Normal csf analysis value and range in different meningitis
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CSF Analysis: Normal Values and Changes in Meningitis
Normal CSF Values
| Parameter | Normal Range |
|---|---|
| Appearance | Clear, colorless (like water) |
| Opening Pressure | 70-180 mm H₂O (adults); <180 mm H₂O |
| WBC Count | 0-5 cells/μL (mononuclear/lymphocytes) |
| PMN (neutrophils) | At most 1 granulocyte; any >1 is abnormal |
| RBC | 0 |
| Protein | 15-45 mg/dL |
| Glucose | 45-100 mg/dL (~2/3 of serum glucose) |
| Lactate | 0.88-2.7 mmol/L |
CSF Findings in Different Types of Meningitis
Comprehensive Comparison Table
| Type | Appearance | Opening Pressure | WBC (cells/μL) | Predominant Cell | Protein (mg/dL) | Glucose (mg/dL) |
|---|---|---|---|---|---|---|
| Normal | Clear, colorless | 70-180 mm H₂O | 0-5 | Mononuclear | 15-45 | 45-100 (>½ serum) |
| Bacterial | Cloudy/turbid, straw-colored | Elevated (>20 cm H₂O) | 100-5000 (often >1000) | PMNs (neutrophils) | 100-500 (often >100) | <40 (markedly low) |
| Viral (Aseptic) | Clear or slightly cloudy | Mildly elevated | 10-1000 | Lymphocytes (PMNs early) | 50-100 | Normal |
| Tuberculous (TB) | Cloudy, straw-colored | Elevated | 50-500 | Lymphocytes | 50-300 (often >100) | Low (<45) |
| Fungal (Cryptococcal) | Cloudy, straw-colored | Elevated (often markedly ↑↑) | 20-500 | Lymphocytes | >45-100 | <40 (low) |
| Listeria meningitis | Variable | Elevated | <1000 | Lymphocytes | Elevated | Near-normal |
| Neurosyphilis (T. pallidum) | Variable | Normal to low | 5-500 | Lymphocytes | 50-150 | 10-45 |
| Lyme (B. burgdorferi) | Variable | Normal | 100-500 | Lymphocytes | 50-150 | 10-45 |
Type-by-Type Summary
1. Bacterial Meningitis
- Pressure: >200 mm H₂O (up to ≥450 mm H₂O in severe cases)
- WBC: Typically >1000 cells/μL (range 100-5000); predominantly PMNs
- Protein: >100 mg/dL (often 100-500)
- Glucose: Markedly low (<40 mg/dL, <10 mg/dL in very severe cases); CSF:serum glucose ratio <0.4
- Appearance: Turbid/cloudy
- Gram stain: Positive in 60-80% of cases
- Lactate: Elevated (>2.7 mmol/L)
- Note: ~10% of bacterial cases may show initial lymphocytosis
2. Viral (Aseptic) Meningitis
- Pressure: Normal to mildly elevated
- WBC: 10-1000 cells/μL; lymphocyte predominance (early cases may show PMNs mimicking bacterial)
- Protein: 50-100 mg/dL (mildly elevated)
- Glucose: Normal - this is the key distinguishing feature
- Appearance: Clear or slightly cloudy
- Lactate: Normal (<2.7 mmol/L)
- Diagnosis: CSF PCR for enteroviruses, HSV, HIV
3. Tuberculous (TB) Meningitis
- Pressure: Elevated
- WBC: 100-500 cells/μL; lymphocyte predominance
- Protein: 50-300 mg/dL (markedly elevated)
- Glucose: Low (10-45 mg/dL); a profoundly low glucose with lymphocytosis is the hallmark
- Appearance: Cloudy, straw-colored; may form a cobweb clot on standing
- AFB smear: Low sensitivity (~30-40%); culture or PCR needed
- Note: Can be subacute/chronic in presentation
4. Fungal Meningitis (e.g., Cryptococcus)
- Pressure: Often markedly elevated (most elevated of all types; can be very high in cryptococcal meningitis)
- WBC: 20-500 cells/μL; lymphocyte predominance
- Protein: >45-100 mg/dL (elevated)
- Glucose: Low (<40 mg/dL)
- Appearance: Cloudy, straw-colored
- Diagnosis: Cryptococcal antigen (CrAg), India ink stain (positive in ~50%), fungal culture
- Gram stain: Negative
5. Neurosyphilis (T. pallidum)
- WBC: 5-500 cells/μL, lymphocytic
- Protein: 50-150 mg/dL
- Glucose: 10-45 mg/dL (mildly low)
- Diagnosis: CSF VDRL (specific but not sensitive)
6. Lyme Meningitis (B. burgdorferi)
- WBC: 100-500 cells/μL, lymphocytic
- Protein: 50-150 mg/dL
- Glucose: Usually normal to mildly low (10-45 mg/dL)
Quick Diagnostic Clues
| Finding | Think of... |
|---|---|
| WBC >1000 + neutrophils + low glucose | Bacterial meningitis |
| WBC <1000 + lymphocytes + normal glucose | Viral meningitis |
| WBC <500 + lymphocytes + low glucose + elevated protein | TB or Fungal meningitis |
| Markedly elevated opening pressure + low glucose + lymphocytes | Cryptococcal meningitis |
| CSF lymphocytosis + profoundly low glucose | TB meningitis (until proven otherwise) |
| Normal CSF + clinical signs of meningism | Consider early viral or partially treated bacterial |
CSF Glucose Interpretation Note
CSF glucose is always interpreted relative to serum glucose. A CSF:serum glucose ratio < 0.4 (or CSF glucose < 2/3 of plasma glucose) is considered low and suggests bacterial, TB, or fungal meningitis. The CSF glucose lags serum glucose by 30-60 minutes, so a simultaneous serum glucose should be drawn.
Sources: Goldman-Cecil Medicine (Table 391-2), Washington Manual of Medical Therapeutics (Table 14-3), Goldman-Cecil Medicine (Table 366-4), Henry's Clinical Diagnosis (Table 66.3), Rosen's Emergency Medicine (Table 95.2)
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