The command centre of the body, your brain sends and receives messages that control everything you do. Its 100 billion brain cells – neurons – need a constant supply of oxygen carried in the blood.

Deprived of oxygen, brain cells can die within seconds.

A stroke is a brain injury caused by a lack of blood, and it happens to 50,000 Canadians each year.

When someone has a stroke, one of two things has happened: a blood clot blocked a vessel giving blood to the brain, or a blood vessel burst, interrupting blood flow to the brain.

When the brain doesn’t get blood, some of its 100 billion brain cells – neurons - can die. When a brain cell dies, it can't regenerate. Because the brain controls the body's every action, a stroke can have many outcomes, affecting things such as movement, speech, behaviour and memory.

Different areas of the brain control different functions, and when a stroke occurs, its effects can vary widely, depending on which section of the brain has had its blood flow restricted.

There are two main types of stroke:

Ischemic

In an ischemic stroke, a blood clot blocks an artery supplying blood to the brain. About 80 per cent of all strokes are ischemic, making it the most common form to afflict people.

There are two classifications of ischemic stroke. If the clot formed in an artery supplying the brain, it’s called a thrombotic stroke. If the clot formed elsewhere in the body and travelled through the bloodstream to a brain artery, it’s called an embolic stroke.

Hemorrhagic stroke

A hemorrhagic stroke occurs when a blood vessel in the brain ruptures, causing bleeding in the brain. Heavy bleeding can kill brain cells.

Hemorrhagic strokes are caused by faults in the brain's blood vessels, such as an aneurysm (a weakness in the wall of a blood vessel that bulges with blood) and a vascular malformation (a collection of malformed blood vessels in the brain that are present at birth, which can rupture and leak blood into the brain).