CSF is normally sterile, colorless and clear. It contains most of the same
constituents as blood, but generally in lower concentrations.
CSF Clarity
Holding the test tube of CSF against a white, printed page, the CSF
should be as clear as a similar test tube filled with water.
- Yellow (+1 to +4) color indicates possible:
- Previous subarachnoid bleeding
- Severe jaundice
- Large amounts of protein (>150 mg/dl)
- Bloody or blood-tinged indicates possible:
- Bloody tap
- Subarachnoid or cerebral hemorrhage
- At least 400 RBCs/µl must be present before the CSF is visibly
bloody
- Turbid CSF usually indicates the presence of:
- WBCs,
- RBCs,
- Bacteria, or
- Other microorganisms
Spinal Fluid Glucose
Spinal Fluid Glucose is decreased in many cases of:
- Bacterial meningitis
- Mumps meningitis
- Meningococcal meningitis
- Tuberculosis meningitis
- Herpes meningitis
- Neurosyphilis
- Sarcoidosis
- Cancer
- Subarachnoid hemorrhage
Spinal Fluid Glucose may be elevated:
- 2-4 hours after hyperglycemia
White Blood Cell Count
Normal CSF has very few WBCs (0-8/cmm). In the presence of an
inflammatory response, WBCs increase. Inflammatory response situations
include:
- Meningitis of all types
- Cerebral abscess
- CNS hemorrhage
- Foreign body reaction
- CNS metastatic tumors
- CNS infarction
A predominence of monocytes (rather than neutrophils) suggests a
non-bacterial source of inflammation, such as:
- Hemorrhage
- Viral infection
- Syphilis
- Tuberculosis
- Multiple sclerosus
Red Blood Cell Count
Normally, there are no RBCs or nearly none (<1 RBC/cmm). While a
traumatic lumbar puncture ("bloody tap") can result in RBCs being
present in the CSF, the blood will progressively clear with each tube of CSF
withdrawn. By the third tube, the CSF should be nearly clear, even with a
bloody tap.
Blood that is evenly distributed throughout the three tubes reflects CNS
bleeding, such as:
- Subarachnoid hemorrhage
- Cerebral hemorrhage
- Spinal cord bleeding
CSF Culture
CSF is normally sterile.
In the presence of bacterial meningitis:
- CSF is cloudy (purulent)
- CSF Glucose is decreased in half the cases
- WBCs are increased
- WBCs are primarily PMNs
In the presence of non-bacterial meningitis (viral, tubercular,
fungal, protozoal, etc.):
- CSF is clear
- CSF Glucose is normal or decreased
- WBC Monocyte count is decreased
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Normal Values*
*These are general values taken from a variety of
sources. The actual normal values may vary from lab to lab and from one
type of testing protocol to another.
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