Is lumbar puncture (LP) contraindicated in Posterior Reversible Encephalopathy Syndrome (PRES)?

Lumbar Puncture in Posterior Reversible Encephalopathy Syndrome (PRES)

Lumbar puncture should be avoided in patients with PRES due to the risk of brain herniation, as PRES commonly presents with vasogenic edema and potential increased intracranial pressure. 1

Pathophysiology and Risk Assessment

PRES is characterized by vasogenic edema primarily affecting the posterior cerebral regions. This condition can lead to increased intracranial pressure and potential brain shift, which are key contraindications for lumbar puncture.

Contraindications to Lumbar Puncture Relevant to PRES

The following contraindications to lumbar puncture are particularly relevant in the context of PRES:

• Signs of increased intracranial pressure or brain shift 1, 2

  • Moderate to severe impairment of consciousness (GCS < 13)
  • Focal neurological signs
  • Abnormal posture or posturing
  • Papilledema
  • Relative bradycardia with hypertension
  • Abnormal "doll's eye" movements

• Recent seizures 1, 3

  • PRES commonly presents with seizures, which can temporarily increase intracranial pressure

• Coagulation abnormalities 1

  • Particularly important as some PRES patients may have underlying conditions with coagulopathy

Diagnostic Approach in PRES

Neuroimaging Before Lumbar Puncture

In patients with suspected PRES:

1. MRI is the preferred imaging modality to diagnose PRES and assess for brain edema or shift
2. Clinical assessment, not CT, should be the primary determinant of whether LP is safe 1
3. Even with normal neuroimaging, LP may still be contraindicated if clinical signs suggest increased intracranial pressure 3

Case Evidence

There is documented evidence of PRES developing following dural puncture 4, suggesting a potential bidirectional relationship between CSF pressure changes and PRES pathophysiology. This further supports caution when considering LP in PRES patients.

Decision Algorithm for Lumbar Puncture in PRES

1. First, determine if LP is clinically necessary

   • Is CSF analysis essential for diagnosis or management?
   • Can alternative diagnostic methods be used?

2. Assess for absolute contraindications:

   • Evidence of brain shift on imaging
   • Clinical signs of increased intracranial pressure
   • Coagulopathy or anticoagulant therapy
   • Local infection at puncture site
   • Recent seizures (until stabilized)

3. If LP is deemed necessary and no absolute contraindications exist:

   • Use atraumatic (non-cutting) needles to reduce complications 1
   • Position patient in lateral decubitus position 1
   • Ensure procedure is performed by experienced operator 1
   • Monitor neurological status closely during and after procedure

Common Pitfalls and Caveats

1. Relying solely on CT findings: Brain shift may not be evident on CT, especially early in PRES. Clinical assessment remains crucial 1, 2

2. Underestimating herniation risk: Even with normal imaging, clinical signs of impending herniation are the best predictors of LP safety 3

3. Failure to recognize PRES as a dynamic condition: Intracranial pressure can fluctuate rapidly in PRES, so assessment immediately before LP is essential

4. Post-LP complications: If LP is performed, be vigilant for post-dural puncture headache, which may complicate assessment of PRES symptoms 1

In summary, while lumbar puncture is not absolutely contraindicated in all PRES cases, the risks generally outweigh the benefits given the pathophysiology of PRES and the potential for brain herniation. Neuroimaging (preferably MRI) and thorough clinical assessment should guide decision-making, with strong consideration for alternative diagnostic approaches when possible.