Understanding Posterior Reversible Encephalopathy Syndrome

Posterior reversible encephalopathy syndrome (PRES) [1, 2] is a clinicoradiological entity that was well described by Hinchey et al. [3] in 1996 based on 15 cases, shortly after two other small case-series were published [4, 5]. This condition has been designated by a variety of names (reversible posterior leukoencephalopathy syndrome, reversible posterior cerebral edema syndrome, and reversible occipital parietal encephalopathy). PRES is now the accepted term [1, 2, 6] but has been challenged recently based on the risk of neurological impairment and up to 15 % mortality rate [7, 8]. PRES is characterized by variable associations of seizure activity, consciousness impairment, headaches, visual abnormalities, nausea/vomiting, and focal neurological signs. The cerebral imaging abnormalities are often symmetric and predominate in the posterior white matter (Fig. 1). Recognition of PRES has evolved with increasing availability of magnetic resonance imaging (MRI). PRES can develop in association with a vast array of conditions. However, regardless of the underlying cause, the main abnormality is cerebral vasogenic edema, the pathogenesis of which is still under debate [1, 2]. PRES is typically reversible once the cause is removed. However, patients with severe manifestations of PRES, such as coma and/or status epilepticus, may require admission to the intensive care unit (ICU) [9, 10]. Moreover, permanent neurological impairment or death occurs in a minority of patients [5, 7, 8]. The objective of this chapter is to provide clinicians with guidance for diagnosing and treating patients with PRES. The diagnostic criteria are described in detail and management recommendations are given with an algorithm.