PMC2911601_01
Diffusion weighted MRI demonstrates several confluent areas of restricted diffusion, consistent with infarction, confined to the bilateral posterior circulation (a,b). This was confirmed on apparent diffusion coefficient maps (not shown). No restricted diffusion was present in the anterior circulation (not shown).
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fig1
MRI of the brain redemonstrated multiple acute infarcts isolated to the posterior circulation (Figure 1). 
3D Time of Flight MRA source images demonstrate a linear filling defect (white arrow) in the distal basilar artery with extension into the right posterior cerebral artery (PCA) P1 segment. Additional images (not shown) demonstrated this defect also extending into the left PCA P1 segment.
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fig2
MRA of the head and neck revealed patent cervical arteries with an apparent dissection flap visualized throughout the basilar artery (Figure 2). 
Left vertebral artery injection demonstrates poor opacification of the basilar artery and posterior cerebral arteries (PCAs) despite an adequate contrast bolus. There is marked enlargement of the distal vertebral artery in the vicinity of the vertebrobasilar junction, extending into the basilar artery and the P1 segments of both PCAs. A linear filling defect is noted originating in, and spiraling around the basilar artery and extending into the proximal bilateral PCAs, consistent with a dissection (arrow B). There are also multiple segments of vascular dilatation and narrowing in the bilateral superior cerebellar arteries and distal PCAs consistent with postpartum angiopathy.
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fig3
In addition, distinct from the vertebrobasilar dissection, there were multiple regions of segmental narrowing and dilatation of the intracranial arteries predominantly in the posterior circulation, consistent with concomitant PPA (Figure 3). 
(a) Baseline Xenon perfusion study (SBP 120 mm Hg) demonstrates decreased cerebral blood flow (CBF) in both posterior cerebral artery (PCA) territories as well as in the right middle cerebral artery (MCA) and left anterior cerebral artery(ACA) territories. (b) With elevation of SBP (130 mm Hg), there is improvement in CBF in the right parietal region, but no significant improvement in the left PCA territory. There is increased perfusion in the right MCA and left ACA distributions. Increased perfusion is seen within the right occipital and left parietal lobe infarctions.
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fig4
This study showed areas of decreased relative cerebral blood volume in the bilateral posterior cerebral, right middle cerebral, and left anterior cerebral vascular territories at an SBP of 120 mmHg which improved by allowing the SBP to rise above 130 mmHg (Figure 4).