Two major types of stroke ischaemic and haemorrhagic
A stroke occurs when a blood clot blocks a blood vessel or artery, or when a blood vessel breaks and interrupts blood flow to an and bleeding occurs into an area of the brain.
Every stroke is different. The symptoms and effects vary according to the type of stroke, the part of the brain affected and the size of the damaged area. For some people the effects are severe, for some mild. Usually the symptoms come on suddenly but they may come on during sleep. Usually injury to one side of the brain affects the opposite side of the body.
There are two major types of stroke:
- An Ischaemic Stroke occurs when an artery carrying blood to part of the brain is blocked. The brain needs the constant supply of oxygen and glucose that the blood brings. If this blood supply is blocked for more than a few minutes then that part of the brain stops working properly and brain tissue at the centre of the area affected begins to die. If the blockage is not cleared within a few hours then that all the part of the brain supplied by the blocked vessel may die; that is, it permanently ceases to work properly. This is called brain infarction. Ischaemic strokes are the most common type of stroke, occurring more than five times as often as haemorrhagic stroke cerebral haemorrhages.
- A Haemorrhagic Stroke Cerebral Haemorrhage occurs when a blood vessel ruptures within the brain (called an intracerebral haemorrhage) or into the space surrounding the brain (called a subarachnoid haemorrhage). Blood in the artery is under pressure and so, as it spurts out, it tears some of the soft brain tissue and forms a large clot (or haematoma) that squashes the surrounding brain. Brain tissue on the rim of thein and around the clot may therefore die.
A mini stroke is called a Transient Ischaemic Attack (TIA).
- About 30% of patients who subsequently have an ischaemic stroke have a small warning episode termed a transient ischaemic attack.
- A TIA is like an ischaemic stroke in that it is results in the sudden loss of function of a particular part of the body because of a sudden lack of blood flow to a part of the brain.
- The difference between a TIA and an ischaemic stroke is that in a TIA the symptoms disappear completely within 24 hours. In 75% of cases the symptoms clear within one hour, often within only a few minutes, because the blockage in the artery clears itself very quickly before the affected brain tissue has died. 30% of people have damage evident on sensitive brain imaging techniques such as MRI after a TIA.
- A TIA is a very important warning that the person is at increased risk of a future stroke. It is essential that proper medical treatment is sought so that this risk can be significantly reduced.
Reviewed by Professor Alastair Corbett, Consultant Neurologist, Concord Hospital, Australia
Date created: 26 September 2003
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