The diagnosis of tuberculous meningitis

The incidence of tuberculosis (TB) is expected to increase substantially during the next 10 years as well as its extrapulmonary manifestations, often in association with the HIV panepidemic. TB meningitis displays some clinical and radiological characteristics but the "gold standard" for diagnosis remains the identification of Mycobacterium tuberculosis in the CSF by direct staining of culture. Direct staining, however, is rarely successful and culturing of M. Tuberculosis can take 4 to 8 weeks. Other techniques may be helpful, such as the detection of an intrathecal synthesis of antimycobacterial antibodies, or the detection in the CSF of the mycobacterial genome by the polymerase chain reaction (PCR). DNA amplification, and especially the "nested" amplification protocol, may represent a major step forward and find its place as a sensitive, specific and rapid test in the routine diagnostic laboratory.