Posterior reversible leukoencephalopathy syndrome (PRES) is a condition in which patients present with headache, altered mental status, confusion, drowsiness, visual disturbances and/or seizures.  

They also have hypertension, metabolic derangements and commonly renal failure.

The etiology is most frequently renal failure with hypertension, but also occurs in eclampsia lower<1%

Pre-eclampsia -5%Immunosupression:Cyclosporine or FK-506

Tacrolimus

Cisplatin

Interferon-alpha

Erythropoietin   

    There are case reports in patients with lupus, polyarteritis nodosa, acute porphyria, and post-organ transplantation, thrombotic thrombocytopenic purpura.  

     Acute hypertension or drug toxicity damages vascular endothelium and breakthrough of autoregulation causes blood brain barrier disruption. 

   Vasogenic edema with arteriolar dilatation with cerebral hyperperfusion. Hydrostatic leakage( extravasation, transduation of fluid and macromacules through arteriolar walls)      

    Interstitial fluid accumulates in cortex,subcortical white matter.   

   Posterior circulation sparsely innervated by sympathetic nerves ( predilection for parietal,occipital lobes) Progression to frank infarction with cytotoxic edema rare in PRES.        

   Patient show edema in the occipital and parietal lobe white and grey matter primarily, but can also have similar findings in the brain stem, basal ganglia and frontal lobes. Rarely enhancement or hemorrhage occurs.

  Differntial Diagnosis:  

Acute Cerebral Ischemia

Acute Cerebral Hyperemia

Inborn Error of Metabolism

Progressive Multifocal Leukoencephalopathy( PML)

Acute Demyelinating Disease 

     Findings are completely reversible, but this may take weeks to months to occur. 

Take Home Message; Favorable outcome with prompt recognition, treatment of hypertension.