In order to understand what a transient ischemic attack (TIA-also known as a "ministroke") is, you must first understand the meaning of the word ischemia.
What is brain ischemia?
The healthy brain requires a constant delivery of oxygen- and nutrient-rich blood to each one of its approximately 100 billion neurons. To accomplish this, and thus to ensure normal brain function, blood travels across multiple blood vessels to every part of the brain. In some people, however, blood vessels become blocked by blood clots, or cholesterol plaques, leaving discrete brain areas transiently disconnected from their blood supply. The resulting lack of oxygen and nutrients in these areas is known as ischemia. Neurons in ischemic areas starve and rapidly stop functioning.
What is a TIA?
As the name implies, a transient ischemic attack, or TIA, is a brief period of lack of blood flow to an area of the brain. Because ischemia impairs the function of brain cells, a person suffering a TIA develops symptoms of brain function impairment, such as difficulty speaking or moving the arm and leg on one side of their body. The symptoms of a TIA can last from a few minutes to a few hours, but by definition they go away in less than 24 hours.
Up to 20% of people who experience TIA symptoms go on to have a major stroke in the next three months. Unfortunately, many people fail to seek medical attention and suffer a stroke before they are seen by a doctor.
What are the symptoms of a TIA?
The symptoms of a TIA begin suddenly and vary depending on the part of the brain that is affected. Transient ischemic attacks that affect areas of the brain used minimally in day to day function cause symptoms that are mild or unnoticeable. By contrast TIAs affecting areas of the brain used heavily in normal day to day function cause symptoms which can be extremely debilitating.
For instance a person who suffers a TIA in one of the smell areas of the brain may develop difficulty smelling certain odors but they may not notice it for several days or months. A different person who experiences a TIA of a similar size in the brainstem, an area of the brain which harbors the centers for gait balance, voice control, and eye movements, might feel temporarily unable to carry on with his or her day because of vertigo, difficulty speaking, or double vision.
TIAs most commonly affect parts of the brain which control movement and feeling in the face, arm, and leg. TIAs can also affect the ability to understand and produce speech. Here is a list of the most common symptoms of a TIA:
- Weakness of the face, and/or arm, and/or leg muscles on one side of body
- Numbness of face and/or arm and/or leg one side of the body
- Inability to understand spoken language
- Inability to speak
- Unexplained dizziness or vertigo
- Loss of vision through one eye
- Double vision or blurry vision
What is the difference between a TIA and a stroke?
By the current definition, the symptoms of TIA disappear completely within 24 hours. Strokes on the other hand leave long-lasting physical impairments. But when one compares the brain of person with a stroke with the brain of a person with a TIA using MRI, very often one cannot tell which is which. Why is this? This is currently a subject of intense study and definitive answers have yet to be produced, but this suggests that even though TIAs only cause temporary symptoms, they can still cause permanent damage to the brain.
I think I had a TIA. What should I do?
The more we learn about TIAs, the more convinced we become that a TIA is a sign that a debilitating stroke might be on the way. This is why no matter how mild or short-lived the symptoms of a TIA might be, it is extremely important that you go to the nearest emergency room immediately after you start feeling stroke-like symptoms.
Even if you had a TIA a few days ago you should still seek medical attention as soon as possible. The urgency of this matter cannot be overemphasized as up to 20% of people who suffer a TIA will go on to suffer a stroke within 90 days.
The high risk of stroke after a TIA has motivated many medical institutions to keep all TIA patients in the hospital for thorough testing even in cases when symptoms have resolved completely by the time the patient arrives in the Emergency Room. In many cases an early search for the cause of a TIA allows for early intervention and successful stroke prevention.
Suggested Reading:
Are you at risk of stroke?
How are strokes diagnosed?
What can I do to lower my risk of stroke?
Source:
Claiborne Johnston, M.D., Ph.D. Transient Ischemic Attack New England Journal of Medicine 347:1687-1692 November 21, 2002
