Temporal course and implications of intracranial atherosclerotic plaque enhancement on high-resolution vessel wall MRI

Purpose: Little is known about the natural history of intracranial atherosclerotic plaque enhancement and its clinical implications. Our objective was to investigate the value of follow-up high-resolution contrast-enhanced vessel wall MRI (VWMRI) for classifying culprit plaques in patients with intracranial atherosclerotic disease (ICAD).

Methods: Fourteen patients with symptomatic ICAD (50% females; median age 48 years) underwent serial 3T VWMRI. Fifty-five plaques were identified and graded based on the likelihood of having caused the ischemic event (non-culprit, indeterminate, culprit) and degree of enhancement (0, 1, 2) at baseline and follow-up (median follow-up, 140 days). For accuracy analysis, plaque enhancement at baseline and stable or increasing plaque enhancement at follow-up was tested to identify a culprit plaque, and areas under the receiver operating characteristic curves (AUCs) were compared.

Results: In 37/55 (67.3%) plaques, enhancement grade remained unchanged. Lack of enhancement was only seen in non-culprit plaques at baseline, and none developed enhancement over time. Enhancement never changed more than one grade. Thirty-seven percent (10/27) of non-culprit plaques that enhanced decreased in enhancement grade at follow-up, but no culprit plaques decreased in enhancement. AUC of baseline and follow-up plaque enhancement combined was significantly larger than AUC of baseline plaque enhancement alone to identify culprit plaques (0.733 vs. 0.567, p = 0.0001).

Conclusion: Contrast enhancement of ICAD can persist months after the ischemic event. Lack of enhancement at baseline or a decrease in enhancement at follow-up suggests that the plaque is not culprit. Persistent enhancement from baseline to follow-up improves accuracy in identifying culprit plaques.