Posterior reversible encephalopathy syndrome, part 1: fundamental imaging and clinical features

Abstract

Posterior reversible encephalopathy syndrome (PRES) is a neurotoxic state coupled with a unique CT or MR imaging appearance. Recognized in the setting of a number of complex conditions (preeclampsia/eclampsia, allogeneic bone marrow transplantation, organ transplantation, autoimmune disease and high dose chemotherapy) the imaging, clinical and laboratory features of this toxic state are becoming better elucidated. This review summarizes the basic and advanced imaging features of PRES, along with pertinent features of the clinical and laboratory presentation and available histopathology. Many common imaging/clinical/laboratory observations are present among these patients, despite the perception of widely different associated clinical conditions.

Fig 1.

The patient is a 28-year-old man with a history of alcohol abuse and drug use, presenting with a necrotic pneumonia and empyema growing Pseudomonas and Klebsiella species. He developed altered mentation and asymmetric neurologic findings on examination. Blood pressure at toxicity fluctuated between 130/100 mm Hg and 130/77 mm Hg. A and B, Axial MR images (fluid-attenuated inversion recovery) demonstrate extensive vasogenic edema in the frontal lobes (arrows), parietal region (curved arrows), occipital lobes (open arrows), and temporal lobes (arrowheads), bilaterally, consistent with PRES. The edema distribution clearly separates medial (ACA and PCA) from lateral (MCA) hemispheric regions typical of the holohemispheric PRES pattern. Cerebellar involvement was also present (not shown). C, Lateral view of the left internal carotid artery injection with left and right ACA opacification. Areas of vessel dilation and constriction are noted in the secondary and tertiary branches of both medial hemispheric vessels (left [arrows] and right [arrowheads] ACAs) and lateral hemispheric vessels (left MCA [curved arrows]) consistent with vasculopathy. D, Lateral view of the vertebral artery CA injection demonstrates a string-of-beads appearance (arrowheads) and areas of vasodilation/vasoconstriction (arrows) in parietal branches of the PCA. E, Oblique 3D TOF MRA reconstructed images of the posterior circulation demonstrate areas of focal vasodilation and vasoconstriction in the PCAs bilaterally (arrows), consistent with vasculopathy, similar to the vertebral artery CA appearance. Posterior inferior cerebellar artery (arrowheads) irregularity is also present.

Fig 2.

The patient is a 38-year-old woman with scleroderma, severe hypertension (190/110 mm Hg), and acute renal failure, with altered mental status that progressed to seizure. A, Axial brain CT image obtained at toxicity demonstrates vasogenic edema in the parietal region bilaterally (curved arrows), consistent with PRES. B, Axial technetiumTc-99m-HMPAO SPECT study performed the following day demonstrates reduced radiopharmaceutical uptake bilaterally in the parietal region (curved arrows), consistent with hypoperfusion.

Fig 3.

The patient is a 56-year-old woman with a thigh abscess (Klebsiella and Enterococcus species), baseline blood pressure of 156/68 mm Hg, and multiple organ failure (coagulopathy, acute respiratory distress syndrome, hepatic dysfunction with shock liver, and renal failure). She developed altered mentation and a seizure with toxicity blood pressure 164/75 mm Hg. A, Axial MR image (fluid-attenuated inversion recovery sequence) demonstrates extensive PRES vasogenic edema in the parietal region bilaterally (curved arrows). B, rCBV color map demonstrates severe flow reduction in the parietal region bilaterally (curved arrows), consistent with the regions of PRES imaging abnormality. PRES cortex rCBV relative to the reference cortex is 31% in the right parietal and 33% in the left parietal region.