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Meningitis
- Viral
Epidemiology
- 11-27 cases/100 000/yr are reported but under-reported
- children and young adults
- worldwide
- higher incidence during summer and autumn in temperate climates
Aetiology
- > 50% due to enterovirus infection: coxsackie-B or echo
- less commmon: HSV I, VZV, mumps, lymphocytic choriomeningitis, HIV
Pathogenesis
- haematogenous infection
- viruses must cross endothelial cell junctions of BBB. Ability to do this
dependent on surface adhesions molecules on cells, surface charges and cellular
receptors of virus and property of entering infected cells
- certain viruses preferentially infect the meninges, choroid plexus and
ependyma causing meningitis while others infect neurons and glia to cause
encephalitis. Considerable overlap
Clinical features
- rapid onset over hrs
- pyrexia
- malaise
- features of meningism
- lethargy
- myalgia
- irritability
- usually easily roused and coherent. If conscious level reduced or focal signs
or fits occur more likely to be encephalitis
- not as severe or prolonged as bacterial meningitis
Investigations
- CT to exclude intracranial mass or dangerously raised ICP
- LP: - normal/slightly raised pressure
- fluid clear to naked eye
- WCC: 500-1000, mainly lymphocytes but sometimes polymorphs. In the latter case
repeat LP 12-24 h later to identify a lymphocytosis and exclude a bacterial
cause
- protein: +/- slightly raised
- glucose: normal/slightly low
- virus isolation from CSF and viral serology
- identification of viral antigen in CSF. Detection of HSV Ag in CSF by PCR may
prove useful
Differential diagnosis
- early stages of bacterial meningitis
- SAH
- other causes of aseptic meningitis:
- partially treated bacterial meningitis
- meningitis caused by fastidious bacteria, fungi and parasites
- parameningeal infection, inflammation or neoplasm
- connective tissue disease
Treatment
- supportive
Course & prognosis
resolution begins within a few days and is complete within 2 weeks in most
persistent malaise and myalgia for weeks in a few
Further reading
Anderson M. Management of cerebral infection. J Neurol, Neurosurg, Psychi,
1993; 56:1243-58
© Charles Gomersall December 1999 | 
