Opening Pressure in Bacterial Meningitis: N. meningitidis vs. Lyme Disease
N. meningitidis (meningococcal meningitis) is significantly more likely to cause high opening pressure than the spirochete from Lyme disease (Borrelia burgdorferi). 1
Opening Pressure Ranges by Pathogen
Neisseria meningitidis
- Opening pressure typically ranges from 200-500 mm H₂O in bacterial meningitis, including meningococcal disease. 1
- Elevated intracranial pressure (defined as opening pressure >200 mm H₂O) is a common feature of acute bacterial meningitis. 1, 2
- The high opening pressure reflects the acute inflammatory response with significant neutrophilic pleocytosis (typically 1000-5000 cells/mm³, with 80-95% neutrophils). 1
Lyme Meningitis (Borrelia burgdorferi)
- Lyme meningitis presents as a chronic basilar meningitis with characteristically mild CSF findings. 3
- The CSF shows a predominantly lymphocytic pleocytosis rather than the high neutrophil counts seen in bacterial meningitis. 3, 4
- While specific opening pressure values are not detailed in the evidence for Lyme meningitis, the clinical presentation as a "chronic basilar meningitis" with "mild meningismus" suggests lower pressures than acute bacterial meningitis. 3
Clinical Distinction
Why the Difference Matters
- Meningococcal meningitis is an acute, life-threatening infection requiring immediate intervention, whereas Lyme meningitis develops more insidiously over weeks to months. 3, 4
- The acute inflammatory response in meningococcal disease produces marked CSF inflammation with high opening pressures, while Lyme meningitis causes a more indolent, chronic inflammatory process. 1, 3
Key Clinical Features
Meningococcal Meningitis:
- Rapid onset with fever, severe headache, altered consciousness, and often purpuric rash (in 89% when rash present). 1
- CSF shows neutrophil predominance (80-95%), elevated protein, and decreased glucose. 1
- Opening pressure commonly 200-500 mm H₂O. 1
Lyme Meningitis:
- Subacute presentation with intermittent severe headache and mild meningismus over weeks to months. 4
- CSF shows lymphocytic pleocytosis. 3, 4
- Often accompanied by cranial neuritis (especially facial palsy) and radiculoneuritis forming a characteristic triad. 4
- Duration of neurologic involvement without treatment: 3-18 months. 4
Clinical Pitfalls
Common diagnostic errors to avoid:
- Do not assume all spirochetal infections cause low opening pressure—syphilitic meningitis can also cause elevated pressures, though this is distinct from Lyme disease. 1
- In Lyme meningitis, facial palsy may be the earliest clinical indicator, often preceding overt meningeal signs. 3
- Lack of consistently positive serum antibody should make Lyme meningitis diagnosis suspect; positive CSF antibody is almost universal in confirmed cases. 3
- Meningococcal meningitis can present without the classic triad of fever, neck stiffness, and altered consciousness (present in <50% of cases). 1