes to atherosclerosis and reduces the body’s ability to dissolve blood clots;
- People who suffer from migraines;
- People with sleep apnea. Apnea can increase blood pressure and contribute to blood clots;
- People with high numbers of red blood cells in the blood (polycythemia);
- People whose close relative has had a stroke.
The two main factors
- Hypertension. This is the most important risk factor. High blood pressure weakens the lining of blood vessels, including those of the brain;
- Hypercholesterolemia. High LDL cholesterol (abbreviation for low-density lipoproteins, or “bad cholesterol”) or triglycerides contributes to atherosclerosis and hardening of the arteries.
- Smoking. It contributes to atherosclerosis. In addition, nicotine acts as a cardiac stimulant and increases blood pressure. As for carbon monoxide present in cigarette smoke, it reduces the amount of oxygen that reaches the brain because it attaches to red blood cells instead of oxygen;
- A poor diet;
- Physical inactivity;
- Chronic stress;
- Excess alcohol or hard drugs, such as cocaine
- Oral contraceptive use, especially for women at risk who are over 35 years of age
- The hormone replacement therapy administered at the time of menopause (it slightly increases the risk).
Medical treatment of stroke
The first objective is to minimize brain damage by restoring blood flow in the event of an ischemic stroke diagnosed by MRI or by reducing the bleeding of blood in the event of a bleeding accident. If the stroke is severe, the person will remain under observation at the hospital for a few days. A period of rehabilitation, at home or in a specialized center, is sometimes necessary. In addition, the cause of the stroke should be sought and treated (for example, by correcting high blood pressure or cardiac arrhythmia).
If an artery is blocked
A single medication to reduce the risk of irreversible brain damage is approved. It is indicated in the case of stroke caused by thrombosis or embolism. It is a tissue plasminogen activator, a blood protein that helps dissolve clots quickly (in an hour or two). To be effective, the drug must be injected intravenously within 3 to 4.5 hours after stroke, which greatly limits its use.
A few hours after a non-bleeding stroke, an anticoagulant or antiplatelet drug is often given. This helps prevent the formation of new blood clots in the arteries. In addition, it prevents the growth of clots already formed. Once the stroke is stabilized, the doctor usually suggests a lighter medication, such as aspirin, to be taken daily in the long term.
During the rehabilitation period, other medications may be helpful. For example, antispasmodic drugs can help relieve muscle spasms.
If there is bleeding
In the hours following this type of stroke, medication to lower blood pressure is usually administered to limit bleeding and the risk of resumption of bleeding. Sometimes bleeding triggers epileptic seizures. They will then be treated with drugs of the benzodiazepine class.
If an artery is blocked
Once the AVC stabilized, the doctor offers various tests to find out if other arteries are weakened by atherosclerosis. He can propose one or the other of the following surgeries as a preventive measure:
- A carotid endarterectomy. This procedure consists in “cleaning” the wall of the carotid artery with atherosclerosis. It has been practiced for about forty years and is intended to prevent the recurrence of stroke;
- Angioplasty. A balloon is placed in the artery affected by atherosclerosis to prevent blockage. A small metal rod is also inserted into the artery to prevent it from shrinking. This procedure is more risky than the previous one because, when the atherosclerotic plaque is crushed by the balloon, it is possible that plaque fragments are released and cause further blockage further into the cerebral artery.
If there is bleeding
It may be necessary to perform brain surgery to remove accumulated blood. If the surgeon discovers an aneurysm at the time of surgery, he/she will treat it to prevent it from breaking and another stroke to occur. The treatment usually consists of placing a platinum filament in the aneurysm. A clot of blood will then form around it and fill the dilatation of the blood vessel.
Note. It may happen that a medical examination reveals the presence of an unruptured aneurysm to the brain. Depending on the context, the doctor will recommend or not preventive surgery. If the patient is under 55, the doctor will usually offer this preventive surgery. If the patient is older, a choice must be made considering the benefits and risks of the operation. Indeed, the latter exposes the patient to a risk of neurological sequelae ranging from 1% to 2% and mortality risk of about 1 %. In addition, more studies are needed to know the real effect of such an intervention on stroke prevention.