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posterior reversible encephalopathy syndrome (PRES)


  • a form of acute hypertensive encephalopathy usually associated with acute severe hypertension which usually resolves within 1-2 weeks of resolution of the hypertension but some may be left with neurologic impairment and in a minority it may result in death
  • thought to be due to failed autoregulation of the brain and/or endothelial dysfunction causing regional cerebral oedema - usually mainly posteriorly
  • may effect any age but most commonly occurs in middle age and is more common in women
  • many patients have significant co-morbidities
  • best detected on MRI scan


3 main MRI patterns

Parieto-occipital dominance

  • 95% of cases

Superior frontal sulcus

  • also has variable involvement of parietal and occipital lobes

Holohemispheric at watershed zones

  • confluent vasogenic oedema in the watershed zones with relative sparing of temporal lobes

Clinical features

  • severe hypertension is usually present but may have occurred 24hrs or more earlier
  • constant mod-severe headache which is not respondent to simple analgesics
  • visual cortex symptoms may include:
    • auras
    • hallucinations
    • hemianopia
    • visual neglect
    • cortical blindness
  • general CNS impairments such as:
    • drowsiness or agitation
    • confusion
    • in severe cases, may progress to coma
    • usually has brisk deep tendon reflexes and often positive Babinski signs are present
  • seizures may occur and may be the presenting feature, and may be recurrent
    • these are usually generalised tonic clonic but may start from a focal seizure with an occipital lobe symptomatology including visual cortex symptoms as above

Differential Diagnosis

  • severe hypoglycaemia
  • posterior circulation stroke (CVA)
  • progressive multifocal leukoencephalopathy (PML)
  • gliomatosis cerebri
  • sagittal sinus thrombosis
  • hypoxic-ischaemic encephalopathy


  • take bloods for FBE, U&E, LFTs, CRP, glucose, HCG (if not known to be pregnant or post-partum)
  • aggressive Mx of preeclampsia if this is the cause with MgSO4, etc - see pre-eclampsia and eclampsia and eclampsia
  • if not preeclampsia:
    • control BP aiming to lower diastolic BP to 100-105 mmHg within first 2-6hrs but avoiding falls of more than 25% of initial value
      • too rapid a drop in BP may cause ischaemic stroke
      • consider iv labetalol
      • oral agents are NOT useful in the early Rx of this condition
    • control seizures with benzodiazepines and phenytoin
    • avoid corticosteroids as this may worsen the hypertension
    • supportive care
    • CT brain to exclude differentials (although is poor at excluding posterior circulation stroke)
      • is usually normal or non-specific although may show white matter hypodensitivities suggestive of PRES
    • MRI brain is needed to demonstrate PRES in which case a MRA should also be done to exclude a posterior circulation stroke
      • MRI findings generally persist for days or even weeks after clinical resolution
pres.txt · Last modified: 2018/08/13 23:25 (external edit)