What Is a Stroke?

Strokes Explained
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Types of strokes

A stroke occurs when blood flow to the brain is interrupted, either by a clot or a rupture in a blood vessel. When the part of the brain that’s deprived of blood can no longer get the oxygen and other nutrients it needs, it begins to die.

There are two types of stroke:

  • Ischemic strokes occur when a clot blocks a blood vessel to the brain. If blood flow is blocked only temporarily, it results in a transient ischemic attack (TIA), also known as a ministroke.
  • Hemorrhagic strokes occur when a blood vessel ruptures, causing blood to leak into the brain.

Ischemic strokes

Ischemic strokes, which account for more than 80 percent of all strokes, occur when a clot obstructs a blood vessel that supplies blood to the brain. Ischemic strokes usually result from atherosclerosis, a condition in which fatty deposits develop on the walls of blood vessels. There are two ways in which atherosclerosis can cause an ischemic stroke:

  • In cerebral thrombosis, a blood clot develops right at the clogged part of the vessel.
  • In a cerebral embolism, a blood clot forms in another location, usually the heart or large arteries of the chest and neck. If part of the clot breaks loose, it will travel through the bloodstream until it reaches a blood vessel that's too small to allow its passage. When this occurs in the brain, the result is a stroke.

Ischemic strokes can also result from atrial fibrillation, a condition in which the upper chambers of the heart beat rapidly and irregularly, causing blood to pool and clot. If one of these clots breaks loose, it can result in a stroke.

Transient ischemic attacks

Sometimes called ministrokes, transient ischemic attacks (TIAs) are warning signs that an ischemic stroke may be looming on the horizon. In a TIA, the blockage of blood flow to the brain is only temporary, so symptoms disappear after a short time. But since TIAs are often precursors of a major stroke, they should be taken just as seriously.

Hemorrhagic strokes

In a hemorrhagic stroke, a blood vessel actually ruptures and bleeds into the brain. This can occur in two ways:

  • In an intracerebral hemorrhage, a ruptured blood vessel bleeds directly into the brain tissue. As blood pools in the brain, it compresses the surrounding brain tissue and may also cause a sudden increase in pressure within the brain. The affected brain cells can be damaged and may begin to die.
  • A subarachnoid hemorrhage occurs when a blood vessel outside of the brain ruptures, filling the subarachnoid space (the area of skull surrounding the brain) with blood. This causes a sudden increase in pressure around the brain, which may result in rapid loss of consciousness or death.

Hemorrhagic strokes usually occur when a blood vessel is already weakened in one of two ways:

  • In an aneurysm, a weakened region of a blood vessel stretches out like a balloon. If left untreated, the ballooning vessel may continue to stretch until it bursts.
  • An arteriovenous malformation (AVM) is a cluster of abnormally formed blood vessels. Although AVMs don't always cause problems, these vessels are more likely to rupture.

Stephanie Trelogan

Stephanie Trelogan writes about heart disease, stroke, and depression issues that concern people caring for their aging parents. See full bio

about 6 years, said...

i had a stroke July 2007 and only regained a fraction of my movement. Speech was not affected but still can't function with my left arm and although i walk with a cane, my balance is still off. If I had a choice between a stroke or heart attack, I would pick the heart attack!!!!

about 6 years, said...

I knew some of the facts but in a muddled way, thank you now I undestand much better, I have come accross several such cases (including one dear family member), but wasn't clear about what had caused these alarming attacks, thanks again,

over 6 years, said...

I think the article was excellent, just as it was.

over 6 years, said...

i'm being tested for possibiliy of a mini stroke and this gives me a better understanding of what they are

over 6 years, said...

I am bothered with a pain that follows a vein from about 5 inches from the top of my left shoulder, up my neck and into my head. It stops just above my eyebrow. This pain will last anywhere from a few minutes to half an hour. My doctor has ordered two dopplers on this vein and the results have shown no abnormality. I have not experienced this now for a couple of months, where I used to have it two or three times a month.

over 6 years, said...

u only name 2 kinds of strokes

over 6 years, said...

Unless the patient has a clot-based stroke there is really nothing a bystander can do during the initial stages of a stroke. You could have a full -blown stroke in front of the best ER docs and neurologists and unless you can be treated with tPA there is NO therapy to be given. They all just wait until you wake up and tell you you had a stroke.

over 6 years, said...

the article is very helpful because here in Nigeria , very many people believe in the myth that stroke is an omen that occur due to spiritual attack of demons, as a result of incantation and invocation from enemies.

over 6 years, said...

Telling what one could do assuming that they are "first on the scene" would help. Description of the various symptoms between the different specific strokes would help as it would seem to me that aspirine (some recommend putting one under the stroke victims toung might improve things) might be contra-productive under certain circumstancesi.e.intercranial bleeding or aracnoid stroke, etc. I mean there "ain't a gonna be a silver billet" but certainly "for warned is for armed". What would universally improve a stroke "incidence" if one were able to intervene at the time the malady actually occured? Thank You

over 6 years, said...

it is very educative

over 6 years, said...

it is helpful because it is very educative.

over 7 years, said...

My stroke was caused from high blood pressure. i had neither a bleed or a clot. So, could you talk about that rather than saying only 2 kinds of strokes............

over 7 years, said...

cookier, You will need to read up on mental imagery which will at least start the neuroplastic changes you need to recover functionality.

over 7 years, said...

I had a stroke and it was neither a clot or a bleed. Mine was caused strictly from high blood pressure. That was 3 years ago and I still do not have the use of my left arm and hand. I have had both physical and occupational therapy. Does anyone know of a mind control therapy wheras you can "will" your body to do things and control the areas of the brain to act and react?

almost 8 years, said...

I understand the terminology used by the nurses now.