posterior reversible encephalopathy syndrome (PRES)

see also:

• encephalopathy
• hypertension

• 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

• acute severe hypertension
• pre-eclampsia and eclampsia
• cytotoxics such as cyclosporine
• autoimmune diseases

• 95% of cases

• also has variable involvement of parietal and occipital lobes

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

• 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

• 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