However, more large scale studies are needed to confirm the above conclusion. Tuberculosis of the central nervous system
Central nervous system tuberculosis takes two major forms: tuberculous meningitis and tuberculoma.Tuberculosis may affect the central nervous system (meninges, brain or spinal cord) in which case it is called TB meningitis, TB cerebritis, and TB myelitis respectively; the standard treatment is 12 months of drugs (2HREZ/10HR) and steroid are mandatory.Diagnosis is difficult as CSF culture is positive in less than half of cases, and therefore a large proportion of cases are treated on the basis of clinical suspicion alone. PCR of CSF does not significantly improve the microbiology yield; culture remains the most sensitive method and a minimum of 5 mL (preferably 20 mL) of CSF should be sent for analysis. TB cerebritis (or TB of the brain) may require brain biopsy to make the diagnosis, because the CSF is commonly normal: this is not always available and even when it is, some clinicians would debate whether it is justified putting a patient through such an invasive and potentially dangerous procedure when a trial of anti-TB therapy may yield the same answer; probably the only justification for brain biopsy is when drug-resistant TB is suspected.It is possible that shorter durations of therapy (e.g., six months) may be sufficient to treat TB meningitis, but no clinical trial has addressed this issue.
Isolates that are multi-resistant to any other combination of anti-TB drugs but not to INH and RMP are not classed as MDR-TB. As of Oct 2006, "Extensively drug-resistant tuberculosis" (XDR-TB) is defined as MDR-TB that is resistant to quinolones and also to any one of kanamycin, capreomycin, or amikacin. The old case definition of XDR-TB is MDR-TB that is also resistant to three or more of the six classes of second-line drugs. This definition should no longer be used, but is included here because many older publications refer to it. The principles of treatment for MDR-TB and for XDR-TB are the same. The main difference is that XDR-TB is associated with a much higher mortality rate than MDR-TB, because of a reduced number of effective treatment options. The epidemiology of XDR-TB is currently not well studied, but it is believed that XDR-TB does not transmit easily in healthy populations, but is capable of causing epidemics in populations which are already stricken by HIV and therefore more susceptible to TB infection. Epidemiology of drug-resistant TB
A 1997 survey of 35 countries found rates above 2% in about a third of the countries surveyed. The highest rates of drug-resistant TB were in the former USSR, the Baltic states, Argentina, India and China, and was associated with poor or failing national Tuberculosis Control programmes.