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What is a stroke?

A stroke is a sudden loss of brain function. It is caused by the interruption of flow of blood to the brain (ischemic stroke) or the rupture of blood vessels in the brain (hemorrhagic stroke). The interruption of blood flow or the rupture of blood vessels causes brain cells (neurons) in the affected area to die.

Stroke is a medical emergency. Recognizing and responding immediately to the stroke warning signs by calling 9-1-1 or your local emergency number can significantly improve survival and recovery.

What causes brain damage from stroke?

In a small number of cases, stroke-like damage to the brain can occur when the heart stops (cardiac arrest). The longer the brain goes without oxygen and nutrients supplied by blood flow, the greater the risk of permanent brain damage. Brain injuries can also result in uncontrolled bleeding and permanent brain damage. This is usually referred to as an Acquired Brain Injury.

What are the types of stroke?

Understanding the brain and the effects of stroke

Your brain is the most complex organ in your body. It consists of over 100 billion specialized nerve cells called neurons and it acts as a command centre for everything you do, think, sense and say. These neurons depend on the blood vessels in your brain for oxygen and nutrients. Neurons cannot duplicate or repair themselves.

Different parts of the brain control different functions. When someone has a stroke, the functions that are affected depend upon which area of the brain was damaged and how much damage occurred. Learning what the different parts of the brain do can help you understand why the effects of stroke can be so different among different people.


Last reviewed August 2009.

Last modified February 2012.