What is Posterior Reversible Encephalopathy Syndrome (PRES)?

Posterior Reversible Encephalopathy Syndrome (PRES)

PRES is a clinical-radiological syndrome characterized by acute neurological deficits including altered consciousness, visual disturbances, headaches, and seizures, typically caused by disruption of the blood-brain barrier due to endothelial injury from abrupt blood pressure changes leading to vasogenic edema. 1

Clinical Presentation

PRES typically presents with:

• Neurological symptoms:

  • Altered consciousness (from impaired attention to confusion and delirium)
  • Visual disturbances (including blindness)
  • Headaches (often severe)
  • Seizures (common presenting symptom)
  • Focal neurological deficits 1, 2

• Onset pattern:

  • Usually acute or subacute presentation
  • Often occurs in the setting of specific risk factors 3

Risk Factors and Etiology

PRES is associated with several conditions:

• Hypertension-related:

  • Acute hypertensive episodes
  • Hypertensive encephalopathy
  • Pre-existing arterial hypertension 1

• Medical conditions:

  • Renal impairment
  • Autoimmune diseases
  • Eclampsia/pre-eclampsia
  • Sepsis 1, 3

• Treatment-related:

  • High-dose antineoplastic therapy
  • Immunosuppressive medications (e.g., cyclosporin)
  • Anti-VEGF therapies (e.g., sorafenib)
  • Allogenic stem-cell transplantation
  • Solid organ transplantation 1, 4

Pathophysiology

The primary mechanism involves:

• Disruption of the blood-brain barrier due to endothelial injury
• Abrupt blood pressure changes that exceed cerebral autoregulation capacity
• Resulting vasogenic edema, predominantly in posterior brain regions
• Posterior brain vulnerability due to less pronounced sympathetic innervation (less effective damping of BP oscillations) 1

Diagnostic Evaluation

Imaging

• MRI (preferred):

  • T2-weighted/FLAIR hyperintensities
  • Bilateral parietal-occipital lobe involvement (classic pattern)
  • Predominance in white matter over gray matter
  • May show atypical patterns including anterior brain involvement 1

• CT:

  • Less sensitive than MRI
  • Useful to exclude other diagnoses, particularly intracranial hemorrhage 1

Clinical Assessment

• Thorough history focusing on:
  • Emergency symptoms (headache, visual changes, neurological symptoms)
  • Medication use (immunosuppressants, chemotherapy, anti-angiogenic agents)
  • Blood pressure history and control 1

Treatment Algorithm

1. Immediate blood pressure management:

   • Very stringent control of blood pressure is crucial 1
   • Target gradual reduction to avoid cerebral hypoperfusion

2. Address underlying cause:

   • Discontinue offending medications (e.g., immunosuppressants, chemotherapy)
   • Manage underlying conditions (e.g., eclampsia, renal disease) 1

3. Seizure management:

   • Antiepileptic treatment for patients with seizures
   • Benzodiazepines may be used for symptomatic treatment 1

4. Supportive care:

   • Correction of electrolyte imbalances if present
   • Neurological monitoring 1

Prognosis

• Typically reversible:

  • Usually resolves within 2 weeks with appropriate supportive management 1
  • Complete resolution of both clinical and radiological findings in most cases 5

• Potential complications:

  • Permanent imaging abnormalities in a minority of patients
  • Residual neurological sequelae possible in severe cases
  • Mortality can occur in malignant forms 2, 5

Poor Prognostic Factors

Several factors associated with worse outcomes:

• Altered sensorium
• Hypertensive etiology
• Hyperglycemia
• Delayed control of causative factors
• Extensive cerebral edema
• Hemorrhage on imaging 2

Special Considerations

• Reintroduction of causative medications:

  • In selected patients, careful reintroduction of previously implicated medications (e.g., anti-VEGF therapies) may be feasible with close monitoring 4

• Differential diagnosis:

  • Consider PRES in patients with unexplained neurological symptoms after procedures such as lumbar punctures or spinal anesthetics 6
  • Must be distinguished from other causes of encephalopathy, stroke, and CNS infections

• Long-term follow-up:

  • While seizures are common in acute presentation, development of epilepsy is rare 2
  • Follow-up imaging may be warranted to confirm resolution

PRES represents an important neurological emergency that requires prompt recognition and management to prevent permanent neurological damage. With appropriate treatment, most patients recover completely.