PMC9946924_01
(A) Axial DWI showing no areas of diffusion restriction; (B) Reformatted coronal TOF MRA showing short segment tight stenosis (arrow) in the M1 segment of the left MCA, with few surrounding collaterals (arrowheads) in left MCA cistern; (C) Axial TOF MRA  showing moderate stenosis involving the cavernous segments of the left internal carotid artery (arrow).. DWI: Diffusion-weighted image, TOF: Time of flight, MRA: Magnetic resonance angiography, MCA: Middle cerebral artery
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FIG1
The MRI brain showed no evidence of infarct or hemorrhage (Figure 1 A). The magnetic resonance angiography (MRA) showed moderate diffuse stenosis involving the cavernous and supraclinoid segments of the left internal carotid artery (Figure 1 C) and tight stenosis of the M1 segment of the left middle cerebral artery (MCA) with few surrounding collaterals in the left MCA cistern (Figure 1 B).
PMC9946924_02
(A) Coronal T2WI image and (B) Axial T2 FLAIR image showing a large area of chronic infarct (arrow) involving the right frontal lobe, right insular region, and right-sided genu of the corpus callosum, and a small chronic infarct (arrowhead) in the left frontal white matter. (C) Coronal reformatted CT Angiogram of the brain showing occluded M1 and M2 segments of the bilateral MCAs replaced by multiple collaterals(arrow)  in the bilateral Sylvian cisterns(more on the left side).. T2WI: T2 weighted image, FLAIR: Fluid-attenuated inversion recovery, MCA: Middle cerebral artery
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FIG2
A CT Angiogram revealed occlusion of the M1 and M2 segments of the bilateral MCAs with multiple collateral formations around the occluded M1 and M2 segments, particularly on the left side (Figure 2 C).
PMC9946924_03
(A) Axial CT brain image showing an acute intraparenchymal hemorrhage in the anterior aspect of the left thalamus (arrowhead) with extensive intraventricular hemorrhage extensions (arrows). (B) Axial reformatted CT angiogram of the brain showing numerous small collaterals in the region of the circle of Willis (arrow) and around the midbrain (arrowhead). (C) Post-processed image of CT angiogram of anterior circulation of the brain showing occluded right internal carotid artery (>>>>), occluded supraclinoid segment of the left internal carotid artery (arrowhead), reformed bilateral MCAs by collaterals (curved arrow) from the vertebrobasilar system. (D) Post-processed image of CT angiogram of posterior circulation of the brain showing mild compensatory dilatation of the basilar artery, and bilateral vertebral arteries with numerous small collaterals in the region of the circle of Willis (<<<. LT: Left thalamus, RT: Right thalamus, MCA: Middle cerebral artery, BAS A: Basilar artery, VERT  A: Vertebral arteries, ICA: Internal carotid artery,  CCA: Common carotid artery, ECA: External carotid artery, INOM A: Innominate artery, SUB A: Subclavian artery
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FIG3
On the CT brain, acute intraparenchymal hemorrhage was seen in the anterior aspect of the left thalamus with extensive intraventricular hemorrhage extension into all the ventricles (Figure 3 A). On CT angiogram (Figure 3 B to D), the right internal carotid artery was not visualized, the supraclinoid segment of the left internal carotid artery was occluded, and the bilateral MCAs were reformed by collaterals from the vertebrobasilar system (numerous collaterals are seen in the region of the circle of Willis and around the midbrain with mild compensatory dilatation of the basilar and bilateral vertebral arteries).