Characterization of non-stenotic plaques in intracranial arteries with multi-contrast, multi-planar vessel wall image analysis.

Objectives: Non-stenotic plaques have been observed in intracranial arteries but are less understood compared to those in coronary and carotid arteries. We sought to compare plaque distribution and morphology between stenotic and non-stenotic intracranial plaques with MR vessel wall imaging (VWI) and quantitative image analysis.

Materials And Methods: Twenty-four patients with intracranial arterial stenosis or luminal irregularity on clinical imaging were scanned with a multi-contrast VWI protocol. Plaques were detected as focal wall thickening on co-registered multiplanar reformats of multi-contrast VWI, with assessment of the location and morphology. TOF-MRA was independently reviewed for any appreciable stenosis using the WAISD criteria.

Results: Across 504 arterial segments, a total of 80 plaques were detected, including 23 (29%) with stenosis on TOF-MRA, 56 (70%) without, and 1 (1%) not covered by TOF-MRA. Plaques involving the ICA were more likely to be non-stenotic than those involving other segments (80% versus 55%, p = 0.030) whereas the basilar artery (40%) and PCA (33%) had the lowest proportions of non-stenotic plaques. Maximum wall thickness, indicative of plaque burden, correlated poorly with degree of stenosis (p = 0.10) and overlapped substantially between stenotic and non-stenotic plaques (1.9 [1.5, 2.4] versus 2.0 [1.5, 2.2] mm, p = 0.074).

Conclusions: Intracranial plaques without appreciable stenosis on TOF-MRA represent a large proportion of lesions throughout arterial segments but disproportionately affect the ICA. Morphological characterization of plaques with and without stenosis shows that luminal stenosis is a poor indicator of the underlying burden of intracranial atherosclerosis.