A Transient Ischemic Attack (TIA, or mini stroke) causes symptoms similar to a stroke, but with a TIA, the symptoms go completely within 24 hours (with a stroke, the symptoms are usually more permanent).
Causes
The most common cause is a tiny blood clot in a blood vessel in the brain.
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 dissolves quickly, or nearby blood vessels are able to compensate.
This diagram shows the main arteries of the brain and a TIA blood clot:
The common site for a small blood clot to form is in a main artery in the neck. The carotid and vertebral arteries are the main arteries in the neck that supply blood to the brain. A small blood clot may break off and is then carried in the bloodstream, towards the brain. The arteries get progressively narrower and the clot travels until it becomes stuck. When it becomes stuck, it blocks the artery and stops the local blood supply.
In some cases a small clot forms inside a heart chamber and is carried in the bloodstream to the brain. This can happen with a condition called atrial fibrillation (AF) – often known by many people as an irregular heartbeat.
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 disappear.
A stroke occurs when part of the brain tissue dies (permanent brain damage) due to a lack of oxygen.
Symptoms
Unless the symptoms get better within a few minutes you need emergency treatment, as the cause might be a stroke rather than a TIA.
A Transient Ischemic Attack (TIA) 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 short-lived and soon go. This means that you recover fully, back to normal. (The word ischemic means a reduced supply of blood and oxygen to a part of the body.)
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.
Note: headache is NOT a typical feature of a TIA (or a stroke).
Diagnosis
Act F.A.S.T.
F – Facial weakness. Has their face fallen on one side? Can they smile?
A – Arm weakness. Can the person raise both arms and keep them there?
S – Speech disturbance. Is their speech slurred?
T – Time. Time to call 911 if you see any single one of these signs.
The FAST checklist does not cover every possible symptom of stroke or TIA. However, it is easy to remember and it is estimated that about 8 or 9 in 10 people with a stroke or TIA will have one or more FAST symptoms.
What tests are usual after a Transient Ischemic Attack?
After a suspected TIA, you will normally be advised to have several tests:
- A brain scan, either a CT or an MRI scan. This is done to make sure that you have not had a stroke rather than a TIA. In a few cases, a stroke can occur with complete and quick recovery. The scan is also done to make sure there are no other brain problems (for example a brain tumor) that may have given you symptoms that mimic a TIA. If you were already taking a blood thinner when you had the symptoms of a TIA, you need an urgent brain scan to make sure that you haven’t had a bleed in the 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. Narrowing (stenosis) of the carotid arteries is a risk factor for TIA and stroke.
- An electrocardiogram (ECG) to check for arrhythmias such as Atrial Fibrillation (AF).
- Blood tests. Your blood will be tested to make sure that you don’t have diabetes or high cholesterol (these are risk factors for TIA and stroke), and to make sure that you are not anemic, and do not have kidney problems. Other blood tests are sometimes done, but these are the main important ones.
- Blood pressure measurement.
Treatment
Warfarin is usually advised if you have a TIA where the source of the blood clot is from your heart (usually if you have the condition AF). Warfarin works by reducing some of the chemicals in the blood that are needed to make blood clot (it is an anticoagulant). The aim is to get the dose just right so the blood is ‘thinner’ than normal (less able to form clots), but not so much as to cause bleeding problems. Therefore, you need regular blood tests if you take warfarin.
Antiplatelet medication
Platelets are tiny particles in the blood that 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
Immediately after a TIA, you will probably be started on a daily dose of aspirin until your hospital investigations have been completed. If you were already taking low-dose (75 mg) aspirin, you will usually be advised to continue it at this dose.
Aspirin (low-dose) is the most commonly used long-term antiplatelet drug. If you are allergic to aspirin, or have had bleeding problems such as a stomach ulcer, other antiplatelet drugs may be used. If you have had a stroke in the past, and have now had a TIA, other antiplatelet drugs are usually used. These other drugs include clopidogrel (Plavix® or Grepid®) and dipyridamole (Persantin®, Persantin® Retard and Asasantin® Retard – which also contains aspirin).
Surgery
About 1 in 20 people with a TIA have severe narrowing of the carotid artery (carotid stenosis) due to a large build-up of atheroma. It might be suspected by listening with a stethoscope to the blood flow in your neck. Blood flow through a narrowed artery is turbulent, and this causes a noise called a bruit (carotid bruit). There is a good chance that you have significant narrowing of the carotid arteries if you have a carotid bruit. A type of ultrasound scan of the neck (called a duplex ultrasound scan) can diagnose this narrowing accurately (although sometimes other types of scans are done for the same reason).
Surgery to remove this narrowing may be an option in some people. It depends on several factors, such as how bad the narrowing is, whether you have had symptoms (such as a TIA or stroke) and what your general fitness is like (in terms of the risks of having major surgery).
General guidelines recommend that after a TIA patients should have a scan of the carotid arteries within a week of the event, and be operated on within another week if severe blockages are found. The main surgical procedure is called carotid endarterectomy (another procedure called carotid artery angioplasty and stenting is sometimes used for blocked carotid arteries).
A recent medical study showed that angioplasty and stenting leads to more short-term (within 30 days) complications, compared with carotid endarterectomy. The complications included stroke and death. At present, only carotid endarterectomy is recommended after TIA or stroke. Further medical trials are being performed comparing the two operations.