A transient ischemic attack, also known as a “mini-stroke,” is often a warning that a major stroke is imminent within a few days, British researchers have found.

Investigators analyzed data from two studies that showed that almost one-fourth of 2,416 people diagnosed with major ischemic stroke – the type of stroke that occurs when a brain artery is blocked – had also experienced a TIA, usually within the week before the major attack. Full findings appear in the March 8 issue of Neurology.

Among people who suffered ischemic strokes, 23% had experienced a mini-stroke beforehand. In 17% of those cases, the TIA occurred on the same day as the major stroke, while in 9% of cases the mini-stroke occurred one day before the major event. A mini-stroke occurred sometime within the week preceding the major stroke in 43% of those cases.

“Guidelines should be changed such that TIA and minor strokes are classified as medical emergencies that deserve urgent attention,” said Dr. Peter M. Rothwell, one of the researchers and a professor of neurology at Oxford University.