Imaging of Atypical and Complicated Posterior Reversible Encephalopathy Syndrome

Abstract

Posterior reversible encephalopathy syndrome (PRES) is a condition clinically characterized by headache, altered mental status, seizures, and visual loss and may be associated with systemic hypertension, preeclampsia/eclampsia, chemotherapy, immunosuppressive therapies in the setting of organ transplantation, and uremic encephalopathy. While brain imaging in patients with PRES typically reveals symmetric vasogenic edema within the parietal and occipital lobes, PRES may present with atypical imaging findings such as central brainstem and deep gray involvement without subcortical edema, and even spinal cord involvement. Additionally, PRES may be complicated in some cases by the presence of cytotoxic edema and hemorrhage. This review will serve to summarize the pathophysiologic theories and controversies underlying PRES, imaging features encountered in atypical and complicated PRES, and the implications these findings may have on patient prognosis.

Keywords: PRES (posterior reversible encephalopathy syndrome); encephalopathy; hypertension; intracranial hemorrhage; pathophsiology.

Figure 1

Fifty-five-year-old man with end stage renal disease and severe hypertension. Axial CT image (A) reveals a focal parenchymal hemorrhage at the junction of the right thalamus and posterior limb of the right internal capsule (arrow). Axial DWI images with ADC inserts (B,C) show foci of diffusion restriction within the right corpus callosum splenium (arrow, B) and left temporo-occipital periventricular white matter (arrow, C). ADC maps confirm diffusion restriction (insert B,C, arrowheads). Again seen is right thalamocapsular hematoma (arrowhead, B). Axial SWI image (D) demonstrates blooming of right thalamocapsular hematoma (arrow) in addition to a punctate hemorrhage within left parietal subcortical white matter (arrowhead). Axial FLAIR images (E,F) show left cerebellar (arrow, E) and confluent bilateral frontoparietal (arrows, F) edema.

Figure 2

Twenty-one-year-old pregnant woman with eclampsia. Axial FLAIR images (A–C) demonstrate bilateral cerebellar hemisphere and vermian (arrows, A), bilateral lentiform/caudate and capsular (arrowheads, B,C), and left parieto-occipital edema. Axial GRE (D) and T2-weighted (E,F) images reveal focal hemorrhage within the left caudothalamic groove (arrow, D,E) extending to the left lateral ventricular body with a small hematocrit level within the left occipital horn (arrow, F) from intraventricular extension of hemorrhage.

Figure 3

Forty-two-year-old woman with history of bone marrow transplantation. Axial FLAIR images (A,B) demonstrate central variant PRES with edema involving the midbrain with extension to the hypothalamus and optic tracts (arrow, A) and pons (arrow, B). Axial GRE image (C) shows petechial hemorrhage at the periphery of the pons (arrow).