New research shows that some stroke survivors may benefit from clotbusting treatment given as much as six hours after symptoms start.
Most strokes result from a blood clot blocking the blood supply to the brain. There's now good evidence that giving a clotbusting drug such as tissue plasminogen activator (tPA) as soon as possible following the onset of symptoms can reduce brain damage and disability.

It's generally believed that the benefits of clotbusters depend on their being given within three hours of the onset of a stroke. But researchers at the University of Melbourne, Australia, now think differently. They have used magnetic resonance imaging (MRI) scanning to see how much brain area is permanently damaged and how much under threat. In patients who had a large area of threatened - but not permanently damaged - brain tissue, the clotbusters could dissolve clots and preserve brain function when given up to six hours after symptom onset. The patients did better when compared to those given no treatment.

More research is needed before MRI can be recommended as a replacement for the standard CT brain scan as a way of picking out the patients who can benefit from late administration of clotbusters. In the meantime, patients should not have to wait for clotbusting treatment - it should be given as soon as possible to minimise the brain damage from a stroke.