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TB meningitis

Up HIV & TB Pulmonary TB TB meningitis


Epidemiology

  • peak incidence in 0-4 year olds in high prevalence areas, in adults in low prevalence areas
  • risk factors
    • HIV infection
    • immunosuppression
    • diabetes mellitus
    • alcoholism

Pathogenesis & pathophysiology

  • transient bacteraemia results in seeding of bacilli in meninges and brain parenchyma with resultant formation of Rich foci
  • tuberculous meningitis occurs when Rich foci rupture into the subarachnoid space
  • thick exudate which forms in response to meningitis results in adhesions. Depending on their anatomical location the adhesions may result in hydrocephalus, cranial nerve palsies and internal carotid stenosis

Clinical features

  • prodrome of:
    • fever
    • headache ± meningism
    • vomiting
    • malaise
  • presentation very variable
  • decreased consciousness
  • fits
  • cranial nerve palsies
    • especially II,III,IV,VI,VII,VIII
  • strokes

Investigations

CSF

  • lymphocytosis
    • 100-1000/ml
    • in first 10 days polymorphs may predominate
  • low glucose
  • high protein
  • acid fast bacilli seen in only 10-87% of patients
    • yield dependent on volume of CSF specimen
    • 10 ml recommended
  • polymerase chain reaction
    • high specificity but only moderate sensitivity

Imaging

CT and MRI

  • ± thickening of basal meninges
  • ± infarcts
  • ± cerebral oedema
  • ± tuberculomas

Management

  • early diagnosis and treatment vital
  • initial therapy: rifampicin, isoniazid and pyrazinamide plus one of
    • streptomycin
    • ethambutol
    • prothionamide
  • steroids
    • patients with disease of intermediate severity
    • comatose patients and patients with mild disease derive only minimal benefit

©Charles Gomersall, April, 2014 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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