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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
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