Neurosurgery notes/Functional/Seizure/Seizure classification/Posterior Reversible Encephalopathy Syndrome (PRES)

Posterior Reversible Encephalopathy Syndrome (PRES)

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Seizure classification

General

  • A misnomer as the syndrome can involve or extend beyond the posterior cerebrum
  • Aka:
    • Reversible posterior leukoencephalopathy syndrome (RPLS)
    • Not the same as
      • Chronic hypertensive encephalopathy,
        • Also known as hypertensive microangiopathy,
        • Results in microhaemorrhages in the basal ganglia, pons, and cerebellum

Definition

  • A neurotoxic state that occurs secondary to the inability of the posterior circulation to autoregulate in response to acute changes in blood pressure.
  • Hyperperfusion with resultant disruption of the blood-brain barrier results in vasogenic oedema, usually without infarction, most commonly in the parieto-occipital regions.

Numbers

  • PRES affects females more commonly than males.

Aetiology

  • Hypertensive encephalopathy,
  • Immunosuppressive therapy,
  • Renal failure
  • Eclampsia

Clinical presentation

  • Headache
  • Seizures
  • Encephalopathy (acute confusion or altered mental state or decreased level of consciousness)
  • Visual disturbance, including reversible cortical blindness
  • In some cases, haemorrhagic events may occur. Lesions typically disappear in two weeks on MRI.

Microscopic appearance

  • During the acute course of PRES:
    • Vasogenic oedema
    • Without inflammation
    • Ischaemia
    • Neuronal damage
  • During the late course of PRES:
    • Demyelination and myelin pallor along with evidence of ischaemia,
    • Anoxic neuronal damage,
    • Laminar necrosis,
    • Older haemorrhage in the white matter and cortex

Radiology

  • Location
    • Extensive subcortical edema mainly confined to the posterior parietooccipital lobes.
      • Bilateral vasogenic oedema within the occipital and parietal regions (70-90% of cases)
    • Can be found in a non-posterior distribution, mainly in watershed areas, including within the frontal, inferior temporal, cerebellar, and brainstem region
  • MRI
    • Signal characteristics of affected areas usually reflect vasogenic oedema, with some exceptions.
    • T1: hypointense in affected regions
    • T1 C+ (Gd): patchy variable enhancement can be seen in ~35% of patients, in either a leptomeningeal or cortical pattern
    • T2: hyperintense in affected regions
    • DWI: usually normal, sometimes hyperintense due to oedema (T2 shine-through) or true restricted diffusion
    • ADC: usually increased signal due to increased diffusion, but restricted diffusion is present in a quarter of cases
    • GRE/SWI: may show haemorrhages (including microhaemorrhages) in 9-50%
    • MRA: may show patterns of vasculopathy with vessel irregularity consistent with focal vasoconstrictions/vasodilatation and diffuse vasoconstriction
    • MRV: tends to be normal
        • T1
        A close-up of a brain AI-generated content may be incorrect.
        T2
        A close-up of a brain scan AI-generated content may be incorrect.
        Flair
        A close-up of a brain scan AI-generated content may be incorrect.
        ADC
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      • Lesions typically disappear in two weeks on MRI.