TB Meningitis Grading System
TB meningitis is classified using the British Medical Research Council (BMRC) staging system, which divides patients into three stages based on level of consciousness and neurological deficits: Stage I (fully conscious, rational, no neurologic signs), Stage II (confused or with neurologic signs such as cranial nerve palsy or hemiparesis), and Stage III (comatose or stuporous with severe neurologic signs). 1, 2, 3
BMRC Staging Criteria
Stage I (Early/Mild Disease)
- Fully conscious and rational 2
- No focal neurologic deficits 2
- Alert mental status 1
- Patients typically present with non-specific symptoms like headache and fever 3
- Approximately 24% have cranial nerve palsies at this stage 3
Stage II (Intermediate Disease)
- Confused or lethargic mental status 1, 2
- Presence of focal neurologic signs including cranial nerve palsies or hemiparesis 2, 3
- Approximately 43% demonstrate cranial nerve involvement 3
- This stage shows the greatest benefit from adjunctive dexamethasone therapy, with mortality reduced from 40% to 15% when steroids are used 1, 4
Stage III (Advanced/Severe Disease)
- Comatose or stuporous 1, 2
- Severe neurologic deficits 2
- Cranial nerve palsies present in approximately 75% of patients 3
- Significantly worse prognosis even with optimal treatment 1
- Mortality remains high (64% with dexamethasone versus 76% without in one study) 1
Clinical Significance of Staging
The stage at presentation is the single most important prognostic factor for TB meningitis outcomes. 5, 6
- Duration of illness before diagnosis is typically >2 weeks in 50% of Stage I patients but approximately 80% in Stage II and III patients 3
- Focal weakness, Glasgow Coma Scale score, and somatosensory evoked potentials are the best predictors of 6-month outcome on multivariable analysis 5
- Presence of hydrocephalus and severity of disease at admission are strongly associated with therapeutic failure 6
Treatment Implications by Stage
Adjunctive corticosteroid therapy is recommended for all patients with TB meningitis, but is particularly critical for Stage II and III disease. 1, 4, 2
- Dexamethasone dosing: 12 mg/day for adults and children ≥25 kg; 8 mg/day for children <25 kg 1, 4
- Duration: Initial dose for 3 weeks, then gradual taper over following 3 weeks 1, 4
- Stage I patients may have better outcomes but still benefit from corticosteroids 1
- Stage II patients show the most dramatic mortality benefit from dexamethasone 1, 4
- Stage III patients have limited benefit from steroids but treatment should still be attempted 1
Critical Pitfalls
Delay in diagnosis directly correlates with worse outcomes, as patients progress from Stage I to more advanced stages. 6
- Empiric treatment should be initiated immediately when TB meningitis is suspected, without waiting for bacteriologic confirmation 3
- Neck stiffness is the most common finding across all stages but is non-specific 3
- CSF culture is positive in only 47% of cases, so negative cultures should not delay treatment 6