Table of contents · 10 sections
In a nutshell. Cerebrospinal fluid (CSF) is a clear, colorless fluid with a total volume of 120–150 ml in adults and a production rate of 500 ml/day. Normal parameters: opening pressure 100–180 mm H₂O, cell count up to 5 × 10⁶/L (lymphocytes), protein 0.15–0.45 g/L, glucose 2.5–4.4 mmol/L (~60% of serum levels), chlorides 120–130 mmol/L. Bacterial meningitis: neutrophilic pleocytosis, ↓↓ glucose, ↑↑ protein. Viral meningitis: lymphocytic pleocytosis, normal glucose. Tuberculous meningitis: lymphocytic pleocytosis + ↓ glucose + decreased chlorides. SAH: xanthochromia, red blood cells.
1. CSF Physiology
- Produced by the choroid plexuses of the ventricles.
- Total volume 120–150 ml in adults, 50 ml in the ventricles, the rest in the subarachnoid space.
- Production rate 0.35 ml/min = 500 ml/day; turnover 3–4 times daily.
- Reabsorption via arachnoid villi (Pachyderm granulations) into the venous sinuses.
- Functions: mechanical protection of the brain, transport of nutrients and metabolites, and a buffer to maintain CNS homeostasis.
2. Indications for lumbar puncture
- Suspected meningitis, encephalitis.
- Subarachnoid hemorrhage (SAH) (when CT is negative after 6 hours — lumbar puncture is indicated).
- Multiple sclerosis (oligoclonal bands).
- Guillain-Barré syndrome (albumin-cytologic dissociation).
- Neuroleukemia, leptomeningeal metastasis.
- Measurement of opening pressure (idiopathic intracranial hypertension).
- Diagnostic/therapeutic paracentesis (normal pressure hydrocephalus — shunt response test).
3. Contraindications
- Absolute: focal neurological deficits and a mass effect with brain shift (CT required before puncture!), skin infection at the puncture site, progressive deterioration of consciousness with signs of herniation.
- Relative: coagulopathy (platelets < 50, INR > 1.5), anticoagulant therapy.
4. Normal reference values
| Parameter | Normal value (adults) |
|---|---|
| Color and transparency | Clear, colorless |
| Pressure | 100–180 mm H₂O in the recumbent position |
| Cell count | 0–5 × 10⁶/L (lymphocytes 70%, monocytes 30%) |
| Protein | 0.15–0.45 g/L |
| Glucose | 2.5–4.4 mmol/L (~60% of serum) |
| Chlorides | 120–130 mmol/L |
| Lactate | < 2.1 mmol/L |
| pH | 7,31–7,34 |
| IgG index | < 0,7 |
In infants: higher protein (up to 1 g/L in newborns), cell count up to 20 × 10⁶/L.
5. CSF differential diagnosis
| Parameter | Normal | Bacterial meningitis | Viral meningitis | Tuberculous meningitis | SAH |
|---|---|---|---|---|---|
| Color | Clear | Turbid, yellowish-green | Clear / opalescent | Opalescent, "fibrin web" | Bloody, xanthochromic |
| Pressure | 100–180 | ↑↑ | N or ↑ | ↑ | ↑↑ |
| Cell count | < 5 | 1000–10,000, neutrophils > 80% | 10–500, lymphocytes | 100–500, lymphocytes | Erythrocytes; leukocytes ~ blood |
| Protein | 0,15–0,45 | ↑↑ (> 1 g/L) | N or ↑ | ↑↑ | ↑ |
| Glucose | 2,5–4,4 | ↓↓ (< 2,0) | N | ↓ | N or ↓ |
| Lactate | < 2,1 | > 3,5 | N | ↑ | ↑ |
6. Clinical interpretation
Bacterial meningitis
- Neutrophilic pleocytosis > 1000 × 10⁶/L, ↓↓ glucose (< 40% of serum), ↑↑ protein, ↑↑ lactate.
- If suspected — before/during antibiotics: Gram stain, culture, PCR, antigens (S. pneumoniae, N. meningitidis, H. influenzae).
Viral meningitis/encephalitis
- Lymphocytic pleocytosis 50–500, normal glucose, normal or mildly ↑ protein.
- PCR: enteroviruses, HSV, VZV, EBV, CMV.
Tuberculous meningitis
- Subacute onset (weeks), lymphocytic pleocytosis 100–500, ↓ glucose, ↑↑ protein, "fibrin web".
- GeneXpert MTB/RIF, culture, ADA > 10 U/L.
Fungal (cryptococcal) meningitis
- Immunocompromised patients (HIV, transplantation).
- Lymphocytic pleocytosis, ↓ glucose, ↑ protein.
- India ink stain, cryptococcal antigen in CSF.
Subarachnoid haemorrhage
- CT-negative SAH at 6–12 h: lumbar puncture with evaluation for xanthochromia.
- 3-tube test to differentiate from traumatic tap (true SAH — color does not change).
Multiple sclerosis
- Mild lymphocytic pleocytosis (up to 50), normal or slightly ↑ protein.
- Oligoclonal IgG (isoelectric focusing) — > 95% sensitivity.
- ↑ IgG index (> 0.7).
Guillain-Barré syndrome
- Albuminocytologic dissociation: ↑ protein (often > 1 g/L), normal or < 10 cytosis.
- Appears from the 2nd week of illness.
7. Puncture and monitoring aspects
- Technique: between L3–L4 or L4–L5; Sprotte/Pencan needle (atraumatic) reduces post-lumbar puncture headache.
- Collection of 3–4 tubes of 2–3 mL each: biochemistry, cytology, microbiology, reserve.
- Post-lumbar puncture headache 10–30%: bed rest, hydration, caffeine, for prolonged cases — blood patch.
- Other complications: infection, bleeding, nerve injury, herniation (in untreated intracranial hypertension).
8. Additional studies
- Cytology: for meningeal tumors, lymphomas, leukemia.
- Immunological: antibodies against neuronal antigens (anti-NMDAR, anti-LGI1).
- 14-3-3 protein: Creutzfeldt-Jakob disease.
- Tau, β-amyloid 1–42: diagnosis of Alzheimer's disease.
- Chromogranin A, lactate, oxypurin — research.
9. Features in children
- Neonates: cytosis up to 20, protein up to 1 g/L, higher glucose (2/3 of serum).
- Classic indicator of bacterial meningitis in children: cytosis > 1000 with a neutrophilic shift, glucose < 2.0.
- Fear of puncture — use an atraumatic needle + local anesthesia; in severe condition and suspected meningitis — do not delay antibiotic therapy while waiting for the puncture!
10. FAQ
When to perform a CT before lumbar puncture?
In case of focal neurological deficits, depressed consciousness, recent TBI, seizures, immunosuppression. For other patients with suspected meningitis — puncture without delay.
Is lumbar puncture possible in thrombocytopenia?
With platelets < 50 × 10⁹/L — increased risk of spinal hematoma. Pre-transfusion if possible. With INR > 1.5 — correction with FFP.
How does xanthochromia differ from a traumatic tap?
Xanthochromia is a yellowish supernatant after centrifugation, appearing 6 hours after SAH; a traumatic tap has a clear supernatant, with erythrocyte count decreasing across tubes.
Why is CSF pressure measured?
Elevation > 250 mm H₂O — intracranial hypertension (tumors, IIH, meningitis). Decreased pressure is rare — CSF leak, spontaneous intracranial hypotension.
What does the CSF glucose-to-serum glucose ratio provide?
A more accurate indicator. Normal > 0.6; bacterial meningitis < 0.4; TB and fungal — decreased; viral — normal.
See also: Meningitis · Stroke (and SAH) · Multiple sclerosis · Tuberculosis · Neurology catalog