What is a stroke?

A stroke, or "brain attack," occurs when a blood vessel in the brain becomes blocked or bursts. The brain cannot store oxygen, so it relies on a network of blood vessels to provide it with blood that is rich in oxygen. A stroke results in a lack of blood supply, causing surrounding nerve cells to be cut off from their supply of nutrients and oxygen. When tissue is cut off from its supply of oxygen for more than three to four minutes, it begins to die.

Types of stroke

Strokes can appear as hemorrhagic strokes, ischemic strokes or transient ischemic attacks.

Hemorrhagic stroke — This type of stroke takes place when a weakened blood vessel in the brain ruptures. A hemorrhage, or bleeding from the blood vessel, occurs suddenly. The force of blood that escapes from the blood vessel can also damage surrounding brain tissue. Hemorrhagic stroke is the most serious kind of stroke. About 13% of all strokes are hemorrhagic. There are two types of hemorrhagic strokes: intracerebral and subarachnoid. Intracerebral hemorrhages are more common and occur when a blood vessel in the deep tissue of the brain ruptures. Subarachnoid hemorrhages usually occur when an aneurysm (a blood-filled pouch ballooned out from an artery) ruptures and bleeds into the space between the brain and the skull. This type of hemorrhagic stroke is most often caused by high blood pressure.

Ischemic stroke — This type of stroke occurs when a blood vessel in the brain develops a clot and cuts off the blood supply to the brain. A blood clot that forms in a blood vessel in the brain is called a “thrombus.” A blood clot that forms in another part of the body, such as the neck or lining of the heart, and travels to the brain is called an “embolus.” Blood clots often result from a condition called “atherosclerosis,” the build-up of plaque with fatty deposits within blood vessel walls. About 87% of all strokes are ischemic. 

Transient ischemic attack (TIA) — A TIA should be treated as seriously as a stroke. A TIA has the same symptoms as a stroke, but they only last several minutes, or up to 24 hours. Unlike a stroke, a TIA does not kill the brain cells, so there is no lasting damage to the brain. A TIA is considered a serious warning sign of stroke. About 1 in 3 people who have a TIA will go on to have a stroke.

What lasting effects can a stroke cause?

The effects of a stroke depend on the extent and the location of damage in the brain. Among the many types of disabilities that can result from a stroke are:

• Inability to move part of the body (paralysis).
• Weakness in part of the body.
• Numbness in part of the body.
• Inability to speak or understand words.
• Difficulty communicating.
• Difficulty swallowing.
• Vision loss.
• Memory loss, confusion or poor judgment.
• Change in personality; emotional problems.

Why does a stroke affect different parts of the body?

Nerve cells in the brain tissue communicate with other cells to control functions including memory, speech and movement. When a stroke occurs, nerve cells in the brain tissue become injured. As a result of this injury, nerve cells cannot communicate with other cells, and functions are impaired. If a stroke occurs on the right side of the brain, the left side of the body is affected, and vice versa.

How can stroke be prevented?

If you want to prevent a stroke, you must understand the risk factors that lead to stroke as well as the strategies that are used to reduce stroke. Make sure that you know the warning signs. Most of the stroke warning signs are painless:

• Sudden numbness or weakness of the face, arm or leg, particularly on one side of the body.
• Sudden difficulty understanding or speaking. May have either slurred speech or confused speech.
• Sudden difficulty seeing in one eye or both eyes.
• Severe dizziness and/or sudden loss of balance, coordination, or ability to walk.
• Sudden and severe headache for no reason.