Internal Medicine

Posterior reversible encephalopathy syndrome (PRES)

Acute neurotoxic syndrome that is characterized by a spectrum reversible neurological and radiological feature from various risk factors.

Acute neurotoxic syndrome that is characterized by a spectrum reversible neurological and radiological feature from various risk factors.


The syndrome was first described in 1996 by Hinchey and colleagues who reported on a series of 15 patients with neurological signs and symptoms including headache, seizures, visual disturbance and other focal neurological deficits. Moreover, computed tomographic (CT) or magnetic resonance imaging (MRI) alterations suggestive of cerebral edema were observed predominantly in the posterior regions. Since this first description of PRES numerous case reports and case series, as well as retrospective observational studies describing the syndrome have been published.


Associated conditions:

Symptoms present acutely or subacutely in the setting of other conditions:
  • Accelerated hypertension
  • Eclampsia
  • Autoimmune disease
  • Immunosuppressive treatment
  • Cancer chemotherapy
The two main hypotheses explaining the pathophysiology of posterior reversible encephalopathy and associated conditions | Fischer, M., & Schmutzhard, E. (2017). Posterior reversible encephalopathy syndrome. Journal of neurology, 264(8), 1608–1616.


Rapidly developing hypertension

Breakdown in cerebral autoregulation
(breakdown of blood-brain barrier + endothelial dysfunction)

(protein and fluid extravasation)

Focal vasogenic edema

Clinical features

Symptoms are reversible, provided that the syndrome is recognized and treated promptly.

  • Headache
  • Visual impairment (e.g., binocular diplopia, vision loss, no light perception vision, hemianopia, or quadrantanopia)
  • Seizures
  • Mental status changes
Frequency of posterior reversible encephalopathy syndrome signs and symptoms seen in a series of 120 cases | Fugate JE, Claassen DO, Cloft HJ, Kallmes DF, Kozak OS, Rabinstein AA. Posterior reversible encephalopathy syndrome: associated clinical and radiologic findings. Mayo Clin Proc 2010; 85:427–32

Physical examination:

  • Ophthalmic examination: Hemianopia, quadrantanopia, visual neglect, cortical blindness, horizontal gaze palsy with intact vestibulo-ocular reflex, papilledema
  • Oral trauma (tongue biting seen during a seizure)
  • Brisk reflexes
  • Active convulsions
  • Urinary and fecal incontinence


Cases can develop life-threatening complications, if prompt treatment is not initiated.
  • Transforaminal cerebellar herniation
  • Focal neurologic deficits


Non-contrast MRI:

  • Reversible cerebral vasogenic oedema (hyperintense T2/hypointense T1 signal), predominantly affecting the parieto-occipital regions (TYPICAL FINDING)
  • Atypical imaging features:
    • Involvement of anterior brain/brainstem
    • Coexistence of ischemia/hemorrhage
Posterior reversible encephalopathy syndrome. (A) Sagittal T2-weighted image shows the distribution of subcortical edema typically involving the posterior frontal, parietal, and occipital lobes. (B) Axial FLAIR (fluid attenuated inversion recovery) imaging eloquently demonstrates the subcortical edema. (C) B1000 images from a diffusion-weighted sequence shows restricted diffusion in the cortex. Findings are usually bilateral and asymmetrical. | Hobson, E. V., Craven, I., & Blank, S. C. (2012). Posterior reversible encephalopathy syndrome: a truly treatable neurologic illness. Peritoneal dialysis international : journal of the International Society for Peritoneal Dialysis, 32(6), 590–594.

Magnetic resonance angiography (MRA) or magnetic resonance venography (MRV):

Typically normal findings
  • Exclude CNS vasculitis (MRA)
  • Exclude sagittal sinus thrombosis (MRV)

Differential diagnosis:

  • Intracranial hemorrhage
  • Subdural hemorrhage
  • Subarachnoid hemorrhage
  • Cerebral sinus venous thrombosis
  • Posterior circulation ischemic or hemorrhagic stroke
  • thrombosis of the basilar artery
  • Vasculitis of the central nervous system
  • Herpes simplex encephalitis
  • Autoimmune encephalitis
  • Uremic encephalopathy
  • Hypoglycemia


Treatment of hypertension and seizures, and withdrawal of causative agents are the mainstays of therapy in PRES.

  • Protect the airway (in obtunded patients)
  • Aggressive blood pressure management
  • Withdrawal of the offending drug
  • Immediate delivery (in eclampsia)
  • Antiepileptics (to treat seizures)
  • Anesthesia and ventilation (in generalized status epilepticus)

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