Advanced brain imaging technology now gives an additional 10 hours or more to respond to some strokes. Uptill now doctors have just six hours to save threatened brain tissue.

While some brain tissue dies in a stroke, collateral blood vessels temporarily take over feeding a larger area that is also starved for blood and oxygen, giving doctors many more hours to save that tissue than they previously believed.

The age-old medical belief that "time is brain" - that millions of neurons die each minute after a stroke - must be reconsidered.

Doctors can respond with clot-dissolving medication within the first few hours and within six hours have been reaching into the blood vessel with clot-removing devices such as stents. But both the new studies show that they may have more time to save brain tissue where the blood supply is being choked off but the tissue has not yet died.

The DEFUSE 3 study looked at 182 people in 38 medical centers who suffered the kinds of blockages in brain arteries that cause 50 to 60 percent of deaths and the most severe kinds of disabilities. About half received typical care, involving blood pressure medication, blood thinners and other medical interventions. The other half had images taken and the clot removal procedure, known as a "thrombectomy," as well as the medications.

When a CT scan that uses a dye shows a larger area of damaged tissue surrounding the dead tissue, doctors can respond by removing the clot as long as 16 hours after the patient was last known to be well.

This is especially important for people who have strokes in their sleep, which may make it impossible to pinpoint when the blockage occurred, or people who live far medical centers where the clots can be removed.

The diagnostic test can be read on a cellphone, with pink and green areas denoting the dead and damaged tissue.

Fourteen percent of the people who had thrombectomies died, compared with 26 percent in the medical therapy group. Forty-five percent in the thrombectomy group escaped severe disabilities and were able to resume "functional independence."

Alberss work confirms and expands on the results of the DAWN study, sponsored by a manufacturer of clot-removing devices and published three weeks ago, which took a more conservative approach to the patients involved. It found that doctors could interveneas late as 24 hours after stroke victims were last known to be well.

Both studies were published in the New England Journal of Medicine. (Chicago Tribune)