Repeat CSF Examination in Follow-up of Aseptic Meningitis
Repeat cerebrospinal fluid (CSF) examination is not routinely required in the follow-up of aseptic meningitis in patients who are clinically improving. 1
Initial CSF Examination in Aseptic Meningitis
The initial CSF examination is essential for diagnosis and includes:
- CSF opening pressure measurement (unless performed in sitting position) 1
- CSF cell count and differential 1
- CSF glucose with concurrent plasma glucose 1
- CSF protein 1
- CSF lactate (if available) 1
- Gram stain and culture 1
- PCR testing for viral pathogens (enterovirus, HSV-1, HSV-2, VZV) 1
Typical CSF Findings in Aseptic Meningitis
- Lymphomonocytic pleocytosis typically <500 cells/μL (though early cases may show neutrophil predominance) 2, 3
- Normal to mildly elevated protein 1, 2
- Normal glucose levels (CSF:plasma glucose ratio >0.66) 1
- Normal lactate levels 2
- Negative gram stain and culture 2, 4
Why Repeat CSF Examination Is Generally Not Needed
- Once viral etiology is established through initial CSF PCR testing, repeat examination adds little diagnostic value 1
- Clinical improvement is a more reliable indicator for treatment decisions than serial CSF examinations 1
- The UK Joint Specialist Societies guideline does not recommend routine follow-up CSF examination for aseptic meningitis with clinical improvement 1
Special Circumstances When Repeat CSF May Be Considered
- Failure to clinically improve despite appropriate treatment 1
- Concern for development of complications 1
- Unusual or atypical presentation suggesting possible alternative diagnosis 1
- Immunocompromised patients (who may have atypical presentations or multiple pathogens) 1
Management Considerations
- Initial empiric antimicrobial therapy may be started until CSF results confirm viral etiology 2
- Once viral etiology is confirmed, antibiotics can be safely discontinued 1
- Specific antiviral therapy is only indicated for herpes family viruses (acyclovir) 2
- Most patients with aseptic meningitis have good outcomes without specific therapy 2, 5
Common Pitfalls to Avoid
- Misinterpreting early neutrophil predominance in viral meningitis as bacterial infection (up to 57% of aseptic meningitis cases can initially present with PMN predominance) 3
- Continuing unnecessary antibiotics after viral etiology is confirmed 1
- Delaying discharge in patients with confirmed viral meningitis who are clinically improving 1
- Failing to consider enterovirus as the most common cause of aseptic meningitis (accounts for approximately 44% of cases) 2, 6
In conclusion, while the initial CSF examination is crucial for diagnosis, follow-up CSF examination in aseptic meningitis is generally unnecessary if the patient is clinically improving, as it does not significantly impact management decisions or outcomes 1.