Tuberculous meningitis is an infection of the meninges (membranes covering the brain and spinal cord). It is caused by Koch's bacillus or Mycobacterium Tuberculosis.

Causes, incidence, and risk factors

Tuberculous meningitis is caused by Mycobacterium tuberculosis, the bacterium that causes tuberculosis. The bacterium spreads to the brain from another site in the body.

• Risk factors include a history of:
• AIDS
• Excessive alcohol use
• Other disorders that compromise the immune system
• Pulmonary tuberculosis

Clinical features

Meningism is the triad of nuchal rigidity (neck stiffness), photophobia (intolerance of bright light) and headache. It is seen in Meningitis.

Some of the key symptoms to look for are

• Fever
• Severe headache
• Neck stiffness
• Nausea and vomiting
• Listlessness
• Loss of appetite
• Sensitivity to light (photophobia)
• Confusion is a late feature and coma bears a poor prognosis. Meningism is absent in 20% of patients with TB meningitis. Patients may also have focal neurological deficits.

Diagnosis

Spinal tap/Lumbar puncture to examine the CSF(Cerebrospinal fluid) is usually followed.

Other tests:

• CSF culture
• CSF stain
• CSF test for protein, glucose and lymphocytes
• PCR-Polymerase chain reaction

Treatment

First-line therapy includes Isoniazid, Rifampicin, Pyrazinamide, Streptomycin and ethambutol. Second-line therapy includes ethionamide, cycloserine, aminoglycosides, capreomycin, and thiacetazone. Usually the duration of treatment is 10-12 months. Steroids are always used in the first six weeks of treatment (and sometimes for longer). A few patients may require immunomodulatory agents such as thalidomide.

Potential new agents include oxazolidinone and isepamicin. Fluoroquinolones useful in the treatment of TBM include ciprofloxacin, ofloxacin, levofloxacin and recently rifapentine.

Prognosis:

Tuberculous meningitis is life-threatening if untreated. Long-term follow-up is needed to detect repeated infections.

Complications

• Brain damage due to infection can cause:
• Abnormal behavior
• Mental impairment
• Motor paralysis
• Seizures

Complications can minimized by initiating the treatment in the early stages.