Cerebrospinal Fluid (CSF) Interpretation
Sleek, galaxy‑neural quick reference for clinicians and learners. Normal values, pattern recognition, and a pragmatic interpretation flow — designed in Aurora Glass.
Use‑Case
Rapid pattern recognition at the bedside or during case review. Integrate with history, exam, and imaging.
Highlights
• Opening pressure • Cells & differential • Protein/Glucose • Lactate • OCB/IgG index • Xanthochromia • Emerging biomarkers
Fast Ratio Tips
CSF/Serum Glucose ≥ 0.6 is typical; ≤ 0.4 suggests bacterial/TB/fungal or malignant involvement.
Normal Composition & Reference Ranges
| Parameter | Normal Range | Notes |
|---|---|---|
| Opening Pressure | 6–20 cm H₂O | Higher with infection, IIH, mass effect. |
| Appearance | Clear, colorless | Turbid = cells/protein; xanthochromia = SAH. |
| WBC | 0–5 cells/µL (lymphocytic) | Pleocytosis pattern guides differential. |
| RBC | 0 cells/µL | See tube trend vs. SAH indicators. |
| Protein | 15–45 mg/dL | ↑ in infection, inflammation, GBS, block. |
| Glucose | 50–80 mg/dL or >0.6× serum | Low favors bacterial/TB/fungal/malignancy. |
| Lactate | < 2.1 mmol/L | > 3.5 mmol/L supports bacterial meningitis. |
| Chloride | 110–125 mEq/L | Decreased in TB (less commonly used now). |
Pattern Recognition — Common Clinical Scenarios
Infectious
Bacterial meningitis: WBC > 1,000/µL (PMN), protein > 100 mg/dL, glucose < 40 mg/dL or CSF/serum < 0.4, lactate > 3.5 mmol/L, Gram stain/culture +.
Viral (aseptic) meningitis: WBC 10–500/µL (lymphocytic), mild protein 50–100 mg/dL, normal glucose, Gram −.
Fungal/TB meningitis: WBC 50–500/µL (lymphocytic), protein 100–200 mg/dL, glucose < 40 mg/dL, India ink or TB PCR + as applicable.
Neurosyphilis: mild pleocytosis, ↑ protein, CSF‑VDRL +.
Autoimmune & Inflammatory
Multiple Sclerosis: Oligoclonal bands present in CSF (not serum), WBC 5–50/µL (lymphocytic), normal protein & glucose.
Guillain‑Barré (GBS): Albuminocytologic dissociation — protein > 100 mg/dL with normal WBC.
Hemorrhagic vs Traumatic Tap
Subarachnoid hemorrhage: Xanthochromia, uniformly elevated RBCs across tubes, ↑ protein.
Traumatic LP: Falling RBCs across tubes, clear supernatant (no xanthochromia).
Neurodegeneration
Alzheimer’s disease: ↓ Aβ42; ↑ total tau & p‑tau; ↑ NfL.
Creutzfeldt–Jakob disease: 14‑3‑3 positive; markedly ↑ total tau.
Emerging & Special Biomarkers
IL‑6: elevated in TBI and encephalitis · PF4: associated with cognitive decline in AD · NfL: increases with axonal injury in neurodegenerative and inflammatory conditions.
Practical Interpretation Flow
- Look: Appearance — clear vs turbid vs xanthochromic.
- Measure: Opening pressure (context: infection, mass, IIH).
- Count: WBC + differential (neutrophilic vs lymphocytic).
- Metabolic: Protein & glucose (and CSF/serum ratio); lactate when concerned for bacterial meningitis.
- Targeted tests: OCB/IgG index, pathogen PCR, VDRL, tau/p‑tau/Aβ42, NfL, 14‑3‑3 as indicated.
- Synthesize: Integrate with history, neuro exam, and imaging before final impression.
Notes
Reference values and patterns summarized from Bailey R Gwyn, “Cerebrospinal Fluid (CSF) Interpretation,” 2025. Educational use only; not a substitute for clinical judgment.