What are the typical features of posterior reversible encephalopathy syndrome (PRES)?

Typical Features of Posterior Reversible Encephalopathy Syndrome (PRES)

PRES presents with acute neurological deficits including altered consciousness, visual disturbances, headaches, and seizures, with characteristic MRI findings of bilateral parietal-occipital lobe hyperintensities predominantly affecting white matter. 1

Clinical Presentation

• Acute neurological symptoms are the hallmark of PRES, including:

  • Altered consciousness (ranging from impaired attention to confusion and delirium) 2
  • Visual disturbances and blindness 2, 3
  • Headaches (often severe and of sudden onset) 2, 4
  • Seizures (a common and prominent feature) 2, 3
  • Focal neurological deficits 4

• The onset is typically acute to subacute, with symptoms developing over hours to days 3

• Mental status changes can range from mild confusion to delirium with psychotic symptoms and decreased consciousness (from drowsiness to coma) 2, 5

Radiological Features

• Characteristic imaging findings include:

  • Bilateral vasogenic edema predominantly affecting parietal-occipital lobes 2, 1
  • White matter involvement more prominent than gray matter 2, 4
  • T2-weighted MRI showing hyperintensities in affected regions 1

• Atypical imaging patterns may include:

  • Involvement of anterior cerebral regions 5
  • Deep white matter and brainstem involvement 5
  • Hemorrhage, contrast enhancement, or restricted diffusion in some cases 3

Pathophysiology

• The primary mechanism involves disruption of the blood-brain barrier due to endothelial injury from abrupt blood pressure changes 2, 1
• This leads to vasogenic edema, particularly in posterior brain regions where sympathetic innervation is less pronounced 6
• Failure of cerebral autoregulation is a key factor, especially when blood pressure is markedly elevated 1, 6

Associated Conditions and Risk Factors

• Common risk factors and associated conditions include:
  • Pre-existing arterial hypertension 2, 1
  • Renal impairment 2, 1
  • Autoimmune diseases 2, 1, 7
  • High-dose antineoplastic therapy 2
  • Allogenic stem-cell transplantation 2
  • Solid organ transplantation 2
  • Immunosuppression (especially cyclosporine) 2, 5
  • Eclampsia/pre-eclampsia 5
  • Cancer chemotherapy 5

Clinical Course and Prognosis

• PRES is typically reversible with appropriate management 2, 3
• Complete spontaneous remission occurs in most cases without sequelae within approximately 2 weeks 2, 1
• However, delayed diagnosis and treatment may lead to permanent neurological sequelae 5
• Factors associated with poor outcomes include:
  • Altered sensorium 3
  • Hypertensive etiology 3
  • Hyperglycemia 3
  • Delayed control of the causative factor 3
  • Extensive cerebral edema and hemorrhage on imaging 3

Diagnostic Approach

• MRI is the gold standard for diagnosis 1, 4

  • T2-weighted or FLAIR sequences are most sensitive for detecting the characteristic edema 1
  • CT can be useful when MRI is not available, particularly to exclude hemorrhage 1

• Clinical suspicion should be high in patients with risk factors who develop acute neurological symptoms 3

Common Pitfalls

• Failure to recognize PRES promptly can lead to delayed treatment and worse outcomes 1, 3
• Missing the underlying trigger or causative agent may result in prolonged illness 1
• Overlooking concomitant conditions (like sepsis or metabolic disturbances) that may complicate management 1
• PRES may be mistaken for other neurological conditions due to overlapping symptoms 8