Posterior reversible encephalopathy syndrome: A review with emphasis on neuroimaging characteristics

Posterior reversible encephalopathy syndrome (PRES) is a clinical and radiological condition that involves the acute onset of headache, confusion, optical impairments, and seizures with accompanying vasogenic edema on brain imaging. PRES is a complex disorder with many causative factors, including underlying conditions such as hypertensive encephalopathy, eclampsia, collagen disease, and severe infection. Although the exact pathophysiological mechanism is not completely understood and remains controversial, the predominant proposed mechanism is endothelial dysfunction, which is preceded by hypertension, immunosuppressive agents, or cytotoxic medication. Magnetic resonance imaging (MRI) facilitates prompt diagnosis and treatment and leads to good outcomes. Findings are characterized by the following: hyperintensity on fluid-attenuated inversion recovery images and apparent diffusion coefficient mapping, and isointensity on diffusion weighted images involving the parieto-occipital or posterior frontal cortical subcortical regions that are recognized in > 90% of patients, and reversibility of neuroimaging abnormalities, with the latter being the most important. As an algorithm to standardize the diagnosis of PRES has not yet been developed, this review presents a diagnostic algorithm based on the types of MRI findings. This algorithm may provide a better understanding of the characteristics that compose PRES and bring us one step closer to the standardization of PRES diagnosis, helping clinicians evaluate individual features while also considering competing differential diagnoses.