A transient ischemic attack (TIA) is an ischemic stroke in which the blood flow is restored quickly and the symptoms disappear within 24 hours. In other words, it's a mini-stroke that you recover from quickly. For most patients with a TIA, the symptoms last less than one hour. The longer the symptoms last, the more likely that there will be permanent brain tissue injury.
TIAs affect 1 in 15 persons over age 65 years, but often go undiagnosed if the symptoms are not recognized. Approximately 15% of strokes are preceded by a warning TIA. Therefore, recognition of TIA symptoms is important because preventative treatment may help to reduce the chance of an impending stroke.
The risk of stroke is highest within the first 3 months following a TIA, especially within the first few days. Within the first month, the average risk of stroke after a TIA ranges from 1 in 20 to 1 in 10. TIAs and strokes generally occur in people with atherosclerosis (hardening of the arteries) or coronary artery disease. In fact, people who have suffered TIAs are even more likely to die of heart attack than of stroke.
A TIA is caused by the same factors that cause ischemic stroke. Ischemia is the medical term for a reduction of blood and oxygen to the cells.
Ischemic stroke occurs when the arteries feeding the brain become blocked. This may result from narrowing (stenosis) of the arteries, which disturbs blood flow, creating areas of turbulence that can lead to blood clot (thrombus) formation. Such a clot may occur in a brain-feeding artery, or it may occur elsewhere in the body, travel up to the brain, and lodge in a narrowed section of a brain artery.
A free-floating particle in the blood is called an embolus, and a free-drifting clot is called a thromboembolism. Local and traveling blood clots are the leading causes of stroke and TIA. The most common sources of brain emboli that cause stroke are the carotid arteries in the neck and the heart.
The risk factors for TIA are exactly the same as those for stroke:
- High blood pressure is the number one risk factor. Even people with borderline high blood pressure have a higher TIA or stroke risk than people with normal blood pressure. Higher pressures mean increased risk. Even a small (6 mm Hg) reduction in diastolic blood pressure leads to a 42% reduction in the risk of stroke.
- Smoking is the number two risk factor in most strokes. Tobacco consumption of up to a pack a day may double your risk. Beyond a pack a day, the figure increases further. Quitting smoking reduces stroke risk - over 5 years, the risk falls to the same level as that of people who have never smoked.
- Heart disease and arrhythmias are often due to risk factors, but some are congenital (present from birth). The type of arrhythmia known as atrial fibrillation is closely associated with stroke. Most people with atrial fibrillation are treated with blood thinners to prevent this complication.
- Heavy alcohol use is a modifiable risk factor. Reducing how much alcohol you consume in a day to the maximum recommended amount can reduce your risk for developing a TIA or stroke.
There are other risk factors that aren't preventable:
- Age naturally increases the risk of stroke and TIAs.
- Diabetes increases the risk of cardiovascular (heart- and blood vessel-related) and cerebrovascular (brain-related) events - controlling blood sugar levels may also reduce the risk.