Tuberculous Meningitis Pleocytosis Levels
Tuberculous meningitis typically causes a lymphocytic-predominant pleocytosis with CSF white cell counts ranging from 10-500 cells/μL, though this range can extend from as low as normal to several hundred cells per microliter. 1, 2
Typical CSF Cell Count Characteristics
The characteristic CSF findings in tuberculous meningitis include:
- Cell count range of 10-500 cells/μL is the most commonly cited range, with lymphocytic predominance being the hallmark finding 2
- The pleocytosis is generally lower than bacterial meningitis (which typically shows 1000-5000 cells/mm³) but higher than viral meningitis (which typically shows 5-1000 cells/μL) 3, 4
- Lymphocytes eventually predominate (>50% lymphocytes), though this may take time to develop 1, 2
Important Temporal Dynamics and Atypical Presentations
A critical pitfall is that tuberculous meningitis does not always present with the classic lymphocytic pattern, particularly in early disease:
- In the first 10 days, neutrophils may predominate (60-80%), with the shift to lymphocytic predominance occurring later in the disease course 5
- Neutrophil predominance (>50%) can be seen in 54% of cases and is actually an independent diagnostic factor for tuberculous meningitis 2
- Some patients may have completely normal CSF parameters including normal cell counts, though this is uncommon 6
- The pleocytosis can persist for extended periods, with some atypical cases showing pleocytosis lasting up to two years 5
Additional Distinguishing Features
Beyond cell count, tuberculous meningitis characteristically shows:
- Elevated protein (>1 g/L in 66% of cases) 2
- Low glucose (<2.2 mmol/L or <40 mg/dL in 58% of cases) 2
- Low CSF-to-plasma glucose ratio (<0.5), which helps distinguish it from viral meningitis 7
- Elevated opening pressure (often 20-30 cm H₂O or higher) 8
Clinical Decision-Making
When tuberculous meningitis is suspected based on subacute presentation and CSF showing lymphocytic pleocytosis with low glucose and elevated protein, empiric anti-tuberculous therapy should be initiated immediately without waiting for definitive microbiological confirmation, as acid-fast smear and culture have low sensitivity. 1, 6
The presence of at least two of the four independent CSF parameters (protein >1 g/L, glucose <2.2 mmol/L, cell count 10-500 cells/μL, and neutrophil predominance >50%) occurs in 84% of tuberculous meningitis cases and should prompt strong consideration for empiric treatment. 2