CSF analysis
Background
- Analysis of cerebrospinal fluid obtained via lumbar puncture
- Essential for evaluation of meningitis, subarachnoid hemorrhage, and other CNS pathology
Normal Values
- Opening pressure: 10-20 cm H2O
- WBC: 0-5 cells/mcL (all lymphocytes)
- RBC: 0
- Glucose: 40-70 mg/dL (>60% of serum glucose)
- Protein: 15-45 mg/dL
- Gram stain: no organisms
Interpretation
| WBC | Predominance | Glucose | Protein | |
| Bacterial meningitis | 1,000-5,000+ | Neutrophils | Low (<40) | High (>200) |
| Viral meningitis | 10-500 | Lymphocytes | Normal | Mildly elevated |
| TB/Fungal | 10-500 | Lymphocytes | Low | High |
| SAH | Elevated RBCs | - | Normal | Elevated |
- Traumatic tap: RBC count decreases from tube 1 to tube 4; true SAH has consistent RBCs across tubes
- Xanthochromia (yellow CSF): suggests SAH; appears >6-12 hours after hemorrhage