A Stroke is a result of a sudden death of brain cells due to lack of oxygen, caused by blockage of blood flow or rupture of an artery to the brain. Also known as a cerebrovascular accident or CVA, occurs when part of the brain loses its blood supply and the part of the body that the blood-deprived brain cells control stops working. This loss of blood supply can be ischemic because of lack of blood flow, or hemorrhagic because of bleeding into brain tissue.
The death rate and level of disability resulting from strokes can be dramatically reduced by immediate and appropriate medical care
The loss of blood supply can be ischemic because of lack of blood flow, or hemorrhagic because of bleeding into brain tissue. This explains why we have two causes of stroke.
This type of stroke may occur when a blood clot or a piece of atherosclerotic plaque (cholesterol and calcium deposits on the wall of the inside of the heart or artery) breaks loose, travels through the bloodstream, and lodges in an artery in the brain. When blood flow stops, brain cells do not receive the oxygen and glucose they require to function and a stroke occurs. This type of stroke is referred to as an embolic stroke. For example, a blood clot might originally form in the heart chamber as a result of an irregular heart rhythm, like atrial fibrillation. Usually, these clots remain attached to the inner lining of the heart, but occasionally they can break off, travel through the bloodstream (embolism), form a plug in a brain artery, and cause a stroke. An embolism can also originate in a large artery (for example, the carotid artery, a major artery in the neck that supplies blood to the brain) and then travel downstream to clog a small artery within the brain.
This stroke is caused by the blockage of an artery in the brain by a clot (thrombosis).It’s the most common cause of a stroke. The part of the brain that is supplied by the clotted blood vessel is then deprived of blood and oxygen. As a result of the deprived blood and oxygen, the cells of that part of the brain die and the part of the body that it controls stops working. Typically, a cholesterol plaque in one of the brain’s small blood vessels ruptures and starts the clotting process.
Risk factors for narrowed blood vessels in the brain are the same as those that cause narrowing blood vessels in the heart and heart attack (myocardial infarction).
Strokes are usually classified by what mechanism caused the loss of the blood supply, either ischemic or hemorrhagic. A stroke may also be described by what part of the brain was affected (for example, a right temporal stroke) and what part of the body stopped working (stroke affecting the left arm).
An ischemic stroke is caused by an artery in the brain being obstructed or blocked, preventing oxygen-rich blood from being delivered to brain cells. The artery can be blocked in a couple of ways. In a thrombotic stroke, an artery can narrow over time because of cholesterol buildup, called plaque. If that plaque ruptures, a clot is formed at the site and prevents blood from passing through to the brain cells downstream, which are then deprived of oxygen.
In an embolic stroke, the artery is blocked because of debris or a clot that travels from the heart or another blood vessel. An embolus or embolism is a clot, a piece of fatty material or other objects that travel within the bloodstream that lodges in a blood vessel to cause an obstruction.
Blood clots that embolize usually arise from the heart. The most common cause of these blood clots is a heart arrhythmia called atrial fibrillation, where the upper chambers of the heart, the atria, do not beat in an organized rhythm. Instead, the chaotic electrical rhythm causes the atria to jiggle like a bowl of Jell-O. While blood still flows to the ventricles (the heart’s lower chambers) to be pumped to the body, some blood along the inner walls of the atrium can form small blood clots. If a clot breaks off, it can travel or embolize to the brain, where it can cause a stroke.
The carotid arteries are two large blood vessels that provide the brain with blood supply. These arteries can narrow, or develop stenosis, with cholesterol plaque that builds up over time. The surface of the plaque is irregular and bits of debris can break off and embolize to block blood vessels downstream in the brain.
A TIA or transient ischemic attack (also known as a mini-stroke) is the same as a stroke, except that the symptoms last for a short amount of time and no longer than 24 hours. If you, or someone else, show any of the signs of stroke you must seek treatment immediately.
TIA symptoms may not last long but are still very serious. It’s a sign that a person is at risk of going on to have a stroke. That is why a TIA is often called a warning stroke yet too many people are unaware of the link between TIA and stroke and is not getting the services and support they need.
When a blood vessel leaks and spills blood into brain tissue, those brain cells stop working. The bleeding or hemorrhage is often due to poorly controlled high blood pressure that weakens the wall of an artery over time. Blood may also leak from an aneurysm (a congenital weakness or ballooning of an artery wall) or from an AVM (arteriovenous malformation), a congenital abnormality where an artery and vein connect incorrectly. The bleeding can form a hematoma that can put pressure on small vessels and decrease or shut off blood flow to brain tissue.
There is no way of knowing whether you are having a mini-stroke or a stroke when the symptoms first start, so you need to seek immediate medical help. Just like stroke, a mini-stroke is a medical emergency. If you think you have had a mini-stroke and have not sought medical attention see your GP urgently.
- There may be no warning signs of a stroke until it occurs. It is why high blood pressure may be one of the risk factors for stroke, is called the silent killer.
- Some patients may experience transient ischemic attack (TIA) that can be thought of as a stroke that has resolved itself. The symptoms may be mild or dramatic and can mimic a stroke with weakness, numbness, facial droop, and speech difficulties, but these symptoms may only last few minutes. TIAs should not be ignored since they may offer an opportunity to look for potentially reversible or controllable causes of stroke. As well, there is no guarantee that the symptoms of stroke will resolve on their own. For that reason, a TIA should be considered an emergency and medical care should be accessed immediately.
- Amaurosis fugax describes the temporary loss of vision in one eye that occurs because of an embolus of a blood clot or debris to the artery that supplies the eye. While it only involves vision, this situation should be considered a type of TIA.
Symptoms of stroke depend upon where the brain function has stopped due to loss of its blood supply. Often, the patient may present with multiple symptoms including the following:
- Acute change in level of consciousness or confusion
- Acute onset of weakness or paralysis of half or part of the body
- Numbness of one-half of the body
- Partial vision loss
- Double vision
- Difficulty speaking or understanding speech
- Difficulty with balance and vertigo
The symptoms of ischemic and hemorrhagic stroke may be the same but patients with hemorrhagic stroke may also complain more of a headache and vomiting.
- High blood pressure (hypertension). This is defined as high pressure (tension) in the arteries, which are the vessels that carry blood from the heart to the rest of the body. Blood readings are given as two numbers. The systolic blood pressure (the top number) equals the pressure in the arteries as the heart contracts. The diastolic pressure (the bottom number) is the pressure in the arteries as the heart relaxes. Normal blood pressure is below 120/80; blood pressure between 120/80 and 139/89 is called “pre-hypertension,” and a blood pressure of 140/90 or above is considered high while a systolic blood pressure of about 90 to 100 is considered low blood pressure.
- High cholesterol
- Diabetes
- Smoking
Recognizing the signs of stroke or mini-stroke and calling for an ambulance is crucial. The quicker a patient arrives at the hospital, the quicker they will receive appropriate treatment and the more likely they are to make a better recovery.
Prevention is always the best treatment, especially when the illness can be life-threatening or life-altering. Ischemic strokes are most often caused by atherosclerosis, or hardening of the arteries, and carry the same risk factors as do heart attacks (myocardial infarction, coronary artery disease) and peripheral vascular disease. These include high blood pressure, high cholesterol, diabetes, and smoking. Stopping smoking and keeping the other three under lifelong control greatly minimizes the risk of ischemic stroke.
Patients who have had a transient ischemic attack (TIA) are often prescribed medications to decrease their risk of a subsequent stroke. These include medications to lower blood cholesterol levels and control blood pressure. In addition, antiplatelet medications may be prescribed to make platelets less likely to promote blood clot formation. These include aspirin,
Patients with a TIA are usually evaluated for carotid stenosis or narrowing of the carotid artery. Surgery to open critically narrowed arteries may decrease stroke risk.
Lifelong control of high blood pressure decreases the risk of hemorrhagic stroke.
Atrial fibrillation is the most common cause of embolic stroke. Ideally the heart rhythm can be converted to normal sinus rhythm but in those patients whose hearts are chronically in atrial fibrillation, anticoagulation or “blood thinning” minimizes the risk of blood clot formation in the heart and subsequent embolization and stroke. Which drug that is used to “thin” the blood depends on the specific patient and their individual situation. Patients who are prescribed blood thinning medication decrease the chance of a stroke but are at risk for bleeding complications
