Unclogging Carotid Artery Fails to Improve Cognition

Cognition often deteriorates when the brain’s main blood lines are clogged, but a Columbia-led study shows that cognition cannot be improved by opening the blockages with stenting or surgery.

“We had hoped that improving blood flow in the brain in this way would improve cognition—and there were tantalizing clues from animal studies and case series that it would,” says study leader Randolph Marshall, MD, the Elisabeth K. Harris Professor of Neurology at Columbia University Vagelos College of Physicians and Surgeons.

“But when we put it to the test in a randomized clinical trial, comparing cognition after opening the blockage or treatment with medication alone, we did not see a difference.”

The study, called CREST-H, was a part of a larger trial to determine the best way to prevent strokes in people with severe carotid artery blockages. That multicenter study, called CREST-2, which Marshall helped design, found that medication combined with stenting, but not blockage-removing surgery, decreased strokes two-fold compared to medication alone.

“Those results do appear to have changed practice already, and more of these patients are getting stents,” says Marshall.

Severe carotid blockages are also associated with cognitive impairment even without stroke, particularly when cerebral blood flow is reduced.

“We’ve thought for a long time that improving cognition by restoring blood flow with stenting or surgery could improve cognition, but until our study, the hypothesis had never been tested in a randomized clinical trial.”

CREST-H enrolled 291 patients with asymptomatic carotid stenosis of 70% or greater and assessed cerebral blood flow and cognition at the time of enrollment and one year later. Though the cognitive scores of both groups improved slightly over this time, there was no difference between the group that had a procedure to increase blood flow to the brain and the group treated only with medication.

“We concluded that revascularization to reverse cognitive decline in these patients cannot be expected. Therefore, we need to reinforce the importance of preventing carotid stenosis to avoid its consequences,” says Marshall.