Stroke is a sudden loss of brain function caused by the interruption of blood flow to the brain, as a result of either an ischemic stroke (a blood clot) or a hemorrhagic stroke (the rupture of a blood vessel and bleeding into or around the brain).
The interruption of blood flow to the brain causes brain cells (neurons) in the affected area to die. The effects of a stroke depend upon which part of the brain was injured and how much damage has occurred. About 80% of strokes are ischemic and 20% are hemorrhagic.
Stroke is a leading cause of disability worldwide, and approximately 400,000 Canadians are living with the effects of a stroke. It is also the third leading cause of death in Canada. About 60% of people who have had a stroke are left with some form of disability such as paralysis, sensory loss, memory loss, language problems, and vision problems. Some people may also suffer from depression or other emotional conditions after a stroke.
Risk factor modification, medications and, in some cases, surgery can help to minimize the risk of having a stroke.
An ischemic stroke is the result of blockage in blood flow to the brain caused by a blood clot. The buildup of plaque in the artery wall (atherosclerosis, or "hardening of the arteries") is an underlying cause for many ischemic strokes.
Atherosclerosis is a process in which fatty deposits (plaques) build up inside the blood vessels of the body, particularly in the carotid arteries of the neck, the coronary arteries of the heart, and the arteries of the legs. Atherosclerotic plaques can lead to a stroke by causing blockage of blood flow, or by dislodged plaque material (emboli) that can travel to the brain.
A hemorrhagic stroke is caused by bleeding into the brain (intracerebral hemorrhage) or bleeding around the brain (subarachnoid hemorrhage), which results from the breakage of a blood vessel. Brain hemorrhages may result from uncontrolled high blood pressure, and, in some cases, can be caused by structural problems within the blood vessels (e.g., aneurysms or vascular malformations).
There are numerous risk factors that can cause a stroke.
Factors you can't control are:
- age: The risk of stroke increases with advancing age.
- ethnicity: People of Indigenous, African, Hispanic, and South Asian descent have greater rates of high blood pressure and diabetes. These conditions increase the risk of stroke.
- family history: The risk of stroke may be higher if a parent or sibling has had a stroke before the age of 65.
- gender: Men have a higher risk of stroke than women who have not reached menopause.
- prior stroke or transient ischemic attack (TIA): Up to one-third of people who survive a first stroke or TIA will have another stroke within 5 years.
Factors you can control are:
- high blood pressure
- heart disease or atrial fibrillation (irregular heartbeat)
- cigarette smoking
- high cholesterol
- physical inactivity
- high alcohol intake (more than 10 drinks per week for women or more than 15 drinks per week for men)
Other factors that can lead to a stroke are:
- other medical conditions such as amyloid angiopathy and antiphospholipid antibody syndrome
- use of illicit drugs such as cocaine or LSD
- some medications, such as tamoxifen*, phenylpropanolamine, and thrombolytics
Other factors such as oral contraceptive use, hormone replacement therapy, or pregnancy and childbirth in women with pre-existing medical conditions may increase the risk of stroke in specific cases. Talk to your doctor about risk factors that may be relevant to you and your risk of stroke.
Symptoms and Complications
The symptoms of stroke appear suddenly, over a few minutes or hours, or at most a couple of days. Individuals should be able to recognize the 5 main symptoms of stroke and seek immediate medical attention if any of these symptoms occur:
- sudden weakness, paralysis or numbness of the face, arm, or leg (usually on only one side of the body)
- sudden loss of speech or trouble understanding speech
- sudden loss of vision (often in one eye only) or double vision
- sudden dizziness or loss of balance or coordination
- sudden severe and unusual headache (often described as "the worst headache of my life") with no known cause
The Heart and Stroke Foundation has a national campaign to help Canadians to recognize the signs of stroke and act quickly. They developed an easy way to remember the major signs of stroke called FAST:
Face is it drooping?
Arms can you raise both?
Speech is it slurred or jumbled?
Time to call 9-1-1 right away.
A transient ischemic attack (TIA) is a "mini-stroke" caused by a temporary interruption of blood flow to the brain. TIA symptoms are the same as those of a stroke except that the symptoms disappear within a few minutes to hours, usually lasting no longer than 24 hours. However, TIAs require immediate medical attention just like strokes. TIAs are important warning signs indicating you may be at risk of having a stroke in the future. Medical treatment is required.
Making the Diagnosis
If you develop symptoms of a stroke or transient ischemic attack (TIA), the doctor will ask about your medical history and any recent events that may be related to your symptoms.
After a physical and neurological examination, other tests can be done to help confirm the diagnosis. These may include imaging scans of the brain, such as CT (computed tomography) or MRI (magnetic resonance imaging), or electrical tests for checking brain activity such as an EEG (electroencephalograph).
Blood flow tests, which include angiography or Doppler ultrasound studies, among others, are often done to see whether there is a blockage of blood flow in the arteries. Additional tests may include blood tests, chest X-rays, and tests of the heart such as an ECG (electrocardiogram) or ultrasound (echocardiogram).
Treatment and Prevention
It is very important to recognize the signs and symptoms of a stroke and seek medical assistance immediately.
Preventing brain damage, disability, and aiding recovery depends on getting treatment in the first few hours following a stroke. Brain cells that are deprived of blood flow and oxygen for even just a few minutes will die.
Getting emergency medical assistance as soon as you experience symptoms of stroke is critical because there are treatments that may be given to help restore blood flow to the brain, prevent further tissue damage in the brain, or prevent recurrent strokes. Unfortunately, a significant number of individuals experiencing a stroke do not arrive at the hospital within the first 3 hours of a stroke to be eligible for potential treatment with clot-dissolving medications.
Medications that may be used for the treatment of stroke include both short-term and long-term medications.
- Short-term treatments include an injection or an oral antiplatelet agent: Thrombolytics (e.g., tissue plasminogen activator, tPA) are clot-dissolving medications that aim to break up the blockage within the affected blood vessel in an attempt to restore normal blood flow and limit damage to brain tissue. These medications can only be used in some individuals within 3 hours after the onset of symptoms and are given intravenously by trained health care professionals.
- Aspirin given within 24 to 48 hours after the stroke is the recommended antiplatelet agent.
Long-term treatments include medications taken by mouth to reduce the risk of recurrent strokes. These include:
- antiplatelets (e.g., acetylsalicylic acid [ASA], clopidogrel, dipyridamole,)
- anticoagulants or "blood thinners" (e.g., dabigatran, warfarin)
Talk to your doctor or pharmacist before using any herbal supplements or over-the-counter products, as these medications may increase the risk of bleeding while you are taking medications for stroke.
Other important treatments to be considered for stroke prevention include:
- blood pressure-lowering medications
- cholesterol-lowering medications
- surgical procedures (e.g., carotid endarterectomy) in some people
Another way to prevent stroke and related long-term illnesses is to reduce your risk factors with the following suggestions.
Modify your lifestyle:
- stop smoking tobacco
- increase your level of physical activity
- limit your alcohol intake to no more than 2 drinks per day (maximum 10 drinks per week) for women and no more than 3 drinks per day (maximum 15 drinks per week) for men
- maintain a well-balanced diet
- reach a healthy weight
- manage stress in your life
Manage your medications and medical conditions:
- take your medications as directed by your doctor and pharmacist
- if you have high blood pressure, monitor your blood pressure regularly
- if you have a heart condition such as congestive heart failure or atrial fibrillation, take medications as recommended by your doctor or pharmacist
- if you have diabetes, use a monitor to check your blood sugar regularly