Head CT (with and without IV contrast): Bilateral temporal/occipital, bilateral parietal, and right frontal hypodensities with extension across the splenium of the corpus callosum. Hypodensities do not enhance post contrast administration. There is no mass-effect associated with these hypodensities.

MR Brain: Areas of high signal throughout the white matter particularly involving the parietal regions with some extension on the right to the frontal lobe and inferiorly bilaterally to involve the occipital and right temporal lobes. No mass-effect is present. High signal on diffusion is appreciated only focally in the parietal regions at the gray-white junction. There is mild mass-effect, without hemorrhage or midline shift.

Posterior Reversible Encephalopathy Syndrome (PRES) or Reversible Posterior leukoencephalopathy syndrome (RPLS) is an increasingly recognized neurologic disorder with characteristic computed tomographic (CT) and magnetic resonance (MR) imaging findings, and it is associated with a multitude of diverse clinical entities. These include acute glomerulonephritis, preeclampsia and eclampsia, systemic lupus erythematosus, and thrombotic thrombocytopenic purpura and hemolytic-uremic syndrome, as well as drug toxicity from agents such as cyclosporine, tacrolimus, cisplatin, and erythropoietin. Most, but not all, cases manifest with acute to subacute hypertension, and seizures are also frequent. Classic CT findings are those of bilaterally symmetric low attenuation in the posterior parietal and occipital lobes, whereas MR imaging demonstrates hyperintensity on T2-weighted images in the same distribution. Since PRES is often unsuspected by clinicians, radiologists may be the first to suggest the diagnosis. As this diagnosis has important therapeutic and prognostic implications, radiologists should be aware of the spectrum of imaging findings in PRES.

Two pathophysiologic mechanisms for RPLS have been proposed. One postulates cerebral vasospasm with resulting ischemia within the involved territories, whereas the other posits a breakdown in cerebrovascular autoregulation with ensuing interstitial extravasation of fluid. Diffusion MR imaging can be used to discriminate between these two possibilities, as the cytotoxic edema of cerebral ischemia demonstrates decreased water mobility, whereas vasogenic edema due to cerebrovascular autoregulatory dysfunction results in increased water mobility.

Pratik Mukherjee, MD, PhD and Robert C. McKinstry, MD, PhD. Reversible Posterior Leukoencephalopathy Syndrome: Evaluation with Diffusion-Tensor MR Imaging. Radiology. 2001;219:756-765.

Case Number: 1775907Last Updated: 06-22-2005
Anatomy: Cranium and Contents   Pathology: Other
Modality: CT, MRExam Date: Access Level: Readable by all users
Keywords: posterior reversible encephalopathy syndrome pres

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