Fig 4. Patient 34 is a 56-year-old woman with long-standing sickle cell disease and a baseline blood pressure of 140/60 mm Hg in a sickle cell crisis with new-onset pneumonia. She developed altered mental status and a seizure with blood pressure at toxicity of 170/110 mm Hg. A, Axial MR imaging (FLAIR sequence) demonstrates typical vasogenic edema in the occipital pole regions bilaterally (open arrows) consistent with PRES and judged edema, grade 3. Occipital lobe rCBV relative to a healthy reference cortex was 63% on the right and 54% on the left. B, Collapsed view of the 3D TOF MRA sequence demonstrates both focal vasospasm (arrows) and pruning of the PCAs bilaterally. Foreshortening of the PCAs and only partial visualization to the midportion of the calcarine arteries are noted bilaterally (arrowheads) and were judged PCA pruning, grade 2. Follow-up MR imaging and MRA (not shown) obtained 1 month after toxicity demonstrated complete resolution of the vasogenic edema in the occipital poles with marked improvement in distal PCA flow bilaterally along with reversal of the pruning and vasospasm.