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About Stroke
Every individual case of stroke is different, which highlights
the problem of understanding the nature of stroke. From a
clinical point of view, a stroke is not a single condition,
but a collection of symptoms which in different people can
differ in severity and duration. Commonly encountered symptoms,
of which just one or several might be experienced, are:
- sudden weakness or numbness of the face, arm or leg on
one side of the body
- sudden loss of vision or dimness, notably in one eye
- speech problems – slurring, finding the right words, understanding
spoken language
- sudden, severe headache with no apparent cause
- dizziness, unsteadiness or sudden falls, especially when
any of the above are present
These symptoms may last for only a few minutes or hours.
If they clear up within 24 hours, the diagnosis is likely
to be a transient ischaemic attack or TIA. If they
last longer than 24 hours, then a stroke must be suspected.
Another common feature is the suddenness with which they start.
Often they will develop within a few minutes (even seconds),
less often in a few hours and only occasionally over a period
of days. Also, all of the symptoms usually develop together,
rather than one after the other. A severe stroke may progress
over a few hours and lead to deep unconsciousness and death.
But why should strokes be so different? The answer is that
there is nothing wrong with the affected part of the body
– the problem lies in areas of the brain which control it.
The symptoms are just a manifestation of an injury that has
occurred in the brain and which is preventing the right messages
being sent out to the body.
Damage in the brain area concerned with vision will affect
eyesight, while damage in the part controlling the leg may
cause instability, loss of use and loss of sensation in the
leg. Medical scientists have mapped the brain and a very accurate
understanding of which areas control which part of the body
is available. Because of that, the location of stroke damage
can often be deduced from the distribution of the symptoms.
The nerves coming from the right side of the brain control
the left side of the body and vice versa, so problems on the
left mean damage on the right side of the brain.
Damage arises because the brain tissue has been starved of
oxygen and energy. The brain has no reserves of either, so
restriction of the blood supply for longer than a few minutes
can have serious consequences. Oxygen reaches the brain in
the blood stream through four main arteries, the left and
right vertebral and the left and right internal carotid arteries,
and damage can result if any of these blood vessels become
blocked or if they rupture and cause internal bleeding.
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