How do strokes work?

In a stroke, something disrupts the normal blood supply to parts of the brain. Without oxygen, affected brain cells will begin to die. Tune in as Marshall explains the causes of -- and treatments for -- strokes.

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Episode Transcript

Speaker 1 (00:00):
Welcome to Brainstuff from how Stuff Works dot com where
smart Happens. Hi Am Marshall Brain with today's question, how
do strokes work? Like strokes that happened inside of people's
brains Over the weekend, a video made the rounds on YouTube.

(00:24):
The video shows a newscaster named Serene Branson giving a
report outside the Grammy Awards. Her first few words are okay,
but then what follows is undecipherable. It appears that she's
forgotten how to speak and can only link unrelated sounds together.
According to early reports, she was quickly rushed to the hospital.

(00:46):
Later reports disputed the early reports, and who knows what
really happened. But when those early reports came out, the
speculation was that she had suffered from a stroke. In
a stroke, something goes wrong with the supply to the brain.
In Branson's case, it appeared that the blood supply to
her speech center was suddenly interrupted. Everyone has heard of

(01:09):
a heart attack because heart attacks are the number one
killer in America according to the c d C, and
most people understand the cause of heart attacks. On the
outside of the heart, there are blood vessels that supply
oxygen and nutrients to the hearts muscle cells. If one
of those blood vessels gets clogged, either with plaque or

(01:29):
with a blood clot, part of the heart muscle runs
out of oxygen and starts dying. A stroke is the
same kind of thing that happens in the brain, cutting
off oxygen to an area of the brain and causing
brain cells to start dying. Strokes are currently the number
three cause of death in the United States. Strokes are

(01:49):
categorized by the way in which the blood supply is interrupted.
In the most common type of stroke, something blocks in artery.
The two things that can blow an artery in the
brain are the same two things that can block an
artery in the heart, either plaque or a blood clot.
Plaque is a fatty substance that builds up on the
inside of arteries, slowly filling them and shrinking the amount

(02:13):
of blood that can flow. If enough plaque builds up,
it cuts off blood flow completely and causes a stroke.
This is the most common way to have a stroke.
Blood clots are less likely than plaque, but they have
exactly the same effect. One advantage of a stroke caused
by a blood clot is that clots can sometimes be
dissolved with clot busting drugs. If dissolved quickly enough, the

(02:36):
brain can sometimes recover. The other type of stroke is
a hemorrhagic stroke, and here there's a rupture instead of
a blockage. One of the blood vessels inside the brain
breaks and starts bleeding. This can not only cut off
the blood supply, but may also cause pressure on parts
of the brain from the blood that escapes. The rupture

(02:57):
can come from an aneurysm, a thin part of a
larger blood vessel that pops like a balloon, or a rupture,
and a small blood vessel often triggered because blood pressure
is too high. Once a stroke occurs, there are a
number of telltale signs that may appear. A sharp, sudden
headache that comes out of nowhere is one of the
classic signs. Slurred speech, as in the case of Serene Branson,

(03:22):
is another. A sudden inability to understand or respond to
spoken commands usually indicates a stroke as well. If a
limb suddenly goes numb or goes limp or it looks
like the muscles on one side of the face have
stopped working, that would be another classic sign of a stroke.
Strange sudden vision problems would be another. The place where

(03:43):
the stroke occurs controls the symptoms. For example, if the
stroke occurs near the part of the brain that controls
the right arm, then the right arm will go limp.
There are something like seven hundred thousand strokes in the
United States every year. They are fairly common events, especially
in older adults. If you're visiting with a friend who

(04:03):
suddenly manifests strange symptoms like those described above, time is
of the essence. The quicker a stroke is treated, the
better the chances of recovery. Call nine one one immediately
and keep the person having the stroke calm until help arrives.
For more on this and thousands of other topics, does
that how stuff works dot com and don't forget to

(04:25):
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