Asymptomatic carotid stenosis may not be asymptomatic after all.
Patients with a stenosis of 50% 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 April 30 at the annual meeting of the American Academy of Neurology.
The study is the first to definitively link asymptomatic carotid stenosis with symptomatic cognitive impairment, primary investigator Brajesh K. Lal said in an interview. But since the stenosis itself is not apparent, and the cognitive changes not profound, patients are not being treated for either, said Dr. Lal, chief of vascular surgery at the Baltimore Veterans Affairs Medical Center, and professor of vascular surgery at the University of Maryland.
Dr. Brajesh Lal
"If the cognitive decline was severe, it probably would have been enough for the patient to be evaluated for dementia. Instead, this is floating beneath the radar. It’s not as 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," he said.
Dr. Lal and his team conducted cognitive testing on 127 patients: 67 with ultrasound-confirmed asymptomatic carotid stenosis of 50% or more, and 60 controls. Although the control patients did not have carotid stenosis, they did have similar vascular comorbidities, including diabetes, hypertension, and coronary artery disease. The investigators used a Cohen’s d 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, Dr. Lal said.
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, he added.
"There are probably somewhere between 8 and 13 million people in the U.S. who have an asymptomatic blockage of 50% or more. And while not every one of them is going to have cognitive decline, this does open the door to the idea that there may be a significant population that is affected."
Right now, the pathophysiologic 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, Dr. Lal said.
Dr. Lal reported that he has several NIH and VA Merit grants focused on developing new methods of diagnosing and treating carotid occlusive disease. He reported having no other financial disclosures.
On Twitter @Alz_Gal