Stenosis could cause cognitive impairment

A symptomatic carotid stenosis may not be asymptomatic after all. Patients with a stenosis of 50 percent or more performed significantly worse on cognitive tests than did those without. Those cognitive issues were very likely clinically significant as well, according to a study to be presented at the annual meeting of the American Academy of Neurology.

The study is the first to definitively link asymptomatic cognitive impairment, a primary investigator said. But because the stenosis itself is not apparent, and the cognitive changes not profound, patients are not being treated for either, said chief of vascular surgery at the BaltimoreVeterans Affairs Medical Center, and professor of vascular surgery at the University of Maryland.

If the cognitive decline was severe, it probably would have been enough for patient to be evaluated with dementia.  Instead, this is floating beneath the radar. It’s not severe as an obvious dementia that would be picked up on cursory evaluation, but it is significant enough to impact activities of daily living, or the patient’s ability to perform a job.

A team conducted cognitive testing on 127 patients: Sixty-seven had ultrasound-confirmed asymptomatic carotid stenosis of 50 percent or more, and 60 were controls. Although the control patients did not have carotid stenosis, they did not have similar vascular comorbidities, including diabetes, hypertension, and coronary artery disease.

The investigators used a Cohen’s test to determine whether any statistically significant cognitive differences were likely to be clinically meaningful. They found that all the detected impairments were at least mild to moderate in severity.

The stenotic group performed worse on the overall neurocognitive composite score, and the motor/ processing speed and learning/ memory domains. The Cohen’s measure of effect size showed that all of these differences would have a mild to moderate effect on cognitive function.

A trend of poorer performance for executive function and attention/ working memory emerged also, although these differences were neither statistically nor clinically significant.

Extrapolating these results out to the number of people who probably have asymptomatic carotid stenosis presents a sobering picture.

There are probably somewhere between eight and 13 million people in the US who have an asymptomatic blockage of 50 percent or more. And while not every one of them is going to have cognitive decline, this does opens door to the idea that there may be a significant population that is affected.

Right now, the path physiologic link between stenosis and cognition remains unclear. It might be related to microemboli shedding from the vascular plaque and causing microinfarcts, or to decreased blood flow and oxygenation to the brain.