What is a stroke?
What happens during a stroke?
During a stroke the blood supply to a part of your brain is interrupted or stopped. All brain cells need a constant supply of blood for normal function. With no blood flow brain cells start to die after just 3 minutes. It doesn’t take long for damage to occur. Brain cells cannot regenerate so once a brain cell has died it cannot recover at all. Unless rapid action is taken to restore blood flow large numbers of cells will die and cause permanent brain damage.
The picture on the right shows a CT scan of the brain after a stroke. The greyish white area inside the white rectangle is the damaged part. Althouigh it doesn't look very big compared to the rest of the brain the effects can be devastating.
How does your brain work?
Your brain is made up of many millions of brain cells. They have a rich network of connections with each cell joined to thousands of others by long thin nerves. The cells communicate or ‘talk’ to each other all the time and control all your everyday activities. For example your nose is itchy. This information goes to the sensory region of the brain via sensory nerves around the nose. The brain decides the itch needs scratching. The sensory part of the brain sends information to the motor part, which sends the information to the muscles, and your nose is scratched. Several different parts of the brain have to ‘talk’ to each other for even a simple action
Types of strokes
There are 2 types of strokes. They are ischaemic and haemorrhagic strokes
Ischaemic strokes
Ischaemic is medical speak for not enough blood. In an ischaemic stroke a clot blocks either the brains’ blood vessel or it is too narrow and not enough blood can flow. Blood cannot reach parts of the brain and the cells soon start to die. It’s the commonest cause of strokes with around 75% of strokes classed as ischaemic strokes. The main risk factors are high blood pressure, atherosclerosis (damage and furring up of blood vessel walls), smoking and an irregular heartbeat.
Haemorrhagic strokes
Haemorrhagic is medical speak for too much blood. In a haemorrhagic stroke the brain blood vessel bursts and the blood leaks and causes brain damage. It happens in around 25% of strokes and can affect any age group from babies to octogenarians. The main risk factors are aneurysms (weak blood vessel walls which stretch like a balloon before ‘popping’), high blood pressure (especially if untreated or unknown) and blood clotting disorders.
What damage occurs?
Your brain’s blood supply is enough for everyday use but there is not really any ‘spare capacity’ in the system. So when you have stroke it’s not really possible to divert blood from elsewhere to compensate.
The trouble is the damaged area swells up over the next day or two. As the skull surrounds the brain it can’t expand out so instead the healthy brain cells next to the damaged areas get squeezed and squashed. If squashed enough they die also and swell which repeats the effect. So over the course of a few days the brain damaged area can get bigger. That’s why initial rapid hospital treatment is essential to cut down on the additional damage.
Why are there such different problems after a stroke?
The problems you have after a stroke depend on the part of the brain damaged. If the left side of your brain is damaged it can affect movement on the right side of your body. It can also cause speech problems, difficulty in comprehension, inability to find the right words and possibly confusion. If the right side of your brain is damaged it affect’s movement on the left side of your body but doesn’t as often cause speech and comprehension problems but still can do.
What’s the point of rehabilitation?
Often after a stroke the initial problems such as with speech and movement start to improve after a few days to weeks. This is because brain cells that aren’t dead but have been damaged need time to recover. However this is only a small silver lining. For better recovery you need months of rehabilitation involving physiotherapy, speech therapy, occupational therapy and writing and reading if necessary.
It was thought the brain was ‘static’ and once damaged no new connections could be made. This is completely untrue. With the right stimulation the brain can make many new connections and bypass the damaged area. It just needs the right stimulation.
This stimulation is information flowing into your brain and you using your brain. Stroke rehabilitation is a whole large topic in itself and being actively researched. Rehabilitation aims to maximise your recovery and stimulate the brain to make the new connections to bypass the damaged areas. Other parts of the brain can also take over control of different functions but NOT automatically. It needs lots of work.
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