Now research from UNC School of Medicine provides the first evidence for which course of treatment is truly best for patients with poor collateral blood vessel formation near the site of stroke they should have their blood pressure lowered to normal levels.

Many neurologists had suspected that blood pressure should be left high in this group of patients because doctors thought high blood pressure might force blood around the blockage and through collateral vessels, which would be beneficial and, therefore, reduce risk of stroke.

But research from William Powers, expart shows that keeping blood pressure high leads to a four-fold increase in the risk of stroke. The study was published in the journal Neurology.

'Up until now doctors would say to patients, ‘well, we think you should do this or we think you should do that' Powers said. But our paper provides the first data that show how patients with poor collateral vessels should be treated.

Andrew Southerland, expart who was not involved in the study, said, “This paper clears up a murky question about how to manage blood pressure in these patients. It’s a pivotal study in our field.”

After a stroke, collateral vessels can help blood flow to an area of the brain that’s cut off from its normal blood supply due to a blocked blood vessel. In the 1980s, Powers led PET scan studies that characterized the importance of these collateral vessels. His team showed that patients with poor collateral flow faced six times the risk of a suffering a second stroke than did patients with good collateral vessel formation. But how to treat those patients with poor collaterals remained debatable.