What is stroke?

A stroke is a "brain attack". It can happen to anyone at any time. It occurs when blood flow to an area of brain is cut off. When this happens, brain cells are deprived of oxygen and begin to die. When brain cells die during a stroke, abilities controlled by that area of the brain such as memory and muscle control are lost.

How a person is affected by their stroke depends on where the stroke occurs in the brain and how much the brain is damaged. For example, someone who had a small stroke may only have minor problems such as temporary weakness of an arm or leg. People who have larger strokes may be permanently paralyzed on one side of their body or lose their ability to speak. Some people recover completely from strokes, but more than 2/3 of survivors will have some type of disability.

FACTS ON STROKE

Here are some key points about stroke. More detail and supporting information is in the main article.

• During a stroke, the brain does not receive enough oxygen or nutrients, causing brain cells to die.
• There are three main kinds of stroke: ischemic strokes, hemorrhagic strokes and transient ischemic attacks.
• Ischemic strokes are caused by a narrowing or blocking of arteries to the brain.
• Hemorrhagic strokes are caused by blood vessels in and around the brain bursting or leaking.
• Strokes need to be diagnosed and treated as quickly as possible in order to minimize brain damage.
• Remembering the F.A.S.T. acronym can help with recognizing the onset of stroke (Face, Arms, Speed, Time - explained below).
• Treatment depends on the type of stroke.
• Ischemic strokes can be treated with 'clot-busting' drugs.
• Hemorrhagic strokes can be treated with surgery to repair or block blood vessel weaknesses.
• The most effective way to prevent strokes is through maintaining a healthy lifestyle.

Hemorrhagic stroke

There are two types of stroke, hemorrhagic and ischemic. Hemorrhagic strokes are less common, in fact only 15 percent of all strokes are hemorrhagic, but they are responsible for about 40 percent of all stroke deaths.

A hemorrhagic stroke is either a brain aneurysm burst or a weakened blood vessel leak. Blood spills into or around the brain and creates swelling and pressure, damaging cells and tissue in the brain. There are two types of hemorrhagic stroke called intracerebal and subarachnoid.

INTRACEREBRAL HEMORRHAGE

The most common hemorrhagic stroke happens when a blood vessel inside the brain bursts and leaks blood into surrounding brain tissue (intracerebal hemorrhage). The bleeding causes brain cells to die and the affected part of the brain stops working correctly. High blood pressure and aging blood vessels are the most common causes of this type of stroke.

Sometimes intracerebral hemorrhagic stroke can be caused by an arteriovenous malformation (AVM). AVM is a genetic condition of abnormal connection between arteries and veins and most often occurs in the brain or spine. If AVM occurs in the brain, vessels can break and bleed into the brain.  The cause of AVM is unclear but once diagnosed it can be treated successfully.

SUBARACHNOID HEMORRHAGE

This type of stroke involves bleeding in the area between the brain and the tissue covering the brain, known as the subarachnoid space. This type of stroke is most often caused by a burst aneurysm. Other causes include:

• AVM
• Bleeding disorders
• Head injury
• Blood thinners

Ischemic stroke

Ischemic stroke occurs when a blood vessel carrying blood to the brain is blocked by a blood clot. This causes blood not to reach the brain. High blood pressure is the most important risk factor for this type of stroke. Ischemic strokes account for about 87% of all strokes. An ischemic stroke can occur in two ways.

CLOSE ALL

EMBOLIC STROKE

In an embolic stroke, a blood clot or plaque fragment forms somewhere in the body (usually the heart) and travels to the brain. Once in the brain, the clot travels to a blood vessel small enough to block its passage. The clot lodges there, blocking the blood vessel and causing a stroke. About 15% of embolic strokes occur in people with atrial fibrillation (Afib). The medical word for this type of blood clot is embolus.

THROMBOTIC STROKE

A thrombotic stroke is caused by a blood clot that forms inside one of the arteries supplying blood to the brain.  This type of stroke is usually seen in people with high cholesterol levels and atherosclerosis. The medical word for a clot that forms on a blood-vessel deposit is thrombus.

Two types of blood clots can cause thrombotic stroke: large vessel thrombosis and small vessel disease.  

Large Vessel Thrombosis

The most common form of thrombotic stroke (large vessel thrombosis) occurs in the brain’s larger arteries. In most cases it is caused by long-term atherosclerosis in combination with rapid blood clot formation. High cholesterol is a common risk factor for this type of stroke.

Small Vessel Disease

Another form of thrombotic stroke happens when blood flow is blocked to a very small arterial vessel (small vessel disease or lacunar infarction). Little is known about the causes of this type of stroke, but it is closely linked to high blood pressure.

Transient ischemic attack (TIA)⁴

TIAs are different from the aforementioned kinds of stroke because the flow of blood to the brain is only briefly interrupted. TIAs are similar to ischemic strokes in that they are often caused by blood clots or other debris.

TIAs should be regarded as medical emergencies just like the other kinds of stroke, even if the blockage of the artery is temporary. They serve as warning signs for future strokes and indicate that there is a partially blocked artery or clot source in the heart.

According to the Centers for Disease Control and Prevention (CDC), over a third of people who experience a TIA go on to have a major stroke within a year if they have not received any treatment. Between 10-15% will have a major stroke within 3 months of a TIA.

Symptoms of stroke

Strokes occur quickly and, as such, symptoms of stroke often appear suddenly without warning.

The main symptoms of stroke are as follows:

• Confusion, including trouble with speaking and understanding
• Headache, possibly with altered consciousness or vomiting
• Numbness of the face, arm or leg, particularly on one side of the body
• Trouble with seeing, in one or both eyes
• Trouble with walking, including dizziness and lack of co-ordination.

Strokes can lead to long-term problems. Depending on how quickly it is diagnosed and treated, the patient can experience temporary or permanent disabilities in the aftermath of a stroke. In addition to the persistence of the problems listed above, patients may also experience the following:

• Bladder or bowel control problems
• Depression
• Pain in the hands and feet that gets worse with movement and temperature changes
• Paralysis or weakness on one or both sides of the body
• Trouble controlling or expressing emotions.

Preventing a stroke

The best way to prevent a stroke is to address the underlying causes. This is best done by living healthily, which means:

• Eating a healthy diet
• Maintaining a healthy weight
• Exercise regularly
• Not smoking
• Avoiding alcohol or moderating consumption.

Eating a healthy diet means getting plenty of fruits, vegetables and healthy whole grains, nuts, seeds and legumes; eating little or no red or processed meat; limiting intake of cholesterol and saturated fat (typically found in foods of animal origin); and minimizing salt intake so as to support healthy blood pressure.

Other measures taken to help reduce the risk of stroke include:

• Keeping blood pressure under control
• Managing diabetes well
• Treating obstructive sleep apnea (if present).