how does tb infect the brain and the early symptom
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replied May 7th, 2011
Especially eHealthy
tiger62,

Tuberculous meningitis is also known as TB meningitis or tubercular meningitis.

Tuberculous meningitis is Mycobacterium tuberculosis infection of the meninges—the system of membranes which envelops the central nervous system. It is the most common form of CNS tuberculosis.

Clinical features: Fever and headache are the cardinal features. Confusion is a late feature and coma bears a poor prognosis. Meningism is absent in a fifth of patients with TB meningitis. Patients may also have focal neurological deficits.

Pathology: Mycobacterium tuberculosis of the meninges is the cardinal feature and the inflammation is concentrated towards the base of the brain. When the inflammation is in the brain stem subarachnoid area, cranial nerve roots may be affected. The symptoms will mimic those of space-occupying lesions. Infection begins in the lungs and may spread to the meninges by a variety of routes.

Blood-borne spread certainly occurs and 25% of patients with miliary TB have TB meningitis, presumably by crossing the blood-brain barrier; but a proportion of patients may get TB meningitis from rupture of a cortical focus in the brain (a so-called Rich focus); an even smaller proportion get it from rupture of a bony focus in the spine. It is rare and unusual for TB of the spine to cause TB of the central nervous system, but isolated cases have been described.

Diagnosis: Diagnosis of TB meningitis is made by analysing cerebrospinal fluid collected by lumbar puncture. When collecting CSF for suspected TB meningitis, a minimum of 1ml of fluid should be taken (preferably 5 to 10ml).

The CSF usually has a high protein, low glucose and a raised number of lymphocytes. Acid-fast bacilli are sometimes seen on a CSF smear, but more commonly, M. tuberculosis is grown in culture. A spiderweb clot in the collected CSF is characteristic of TB meningitis, but is a rare finding.

ELISPOT testing is not useful for the diagnosis of acute TB meningitis and is often false negative, but may paradoxically become positive after treatment has started, which helps to confirm the diagnosis.

More than half of cases of TB meningitis cannot be confirmed microbiologically, and these patients are treated on the basis of clinical suspicion only. The culture of TB from CSF takes a minimum of two weeks, and therefore the majority of patients with TB meningitis are started on treatment before the diagnosis is confirmed.
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