Can viral meningitis cause high opening pressure?

Can Viral Meningitis Cause High Opening Pressure?

Yes, viral meningitis can cause elevated opening pressure, though it is typically normal or only mildly raised compared to bacterial meningitis, and when significantly elevated, should prompt consideration of alternative or concurrent diagnoses.

Expected Opening Pressure Patterns

According to UK Joint Specialist Societies guidelines, the classical CSF profile for viral meningitis shows normal or mildly raised opening pressure (normal range: 12-20 cm CSF), in contrast to bacterial meningitis which typically presents with raised opening pressure 1.

However, this traditional teaching does not capture the full clinical picture:

• Viral meningitis can be associated with elevated intracranial pressure more often than commonly recognized, as demonstrated in a case series of 7 patients with elevated ICP and CSF findings consistent with viral or aseptic meningitis 2
• One patient in this series had confirmed Enterovirus meningitis with elevated opening pressure, while the remainder had nonspecific viral meningitis 2
• Enterovirus and Varicella have been specifically described in association with increased intracranial pressure, though this remains underreported in the literature 2

Clinical Implications and Diagnostic Approach

When encountering elevated opening pressure with CSF findings suggesting viral meningitis, consider the following:

• Do not automatically classify these cases as "atypical idiopathic intracranial hypertension" - a diagnosis of IIH requires normal CSF by definition, so infection with secondary intracranial hypertension is more likely 2
• The CSF white cell count in viral meningitis is typically raised (5-1000 cells/μL) with lymphocytic predominance, though neutrophils may predominate early in enteroviral meningitis 1
• CSF protein is mildly raised and glucose is normal or slightly low in viral meningitis, helping distinguish it from bacterial causes 1

Management Thresholds

While specific guidelines for managing elevated ICP in viral meningitis are lacking, principles from fungal meningitis management can inform practice:

• Opening pressure ≥250 mm H₂O (approximately 25 cm CSF) represents a critical threshold requiring therapeutic intervention based on cryptococcal meningitis guidelines 3
• For pressures ≥250 mm H₂O, perform CSF drainage to achieve closing pressure <200 mm H₂O or reduce by 50% of initial opening pressure 3
• If elevated pressure persists with symptoms, repeat lumbar puncture daily until pressure and symptoms stabilize 3

Important Caveats

• Brain imaging (CT or MRI) must be performed before lumbar puncture in patients with focal neurological signs or altered mental status to rule out mass lesions 4, 5
• The presence of significantly elevated opening pressure (>25 cm CSF) with viral CSF profile should prompt careful consideration of whether bacterial meningitis has been adequately excluded, particularly if antibiotics were given prior to lumbar puncture 1
• CSF sterilization may occur within 2 hours for meningococcus and 4 hours for pneumococcus after antibiotic administration, potentially leaving a "viral-appearing" CSF profile in partially treated bacterial meningitis 1