Carotid Web an Underappreciated Stroke Risk Factor

Megan Brooks

December 15, 2016

A case-control study shows a statistically significant association between carotid artery web and ischemic stroke in young patients who lack an alternative cause of stroke.

"Carotid web may be an underappreciated risk factor for stroke," the researchers say.

"Carotid artery webs are relatively easy to diagnose using routine vascular imaging (CT [computed tomography] angiography or [magnetic resonance] angiography)," senior author Daniel M. Mandell, MD, PhD, from University of Toronto, Ontario, Canada, told Medscape Medical News.

"But webs are often ignored as they look harmless compared with the aggressive-looking atherosclerotic plaques which physicians are used to being concerned about. The problem is that harmless-looking carotid webs can be a source of thromboembolism, and they are likely an underdiagnosed cause of ischemic stroke," Dr Mandell said.

The study was published online November 18 in Neurology.

"A carotid web is a thin, membrane-like shelf of tissue that extends from the wall of the carotid artery into the lumen, usually at the origin of the internal carotid artery," the authors explain in their article. Carotid webs were first described in the early 1970s in a study of catheter angiograms at the Massachusetts General Hospital in Boston, and subsequent case reports have added roughly 50 cases to the literature.

"It is hypothesized that blood stasis along the downstream surface of a web may lead to thrombus formation and thromboembolic stroke. However, evidence of an association between carotid web and ischemic stroke has been only anecdotal," Dr Mandell and colleagues point out.

They studied the association between carotid artery web and ischemic stroke in a single-center case-control study. Cases were patients with anterior circulation ischemic stroke of undetermined cause, and controls were patients with cerebral aneurysms, arteriovenous malformations, or primary intracerebral hemorrhages. All participants were younger than 60 years and had CT angiography of the neck. Two neuroradiologists diagnosed carotid artery web on the basis of published criteria.

Fifty-three of 62 case-patients (85%) were matched by age (within 1 year) and sex to 102 control patients. A carotid web was diagnosed in 4 of 53 cases (9.4%) vs 1 of 102 controls (1.0%). In this analysis, carotid web was 8 times more common in patients with stroke than in controls (odds ratio [OR], 8.0; 95% confidence interval [CI], 1.2 - 67; P = .032).

In a separate analysis, 56 of 62 case-patients (90%) were matched by age (within 3 years) and sex to 108 control patients. This match included all webs identified in the both the case and control groups. There was a carotid web in 5 of 56 cases (8.9%) vs 2 of 108 controls (1.9%), yielding an OR of 5.0 (95% CI, 1.1 - 35; P = .040).

There was agreement on diagnosis of carotid artery web for 163 of 164 patients (99%) and 7 of 8 webs (88%). The Cohen kappa for interobserver agreement was 0.93.

Among the cases with webs, 4 of 5 patients were women, ranging in age from 34 to 57 years. Each of these cases had a web ipsilateral to the ischemic stroke, and 2 patients also had a contralateral web. No patient underwent surgical removal of a web.

Diabetes was more common in cases (10 of 53 [19.2%]) than controls (7 of 102 [6.9%]), but there was no difference in prevalence of 3 other atherosclerotic risk factors (hypertension, dyslipidemia, and coronary artery disease). In a model adjusted for diabetes, the OR (for presence of a carotid web in 4 of 53 cases vs 1 of 102 controls) was 9.4 (95% Wald CI, 1.0 - 86; P = .022).

There was no difference between cases and controls in the prevalence of nonstenotic atherosclerotic disease on CT angiography.

"For patients who have an ischemic stroke and a carotid web in the artery supplying the territory of the stroke, particularly if there is no other apparent cause of the stroke, physicians should strongly consider treatment to prevent recurrent thrombus formation on the web," Dr Mandell told Medscape Medical News. "We don't have high-quality data to guide optimal therapy, but there is some evidence that antiplatelet therapy is not sufficient. Other treatment options are anticoagulation, angioplasty, or endarterectomy."

Reached for comment, Bijoy K. Menon, MD, from the Calgary Stroke Program and University of Calgary, Alberta, Canada, told Medscape Medical News, "This study is reporting an association, but the case-control nature supports causality."

The study is "well done," he added, and lends support to a study his group published in 2015 in the American Journal of Neuroradiology that found carotid web may contribute to recurrent ischemic stroke in patients with no other determined stroke mechanism.

Dr Menon cautioned, however, that the implications of this association for patient care "still need to be researched."

Rohan Arora, MBBS, director, Stroke Program, Long Island Jewish Forest Hills Hospital, in Forest Hills, New York, a member of Northwell Health, also reviewed the study for Medscape Medical News.

"It's definitely an interesting study for stroke neurologists," he said, "but not sure if this will be equally appreciated by practicing general neurologists since the incidence of carotid webs is very low and the stroke literature only describes a few retrospective studies and case reports on this condition."

"The findings from this study," Dr Arora added, "should advise stroke physicians to consider carotid web in their differential diagnosis, especially for young patients where there is no clear cause of stroke identified. So far, carotid webs have been an underreported and underappreciated risk factor for stroke, and larger studies may be necessary to conclude that they have immediate implications for patient care," he said.

The study had no targeted funding, and the authors have disclosed no relevant financial relationships.

Neurology. Published online November 18, 2016. Abstract

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