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Viral meningitis

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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


©Charles Gomersall, January, 2018 unless otherwise stated. The author, editor and The Chinese University of Hong Kong take no responsibility for any adverse event resulting from the use of this webpage.
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