"Many more stroke victims than previously thought can be saved from disability or death if doctors remove blood clots that are choking off circulation to the brain a new study has shown. These striking results will have an immediate impact and save people from lifelong disability or death Dr. Walter J. Koroshetz director of the National Institute of Neurological Disorders and Stroke said in a statement. I really cannot overstate the size of this effect. The key finding is that there is often more time than doctors realized in which brain cells can still be rescued by a procedure to remove the clot https Traditional guidelines have set a limit of six hours after stroke symptoms begin and said after that it would be too late to help. The study showed that the time window could be expanded to  hours. However the findings do not apply to every stroke victim. The researchers used a special type of brain imaging to identify the patients who still had live brain tissue that could be saved if the blood supply was restored. Only about half the patients who were screened qualified for treatment known as thrombectomy which uses a mechanical device to pull clots out of a blood vessel. Advertisement The study involving  patients at  hospitals in the United States was stopped early because patients who had clots removed fared so much better than those who did not. Ninety days after treatment  percent of the thrombectomy patients were well enough to be functionally independent as opposed to  percent of those who did not have the procedure. The death rates were  percent in the thrombectomy group and  percent in those whose clots were not removed. The results were published http on Wednesday in The New England Journal of Medicine. The study was paid for by the National Institutes of Health and led by researchers from Stanford University. The Stanford team said it expected the study would lead the American Heart Association to change the guidelines for stroke treatment extending the time window for thrombectomy. It is not uncommon for strokes to begin during sleep and some of those patients miss out on treatment because it is not clear what time the stroke began. Medical practice has been to set the beginning of the time window as the last moment they were known to be well and if they have slept most of the night the sixhour window may be over by the time they wake up. New guidelines may allow such patients to be treated. About  people a year suffer strokes in the United States and  percent of those are caused by clots  the same type treated in this study. Symptoms include speech difficulty arm weakness and facial drooping. Experts urge patients or their families to call  immediately so that treatment can be started as soon as possible."