High-resolution magnetic resonance imaging features of time-of-flight magnetic resonance angiography signal loss and its relevance to ischemic stroke.

Background: Focal signal loss of intracranial artery stenosis is commonly observed on three-dimensional time-of-flight magnetic resonance angiography (3D-TOF-MRA). We aimed to investigate the underlying pathophysiology of vessel signal loss observed on 3D-TOF-MRA and its relevance to recent ischemic stroke.

Methods: High-resolution magnetic resonance imaging (HR-MRI) was performed in 401 patients with unilateral or bilateral moderate-to-severe stenosis (50-99%) of the middle cerebral artery (MCA) on TOF-MRA. The patients were classified according to the presence or absence of focal signal loss in the M1 segment of the MCA. The wall features between the vessels with and without signal loss were compared, and their relationship with recent ischemic stroke was analyzed.

Results: A total of 414 stenotic lesions caused by atherosclerotic plaque were detected, including 231 with signal loss on TOF-MRA and 183 without. The signal loss group, compared to the group without signal loss, showed a higher degree of stenosis (P<0.001), grade 2 enhanced plaques (82.3% 28.4%; P<0.001), and concentric pattern (63.2% 34.4%; P<0.001). Multivariate analysis suggested grade 2 enhanced plaques and concentric pattern were independently associated with signal loss. Patients in the signal loss group were more likely to have had a recent ischemic stroke (62.4% 40.4%; P<0.001).

Conclusions: In addition to the degree of stenosis, the vulnerability and morphology of plaques on HR-MRI may influence signals on 3D-TOF-MRA. The presence of signal loss on 3D-TOF-MRA is associated with recent ischemic stroke.