Tuberculosis Meningitis

Tuberculosis meningitis (TBM), also known as tuberculous meningitis, is the most severe form of extrapulmonary tuberculosis, involving inflammation of the meninges due to Mycobacterium tuberculosis. TBM presents significant diagnostic and therapeutic challenges and is associated with high morbidity and mortality, especially in resource-limited settings.

Pathogenesis of TB Meningitis

Tuberculosis meningitis develops as a complication of primary or reactivated pulmonary TB. The infection disseminates hematogenously to the central nervous system (CNS), forming Rich foci—small granulomatous lesions—that eventually rupture into the subarachnoid space, initiating a meningeal inflammatory response.

Epidemiology and Risk Factors

Tuberculosis meningitis predominantly affects:

Children under 5 years
Immunocompromised individuals (especially those with HIV)
Individuals in TB-endemic regions

Key Risk Factors:

Active or previous pulmonary TB
HIV infection
Malnutrition
Diabetes mellitus
Poor access to healthcare

Clinical Presentation of Tuberculosis Meningitis

The symptoms of TB meningitis often develop insidiously over several days to weeks and progress through three clinical stages.

Stage I: Prodromal Phase

Low-grade fever
Malaise
Headache
Irritability

Stage II: Meningeal Phase

Neck stiffness
Photophobia
Vomiting
Lethargy
Cranial nerve palsies (especially VI and VII)

Stage III: Paralytic Phase

Seizures
Hemiparesis or paraplegia
Coma
Death if untreated

Diagnostic Evaluation of TB Meningitis

Timely diagnosis is crucial but often delayed due to non-specific early symptoms.

Lumbar Puncture and CSF Analysis:

High opening pressure
Elevated protein (>100 mg/dL)
Low glucose (<40 mg/dL)
Lymphocytic pleocytosis

Confirmatory Tests:

CSF AFB stain (low sensitivity)
CSF culture for M. tuberculosis (gold standard, but slow)
Nucleic acid amplification tests (e.g., Xpert MTB/RIF Ultra)
CSF adenosine deaminase (ADA) may support diagnosis

Imaging:

MRI with contrast is preferred; findings may include:
- Basal meningeal enhancement
- Hydrocephalus
- Infarcts
- Tuberculomas

Differential Diagnosis

TB meningitis must be differentiated from other causes of chronic meningitis:

Viral meningitis (especially HSV and enteroviruses)
Cryptococcal meningitis (particularly in HIV patients)
Carcinomatous meningitis
Neurosarcoidosis
Fungal meningitis (e.g., Candida, Histoplasma)

Treatment of Tuberculous Meningitis

Antitubercular Therapy (ATT):

A prolonged course of ATT is essential.

Initial Phase (2 months):

Isoniazid
Rifampicin
Pyrazinamide
Ethambutol

Continuation Phase (10 months or longer):

Isoniazid
Rifampicin

Adjunctive Corticosteroids:

Dexamethasone or Prednisolone reduces mortality and neurological complications.
Particularly beneficial in patients with raised intracranial pressure or cerebral edema.

Management of Complications:

Hydrocephalus: May require ventriculoperitoneal shunt or external ventricular drainage.
Seizures: Antiepileptic therapy.
Hyponatremia: Often due to SIADH or cerebral salt wasting; managed accordingly.

Prognosis and Long-Term Outcomes

TB meningitis carries a guarded prognosis, particularly when diagnosis and treatment are delayed.

Prognostic Indicators:

Stage at presentation (poor outcomes in stage III)
Level of consciousness
Presence of focal deficits
Drug resistance

Possible Sequelae:

Cognitive impairment
Motor deficits (e.g., hemiparesis)
Vision and hearing loss
Hydrocephalus requiring long-term shunting