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

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 septicaemia
• Beware bacterial meningitis
• Involve ID and neurology teams early
• Dexamethasone
• Beware obstructive hydrocephalus
  • (mannitol ± neurosurgeons)
• Triple therapy
  • (isoniazid, rifampicin, pyrazinamide etc)