Tuberculous Meningitis

Meningitis from hematogenous or, more commonly, contiguous spread of Mycobacterium tuberculosis from a subependymal or subpial granuloma (Rich focus) that ruptures into the subarachnoid space.

Carries the highest mortality and morbidity of any form of TB, and disproportionately affects young children and those with HIV coinfection.

Onset is typically subacute, over 1 to 3 weeks (in contrast to the more acute presentation of bacterial meningitis): low-grade fever, headache, malaise, and personality change progress to meningism, cranial nerve palsies (particularly VI, from the basal exudate characteristic of TB meningitis), and, if untreated, declining consciousness, seizures, and focal deficits from vasculitis-related infarction or developing hydrocephalus.

British Medical Research Council (MRC) staging (I: GCS 15 without focal signs; II: GCS 11--14 or focal signs; III: GCS ≤10) correlates with outcome and guides prognostic counseling.

CSF typically shows a lymphocytic pleocytosis, markedly elevated protein, and low glucose (CSF:plasma glucose ratio often below 0.5), though a neutrophilic predominance can occur early.

GeneXpert MTB/RIF Ultra on CSF offers rapid molecular confirmation and rifampicin resistance detection; AFB smear has low sensitivity given typically low bacillary burden; mycobacterial culture remains valuable but slow.

A large volume of CSF (10 mL or more) improves diagnostic yield.

MRI/CT brain assesses for basal meningeal enhancement, hydrocephalus, tuberculomas, and infarction. HIV testing in all cases.

• Standard four-drug antituberculous therapy (isoniazid, rifampicin, pyrazinamide, ethambutol) for a 2-month intensive phase, followed by isoniazid and rifampicin for a continuation phase, with total duration extended to 9 to 12 months given the difficulty of achieving adequate CSF drug penetration
• Pyridoxine 10 to 25 mg/day with isoniazid as standard
• Adjunctive corticosteroids (dexamethasone, tapering course over 6 to 8 weeks, or prednisolone equivalent) are recommended for all cases regardless of severity, given demonstrated mortality benefit, most pronounced in HIV-negative patients
• Hydrocephalus, common and often requiring ventriculoperitoneal shunting or external ventricular drainage where obstructive, is managed neurosurgically alongside continued antituberculous therapy
• HIV co-infected patients: ART is typically delayed 4 to 8 weeks after starting TB treatment given a particularly high risk of severe immune reconstitution inflammatory syndrome (IRIS) with early ART initiation in TB meningitis specifically (see IRIS entry)

Referral: infectious disease/neurology for all cases; neurosurgery for hydrocephalus.