from the Website Patient.co.uk
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.)
What is the cause of a transient ischaemic attack (TIA)?
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 anaemia 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.)
Where does a blood clot come from to cause a TIA?
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 may 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 bloodstream, 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 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.
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. For example, in one research study published in 2007, the conclusion stated…”Early initiation of existing treatments after TIA or minor stroke was associated with an 80% reduction in the risk of early recurrent stroke.”
Therefore, see a doctor urgently if you suspect that you have had a TIA. Tests should be carried out quickly (within days of the TIA event) and treatment started promptly.
What tests are usual after a TIA?
You will normally 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. Tests that are commonly done include:
• A scan of your brain.
• An ultrasound scan of your carotid arteries. This is to see if you have severe narrowing of one of these arteries caused by atheroma.
• An ECG (electrocardiogram) to check for abnormal heart rhythms such as atrial fibrillation.
• Various blood tests.
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 some cases).
Medication reduces the risk of further blood clots forming.
Platelets are tiny particles in the blood which help blood to clot. Antiplatelet medication is usually advised if you have had a TIA. Antiplatelet medication reduces the ‘stickiness’ of platelets. This helps to prevent blood clots forming inside arteries, which helps to prevent a further TIA or a stroke. Aspirin (low dose) is the most commonly used antiplatelet drug. Other antiplatelet drugs that may be used include clopidogrel and dipyridamole.
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 clotable), but not so much as to cause bleeding problems. Therefore, you need regular blood tests if you take warfarin. See separate leaflets called ‘Atrial Fibrillation’ and ‘Atrial Fibrillation and Warfarin’ for details.
REDUCING RISK FACTORS
As described above, a common reason why a blood clot forms is because it develops over a patch of atheroma on the lining of an artery. Certain ‘risk factors’ increase the chance of atheroma forming – which increase your risk of having a stroke (and heart attack). You can reduce the risk of these if you reduce your ‘risk factors’. These are briefly mentioned below, but see separate leaflet called’Preventing Cardiovascular Diseases’ for more detail. Briefly, risk factors that can be modified are:
• Smoking. If you smoke, you should make every effort to stop. The chemicals in tobacco are carried in your bloodstream and can damage your arteries. If you smoke, stopping smoking can greatly cut your risk of having a stroke.
• High blood pressure. Make sure your blood pressure is checked at least once a year. If it is high it can be treated. High blood pressure usually causes no symptoms, but can be damaging to the arteries. If you have high blood pressure, treatment of the blood pressure is likely to have the greatest effect on reducing your risk of having a stroke.
• If you are overweight, losing some weight is advised.
• A high cholesterol. This can be treated if it is high.
• Inactivity. If able, you should aim to do some moderate physical activity on most days of the week for at least 30 minutes. For example, brisk walking, swimming, cycling, dancing, gardening, etc.
• Diet. You should aim to eat a healthy diet. Briefly, a healthy diet means:
o AT LEAST five portions of a variety of fruit and vegetables per day.
o THE BULK OF MOST MEALS should be starch-based foods (such as cereals, wholegrain bread, potatoes, rice, pasta), plus fruit and vegetables.
o NOT MUCH fatty food such as fatty meats, cheeses, full-cream milk, fried food, butter, etc. Use low fat, mono-, or poly-unsaturated spreads.
o INCLUDE 2-3 portions of fish per week. At least one of which should be ‘oily’ (such as herring, mackerel, sardines, kippers, pilchards, salmon, or fresh tuna).
o If you eat meat it is best to eat lean meat, or poultry such as chicken.
o If you do fry, choose a vegetable oil such as sunflower, rapeseed or olive oil.
o Try not to add salt to food, and limit foods which are salty.
o Alcohol. A small amount of alcohol (1-2 units per day) may be beneficial. One unit is in about half a pint of normal strength beer, or two thirds of a small glass of wine, or one small pub measure of spirits. However, too much can be harmful. In particular, binge drinking can increase your blood pressure.
o Men should drink no more than 21 units per week (and no more than four units in any one day).
o Women should drink no more than 14 units per week (and no more than three units in any one day).
o Diabetes is a risk factor. If you have diabetes, treatment to keep your blood sugar as near normal as possible is important.
About 1 in 20 people with a TIA has 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.