Does Lyme meningitis cerebrospinal fluid (CSF) resemble viral meningitis CSF?

Cerebrospinal Fluid Characteristics in Lyme Meningitis vs. Viral Meningitis

Lyme meningitis cerebrospinal fluid (CSF) does resemble viral meningitis CSF, with both typically showing lymphocytic pleocytosis and mildly elevated protein, making differentiation challenging without specific testing for Borrelia burgdorferi. 1, 2

CSF Characteristics Comparison

Lyme Meningitis CSF:

• Cell count: Lymphocytic pleocytosis (typically 5-500 cells/μL) 1
• Predominant cell type: Lymphocytes and plasma cells 3
• Protein level: Moderately elevated (median 0.9 g/L) 2
• Glucose level: May be lower than in viral meningitis (median 2.9 mmol/L) 2
• Appearance: Clear to slightly cloudy 1
• Opening pressure: May be mildly elevated 1

Viral Meningitis CSF:

• Cell count: Lymphocytic pleocytosis (typically 5-1000 cells/μL) 1
• Predominant cell type: Lymphocytes (though neutrophils may predominate early) 1, 4
• Protein level: Mildly elevated (typically <0.6 g/L) 1
• Glucose level: Normal to slightly low (typically normal CSF:plasma ratio >0.66) 1
• Appearance: Clear 1
• Opening pressure: Normal to mildly raised 1

Key Distinguishing Features

1. Temporal Evolution:

   • Early viral meningitis may show neutrophil predominance that shifts to lymphocytes after 24 hours 4
   • Lyme meningitis typically maintains lymphocytic predominance throughout 3

2. Glucose Levels:

   • Lyme meningitis may have lower glucose levels than typical viral meningitis 2
   • In some cases (10% of Lyme meningitis), glucose can be very low (<2.1 mmol/L), resembling tuberculous meningitis 2

3. Cellular Composition:

   • Lyme meningitis often shows immunoblasts, plasma cells, and foamy macrophages 3
   • Viral meningitis typically shows primarily lymphocytes with fewer plasma cells 1

4. Intrathecal Antibody Production:

   • Lyme meningitis frequently shows evidence of intrathecal antibody production 1, 5
   • This finding is less common in viral meningitis 6

Diagnostic Approach

1. Initial CSF Analysis:

   • Complete cell count with differential
   • Protein and glucose levels (with simultaneous serum glucose)
   • CSF:plasma glucose ratio calculation
   • CSF lactate (helpful to rule out bacterial meningitis) 6

2. Specific Testing:

   • For Lyme: Serum and CSF antibodies to B. burgdorferi with demonstration of intrathecal antibody production 1
   • For viral etiologies: PCR panel for HSV-1, HSV-2, VZV, and enteroviruses 6

3. When to Suspect Lyme Meningitis:

   • Lymphocytic pleocytosis with moderately elevated protein
   • History of tick exposure or residence in endemic area
   • Presence of other Lyme disease manifestations (erythema migrans, cranial neuropathy, radiculopathy)
   • Lower CSF glucose than typically seen in viral meningitis 2

Clinical Pitfalls to Avoid

1. Don't rely solely on CSF cell count pattern:

   • Early viral meningitis can have neutrophil predominance 4
   • Some Lyme meningitis cases may have minimal pleocytosis 1

2. Don't dismiss Lyme with low glucose:

   • While uncommon, Lyme meningitis can present with very low CSF glucose levels that mimic tuberculous meningitis 2

3. Don't forget timing considerations:

   • CSF findings in viral meningitis evolve from neutrophilic to lymphocytic over the first 24 hours 4
   • Lyme antibody tests may be negative early in infection 1

4. Don't overlook the need for specific testing:

   • Standard CSF analysis cannot definitively distinguish between viral and Lyme meningitis
   • Specific testing for B. burgdorferi antibodies and PCR for viral pathogens is essential 1, 6

In summary, while Lyme meningitis and viral meningitis share many CSF characteristics, particularly lymphocytic pleocytosis and elevated protein, subtle differences in glucose levels, cellular composition, and evidence of intrathecal antibody production can help differentiate between them when combined with appropriate specific testing and clinical context.