Fig. 4

a 3D axial T1-weighted post-contrast image showing diffuse vessel wall and luminal enhancement (white arrow) of the right M1 segment in a patient with left-sided weakness, sensory loss and neglect. b 3D axial T2-weighted image of the same section of the right M1 segment with hyperintense signal in the vessel lumen, consistent with occlusive thrombus from recently diagnosed atrial fibrillation, resulting in a large right MCA territory ischemic stroke (dotted white arrow). c Anterior-posterior digital subtraction angiogram in a second patient who presented with post-coital headache and was found to have multifocal luminal narrowing in the bilateral M2 branches (dotted and solid white arrows). d Axial diffusion-weighted image showing a right hemisphere ischemic stroke in the same patient. e 3D axial T1-weighted post-contrast image showing the absence of vessel wall enhancement at the M2 segments corresponding to the narrowing seen on the angiogram in image (c), consistent with reversible cerebral vasoconstriction syndrome, which should result in very subtle or no enhancement of the vessel wall at sites of vasospastic narrowing