Transient ischemic attack, or TIA, is
the medical term for neurologic symptoms, such as weakness or numbness,
which begin suddenly, resolve rapidly and completely, and are caused by a
temporary lack of blood in an area of the brain. TIAs are common,
affecting at least 240,000 people each year in the United States.
Some
people call TIAs "warning spells" because anyone who has a TIA is at
risk for stroke. As a result, it is important to be aware of the signs
and symptoms of TIA and seek treatment as soon as possible.
This
topic discusses the symptoms, diagnosis, and treatment of transient
ischemic attacks. Topics that discuss strokes are available separately.
WHAT IS A TRANSIENT ISCHEMIC ATTACK? — A
transient ischemic attack (TIA) is an episode in which a person has
signs or symptoms of a stroke (eg, numbness; inability to speak) that
last for a short time. Symptoms of a TIA usually last between a few
minutes and a few hours. A person may have one or many TIAs. People
recover completely from the symptoms of a TIA.
A TIA is a warning
sign that a person may be at high risk for a stroke; immediate treatment
can decrease or eliminate this risk. It is important to get help right
away if you think you may be having a TIA or a stroke.
Most
TIAs result from narrowing of the major arteries to the brain, such as
the carotid arteries. These blood vessels provide oxygenated blood to
brain cells. These arteries can become clogged with fatty deposits,
called plaques. Plaques partially block the artery, and can lead to the
formation of a blood clot. This blood clot (thrombus) can further or
completely block the artery. More frequently, a blood clot will detach
from the wall of the artery, travel along the bloodstream to smaller
branches, and block blood flow to the area of brain fed by that artery.
In
some cases, TIAs can be caused by blood clots that form in the heart
and travel to the brain (called emboli). TIAs can also occur as a result
of narrowing and closure of small blood vessels deep inside the brain.
If
an artery remains blocked for more than a few minutes, the brain can
become damaged or infarcted (that is, the tissue in that area dies).
- With a TIA, the symptoms resolve completely (usually within a few hours or less)
- With a stroke, the symptoms may not resolve completely
Many
people do not have a TIA before a stroke. However, a TIA is a warning
sign that a person is at risk for a stroke. It is important to recognize
and treat the symptoms of TIA to reduce the risk of having a stroke.
Transient ischemic attack symptoms — Symptoms
of TIA are typically short-lived, lasting only a few minutes to hours. A
TIA may occur only once, or may be recurrent (several times per day or
once per year).
The most common symptoms of TIA include the following:
- Hand, face, arm, or leg weakness or numbness
- Difficulty speaking (garbled speech), slurred speech, or inability to speak at all
- Blurred, doubled, or decreased vision in one or both eyes
These
symptoms are identical to those of a stroke. When the symptoms first
develop, it is not easy to tell if a person is having a stroke or TIA.
TRANSIENT ISCHEMIC ATTACK RISK FACTORS — A number of factors can increase a person's risk of TIA, including the following:
- Age greater than 40 years
- Heart disease (eg, atrial fibrillation, carotid stenosis)
- High blood pressure
- Smoking
- Diabetes
- High blood cholesterol levels
- Illegal drug use or heavy alcohol use
- Recent childbirth
- Previous history of transient ischemic attack
- Sedentary lifestyle and lack of exercise
- Obesity
- Current or past history of blood clots
Risk of stroke after TIA — The
risk of stroke after a TIA is highest in the first few days to weeks
after the TIA. For example, the risk of having a stroke in the first two
days after TIA has been estimated to be 4 to 10 percent. People with
certain characteristics are thought to have a higher risk (eg, closer to
10 percent) of stroke compared to people without these characteristics.
- Diabetes
- Older than 60 years
- Blood pressure (higher than 140/90), measured after the TIA
- Weakness on one side of the body (eg, face, arm, leg) during the TIA
- Speech problems during the TIA
- TIA symptoms for 60 minutes or longer
TRANSIENT ISCHEMIC ATTACK DIAGNOSIS — Despite
the fact that the symptoms of TIA usually resolve quickly, TIA is a
medical emergency that should be evaluated as soon as possible because
there is a high risk of a stroke after TIA.
When to call for emergency medical assistance — Anyone
who is concerned that they are having a TIA should call for emergency
medical attention immediately. Emergency medical services are available
in most areas of the United States by calling 911.
Emergency
medical services (EMS) personnel will respond as rapidly as possible,
and will take the person to a hospital equipped to care for people
during and after a TIA. Most clinics and medical offices do not have the
ability to diagnose and treat people with a TIA. For these people,
every minute is important.
Anyone who may be having a TIA should not
drive to the hospital and should not ask someone else to drive, but
should call 911. In addition, it is not necessary to call a doctor or
nurse to ask for advice because precious time will be lost waiting for a
return call. Getting to the Emergency Department quickly is the best
option. Calling 911 is safer than driving for two reasons:
- From
the moment EMS personnel arrive, they can begin evaluating and treating
the patient. If the patient drives to the hospital, treatment cannot
begin until after arriving in the emergency department.
- If a
dangerous complication of a TIA occurs on the way to the hospital, EMS
personnel may be able to treat the problem immediately.
Brain imaging — Depending
upon the results of the history and physical examination, the clinician
will usually order blood tests and a brain imaging test (eg, CT scan or
MRI). The imaging test allows the clinician to see the area of the
brain affected by the TIA.
Blood vessel imaging — The
larger blood vessels that supply the brain can also be imaged using CT
or MRI; these scans are referred to as CTA (computed tomography
arteriogram) and MRA (magnetic resonance arteriogram). Ultrasound can be
used to determine if there are blockages in blood vessels.
Occasionally,
a catheter must be inserted through a blood vessel in the groin and
threaded up to the blood vessels of the neck, where dye is injected to
highlight any areas of blockage. This is called conventional
arteriography.
Heart testing — Because
a large number of people with TIA also have coronary artery disease,
there is a risk of ischemia (lack of blood flow) in the heart during the
TIA. In some cases, the person is not able to tell the clinician that
he or she feels chest pain. An electrocardiogram (ECG) is usually
performed to help the clinician diagnose and treat heart problems as
quickly as possible.
In some people with TIA, the heart or the
aorta can be the source of a TIA-causing blood clot. Other heart
testing, such as an echocardiogram, may be needed. This test uses sound
waves to examine the heart and the aorta (the large vessel that arises
directly from the heart; blood vessels that supply blood to the brain
originate in the aorta).
Heart monitors (also called Holter or
loop monitors) may be used to monitor the heart's rhythm for an extended
period of time to detect paroxysmal (intermittent) atrial fibrillation.
TRANSIENT ISCHEMIC ATTACK TREATMENT — The
optimal treatment of a TIA depends upon the presumed cause of the TIA,
the time since the first TIA symptoms occurred, and the person's
underlying medical problems.
The goal of treatment is to reduce the risk of having a stroke. There are several types of treatment:
- Treating risk factors, such as high blood pressure
- Antiplatelet therapy
- Anticoagulant therapy
- Revascularization
Treating risk factors — Anyone
who has had a TIA has an increased risk of having a TIA or stroke in
the future, especially within the first 48 hours after the TIA. The
treatments discussed above can significantly reduce this risk. In
addition, lifestyle changes and careful management of underlying medical
problems can help to reduce the risk of future strokes. These include
the following:
- Treatment of high blood pressure
- Controlling diabetes
- Stopping smoking
- Treating high cholesterol and lipids
Antiplatelet therapy — Platelets
are a type of cell circulating in the blood that normally clump
together to stop bleeding. In TIA, platelets clump together and form
clots inside narrowed arteries. The platelets "plug" themselves and/or
the clot that forms around the plug can temporarily block blood flow in
the brain. Antiplatelet therapy is given to help prevent new clots from
developing.
Current guidelines from the
American Heart Association/American Stroke Association and the American College of Chest Physicians
recommend that most patients with a TIA and no contraindication receive
an antiplatelet agent to reduce the risk of subsequent stroke. These guidelines note that
aspirin,
clopidogrel, and the combination of aspirin plus extended-release
dipyridamole
(Aggrenox) are all acceptable options for treatment. An exception is
that patients who have a TIA caused by embolism from the heart due to an
irregular heart rhythm (atrial fibrillation) should be treated with
anticoagulation.
Dipyridamole and aspirin —
Dipyridamole
is a medication that may be given after a TIA to reduce the risk of
stroke. It is often given in an extended-release form, which combines
dipyridamole with
aspirin (called Aggrenox®, which contains 200 mg dipyridamole (ER-DP) and 25 mg aspirin). It is taken two times per day.
Side effects of
dipyridamole include headache, upset stomach,
and/or diarrhea. Headaches usually improve over the first week.
Aspirin —
Aspirin can help to reduce the risk of a future stroke by approximately 25 percent.
The recommended dose of aspirin is between 50 and 325 mg per day.
Higher doses of aspirin have no additional benefit but do increase the
risk of gastrointestinal bleeding.
In the United States, one advantage of
aspirin
compared to other antiplatelet medications is cost; a one-month supply
of aspirin costs approximately $3 compared to at least $160 per month
for combined
dipyridamole and aspirin and at least $135 per month for
clopidogrel.
Clopidogrel —
Clopidogrel (Plavix®) is an antiplatelet medication that is also used in patients after TIA to reduce the risk of stroke.
Compared to
aspirin,
clopidogrel
causes a slightly higher frequency of rash and diarrhea, but a slightly
lower frequency of stomach upset or gastrointestinal bleeding.
Clopidogrel is not usually recommended in combination with
aspirin because the combination is no more effective at preventing another stroke than clopidogrel alone.
Anticoagulant therapy — Anticoagulants
are often, but incorrectly, referred to as blood thinners. They work by
decreasing the formation of blood clots. Anticoagulant therapy is
usually recommended for selected people with an irregular heart rhythm
(atrial fibrillation) who have had a TIA or are at risk for a TIA or
stroke. The oldest and the most commonly used anticoagulant in this
situation is
warfarin.
Newer anticoagulants are now available that appear to have more a more
favorable side effect profile (ie, fewer excessive bleeding events)
compared with warfarin.
Warfarin (Coumadin®) —
Warfarin is a pill that is taken by mouth. People who take warfarin must be
closely monitored with blood tests to ensure that the correct dose is
used and that the risk of excessive bleeding or developing blood clots
is minimized.
Revascularization — Revascularization
is the medical term for reestablishing blow flow to an area. In people
who have had a TIA, revascularization usually refers to a surgical
procedure (carotid endarterectomy) that opens a blocked artery in the
neck (the carotid artery), which improves blood flow to the brain and
reduces the risk of stroke. The amount of blockage in the carotid artery
can be measured with a non-invasive test, such as ultrasound, CT, or
MRI.
Carotid
endarterectomy is most successful when it is performed by a vascular
surgeon who has specialized training and experience with the procedure.
However, even in experienced hands, the procedure has risks, including
bleeding, brain injury, stroke, and even death.
Some people are
likely to benefit from carotid endarterectomy. For others, the risks of
the procedure are greater than the potential benefits. Placement of a
stent in the carotid artery is an alternative if carotid endarterectomy
is not an option or if the person prefers not to have surgery.
WHERE TO GET MORE INFORMATION — Your healthcare provider is the best source of information for questions and concerns related to your medical problem.