General description

Posterior reversible encephalopathy syndrome (PRES) is a condition characterized by reversible vasogenic edema primarily affecting the posterior white matter of the brain, particularly the occipital lobes. Common symptoms include altered consciousness, seizures, headaches, and visual disturbances, which are nonspecific but frequently observed in both adults and children. PRES can occur across all age groups, but is more common in young to middle-aged adults, with a higher prevalence in women.

The pathophysiology of PRES involves a breakdown of the blood-brain barrier due to dysregulated cerebral autoregulation caused by abrupt blood pressure elevations or fluctuations. This results in vasogenic edema, particularly in the occipital region, where sympathetic innervation for autoregulation is weaker. Additional factors, such as endothelial injury caused by hypertension, immunosuppressive medications (e.g., cyclosporine, tacrolimus), or conditions like eclampsia, also contribute. Other risk factors include autoimmune diseases, such as systemic lupus erythematosus (SLE), Crohn’s disease, and Sjögren syndrome, as well as sepsis, shock, and organ failure, including renal failure.

PRES is frequently linked to various clinical backgrounds, including bone marrow transplantation, autoimmune diseases, and infections or sepsis. In children, hematological disorders, renal disease, and cytotoxic medications are significant risk factors. Common associated conditions include glomerulonephritis, acute leukemia, Henoch-Schönlein purpura, and hemolytic-uremic syndrome. Medications, including VEGF inhibitors like bevacizumab, sunitinib, and sorafenib, and transplant-related immunosuppressants such as cyclosporine and tacrolimus, are also known triggers.

Radiographic features

Typical distribution

Typical distribution is characterized by bilateral vasogenic edema primarily affecting the occipital and parietal regions, likely related to the posterior cerebral artery supply. The subcortical white matter is always involved, and the cortical regions are frequently affected as well. While the edema is almost always bilateral, it is often asymmetrical.

MRI shows T2WI and FLAIR hyperintensity accompanied by DWI hyperintensity with an increased ADC value, consistent with vasogenic edema in the affected area.

Atypical distribution

Vasogenic edema in PRES may also involve atypical regions such as the frontal and temporal lobes, basal ganglia, brainstem, and cerebellum. However, these atypical areas are often accompanied by edema in the parieto-occipital regions. When edema is entirely unilateral or limited to the brainstem or cerebellum, alternative diagnoses should be considered.