Transient Ischemic Attack
- reversible ischemic neurologic disease (RIND)
A transient ischemic attack (TIA) is an injury to the brain caused by a temporary interruption in its blood supply. A TIA is like a stroke, except that it lasts only a brief time. The occurrence of a TIA is a signal that the person may have a stroke in the near future.
What is going on in the body?
During a transient ischemic attack, there is a lack of blood flow to a portion of the brain. This causes symptoms in the body depending on the part of the brain that is affected. A TIA can last up to 24 hours. However, typical TIAs often last less than 30 minutes. The person remains conscious during the episode.
What are the causes and risks of the condition?
Transient ischemic attacks are caused by a temporary interruption of the blood flow to brain cells. Since a TIA is a short-term type of stroke, the risk factors for stroke apply to TIAs as well.
The American Heart Association has recently issued guidelines for stroke prevention. The guidelines discuss risk factors for stroke in 3 categories: nonmodifiable, well-documented modifiable, and less well-documented or potentially modifiable.
The nonmodifiable factors are ones that cannot be changed by the individual and include:
- increasing age. A person's risk of stroke doubles each year after age 55.
- race. Strokes occur approximately twice as often in blacks and Hispanics as they do in whites.
- gender. Men have a 50% higher chance of stroke than women do.
- family history of stroke or transient ischemic attack
Well-documented modifiable risk factors are those that can be changed by the individual in conjunction with his or her healthcare professional. These factors are linked to stroke by strong research findings, and there is documented proof that changing the risk factor lowers a person's risk of stroke.
These factors include:
high blood pressure
carotid artery arthrosclerosis, or narrowing of one of the arteries in the neck
sickle cell anemia, a blood disorder that forms abnormal red blood cells
high cholesterol levels in the blood, including total cholesterol and LDL (known as "bad" cholesterol). Low levels of HDL ("good" cholesterol) are also cause for concern.
atrial fibrillation, an abnormal heart rhythm
Less well-documented or potentially modifiable risk factors for stroke are those that have less proof of either a link to stroke or the impact of modifying the risk factor. These factors include:
high blood levels of homocysteine, a blood component sometimes associated with a higher risk of stroke
drug abuse such as cocaine
blood disorders, such as blood that clots easily or deficiencies of various blood components
hormone replacement therapy (HRT). The AHA currently states that the risk of stroke associated with HRT appears low but needs further study.
use of birth control pills, or oral contraceptives
Several recent studies have identified factors that seem to increase or decrease the risk of stroke in particular groups of people. These studies, which warrant further investigation, include these findings:
People who were treated for high blood pressure with thiazide diuretics, such as hydrochlorothiazide, had a significantly lower stroke risk than people on ACE inhibitors or calcium channel blockers.
Women ages 39 to 50 who ate more fish and omega-3 polyunsaturated fatty acids had a reduced risk of stroke. This was particularly true in women who did not take aspirin regularly.
Individuals who drank the equivalent of one glass of wine a day had a 32% lower risk of stroke than those who did not drink alcohol.
Phenylpropanolamine, a compound contained in appetite suppressants and cold remedies, significantly increased the risk of hemorrhagic stroke in women 18 to 49 years of age. The Food and Drug Administration (FDA) has since asked manufacturers to remove phenylpropanolamine from their products.
What can be done to prevent the condition?
Transient ischemic attacks can be minimized by addressing known risk factors for stroke. The American Heart Association guidelines for stroke prevention address both modifiable and less well-documented or potentially modifiable risk factors.
Measures to reduce the modifiable risk of high blood pressure
- measurement of blood pressure in adults at least every 2 years to screen for high blood pressure
- weight control
- physical activity
- moderation in alcohol intake
- moderate sodium intake
- for those who smoke, quitting smoking
- medications to treat high blood pressure if the person's blood pressure is over 140/90 after 3 months of these lifestyle modifications, or if the initial blood pressure is over 180/100
Other measures to reduce an individual's modifiable risk factors for stroke may include:
- smoking cessation using nicotine patches, counseling, and formal smoking programs
- control of blood sugar levels in a person with diabetes through medication, diet, and exercise
- the use of ramipril in people with diabetes. A recent study showed that people with diabetes have a 33% lower risk of stroke if they take ramipril.
- careful evaluation of asymptomatic carotid stenosis to determine the need for surgery.
- semiannual screening of children with sickle cell anemia, using ultrasound to determine the child's risk of stroke
- treatment of atrial fibrillation with blood thinners such as aspirin or warfarin, depending on the person's age and other risk factors
- monitoring of high levels of total cholesterol or LDL, as well as low levels of HDL. Depending on the blood levels and the person's other risk factors, medications to lower cholesterol may be given.
Coronary artery surgery, such as an endarterectomy, may be indicated. An endarterectomy opens the narrow portion of the artery and increases the blood flow to the brain. People with carotid stenosis should also work closely with their healthcare providers to control other risk factors for stroke.
Measures to reduce less well-documented or potentially modifiable risks for stroke may include:
- weight reduction in overweight persons
- 30 or more minutes of moderate exercise a day for most individuals. People with heart disease or disabilities should be in a medically supervised exercise program.
- a healthy diet for preventing heart disease, containing at least 5 fruits and vegetables a day
- for those who drink alcohol, drinking in moderation. The AHA defines moderate drinking as no more than 2 drinks a day for men and 1 drink a day for women.
- seeking treatment for drug abuse
- monitoring of blood levels of homocysteine. For most individuals, a well-balanced diet following the food guide pyramid will provide enough folic acid and B vitamins to maintain a healthy homocysteine level. For people with elevated homocysteine levels, supplements containing folic acid and B vitamins may be recommended.
- avoiding the use of oral contraceptives in women with other stroke risk factors
How is the condition diagnosed?
The first step in diagnosis of transient ischemic attack is a medical history and physical exam. This may be all that is needed to make the diagnosis. In other cases, further tests may be needed. Cranial MRIs and cranial CT scans can show whether or not there is bleeding in the brain, which can help with some treatment decisions.
Other tests may be ordered to help determine the cause of the TIA. For instance, an ultrasound of the carotid arteries can detect blockage. An ultrasound of the heart or echocardiogram can reveal heart muscle damage or a clot. A heart tracing (ECG) can show abnormal heartbeats, such as atrial fibrillation, or certain changes from a heart attack.
Long Term Effects
What are the long-term effects of the condition?
There are usually no long-term effects of the transient ischemic attack itself. However, a recent study showed that people who had a TIA increased their chance of having a stroke by 50% in the 3 months following the TIA. Twenty percent of these strokes were fatal, and two-thirds were disabling.
Furthermore, the increased risk of stroke in the 3 months after a TIA was linked to 5 factors:
- age over 60 years
- a TIA lasting more than 10 minutes
with the TIA
- speech impairment
with the TIA
What are the risks to others?
TIAs are not contagious and pose no risks to others.
What are the treatments for the condition?
Most people with transient ischemic attacks are treated immediately with aspirin, and then with blood thinners if they do not have bleeding into the brain. Blood thinners help prevent further TIAs or strokes. Because the symptoms of a TIA are the same as those of a stroke in its beginning stages, the emergency medical system should be contacted immediately.
These symptoms include a sudden onset of:
- severe headache
- weakness or numbness of the face, arm, or leg, especially on one side of the body
- trouble walking or loss of balance, known as ataxia
- speech impairments, including trouble speaking or understanding speech
- visual impairments
Specific types of medication may be needed in special cases. For instance, those with a heart infection may be given antibiotics. Those with arteritis are often given corticosteroids, such as prednisone, to reduce inflammation in the brain.
If an individual has significant narrowing of the carotid arteries, a carotid endarterectomy may be recommended to widen them. This surgical procedure removes the cholesterol plaques and may prevent future strokes. The decision to perform surgery will depend on the person's neurological status, the type of plaque clogging the artery, and whether the plaque has a break in it, known as a rupture.
What are the side effects of the treatments?
Side effects depend on the treatments used. For instance, aspirin may cause allergic reactions, stomach upset, or bleeding. Clot-busting medications can cause excessive bleeding. A ventilator may sometimes cause damage to the lungs or an infection.
A carotid artery endarterectomy can be complicated by bleeding, infection, or an allergic reaction to the anesthetic. On rare occasions, carotid endarterectomy can cause a stroke or heart attack to occur.
What happens after treatment for the condition?
Generally, a person recovers from a TIA with no further problems. However, it is important to contact the healthcare professional for follow-up, since the TIA may be a warning sign of an upcoming stroke.
How is the condition monitored?
Monitoring is related to the cause of the transient ischemic attack. For instance, those with clots in their heart need repeat blood tests, such as a prothrombin time (PT) test, to monitor the effects of medications used to thin the blood.
Since a TIA is a significant indicator that the person is at risk for stroke, any new or worsening symptoms should be reported to the healthcare professional.