A transient ischemic attack (TIA) is a short period of symptoms similar to those of a stroke. It's caused by a brief blockage of blood flow to the brain. A TIA usually lasts only a few minutes and doesn't cause long-term damage. However, a TIA may be a warning. About 1 in 3 people who has a TIA will eventually have a stroke, with about half occurring within a year after the TIA. Often called a ministroke, a TIA can serve as both a warning of a future stroke and a chance to prevent it.