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Asymptomatic intracranial stenosis was common in older adults but appeared fairly benign in the context of intensive medical therapy after a minor stroke or transient ischemic attack (TIA) in the Oxford Vascular Study (OXVASC).

The prevalence of any asymptomatic intracranial stenosis (with 50% or more narrowing) increased from 3.8% in people under 50 years to 34.6% in those 90 and older (OR per decade 1.96, 95% CI 1.69-2.27), according to the population-based study.

Asymptomatic intracranial stenosis was twice as prevalent as asymptomatic carotid stenosis (14.8% vs 7.2%, RR 2.04, 95% CI 1.63-2.55), reported Peter Rothwell, MD, PhD, of John Radcliffe Hospital in Oxford, England, and colleagues. Their paper was published online in .

"However, the prognosis of asymptomatic intracranial stenosis was relatively benign while receiving medical treatment alone, with no increase in risk of recurrent ischemic stroke, major ischemic vascular events, or death compared with patients with no intracranial stenosis," they found.

Asymptomatic intracranial stenosis was associated with a roughly 1% annual risk of any recurrent ischemic stroke, which fell to about 0.6% per year for ischemic stroke in the same territory of the previously asymptomatic stenosis.

Ischemic stroke rates over an average 3 years of follow-up were statistically indistinguishable between people with only asymptomatic intracranial stenosis and those with no intracranial stenosis (unadjusted HR 1.03, 95% CI 0.49-2.17).

"This is reminiscent of the well-known difference in prognosis between symptomatic and asymptomatic carotid stenosis," commented Seemant Chaturvedi, MD, of University of Maryland School of Medicine in Baltimore, in an .

The findings should be useful for patient counseling and provide "guidance on rational imaging and treatment strategies, as well as some good news: with the implementation of modern medical therapy, asymptomatic intracranial stenosis is one less thing to worry about," according to Chaturvedi.

"The clinical implication of our findings is that no specific additional treatments or follow-up imaging are routinely required for patients with TIA/stroke with asymptomatic intracranial stenosis. Patients with these imaging findings should be treated per standard guidelines for stroke secondary prevention," Rothwell's group concluded.

OXVASC included 1,579 patients recruited after TIA and minor ischemic stroke (NIH Stroke Scale score 3 or below). All were on intensive medical treatment without stenting. Therapy included antiplatelet therapy, high-dose statins, and blood pressure control targeting levels less than 130/80 mm Hg.

Out of the overall cohort, 1,368 people had intracranial vascular imaging and were eligible for the present analysis (mean age 69.2 years, 51.2% men). On imaging, 19.0% of those patients showed any intracranial stenosis (14.8% asymptomatic).

"Although valuable, the study has certain limitations. First, the OXVASC population is 94% white and it is well known that other racial/ethnic groups (e.g., African American and Asian individuals) have higher rates of intracranial artery stenosis," Chaturvedi noted.

Rothwell's team cautioned that patients who did not receive intracranial vascular imaging were older with a higher burden of vascular risk factors, which could have led them to underestimate the prevalence and prognosis of asymptomatic intracranial stenosis -- especially at older ages.

Imaging methods were also not uniform throughout the study: MRI angiography was preferred, the second choice being CT angiography, with transcranial Doppler and carotid ultrasonography performed if the first two were contraindicated.

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