TB Meningitis (TBM)

Clinical

  • Meningism +/- prodromal constitutional symptoms
  • Focal neurological (? stroke) = assoc. vasculitis
  • Raised ICP (basal cisterns involved)
  • Cranial nerve palsy (VI) and eye signs
  • +/- local spinal cord signs
  • Hyponatraemia (+/- SIADH)
  • Extremes of age and HIV at risk (increasing incidence)

SIADH Criteria

  • hyponatraemia
  • hypotonicity
  • urinary sodium > 20 mmol/l
  • urine osmolality > plasma osmolality
  • normovolaemia
  • elevated serum ADH
  • correction with water restriction
  • failure to drop urinary osmolality with fluid challenge
  • absence of renal, hepatic, cardiac, thyroid disease
  • absence of drugs that effect renal water handling

Pathology

  • 10 Gohn usually lungs (bacilli in macrophages)
  • Metastatic Rich foci in brain
  • +/- meningitis
  • Exudates @ cerebral arteries = vasculitis

Investigations

CSF

  • Raised protein, low glucose
  • Lymphocytes
  • Raised ADA (adenosine deaminase)
  • TB PCR positive
  • Ziehl-Neelsen staining positive

Imaging

  • Brain CT +/- MRI
  • CXR +/- CT

Treatment

  • ABCs
  • Consider differential Dx
  • Beware speticaemia
  • Beware vbacterial meningitis
  • Involve ID and neurology teams early
  • Dexamethasone
  • Beware obstructive hydrocephalus
    • (mannitol +/- neurosurgeons)
  • Triple therapy
    • (isoniazid, rifampicin, pyrazinamide etc)