For the study, researchers enrolled 430 patients with unclear onset stroke – defined as the stroke where patients do not know when the symptoms began.

Researchers used diffusion-perfusion MRI, which shows tissue death and blood flow in the brain, to study the areas where tissue remained alive even though it lacked blood flow.

Patients were excluded if they had extensive tissue death in the brain area supplied by a major artery, or if the time of tissue death had elapsed.

More than 80 patients were found eligible for clot-busting therapy, which involved administration of the drug tissue plasminogen activator (tPA) and the drug urokinase into the blocked brain vessels.

Among the patients who received drug therapy, 45% had at least a good clinical outcome, ranging from no symptoms to slight disability with curtailed activities.

Nearly 29% of patients had an excellent clinical outcome, which indicated that they were able to perform all their usual activities with little or no impairment.