Extrapulmonary tuberculosis: tuberculous meningitis new developments

Tuberculosis (TB) can involve any organ system in the body. Extrapulmonary involvement can occur in isolation or along with a pulmonary focus as in the case of patients with disseminated tuberculosis. Tuberculosis meningitis (TBM) is the most severe form of extrapulmonary tuberculosis. TBM a medical emergency, is still a major cause of serious illness in many parts of the world. TBM remains difficult to diagnose, and it is usually due to hematogenous dissemination of the tubercle bacillus. The exact incidence and prevalence are not known. The clinical spectrum is broad and may be non-specific making early diagnosis difficult. Improved outcome requires early recognition and treatment of these conditions. Clinical features included fever for more than 7 days, headache, or neck stiffness. While TBM is a disease of childhood, tuberculomas and spinal tuberculosis are invariably an adult manifestation. In HIV infection, TB is often atypical in presentation, frequently causing extrapulmonary disease, and patients have a high incidence of TBM. Clinical response to antituberculous therapy in all forms of neurotuberculosis is excellent if the diagnosis is made early before irreversible neurological deficit is established. Diagnosis is based on the characteristic clinical picture, neuroimaging abnormalities, cerebrospinal fluid changes and the response to anti-tuberculosis drugs. Diagnosis is best made with lumbar puncture and examination of the cerebrospinal fluid (CSF). Suspect TBM if there is a CSF leucocytosis (predominantly lymphocytes), the CSF protein is raised, and the CSF plasma glucose is <50%. Rapid techniques based on nucleic acid amplification such as PCR are more sensitive and specific as they attempt to detect specific DNA sequences of the organism. The hallmark pathological processes are meningeal inflammation, basal exudates, vasculitis and hydrocephalus. Treatment delay is strongly associated with death and empirical anti-tuberculosis therapy should be started promptly in all patients in whom the diagnosis of TBM is suspected. Corticosteroids reduce the number of deaths. Development of an effective vaccine against tuberculosis hinges on an improved understanding of the human immune response to Mycobacterium tuberculosis (Mtb). The emergence of drug resistant tuberculosis poses a serious threat to the control of this pathogen, and the development of drugs that are active against the resistant strains is vital. Further research into the epidemiology, immune mechanisms, diagnosis, treatment, and prevention of TBM is urgently needed.