Posterior Reversible Encephalopathy Syndrome (PRES)

Fig. 1: Axial non-contrast CT image in a 57-year-old hypertensive man shows ill-defined areas of low attenuation in the posterior occipital lobe (arrows).
Fig. 2: Axial FLAIR MR image confirms the abnormality in cortical and subcortical white matter of the posterior aspect of the occipital lobes (arrows), relative sparing of the paramedian occipital regions. There is no contrast enhancement or restricted diffusion.

Facts: Posterior Reversible Encephalopathy Syndrome (PRES)

• Usually reversible neurologic syndrome presenting with reversible headache, altered consciousness or vision loss accompanied by reversible imaging abnormalities
• Related to hypertension, eclampsia and preeclampsia and immunosuppressive medication (and several other causes have been described)
• Believed to be due to hyperperfusion state with blood brain barrier breakthrough

Typical Imaging Appearances

• CT is often abnormal at the time of presentation. MRI shows more lesions and extent.
• Cortical or subcortical edema
• Preferential involvement of posterior aspect of the lobes, particularly parieto-occipital lobes (gradient effect present)
• Sparing of calcarine and paramedian occipital lobe structures
• Usually bilateral

Our case: PRES (typical imaging appearance)

References:

1. Hinghey J, Chaves C, Appignani B, et al. A reversible posterior leukoencephalopathy syndrome. New Eng J Med 1996;334:494-500.

2. McKinney AM, Short J, Truwit CL, et al. Posterior reversible encephalopathy syndrome: incidence of atypical regions of involvement and imaging findings. AJR 2007;189:904-912.