What is a stroke?
A stroke happens when there is a loss of blood flow to part of the brain. Your brain cells cannot get the oxygen and nutrients they need from blood, and they start to die within a few minutes. This can cause lasting brain damage, long-term disability, or even death.
There are several possible underlying causes:
- Cerebral thrombosis: Sudden blockage of one of the branches of a cerebral artery. As in a heart attack, a clot forms in an already diseased (atheromatous) artery – blocking it. The affected part of the brain loses its supply of oxygen and nutrition. The brain cells die very quickly – within a few minutes – much faster than heart muscles similarly affected.
Sometimes the effect is very short lived – maybe because the artery is in spasm or not completely blocked. If the symptoms settle within twenty four hours the attack is called a Transient Ischaemic Attack (TIA).
- Cerebral embolus: A small clot, usually from the heart, is thrown out into the cerebral circulation and causes a sudden blockage. The underlying cause is almost always a disturbance of heart rhythm called atrial fibrillation (AF). AF is very common in older people and for most of them the cause of this rhythm disturbance is unknown. It affects about 7 in 100 people over the age of 65 and becomes gradually more common with increasing age. CVD risk factors such as obesity, hypertension and diabetes all increase AF risk. Older people with AF should take blood thinners for life to prevent this type of stroke.
- Cerebral haemorrhage – or bleed: Bleeding into or around the brain causes increased in pressure in that area and thus prevents blood getting to where it should – hence the brain damage and the resultant stroke. This is very different to cerebral thromboses or TIAs. It occurs in younger people and is often caused by congenital weakness in one of the cerebral arteries.
This the commonest form of stroke seen in Westernised societies and the type which I will be talking about here – though I will talk a bit about atrial fibrillation next time. According to the Stroke Association, there are more than 100,000 strokes in the UK each year and more than 1.2 million stroke survivors, many with severe ongoing disabilities. Stroke is the fourth biggest killer in the UK and costs the country about £26 billion annually.
These strokes occur against a background of long-standing arterial disease – atheroma – and share many of the risk factors of other forms of arterial disease like coronary disease and peripheral vascular disease, both of which I have covered recently. The risk factors, however, have a somewhat different emphasis in stroke. Raised blood pressure, for instance, is more important as a provoker of strokes but cigarette smoking, obesity, diabetes and metabolic syndrome are all important.
What does a stroke look like?
That all depends upon how big it is and which part of the brain is affected. There is rapid loss of brain tissue, and the most recognisable result is loss of movement of one side of the body – so called “hemiplegia”. The full blown picture includes drooping of one side of the face with loss of use of the arm and leg on the same side. If this is the dominant side, speech is usually lost as well.
Damage to the brain can be reduced by rapid introduction of a stent into the damaged artery or by giving blood-clot-dissolving drugs – hence the public health campaign ‘FAST’ designed to promote rapid diagnosis and transfer to hospital. F=facial weakness, A=Arm weakness, S=Speech difficulties and T =Time – get on with urgent referral.
Hemiplegia is just one of the possible features of a stroke. Any region of the brain can be involved and may produce such disparate damage as loss of speech, severe giddiness, changed behaviour, numbness, loss of sight and loss of cognition. One very serious outcome of cerebrovascular disease is “vascular dementia” which is the gradual deterioration in brain function caused by repeated small strokes or stroke-like episodes. Vascular dementia is very common and it is nearly as common a cause of dementia as Alzheimer’s disease.
Usually, after a few days, spontaneous recovery begins as other regions of the brain take over some of the functions of the damaged area. It is at this stage that muscle building exercise becomes so important in promoting recovery and the restoration of function as completely as is possible.
Next time I will talk more about exercise, both as treatment but also its role in prevention this devastating condition.