Posterior Reversible Encephalopathy Syndrome (PRES)

25 yrs old post partum female

Axial FLAIR images of brain:
Irregular cortical and subcortical symmetric hyperintensities in bilateral parieto occipital regions 



Axial FLAIR images of brain:
Similar hyperintensities in bilateral posterior parietal regions

·        Neurotoxic state.

·        The parietal and occipital lobes are most commonly affected, followed by the frontal lobes, the inferior temporal-occipital junction, and the cerebellum. Lesion confluence may develop as the extent of edema increases.

·        The edema usually completely reverses.

·        The basic PRES pattern resembles the brain watershed zones, with the cortex and subcortical and deep white matter involved to varying degrees.

·        Three hemispheric pattern variants may be encountered with similar frequency (holohemispheric, superior frontal sulcal, and primary parietal-occipital)

·        Focal/patchy areas of PRES vasogenic edema may also be seen in the basal ganglia, brain stem, and deep white matter.

·        Restricted diffusion is associated with poor outcome.

·        Haemorrhage can be seen in 15% of cases.

·        Causes

·          Preeclampsia/ eclampsia

·          Infection/sepsis/shock

·          Autoimmune disease

·          Chemotherapy

·          Transplantation

·          Hypertension

References :

Posterior Reversible Encephalopathy Syndrome, Part 1: Fundamental Imaging and Clinical FeaturesAJNR June 2008 29: 1036-1042