What is Posterior Reversible Encephalopathy Syndrome (PRES)?

Posterior Reversible Encephalopathy Syndrome (PRES)

PRES is an acute neurotoxic syndrome characterized by reversible vasogenic edema predominantly affecting the posterior regions of the brain, presenting with headache, altered consciousness, visual disturbances, and seizures, typically triggered by hypertension, immunosuppressive medications, autoimmune disorders, or renal failure. 1

Clinical Presentation

• PRES presents with acute neurological deficits including altered consciousness, visual disturbances, headaches, and seizures in patients with various underlying conditions such as cancer or autoimmune diseases 1
• Common neurological symptoms include impairment in level of consciousness, seizures, visual dysfunction, and focal neurological deficits 2
• The onset is typically acute or subacute, with symptoms developing rapidly 3

Pathophysiology

• The pathophysiology involves disruption of the blood-brain barrier due to endothelial injury from abrupt blood pressure changes, leading to vasogenic edema 1
• When blood pressure is markedly elevated and cerebral autoregulation fails, cerebral edema develops, especially in posterior brain areas where sympathetic innervation is less pronounced 4
• The posterior circulation is particularly vulnerable due to less effective damping of blood pressure oscillations in these regions 4

Diagnostic Imaging

• Diagnosis is confirmed by T2-weighted MRI showing hyperintensities in bilateral parietal-occipital lobes, predominantly affecting white matter 1
• MRI is the gold standard, showing increased signal intensity on T2-weighted or fluid-attenuated inversion recovery (FLAIR) imaging in posterior brain regions 1
• CT scan can be useful to exclude intracranial hemorrhage when MRI is not feasible 1
• Atypical imaging features may include involvement of other brain regions, cortical involvement, restricted diffusion, hemorrhage, and contrast enhancement 2
• Rarely, PRES can present unilaterally, making diagnosis more challenging 5

Common Triggers and Risk Factors

• Common triggers include:
  • Pre-existing arterial hypertension 1
  • Renal impairment 1
  • Autoimmune diseases 1
  • High-dose antineoplastic therapy 1
  • Allogenic stem-cell transplantation 1
  • Solid organ transplantation 1
  • Immunosuppression, particularly with cyclosporine 1
  • Eclampsia/preeclampsia 3
  • Exposure to vasoactive substances 6

Management Algorithm

Step 1: Identify and Address Underlying Causes

• Discontinue the offending agent immediately (e.g., anticancer therapy, immunosuppressants) 1
• Identify and treat any underlying conditions such as autoimmune disorders or infections 1

Step 2: Blood Pressure Management

• Implement stringent blood pressure control with gradual reduction to avoid cerebral hypoperfusion 1
• Monitor blood pressure frequently during the acute phase 1

Step 3: Seizure Management

• Administer antiepileptic treatment for patients who develop seizures 1
• Consider prophylactic anticonvulsants in high-risk patients with significant neurological deficits 1
• Benzodiazepines may be used for symptomatic treatment of acute seizures 1

Step 4: Supportive Care

• Implement aspiration precautions and intravenous hydration for patients with altered consciousness 1
• Avoid medications that cause CNS depression in patients with encephalopathy 1
• Position patients with head elevated at 30 degrees to help reduce intracranial pressure 7
• For declining level of consciousness, consider urgent assessment for airway protection 7

Step 5: Electrolyte Management

• Correct electrolyte imbalances if present 1
• Monitor renal function, especially in patients with pre-existing renal impairment 1

Prognosis

• Complete spontaneous remission occurs in most cases without sequelae 1
• Early detection and management are key factors for rapid recovery and good outcomes 1, 3
• While clinical and radiographic reversibility is common, long-standing morbidity and mortality can occur in severe forms 2
• Factors associated with poor outcome include:
  • Altered sensorium 2
  • Hypertensive etiology 2
  • Hyperglycemia 2
  • Longer time to control the causative factor 2
  • Elevated C-reactive protein 2
  • Coagulopathy 2
  • Extensive cerebral edema 2
  • Hemorrhage on imaging 2

Common Pitfalls to Avoid

• Failure to identify and discontinue the triggering agent can lead to prolonged illness and increased risk of complications 1
• Missing concomitant conditions that may complicate management, such as sepsis or metabolic disturbances 1
• Delayed diagnosis due to atypical presentations or imaging findings 5
• Although seizures are common in PRES, epilepsy is rare, so long-term antiepileptic treatment is usually unnecessary 2