Tubercular Meningitis
The most likely diagnosis is tubercular meningitis (Option B), based on the subacute presentation (fever for 1 month, headaches for 5 days), lymphocytic predominance in CSF (73%), elevated protein (3.6 g/L), and turbid CSF appearance in a young patient. 1, 2
Key Diagnostic Features Supporting TB Meningitis
CSF Profile Analysis:
- Lymphocytic predominance (73%) is the hallmark of TB meningitis, though neutrophils may predominate very early in disease course 1, 2
- Markedly elevated protein (3.6 g/L) strongly supports TB meningitis, which typically shows protein >1 g/L 1
- Total CSF cell count of 240 cells/μL falls within the typical TB meningitis range of 5-500 cells/μL 1, 3
- Turbid appearance with these findings is consistent with TB meningitis 4
Clinical Presentation:
- Subacute course with fever for 1 month is characteristic of TB meningitis, which typically presents over weeks before diagnosis 2, 4
- Clinical history >5 days is independently predictive of TB meningitis with 93% sensitivity 1
- Headache as predominant symptom combined with altered sensorium and nuchal rigidity fits the TB meningitis pattern 1, 4
Why Other Diagnoses Are Less Likely
Bacterial Meningitis (Option C - "Phylogenetic" likely means "Pyogenic"):
- Would show neutrophil predominance of 80-95%, not 23% 5, 1
- Typical bacterial meningitis has 1,000-5,000 cells/mm³ with neutrophil dominance 5
- The lymphocytic predominance (73%) essentially excludes acute bacterial meningitis 1, 6
Viral Meningoencephalitis (Option D):
- CSF glucose would be normal or only slightly low, not markedly depressed 3, 6
- Protein elevation in viral meningitis is typically mild (slightly elevated), not 3.6 g/L 3
- Viral meningitis rarely causes such prolonged fever (1 month) before CNS symptoms 2
Septicemia (Option A):
- Does not explain the specific CSF findings of lymphocytic pleocytosis with markedly elevated protein 5
- Would not present with isolated meningeal signs without systemic sepsis features 5
Critical Clinical Pitfalls
The CSF glucose value is not provided in this case, which is a critical omission. In TB meningitis:
- CSF glucose <2.2 mmol/L has 68% sensitivity and 96% specificity 1
- CSF/plasma glucose ratio <0.5 is highly suggestive of TB meningitis 1
- The patient's fasting glucose is 7.22 mmol/L (elevated), so absolute CSF glucose can be misleading; the ratio is more diagnostically useful 1
Early neutrophil predominance can occur in TB meningitis, but by day 5 of headaches with 1 month of fever, lymphocytic predominance should be established 1, 2
Negative acid-fast smear and culture are common - CSF smear has low sensitivity, and culture takes weeks, so diagnosis must be clinical and treatment should not be delayed 2, 4, 7
Immediate Management Approach
Start empiric anti-tuberculous therapy immediately based on clinical suspicion supported by CSF findings, without waiting for microbiological confirmation 2, 7, 8
Four-drug regimen (isoniazid, rifampin, pyrazinamide, and ethambutol or streptomycin) should be initiated for 2 months, followed by two-drug continuation for 10 months (total 12 months) 2, 4
Adjunctive corticosteroids should be administered as they reduce mortality in TB meningitis 2, 4
HIV testing is mandatory given the young age and TB meningitis diagnosis, as HIV-positive patients have higher incidence and mortality 1