A transient ischemic attack is a "mini-stroke" caused by temporary disturbance of blood supply to an area of the brain, which results in a sudden, brief decrease in brain function.

In a TIA, the blood supply is only temporarily blocked. For example, a blood clot may dissolve and allow blood to flow normally again.

A TIA is different than a small stroke. The symptoms of TIAs go away in less than 24 hours, usually less than one hour. TIAs do not show lasting changes on CT or MRI scans. (Small strokes do show changes on such tests.) TIAs are like warnings that a true stroke may happen in the future if something is not done to prevent one.

A brief interruption in the blood flow to the brain can cause a decrease in brain function. This is called a neurologic deficit. Too little blood flow to the brain for some time can cause brain cells to die.

The loss of blood flow to the brain can be caused by:

• Narrowing of a blood vessel
• Blood clot within an artery of the brain
• Blood clot that travels to the brain from somewhere else in the body (for example, the heart)
• Injury to blood vessels

Atherosclerosis ("hardening of the arteries") is a condition where fatty deposits occur on the inner lining of the arteries. This condition dramatically increases the risk for both TIAs and stroke. Approximately 80-90% of people who have a stroke due to atherosclerosis had a TIA episode before.

Less common causes of TIA include:

• Blood disorders (including polycythemia, sickle cell anemia, and hyperviscosity syndromes where the blood is very thick)
• Spasm of the small arteries in the brain
• Problems with blood vessels caused by disorders such as fibromuscular dysplasia, inflammation of the arteries (arteritis, polyarteritis, granulomatous angiitis), systemic lupus erythematosus, and syphilis.

In some cases, hypotension (low blood pressure) may be seen before symptoms of a TIA occur. Other risks for TIA include high blood pressure (hypertension), heart disease, migraine headaches, smoking, diabetes, and increasing age.

About a third of those diagnosed with TIA will later have a stroke. TIAs are more common among men and black people.

Symptoms of TIA are the same as those that occur in stroke and include the sudden development of:

• Numbness, tingling, changes in sensation
• Weakness, heavy feeling of extremities
• Speech difficulty (garbled speech; slurred speech)
• Vision changes
  • Loss of vision in one eye
  • Decreased vision
  • Double vision
• Sensation that the person or the room is moving (vertigo)
• Loss of balance
• Lack of coordination
• Gait changes, staggering
• Falling (caused by weakness in the legs)

Additional symptoms:

• Facial paralysis
• Eye pain
• Confusion

Note: Symptoms begin suddenly, last only a short time (from a few minutes to 24 hours), and disappear completely. Symptoms may occur again at a later time. Symptoms usually occur on the same side of the body if more than one body part is involved.

Because symptoms and signs may have completely disappeared by the time one gets to the hospital, A diagnosis of a TIA may be made on a person's medical history alone.

A physical examination should include a neurological exam, which may be abnormal during an episode but normal after the episode has passed.

Blood pressure may be high. The doctor will use a stethoscope to listen to your heart and arteries. An abnormal sound called a bruit may be heard when listening to the carotid artery in the neck or other artery. A bruit is caused by irregular blood flow.

Tests will be done to rule out a stroke or other disorder that may cause the symptoms. Tests to diagnose a TIA may include:

• CBC and PT tests to rule out a blood disorder
• Head CT scan or cranial MRI
• Carotid duplex (ultrasound)
• Echocardiogram
• Cerebral arteriogram

Additional tests and procedures may include:

• Blood glucose
• Blood chemistry
• Serum lipids
• ESR (Sedimentation rate)
• Tests for syphilis
• ECG
• Chest x-ray

Your doctor may use these tests to check for hypertension, heart disease, diabetes, high blood lipids, vasculitis, and peripheral vascular disease.