Tuberculosis is an ancient disease caused by a mycobacterium-M. tuberculosis. The organism needs oxygen to grow, so it targets organs where there is a high oxygen concentration, such as lungs and brain. Tuberculous meningitis is the severest form of the disease with approximately a 50 percent mortality rate or severe neurological deficit in spite of appropriate anti-tuberculosis therapy. Risk factors for tuberculous meningitis are pulmonary TB, AIDS and excess alcohol intake.
Pulmonary TB
According to Branch, approximately 90 percent of active TB in the U.S. is due to reactivation of a TB infection (secondary infection), for example, from the top part of an infected lung. Any person exposed to TB (latent infection) as shown by a positive PPD skin test may develop TB at some later point in life.
Tuberculous meningitis is seen most commonly in young children, but also in adults. During primary or secondary TB infection small "seed-like" TB organisms travel through the bloodstream and lodge in the brain. These TB organisms grow and the body contains them by walling them off, a process called caseation (or "turning into cheese"); if they rupture into the subarachnoid space around the brain, they cause meningitis.
HIV/AIDS
According to UMDNJ.edu, there are medical conditions that alter the immune responsive and predispose a person to TB, most importantly HIV infection, but also immunosuppressive therapy, hematologic malignancies, chronic renal failure and malnutrition. In patients with HIV, TB is usually the first serious infection and may present before the HIV diagnosis.
In sub-Saharan Africa, due to the high prevalence of HIV/AIDS, tuberculosis is now the most common form of bacterial meningitis. HIV-infected patients are also the ones who are infected with TB organisms resistant to standard therapies (multi-drug resistant (MDR) and extensive drug-resistant (XDR)). Infection with HIV and a resistant TB organism is a combination that can be fatal and extremely challenging to treat. MDR tuberculosis is a serious problem in the former Soviet Union and Asia. According to a recent "Wall Street Journal" article, the FDA is developing guidelines on how to test and approve cocktails of drugs with new mechanisms of action against resistant TB strains.
Alcohol
Heavy alcohol use has long been associated with active tuberculosis. According to Alcohol, Drugs and Development, a 2009 meta-analysis published in the journal "Addiction" found a threefold increased risk of active TB for those who drink more than 40 grams of alcohol per day.
For alcohol abusers, close supervision--preferably using directly observed therapy (DOT)--is necessary to ensure adherence and monitor for adverse reactions to medications.
References
- "Office Practice of Medicine"; WT Branch; 2003
- CDC Core Curriculum; Chapter Seven: Treatment of TB Disease
- Alcohol, Drugs and Development: Scientific review of linkages between alcohol, TB and HIV/AIDS; Addiction; 2009
- "Wall Street Journal"; FDA Is Easing Way For Drug Cocktails; March 18, 2010
