Plaque Enhancement Grade on High-Resolution MRI and Recurrent Ischemic Events in Intracranial Stenosis: A Retrospective Cohort Study

Recurrent ischemic events may occur in patients with mild-to-moderate intracranial atherosclerotic stenosis despite standardized medication; stenosis rate alone is insufficient for risk stratification, and plaque activity imaging markers are needed. Because plaque enhancement may reflect plaque activity beyond luminal narrowing, we hypothesized that higher enhancement grade would predict recurrent ischemic events of stenosis rate. This study evaluated the association between high-resolution magnetic resonance imaging (HR-MRI) plaque enhancement grading and recurrent ischemic events and examined its incremental value beyond stenosis rate. In a retrospective medication-treated cohort, patients aged 18-85 years with ischemic stroke or TIA and responsible intracranial arterial stenosis of 30%-69% completed contrast-enhanced HR-MRI within 14 days of onset and received standardized secondary prevention. Enhancement referenced to the pituitary stalk was graded 0-2 with blinded reading. The primary outcome was recurrent ischemic events (stroke or TIA) in the responsible vascular territory. Time-to-event analysis used left truncation. Kaplan-Meier and Cox models adjusted for stenosis rate, LDL-C, age, and imaging interval. Among 381 patients, loss to follow-up was 4.72%. Recurrence occurred in 52 (13.65%) patients; median event time was 171.84 days. Recurrence-free survival differed by enhancement grade (log-rank P = 0.002). Versus grade 0, grade 2 was associated with higher recurrence risk (simplified adjusted HR = 2.50, 95% CI 1.30-4.82; fully adjusted HR = 2.31, 95% CI 1.17-4.56). Per 1-grade increase, risk increased (fully adjusted HR = 1.33, 95% CI 1.07-1.65; trend P = 0.01); grade 1 vs grade 0 was not significant. For stroke recurrence, grade 2 remained associated with higher risk (aHR = 2.63, 95% CI 1.03-6.69). Higher-grade HR-MRI plaque enhancement independently predicts recurrent ischemic events in mild-to-moderate intracranial arterial stenosis and provides incremental risk stratification beyond stenosis rate, supporting the study hypothesis and identifying patients requiring intensified follow-up and risk-factor target achievement.