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Case of the Week

Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada

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November 25, 2021

Central-Variant Posterior Reversible Encephalopathy Syndrome (PRES)

  • Background:
    • PRES reflects a neurotoxic state with unique imaging features linked to several conditions, including drug toxicity and severe hypertension.
    • Generally seen as a regional vasogenic edema pattern with characteristic distribution
    • Thought to reflect sequelae of failure of cerebrovascular autoregulation and hyperperfusion secondary to blood-brain barrier disruption; dilated arterioles lead to an influx of parenchymal fluid and proteins/red cells.
    • Findings may completely reverse with treatment of the underlying etiology.
  • Clinical Presentation:
    • Typically presents with seizures or encephalopathy
    • Can also demonstrate headache, vomiting, visual changes, and weakness.
    • Large percentage of patients (70–80%) with moderate-to-severe hypertension
  • Key Diagnostic Features:
    • PRES typically demonstrates regional parenchymal T2/FLAIR high-signal vasogenic edema affecting the parieto-occipital or posterior frontal lobes, but can also or independently involve the periventricular white matter and central basal regions.
    • Generally follows 1 of 3 patterns: holohemispheric, superior frontal sulcal, or parieto-occipital
    • Can demonstrate reduced diffusivity in a small percentage of cases
    • Can show punctate enhancement; enhancement does not portend worse outcome.
    • May demonstrate hemorrhage on T2* GRE/SWI, usually linked to worse prognosis
    • Rarer central-variant PRES shows expansile changes of primarily the central brainstem, usually of the pons and middle cerebellar peduncles, which may be in concert with supratentorial involvement.
  • Differential Diagnoses:
    • Brainstem infarction: Generally unilateral or follows a vascular distribution; demonstrates reduced ADC values
    • Infectious encephalitis: Enhancement is common; may show stereotypic supratentorial lesions depending on the infectious agent
    • Central pontine myelinolysis: Involves the central pons; can show classic trident shape
    • Pontine glioma: More common in the pediatric population; marked expansile enlargement; may encase basilar artery; may show heterogeneous enhancement
  • Treatment:
    • Control blood pressure if elevated
    • Treat inciting etiologies

Suggested Reading

  1. Bartynski WS. Posterior reversible encephalopathy syndrome, part 1: fundamental imaging and clinical features. AJNR Am J Neuroradiol 2008;29:1036–42
  2. Chen T-Y, Lee H-J, Wu T-C, et al. MR imaging findings of medulla oblongata involvement in posterior reversible encephalopathy syndrome secondary to hypertension. AJNR Am J Neuroradiol 2009;30:755–57
  3. Casey SO, Truwit CL. Pontine reversible edema: a newly recognized imaging variant of hypertensive encephalopathy? AJNR Am J Neuroradiol 2000;21:243–45
  4. Tortora F, Caranci F, Belfiore MP, et al. Brainstem variant of posterior reversible encephalopathy syndrome: a case report. Neuroradiol J 2015;28:634–37

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