What are the characteristic cerebrospinal fluid (CSF) findings that suggest Guillain-Barré Syndrome (GBS)?

Characteristic CSF Findings in Guillain-Barré Syndrome

The classic cerebrospinal fluid finding in Guillain-Barré Syndrome is albumino-cytological dissociation, characterized by elevated CSF protein levels with a normal cell count. 1

Key CSF Characteristics in GBS

Primary Diagnostic Finding

• Albumino-cytological dissociation: Elevated CSF protein with normal cell count 1, 2
  • First described by Guillain, Barré, and Strohl in their original paper 3
  • Serves as a hallmark finding supporting GBS diagnosis

Important Temporal Considerations

• Protein elevation timing:
  • Normal protein levels in 30-50% of patients during the first week of symptoms 1
  • Normal protein levels in 10-30% of patients during the second week 1
  • Protein levels tend to increase with disease progression 4
  • Longer duration from symptom onset to lumbar puncture increases diagnostic yield 5

Cell Count Parameters

• Normal cell count: Typically <5 cells/μl
• Mild pleocytosis (10-50 cells/μl) may be compatible with GBS but should prompt consideration of alternative diagnoses 1
• Marked pleocytosis (>50 cells/μl) suggests alternative pathologies such as:
  • Leptomeningeal malignancy
  • Infectious or inflammatory diseases of the spinal cord or nerve roots 1

Alternative CSF Measurements

• CSF/serum albumin quotient (Qalb):
  • Strongly correlates with CSF total protein (r = 0.95) 5
  • Has similar diagnostic yield to total protein measurement
  • Advantage of method-independent reference ranges 5
  • Can be calculated using either Reiber's or Hegen's age-adjusted formulas

Clinical Correlations

• Higher CSF protein levels correlate with:
  • Greater clinical severity 4
  • Poorer prognosis (negative correlation with MRC scores at 6 months) 6
  • Disease progression 4

Important Caveats

• Normal CSF protein does NOT rule out GBS, especially early in the disease course 1
• CSF examination should be performed during initial evaluation primarily to rule out other causes of weakness 1
• B-CSFB (blood-CSF barrier) dysfunction is present in only about half of GBS patients during the first week 4
• Paradoxically, a low B-CSFB dysfunction response during follow-up has been associated with poorer outcomes 4

Practical Application

When evaluating a patient with suspected GBS:

1. Perform lumbar puncture as part of initial evaluation
2. Look specifically for albumino-cytological dissociation
3. If protein is normal but clinical suspicion remains high, consider:
   • Timing (may be too early in disease course)
   • Repeating CSF analysis after 1-2 weeks if diagnosis remains uncertain
4. Be alert to cell counts >50/μl, which should prompt investigation for alternative diagnoses

Remember that while CSF analysis is valuable, it should be interpreted alongside clinical features and electrodiagnostic studies for a comprehensive GBS diagnosis.