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Stroke

What Is A Stroke?

Last modified: 
17/04/2013 - 15:24

Contributing Author: Guy Slowik FRCS

A stroke occurs when the blood flow to a part of the brain is disrupted. Not enough blood reaches the affected part of the brain. The cells in the part of the brain affected do not get enough oxygen and begin to die.

Damage to the brain can cause loss of speech, vision, or movement in an arm or a leg, depending on the part of the brain that is affected. 

 

 

 

There are two main types of stroke:

In addition, some people experience brief warning signals that a major stroke is going to happen in the future. The medical term to describe these symptoms is transient ischemic attack or TIA. Sometimes called "mini-strokes", TIAs are exactly like a stroke, but they last only a few minutes (or sometimes as long as an hour) and leave no disability.

In many cases, a stroke will affect only one side of the body:

  • A stroke that damages the right side of the brain will affect the left side of the body.
  • A stroke that damages the left side of the brain will affect the right side of the body.

1. Stroke Caused By Blocked Blood Flow

About 85 percent of all strokes happen because not enough blood gets to the brain. Blood flow stops when an artery carrying blood to the brain becomes blocked. The technical name for this type of brain attack is cerebral infarction. It is also called ischemic stroke. "Ischemic" refers to a condition caused by a decreased supply of oxygenated blood to a body part.

The blockage can be caused either by a blood clot that forms in an artery in the brain, or by a blood clot formed elsewhere in the body that travels through the bloodstream to the brain. If this clot becomes stuck in an artery in the brain, a stroke can result.

Clots are more likely to form in arteries that are damaged by atherosclerosis, also called "hardening of the arteries," due to the buildup of cholesterol and other thick, rough, fatty deposits in the arteries.

The blockage also can be caused by a small piece of tissue, usually a blood clot, that has traveled through the bloodstream from elsewhere in the body.

In ischemic stroke, one of two major arteries is usually involved:

  • The carotid artery (most commonly involved site)
  • The basilar artery

The carotid arteries start at the aorta (just above the heart) and lead up through the neck, around the windpipe, and into the brain. The basilar artery is formed at the base of the skull from the arteries that run up along the spine, and branches off in the brain.

2. Stroke Caused By Bleeding In The Brain

The other 15 percent of strokes happen when an artery carrying blood to the brain bursts suddenly. The bursting can happen because of a weak spot in the wall of an artery called an aneurysm. This type of brain attack is called a hemorrhagic stroke.

Two kinds of stroke are caused by bleeding in the brain:

  • subarachnoid hemorrhage occurs when a blood vessel on the brain bursts and bleeds into the fluid-filled space between the brain and the skull. This type of stroke can happen at any age.
  • An intracerebral hemorrhage occurs when an artery bursts inside the brain, flooding the surrounding brain tissue with blood. This type of stroke is often associated with high blood pressure.

What Are "Mini-Strokes"?

A "mini-stroke" is exactly like a stroke, but it lasts only a short time and leaves no disability. The term for this event is transient ischemic attack or TIA.

A TIA happens when a blood clot clogs an artery temporarily, cutting off blood flow and, consequently, the supply of oxygen to cells. But the difference between a TIA and a stroke is that, with TIA, the blood clot dissolves on its own and blood flow is restored before permanent damage to the brain can occur.

TIAs are an extremely important warning sign for stroke and should never be ignored.

Nice To Know:

About 10 percent to 15 percent of strokes are preceded by TIAs ('mini-strokes'), which can happen days, weeks, or even months before a major stroke. However, not everyone who experiences a TIA will have a stroke in the future.

Nice To Know:

General recovery guidelines for stroke show:

  • 10 percent of stroke survivors recover almost completely
  • 25 percent recover with minor impairments
  • 40 percent experience moderate to severe impairments requiring special care
  • 10 percent require care in a nursing home or other long-term care facility
  • 15 percent die shortly after a stroke

Facts About Stroke:

  • Nearly 4 million people in the United States have survived a stroke and are living with the after-effects.
  • Each year, more than 500,000 Americans have a stroke.
  • Although stroke is still the third leading killer in the United States, the death rate from strokes has been cut nearly in half over the last two decades.
  • A stroke is always serious. Cells in the brain that become damaged cannot be repaired or regenerated. But other areas of the brain may take over the work of the damaged portion.
  • Most people know they should seek emergency medical help immediately if they are having symptoms of a heart attack. But the average stroke patient waits more than 12 hours before going to a hospital emergency department, losing precious time that could be critical to treatment.
  • Stroke was first recognized more than 2,400 years ago by Hippocrates, the father of medicine, who described a condition marked by the sudden onset of paralysis.
  • There are steps you can take to help prevent a stroke. Healthy living is very important in stroke prevention. There also are successful treatments if it does happen.

 

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Stroke

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From Andrew Maynard - Chair of the University of Michigan Department of Environmental Health Sciences, with help from David Faulkner - 2013 Master of Public Health graduate.