Tuberculous meningitis
- G Thwaitesa,e,
- T T H Chaub,
- N T H Maib,
- F Drobniewskic,
- K McAdamd,
- J Farrare,f
- aDepartment of Microbiology, St Thomas's Hospital, London UK, bCentre for Tropical Diseases, 190 Ben Ham Tu, Quan 5 Ho Chi Minh City Viet Nam, cPHLS Mycobacterium Reference Unit, King's College School of Medicine, London UK, dMedical Research Council Laboratories Banjul The Gambia, eWellcome Trust Clinical Research Unit, Centre for Tropical Diseases, Ho Chi Minh City, Viet Nam, fCentre for Tropical Medicine, Nuffield Department of Medicine, University of Oxford, UK
- Dr Guy Thwaites, Department of Microbiology, St Thomas's Hospital, London SE1 7EH, UK email Guy.Thwaites{at}gstt.sthames.nhs.uk
- Received 4 October 1999
- Accepted 11 October 1999
Uncertainty and doubt dominate all aspects of tuberculous meningitis (TBM). The variable natural history and accompanying clinical features of TBM hinders the diagnosis. Ziehl-Neelsen staining lacks sensitivity and culture results are often insufficiently timely to aid clinical judgement. New rapid diagnostic methods are incompletely evaluated, and many are not suitable for laboratories in low income countries. The duration of chemotherapy for TBM is unclear and the benefits of adjuvant corticosteroids remain in doubt. The only uncomfortable certainties lie in the fatal consequences of missed diagnoses and delayed treatment.
This review will discuss the current uncertainties surrounding TBM. More attention will be given to diagnosis and management, as these areas have a direct bearing on patient outcome.
Epidemiology
About 2000 million people in the world today are infected with tuberculosis,1 but only 10% develop clinical disease. Why some people develop clinical disease remains unclear. The reasons are likely to be multifactorial: inherent not just to the individual person, but to their given population and environment.
Before HIV the most important determinant for the development of TBM was age. In populations with high TB prevalence TBM differs from pulmonary, and other extrapulmonary tuberculosis, in that the peak age is from 0–4 years.2 In populations with lower TB prevalence, most cases of TBM are in adults. Risk factors identified for these people are alcoholism, diabetes mellitus, malignancy, and recent corticosteroid use.3-5 Coinfection with HIV now dwarfs these risk factors. HIV increases the lifetime risk of developing clinical TB postinfection to 1 in 3.6 HIV also predisposes to the development of extrapulmonary TB, and in particular TBM,7 a risk which increases as the CD4 count declines.8 The disease constitutes either reactivation of latent infection, or new infection. Evidence from DNA fingerprinting of strains using restriction fragment length polymorphism suggests …
