Characteristic CSF Picture in Tubercular Meningitis
CSF Parameters in Tubercular Meningitis
- The characteristic cerebrospinal fluid (CSF) picture in tubercular meningitis includes raised opening pressure, clear or cloudy appearance, lymphocytic pleocytosis, markedly elevated protein, very low glucose, and very low CSF/plasma glucose ratio 1, 2, 3
- Opening pressure is typically raised in tubercular meningitis 1
- CSF appearance is usually clear or cloudy, unlike the turbid or purulent appearance commonly seen in bacterial meningitis 1
- CSF white cell count (WCC) is typically elevated, ranging from 5-500 cells/μL 1
- Lymphocytes predominate in the cell differential, though neutrophils may predominate early in the disease course 1, 3
- CSF protein is markedly raised, typically >1 g/L, which has a sensitivity of 78% and specificity of 94% for diagnosing tubercular meningitis 1
- CSF glucose is very low, with values typically <2.2 mmol/L (sensitivity 68%, specificity 96%) 1
- CSF/plasma glucose ratio is very low, typically <0.5 (sensitivity 90%) 1
Comparison with Other Types of Meningitis
| Parameter | Tuberculous | Bacterial | Viral | Fungal |
|---|---|---|---|---|
| Opening Pressure | Raised | Raised | Normal/mildly raised | Raised |
| Appearance | Clear or cloudy | Turbid, cloudy | Clear | Clear or cloudy |
| WCC (cells/μL) | 5-500 | >100 | 5-1000 | 5-500 |
| Cell type | Lymphocytes* | Neutrophils | Lymphocytes | Lymphocytes |
| Protein (g/L) | Markedly raised | Raised | Mildly raised | Raised |
| Glucose | Very low | Very low | Normal/slightly low | Low |
| CSF/plasma glucose ratio | Very low | Very low | Normal/slightly low | Low |
*May be neutrophils early in the disease 1, 3
Clinical Pearls and Pitfalls
- CSF findings alone cannot provide an absolute diagnosis; they must be interpreted in the clinical context 3