Transient Ischaemic Attack (TIA)

What is a transient ischaemic attack (TIA)?

A transient ischaemic attack (TIA) is a set of symptoms that lasts a short time and occurs because of a temporary lack of blood to part of the brain. It is sometimes called a 'mini stroke'. However, unlike a stroke, the symptoms are transient and soon go. (The word 'ischaemic' means a reduced supply of blood and oxygen to a part of the body.)

In most cases, a TIA is caused by a tiny blood clot that becomes stuck in a small blood vessel (artery) in the brain. This blocks the blood flow, and a part of the brain is starved of oxygen. The affected part of the brain is without oxygen for just a few minutes, and soon recovers. This is because the blood clot either breaks up quickly, or nearby blood vessels are able to compensate.

(There are other uncommon causes of a TIA. These include: blood clotting problems, tiny bleeds into the brain, blood disorders such as polycythaemia and sickle cell anemia where the blood is very thick, spasm of a small artery in the brain, and other uncommon problems of the brain or its blood vessels. These are not dealt with further in this leaflet.)

The common site for a small blood clot to form is on a patch of atheroma in a main artery (blood vessel) in the neck. (Atheroma is explained below.) The carotid and vertebral arteries are the main arteries in the neck which take blood to the brain. Either the small blood clot make break off from the atheroma, or a tiny part of the blood clot may break off. This then travels up the artery carried by the bloodstream until it becomes stuck in a smaller artery in the brain.

In some cases a small clot forms in a heart chamber and is carried in the bloodstream to the brain.

A small blood clot is likely to break up quickly when it gets stuck. Therefore, no permanent damage is done to the brain during a TIA, and symptoms soon go. (However, if a larger blood clot forms and breaks away into the bloodstrem, it is likely to cause a stroke - where permanent damage to the brain occurs. There is a separate leaflet that deals with stroke.)

Why does a blood clot form in a blood vessel or heart chamber?

A blood clot can form if platelets stick to a patch (plaque) of atheroma.

• Platelets are tiny particles in the blood which help the blood to clot when a blood vessel (an artery or vein) is cut.
• Atheroma plaques are like fatty lumps that develop within the inside lining of arteries.
• Platelets sometimes stick onto an atheroma plaque inside an artery and form a clot.

A common site for atheroma to develop, and a blood clot to form, is in a large artery in the neck. A blood clot may also form as a complication of some heart conditions. For example, people with a condition called 'atrial fibrillation' have a turbulent (rough) flow of blood in the heart which may cause a small blood clot to form.

What are the symptoms of a TIA?

Symptoms of a TIA are transient (temporary). They develop suddenly, and usually peak in less than a minute. The duration of symptoms varies, but symptoms usually go within an hour (typically within 2-15 minutes). Sometimes symptoms last up to 24 hours. The symptoms that develop depend on which part of the brain is affected. Different parts of the brain control different parts of the body. Therefore, symptoms may include one or more of the following.

• Weakness or clumsiness of a hand, arm, or leg.
• Difficulties with speech.
• Difficulties with swallowing.
• Numbness or pins and needles of a part of the body.
• Brief loss of vision, or double vision.

How serious is a TIA?

In itself, a TIA does no harm or permanent damage to the brain, and the symptoms soon go. However, a TIA indicates that you have a tendency to form blood clots in your blood vessels or heart. Therefore, if you have a TIA you have a higher than average risk of developing a larger blood clot which may cause a stroke or heart attack in the future. (A stroke causes permanent rather than temporary symptoms.)

• Without treatment - about 1-2 in 10 people who have a TIA have a stroke within the following year. This is much higher than the average risk of someone of the same age having a stroke who has not had a TIA. The most risky time is within the first month following a TIA - which is why treatment is advised as soon as possible after you have a TIA. Also, within a year of having a TIA, about 3 in 100 people have a heart attack (myocardial infarction) due to a blood clot in a blood vessel of the heart.
• With treatment - the above risks are reduced.

How common is a TIA?

The exact number of cases is not known. This is because many people who have a TIA do not report it to their doctor as the symptoms go away, and the importance of the symptoms is not recognised. However, it is estimated that a TIA occurs in about 35 per 100,000 people each year in the UK. About 1 in 5 people who have a stroke have had a TIA in the past.

Are any tests usual after a TIA?

You will usually be advised to have various tests. The main aim of the tests is to find if there is any problem that may increase your risk of blood clots forming, and to check for other uncommon causes of TIA. For example:

• An ECG (electrocardiogram) to check for abnormal heart rhythms such as atrial fibrillation.
• Various blood tests.
• A scan of your brain to check for other causes of a TIA.
• An ultrasound scan of your carotid arteries may also be advised. This is to see if you have severe narrowing of one of these arteries caused by atheroma.

What is the treatment if you have a TIA?

The aim of treatment after a TIA is to reduce your risk of having a stroke, heart attack, or further TIAs. Aspects of treatment include the following.

• Medication to reduce the risk of blood clots forming.
• To reduce any 'risk factors' that you may have.
• Surgery (but this is only suitable in a minority of cases).

MEDICATION

Medication reduces the risk of further blood clots forming. Current guidelines recommended that following a TIA, most people should take two medicines each day - low dose aspirin and dipyridamole. After two years, the dipyridamole is usually stopped but the aspirin is usually continued for life. Some people take clopidogrel or warfarin.

Aspirin (low dose)
Aspirin at low dose is an an antiplatelet drug (it reduces the 'stickiness' of platelets). This reduces the risk of a blood clot forming. The risk of having a stroke after a TIA is cut by about a quarter if you take a daily low dose of aspirin. This means that about 1 in 4 strokes that would have occurred without aspirin treatment are prevented. The risk of a heart attack is also reduced. The usual dose is 75 mg daily (which is a lower dose than you would take when using aspirin for pain relief. It is 'low-dose' aspirin that is used to prevent blood clots.)

Most people who take a daily low dose of aspirin have no side-effects. However, a small number of people have side-effects. These include:

• Bleeding of the stomach or guts. This is more common if you have a stomach or duodenal ulcer. See a doctor soon if you are taking aspirin and develop a persistent stomach upset or pain, blood in vomit, or black faeces (stools).
• Rarely, some people are allergic to aspirin.
• Aspirin sometimes makes breathing symptoms worse if you have asthma.

Read the leaflet that comes with the medicine packet for full details of possible side-effects.

Dipyridamole
Dipyridamole is also an antiplatelet drug but works in a different way to aspirin to prevent platelets from sticking together. Aspirin plus dipyridamole reduces the risk of having a stroke more than either alone, which is why both medicines are usually advised.

Some people develop side-effects from dipyridamole. These include: headache, dizziness, feeling sick and diarrhoea. However, these effects are often short-lived and tend to pass if you persevere with treatment. Allergy (hypersensitivity) to dipyridamole is rare. Some people with angina find that their angina symptoms become worse after staring dipyridamole. Read the leaflet that comes with the medicine packet for full details of possible side-effects.

Clopidogrel
Clopidogrel is another antiplatelet drug that is sometimes used if there is problems with taking aspirin that cannot be overcome. For example, if you are allergic to aspirin or have severe side-effects from aspirin.

Warfarin
Warfarin is usually advised if you have a TIA where the source of the blood clot is from your heart. (Usually if you have a condition called atrial fibrillation.) Warfarin works by reducing some of the chemicals in the blood that are needed to make the blood clot (it is an anticoagulant). The aim is to get the dose of warfarin just right so the blood is 'thinner' than normal (less clottable), but not so much as to cause bleeding problems. Therefore, you need regular blood tests if you take warfarin. For details see separate leaflets called 'Atrial Fibrillation' and 'Atrial Fibrillation and Warfarin'.

REDUCING RISK FACTORS

As described, a common reason why blood clots form is because they develop over plaques of atheroma on the lining of blood vessels. One aim of treatment is to prevent a build up of atheroma. Certain 'risk factors' increase the risk of damaging arteries and causing other effects which increase the risk of atheroma forming. The following risk factors may be relevant for some people who have had a TIA.

• High blood pressure. This usually causes no symptoms, but can be damaging to the arteries. If you have a TIA and have high blood pressure, treatment to reduce blood pressure is likely to have the greatest effect on reducing your risk of having a stroke.
• Diabetes is a risk factor. If you have diabetes, treatment to keep your blood sugar as near normal as possible is important.
• Cholesterol and blood lipids (fats). A diet high in fats can lead to a build up of cholesterol and other fats in your bloodstream. This can contribute to atheroma forming. Diet sheets showing which foods are best, and which to avoid, are commonly available. Medication is also commonly advised to lower your cholesterol level.
• Smoking is a big risk factor. The chemicals in tobacco are carried in your bloodstream and can damage your arteries. Smokers can reduce their risk of having a stroke or heart attack by quitting smoking.
• Exercise. On average, people who exercise regularly are less prone to develop atheroma. Regular exercise is advised for most people. It does not matter how old you are, it is never too late to start building up fitness. Any exercise is good. A daily brisk walk for at least 30 minutes is a good start. (However, you may not be able to exercise if you have certain other medical problems.)
• Obesity is a risk factor. Try to lose some weight if you are overweight.
• Alcohol in excess is a risk, but a moderate amount is beneficial. It is thought that 1-2 glasses of wine, or up to a pint of beer per day, may help to prevent heart and stroke disease.

SURGERY

About 1 in 20 people with a TIA have severe narrowing of the carotid artery due to a large build up of atheroma. Surgery to remove this may be an option. Successful surgery reduces the risk of a future stroke by about a half. However, like all operations, there is a small risk from the operation itself. A specialist will advise on the pros and cons of this operation if you are found to have severe narrowing of a carotid artery.

© EMIS and PIP 2005   Updated: September 2005   PRODIGY Validated