Case of the Month #41 Posterior Reversible Encephalopathy Syndrome (PRES)

Published 20/07/2023

How can a diagnosis of PRES be confirmed?

  • MRI demonstrating hyperintensity in T2 and FLAIR sequences is the gold standard for making the diagnosis. It may not be visible on CT. [5] 

  • Neither the pattern nor severity of vasogenic oedema are related to the severity of clinical symptoms. 

  • Oedema tends to occur in a bilateral pattern within the posterior white matter, at the watershed areas [3, 5].  The oedema can be described in the following distributions: 

    • Parieto-occipital (~50%)  
    • Superior frontal sulcus pattern (~25%)  
    • Holohemispheric watershed pattern (~25%)  
    • Central pattern (~10%)  
  • Additional common findings:  infarct, parenchymal microhaemorrhages, sub-arachnoid haemorrhages. [1]