Nonstenotic Culprit Plaque: The Utility of High-Resolution Vessel Wall MRI of Intracranial Vessels after Ischemic Stroke

Abstract

Intracranial atherosclerotic disease (ICAD) accounts for 9-15% of ischemic stroke in the United States. Although highly stenotic ICAD accounts for most of the strokes, it is assumed that nonstenotic ICAD (nICAD) can result in stroke, despite being missed on standard luminal imaging modalities. We describe a patient with nICAD who suffered recurrent thromboembolic stroke and TIA but had a negative conventional stroke workup. As a result, they were referred for high-resolution magnetic resonance imaging (HR-MRI) of the arterial vessel wall, which identified a nonstenotic plaque with multiple high-risk features, identifying it as the etiology of the patient's thromboembolic events. The diagnosis resulted in a transition from anticoagulation to antiplatelet therapy, after which the patient's clinical events resolved. HR-MRI is an imaging technique that has the potential to guide medical management for patients with ischemic stroke, particularly in cryptogenic stroke.

Figure 1

(a) Axial diffusion-weighted MRI showed punctate cortical areas of diffusion restriction (white arrow), consistent with an embolic source of ischemia. (b) Sagittal CT angiogram shows high-grade narrowing (white arrow) of the right supraclinoid ICA, presumed secondary to thrombus which was in close proximity to focal ICA calcification (not seen). (c) Lateral DSA performed two weeks after the prior CTA shows no significant stenosis or other vascular abnormality of the right anterior circulation. (d) Lateral DSA shows a patent right cervical internal carotid artery. (e) Sagittal T2-weighted HR-MRI of the supraclinoid ICA shows atherosclerotic plaque along the anterior wall of the supraclinoid ICA, with discontinuous juxtaluminal T2 hyperintense band (white arrows), and deeper T2 hypointensity representing the lipid necrotic core (red arrows). (f) Sagittal T1 postcontrast HR-MRI at the same level shows T1 hypointense plaque with focal enhancement along the juxtaluminal surface, which was not present on the precontrast T1 image, and a normal to eccentrically enlarged vessel lumen (white arrow).