Strokes occur when there is disruption in the blood supply to an area of the brain. Also known as cerebrovascular accidents (CVAs), there are two types: ischemic stroke, which occurs when a narrowed artery interrupts the blood supply, or hemorrhagic stroke, when there is actual bleeding or haemorrhage into the brain.
More than 80 per cent of strokes are ischaemic in type. This may occur when a partial clot forms in the heart or in the blood vessels of the neck which is carried in the bloodstream to the brain and gets lodged in an artery.
Up to 20 per cent of strokes are caused by a bleed into the brain from a burst blood vessel. This is called a cerebral haemorrhage and often causes a more serious kind of stroke.
The effects of a stroke can vary widely from one person to another. While a stroke may leave one person with a mild weakness, another may experience complete paralysis on one side of the body. As each area of the brain is responsible for different functions, the resulting problems will depend primarily on the site and size of the area affected by the stroke.
The effects of a stroke can be temporary or permanent. When the temporary effects last less than 24 hours, this is called a transient ischaemic attack (TIA). Also known as a mini-stroke, a TIA may be a warning of a full-blown stroke to come in the weeks and months ahead.
Both stroke and TIA may lead to loss of power in the muscles but there may also be difficulties with speech, emotions and behaviour. Intellectual abilities, the sensation of pain, heat, cold and pressure, and awareness of body parts may also be affected. These and problems with spatial awareness and orientation can lead to difficulties in carrying out self-care tasks and other activities.
About 2,000 people die from stroke in Ireland each year, while some 10,000 people are admitted to hospital with stroke. CVA is the third most common cause of death and the most common cause of acquired physical disability in Ireland.
CAUSES, SIGNS, SYMPTOMS AND DIAGNOSIS
The direct cause of stroke is the loss of blood supply to cells in the brain. Stroke destroys two million brain cells every minute so it is important to respond as quickly as possible to a suspected CVA. Indirectly, stroke is caused by the same pathological process that leads to heart attacks. Blood vessels supplying the brain get furred up due to atherosclerosis. Bits of clot may then break off and block an artery within the brain.
Stroke symptoms include:
- Numbness, weakness, or paralysis on one side of the body
- Slurred speech, difficulty thinking of words or understanding other people
- Confusion
- Sudden blurred vision or sight loss
- Being unsteady on your feet
- Severe headache
The FAST acronym is useful to help bystanders recognise when someone is having a stroke. FAST stands for:
F – Face: Has their face fallen on one side? Can they smile?
A – Arms: Can they raise both arms and keep them there?
S – Speech: Is their speech slurred?
T – Time to call 999 if you spot any single one of these signs.
The diagnosis of stroke is usually made on the basis of the person’s symptoms combined with the clinical signs identified by a doctor. One of the most useful tests for stroke is a CT scan. Computed tomography takes images of the brain in “slices” before they are reassembled to produce good-quality pictures of the brain structure. It is possible to identify even small strokes using this investigation. An important reason to carry out a CT scan is to establish whether the stroke is ischaemic or haemorrhagic. Clot-busting drugs are an important treatment for ishaemic strokes but are contraindicated if the cause is haemorrhagic.
PREVENTION AND DIAGNOSIS
When brain tissue is damaged as a result of a stroke, its recovery will depend on a number of factors including the site and extent of the damage. Many people find that over the first few weeks, some degree of function returns because while some brain cells have died, others have only been damaged and have the ability to recover. In some cases, other parts of the brain take over the functions previously undertaken by the affected area.
A good rehabilitation programme will encourage your return to as much normal function as possible through improved physical conditioning, reawakening of old skills and the acquisition of new ones. A physiotherapist, occupational therapist, and speech therapist working as a team in a dedicated stroke unit bring about the best rehabilitation outcomes.
Medical treatment in the form of clot-busting drugs is used for the majority of stroke patients diagnosed with ischaemic stroke.
Also known as thrombolytic therapy, the drugs are used to dissolve blood clots. When a blood clot forms it can travel to the brain causing blockage of a blood vessel, starving an area of the brain of blood and oxygen. Thrombolysis works by dissolving the blood clot quickly, allowing the return of blood to the tissue to help prevent further damage. Research has shown that clot-busting treatment given up to 4½ hours after onset of stroke symptoms helps improve clinical outcomes in patients with acute ischaemic stroke. In cases of haemorrhagic stroke, clot-busting drugs are not given as they could worsen the damage by increasing bleeding from the damaged blood vessel in the brain. The treatment is also contraindicated in those with severe high blood pressure, a history of recent trauma, or someone with active peptic ulcer disease.
A select group of people with blockages in the main neck arteries – the carotids – may be advised to have a surgical operation called a carotid endarterectomy. Designed to remove plaque from the carotid arteries, endarterectomy is a procedure which aims to reduce the risk of stroke. Performed under general anaesthetic, a small incision is made in the neck below the jaw to expose the carotid artery. Blood is rerouted via a tube (shunt) connecting the vessels below and above the surgical site. The carotid artery is opened and the plaque deposits removed.
Preventing stroke is similar to the prevention of coronary heart disease. Regular exercise, a good diet, not smoking and a moderate alcohol intake all help. You may require a lipid-lowering drug if your cholesterol is too high. And daily aspirin has been shown to protect against stroke. Patients with a heart rhythm disturbance called atrial fibrillation are at increased risk of stroke and are often prescribed warfarin or other blood-thinning drugs to lower their risk.
USEFUL RESOURCES
The Irish Heart Foundation and Croí, the west of Ireland cardiac foundation, are both excellent sources of information about stroke.
See www.irishheart.ie or phone 01-6685001 and www.croi.ie or phone 091-544310
[ www.nhs.co.uk/conditions/strokeOpens in new window ]
[ www.strokeassociation.org Opens in new window ]
Dr Muiris Houston is a specialist in general practice and occupational medicine and a medical education consultant