But no added stroke risk, OXVASC study finds

The prevalence of asymptomatic intracranial stenosis (ICS) rose with age in patients with transient ischemic attack (TIA) or minor ischemic stroke, but with medical therapy there was no added risk for stroke in that territory, a prospective study found.

In participants younger than 70, the prevalence of any asymptomatic ICS was 4.8%, but for those 90 or older, prevalence was 34.6% (OR per decade 1.96; 95% CI 1.69-2.27), reported Peter Rothwell, MD, PhD, of the John Radcliffe Hospital in Oxford, England, and coauthors in JAMA Neurology.

Asymptomatic intracranial stenosis of 50% or more, regardless of other findings, was seen in 14.8% of patients in the Oxford Vascular Study with minor stroke (NIHSS score 3 or less) or TIA who had vascular imaging with MRI, CT angiography, or Doppler ultrasound. Asymptomatic ICS alone was seen in 11.3%, and the presence of both asymptomatic and symptomatic ICS was 3.4%.

Those with only asymptomatic ICS had no increase in risk of ischemic stroke compared with those with no ICS (unadjusted HR 1.03, 95% CI 0.49-2.17) and annualized risk for stroke in the territory of the ICS of 0.59% (95% CI 0.12-1.73).

“The prevalence of asymptomatic ICS increases with age in white patients with TIA and minor stroke and is greater than that of asymptomatic carotid stenosis, but asymptomatic ICS does not increase the short- or medium-term risk of distal recurrent ischemic stroke for patients receiving standard medical treatment,” Rothwell and colleagues wrote.

This analysis provides useful data for patient counseling, noted Seemant Chaturvedi, MD, of the University of Maryland, in an accompanying editorial. “This study also provides 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,” he wrote.

ICS accounts for up to 10% of ischemic strokes in the U.S. and up to 30%-50% of strokes in Asian people. Over the last two decades, clinical trials have refined the treatment approach for patients with recent stroke or TIA due to symptomatic ICS.

In WASID, patients with symptomatic 50%-99% ICS randomized to warfarin had no benefit over aspirin but had higher rates of adverse events. The SAMMPRIS trial found that aggressive medical management was superior to use of the Wingspan stent system in symptomatic ICS, with increased risk of stroke after stenting and a lower-than-expected risk of stroke with medical therapy alone. A study to determine if the patients in SAMMPRIS were lower risk (accounting for a relatively low stroke rate) in comparison to WASID found that on the contrary, WASID patients had higher risk, suggesting that the lower event rate in SAMMPRIS resulted from more aggressive medical management.

Less well characterized and less consistently reported is asymptomatic ICS. In the WASID symptomatic ICS trial, a subset of about 19% (4 vessel angiogram) or 27% (MRA) also had asymptomatic ICS, with 3.5% 1-year risk for stroke in that territory. A 2004 study of asymptomatic middle cerebral artery ICS found a benign long-term prognosis, though 38 of 50 patients had stenosis of <50%.

Rothwell and colleagues included data from 1,368 patients in the Oxfordshire, England region evaluated for TIA or stroke with NIHSS scores of 3 or less between March 2011, and March 2018, who were medically treated without stenting and had imaging showing asymptomatic ICS using CT angiography (16%), MRA (66%), or Doppler ultrasound (5.2%). ICS was most commonly seen in the distal internal carotid, middle cerebral, posterior cerebral, and distal vertebral arteries.

The prevalence of any asymptomatic ICS was greater than the prevalence of 50% or more asymptomatic carotid bifurcation stenosis (14.8% versus 7.2%; RR 2.04, 95% CI 1.63-2.55; P < 0.001). At each age, asymptomatic ICS was more common than asymptomatic extracranial carotid stenosis, and was predicted by increasing age, hypertension, and prior stroke or TIA.

Among those with asymptomatic ICS only, there were eight recurrent strokes during 506 years of patient follow-up, with 7-year risk of recurrent ischemic stroke of 6.8%.

For Chateurvedi, the results hold three messages for clinicians:

  • If you look for asymptomatic ICS, you will find it: asymptomatic extracranial carotid disease was less common than asymptomatic ICS at all ages of the OXVASC population.
  • With intensive medical therapy, the stroke rate was relatively low in patients with asymptomatic ICS.
  • The relatively low stroke rate observed suggests that follow-up imaging is not necessary to track the status of an asymptomatic ICS.

Limitations of the study include a 94% white population and index events of minor stroke or TIA, limiting generalizability to other racial or ethnic groups and other stroke severities. Also, imaging type varied with use of MRI, CT angiography, and Doppler ultrasound.

  1. The prevalence of asymptomatic intracranial stenosis (ICS) rose with age in patients with transient ischemic attack (TIA) or minor ischemic stroke, but with medical therapy there was no added risk for stroke in that territory, a prospective study found.

  2. Data was from the OXVASC study and the population was 94% white. The limitation is significant here because ICS variation among populations is large, with a very high prevalence among Asian people.

Paul Smyth, MD, Contributing Writer, BreakingMED™

The Wellcome Trust, Wolfson Foundation, British Heart Foundation, National Institute for Health Research, National Institute for Health Research Oxford Biomedical Research Centre, and Association of British Neurologists provided support for this study.

Rothwell had no disclosures. Chaturvedi reported grants from the National Institute of Neurological Disorders and Stroke outside the submitted work.

Cat ID: 130

Topic ID: 82,130,730,130,192,925