Unifying Concepts

Diagnosis of Posterior Reversible Encephalopathy Syndrome (PRES)

The posterior reversible encephalopathy syndrome (PRES) is a neurological disorder of (sub)acute onset characterized by varied neurological symptoms, which may include headache, impaired visual acuity or visual field deficits, disorders of consciousness, confusion, seizures, and focal neurological deficits.

Diagnostic findings in patients with posterior reversible encephalopathy syndrome

Diagnostic tool Finding
Laboratory data Hypomagnesemia
Lactate dehydrogenase ↑
Liver function parameters ↑
Creatinine ↑
Albumin ↓
Cerebrospinal fluid Albumin ↑
Albuminocytologic dissociation
EEG Diffuse theta slowing
Delta slowing
Rhythmic delta activity
Sharp-slow wave activity
Periodic lateralizing epileptiform discharges
Diffuse or focal (symmetric) slowing of background activities
CT and MRI Vasogenic edema
Watershed distribution
Parieto-occipital pattern
Frontal and temporal lobe involvement
Subcortical white matter lesions
Bilateral, frequently symmetric distribution
Hyperintense T2-weighted and FLAIR sequences
Iso-, hypo-, or hyperintense lesions on DWI
Facultative contrast enhancement
Microbleeds, intracerebral hemorrhage possible
Increased or decreased ADC values depending/indicating (ir)reversibility of lesions
Angiography Vasoconstriction, vasospasm (diffuse or focal)

EEG electroencephalogram, CT computed tomography, MRI magnetic resonance imaging, FLAIR fluid-
attenuated inversion recovery, DWI diffusion-weighted imaging, ADC apparent diffusion coefficient

Suggested criteria for the diagnosis of posterior reversible encephalopathy syndrome

  • neurological symptoms of acute onset
  • (focal) vasogenic edema on neuroimaging
  • reversibility of clinical and/or radiological findings



  1. Fischer M, Schmutzhard E. Posterior reversible encephalopathy syndrome. J Neurol. 2017 Aug;264(8):1608-1616. [Medline]
  2. Geocadin RG. Posterior Reversible Encephalopathy Syndrome. N Engl J Med. 2023 Jun 8;388(23):2171-2178. [Medline]


Created Jan 03, 2024.

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