Tuberculous meningitis usually occurs a few months after the primary TB infection, especially in small children below 3 years of age. It is the most dangerous complication of pulmonary tuberculosis. The TB bacilli reach the meninges via the blood stream, usually from the lungs. Most children with tuberculous meningitis have a positive Mantoux skin test, an abnormal chest X-ray and a history of contact with an adult suffering from pulmonary tuberculosis, but all of these could be absent.
For the first few days and weeks the child is generally unwell with fever and lethargy. Then signs of meningitis appear (headache, irritability, vomiting and neck stiffness) followed by confusion, a depressed level of consciousness, convulsions and neurological signs (weakness or paralysis). The classical signs of meningitis are often not present for the first few days. The risk of permanent brain damage (hydrocephalus, paralysis, deafness, blindness, convulsions and mental retardation) or death is high, especially if the diagnosis is made late. However, recovery can be complete with early treatment.
Examination of the cerebrospinal fluid (CSF) obtained by lumbar puncture is helpful in making the clinical diagnosis. The diagnosis is only confirmed by finding TB bacilli (by staining or culture) in the CSF.
In TB meningitis the CSF typically has a markedly raised protein, low sugar and low chloride, with a dominance of lymphocytes and total cell count usually below 500/ul. In early TB meningitis the CSF may be normal. The Gram stain is negative. Unfortunately TB bacilli are rarely seen while the culture takes a few months.
All children with suspected tuberculous meningitis must be referred urgently to hospital for investigation and treatment (and treatment preferably started immediately).