Eighty percent of strokes are ischemic, and are caused by the narrowing of the large or small arteries of the brain, or by clots that block blood flow to the brain.
A warning stroke or mini-stroke may occur as early as seven days before a stroke happens. The TIA ( transient ischemic attack) usually lasts less than five minutes, has symptoms similar to a stroke and does not injure the brain, but does need urgent treatment to prevent serious damage to the brain.
In study led by Peter M. Rothwell, MD, PhD, FRCP, Department of Clinical Neurology at Radcliffe Infirmary in Oxford, England, out of 2,416 people who had experienced an ischemic stroke, 549 patients, experienced a warning prior to the ischemic stroke and in most cases it happened within the previous seven days: 17 percent occurred on the day of the stroke, 9 percent on the day before, and 43 percent at some point during the seven days prior to the stroke.
It has been known for some time that TIAs are often a precursor to a major stroke but doctors have been unable to determine how urgently patients must be assessed following a TIA in order to receive the most effective preventive treatment. The study indicates the timing of a TIA is critical, and the most effective treatments should be initiated within hours of a TIA in order to prevent a major attack.Clinical guidelines should be amended accordingly.
The study included two population-based studies (Oxford Vascular Study and Oxfordshire Community Stroke Project) as well as two randomized trials (UK-TIA Aspirin Trial and European Carotid Surgery Trial).