When to use MRI with or without contrast?

MRI With or Without Contrast for PRESS (Posterior Reversible Encephalopathy Syndrome)

For suspected PRESS (Posterior Reversible Encephalopathy Syndrome), MRI with contrast is recommended as it provides optimal evaluation of the extent of disease and helps differentiate between PRESS and other conditions that may mimic it. 1

Imaging Protocol Recommendations

Primary Recommendation

• MRI with AND without contrast is the preferred imaging modality for PRESS evaluation 1, 2
  • Provides best differentiation of soft tissue abnormalities
  • Allows assessment of blood-brain barrier disruption
  • Helps rule out other pathologies that may mimic PRESS

Rationale for Contrast Use in PRESS

1. Enhanced diagnostic accuracy:

   • Contrast helps differentiate between PRESS and other conditions like:
     • Ischemic stroke
     • Tumor
     • Infection
     • Demyelinating disease

2. Assessment of complications:

   • Helps identify potential complications such as:
     • Hemorrhage
     • Infarction
     • Mass effect
     • Herniation

3. Disease extent evaluation:

   • Contrast enhancement allows better visualization of the full extent of involvement 1
   • Helps identify subtle areas of blood-brain barrier disruption

When to Consider Non-Contrast MRI Only

While contrast is generally preferred, non-contrast MRI may be sufficient in certain scenarios:

• Contraindications to gadolinium administration 3:

  • Severe renal impairment (GFR < 30 mL/min)
  • Pregnancy
  • Known allergic reaction to gadolinium-based contrast agents

• Follow-up imaging 4:

  • For patients with established diagnosis of PRESS
  • When monitoring known lesions for resolution

Clinical Decision Algorithm

1. Initial presentation with suspected PRESS:

   • MRI with AND without contrast is the first-line imaging choice 1, 2

2. If gadolinium is contraindicated:

   • Proceed with non-contrast MRI
   • Consider additional sequences (FLAIR, DWI, SWI) to maximize diagnostic yield

3. For follow-up imaging:

   • Non-contrast MRI is usually sufficient to monitor resolution 4
   • Consider contrast only if new symptoms develop or unexpected progression is seen

Important Technical Considerations

• MRI protocol should include:

  • T1-weighted images (pre and post-contrast)
  • T2-weighted images
  • FLAIR (Fluid-Attenuated Inversion Recovery)
  • DWI (Diffusion-Weighted Imaging)
  • SWI (Susceptibility-Weighted Imaging) to detect hemorrhage

• Contrast administration:

  • Standard dose of gadolinium-based contrast agent (0.1 mmol/kg) 3
  • Careful monitoring for adverse reactions

Common Pitfalls to Avoid

1. Relying solely on non-contrast imaging for initial diagnosis:

   • May miss subtle abnormalities
   • Can lead to misdiagnosis with other conditions

2. Unnecessary contrast administration for routine follow-up:

   • Exposes patient to potential gadolinium-related risks 5
   • Non-contrast MRI is typically sufficient for monitoring known PRESS 4

3. Failure to consider differential diagnoses:

   • PRESS can mimic other neurological conditions
   • Contrast helps narrow the differential diagnosis

By following these evidence-based recommendations, clinicians can optimize the diagnostic accuracy of MRI for PRESS while minimizing unnecessary contrast administration.