Posterior reversible encephalopathy syndrome

Posterior reversible encephalopathy syndrome (PRES) is a clinicoradiological syndrome characterized by acute cerebral endotheliopathy with consecutive disruption of the blood-brain barrier and vasogenic edema. Since its first description in 1996, PRES is increasingly recognized. However, many aspects of this syndrome with its wide spectrum of clinical and radiological features are still incompletely understood. In this review, possible pathophysiological mechanisms, approaches to diagnosis, recent study results on outcome, and future directions of research are described.

Clinical manifestations of PRES include seizures, headache, visual disturbances, altered mental state, and more rarely hemiparesis or aphasia. Vasogenic edema predominantly occurs in the parieto-occipital region, but lesions affecting formerly called 'atypical' regions such as frontal lobe, cerebellum, or basal ganglia are common. If treated early and adequately, that is by removal of the underlying cause, PRES has a favorable prognosis, but neurological residual symptoms and even mortality can occur, particularly in patients with complications such as intracranial hemorrhage.

In summary, validated diagnostic criteria and algorithms are warranted to standardize the diagnosis of PRES. This is essential for further research and future prospective studies that should investigate risk factors for unfavorable outcome and identify the roles of imaging features, clinical symptoms, and other biomarkers in predicting outcome.