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 brain tissue injury.

A transient ischemic attack 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 travelling blood clots are the leading causes of stroke and TIA.