4. CSF Formation and Physiology
First recognized by Cotugno in 1764, cerebrospinal fluid
(CSF) is a major fluid of the body.
CSF provides a physiologic system to supply nutrients
to the nervous tissue, remove metabolic wastes, and
produce a mechanical barrier to cushion the brain
and spinal cord against trauma.
CSF is produced in the choroid plexuses of the two
lumbar ventricles and the third and fourth venticles. In
adults, approximately 20 mL of fluid is produced every
5. Formation and Physiology
The fluid flows through the subarachnoid space
located between the arachnoid and pia mater.
To maintain a volume of 90 to 150 mL in adults
and 10 to 60 mL in neonates.
the circulating fluid is reabsorbed back into the
blood capillaries in the arachnoid
granulations/villae at a rate equal to its
6. Cerebrospinal fluid (CSF)
– Fluid in the space called sub-arachnoid space between the
arachnoid mater and pia mater
– Protects the underlying tissues of the central nervous
– Serve as mechanical buffer to
• prevent trauma,
• regulate the volume of intracranial pressure
• circulate nutrients
• remove metabolic waste products from the CNS
• Act as lubricant
– Has composition similar to plasma except that it has less
protein, less glucose and more chloride ion
8. CSF Normal Adult Lab Ranges
• Normal CSF Levels:
Protein (10 - 45 mg/dL)
Glucose (40 - 70 mg/dL)
• Physical Appearance
• Maximum volume of CSF
– Adults 150 mL
– Neonates 60 mL
• Rate of formation in adult is 450-750 mL per day or 20 ml per hour
– reabsorbed at the same rate to maintain constant volume
• Collection by lumbar puncture done by experienced medical
• About 1-2ml of CSF is collected for examination
– lumbar puncture is made from the space between the
4th and 5th lumbar vertebrae under sterile conditions
10. Collecting CSF specimen
Collected in three sequentially labeled tubes
Tube 1 Chemical and immunologic tests
Tube 2 Microbiology
Tube 3 Hematology (gross examination, total WBC & Diff)
This is the list likely to contain cells introduced by the
11. Report the appearance of the c.s.f.
• As soon as the c.s.f. reaches the laboratory,
note its appearance.
Report whether the fluid:
• – is clear, slightly turbid, cloudy or definitely
purulent (looking like pus),
• – contains blood,
• – contains clots.
Normal c.s.f. Appears clear and colourless.
12. Report the appearance of the c.s.f…
• Purulent or cloudy c.s.f.
Indicates presence of pus cells, suggestive of acute
pyogenic bacterial meningitis.
• Blood in c.s.f.
This may be due to a traumatic (bloody) lumbar
puncture or less commonly to haemorrhage in the
central nervous system. When due to a traumatic
lumbar puncture, sample No. 1 will usually
contain more blood than sample No. 2.
13. Report the appearance of the c.s.f…
• Following a subarachnoid haemorrhage, the
fluid may appear xanthrochromic, i.e. yellow-
red (seen after centrifuging).
• Clots in c.s.f. Indicates a high protein
• with increased fibrinogen, as can occur with
• pyogenic meningitis or when there is spinal
14. Clinical Significance
Diagnosis of meningitis of bacterial, fungal,
mycobacterial and amoebic origin or
differential diagnosis of other infectious
subarachnoid hemorrhage or intracerebral
15. Principle of the test
• CSF specimen examined visually and microscopically and
total number of cells can be counted and identified
• the third tube in the sequentially collected tubes
• must be counted within 1 hour of collection (cells
disintegrate rapidly). If delay is unavoidable store 2-8oC.
• All specimens should be handled as biologically
16. Microscopic Observations of Cerebral
• Color – Xanthochromia
– Increased Protein
– Increased White Blood Cells (Pleocytosis)
17. CSF Supernatant
• A traumatic tap shows progressively decreasing
RBC in serial samples
• Generally, in subarachnoid hemorrhage, the RBC
would be consistent from one tube to the next
• After the CSF is centrifuged, the supernatant fluid
is clear in a traumatic tap, but it is xanthochromic
in a subarachnoid hemorrhage
• Xanthochromia of the CSF refers to a pink,
orange, or yellow color of the supernatant after
the CSF has been centrifuged
18. Cell Count
• The white cell count is increased when there is
inflammation of the central nervous system,
particularly the meninges
• Bacterial infections are usually associated with
the presence of neutrophils in the CSF
19. Cell Count…
• Viral infections are associated with an increase in
• An increase in mononuclear cells may also be seen
– cerebral abscess
– acute leukemia
– intracranial vein thrombosis
– cerebral tumor
– multiple sclerosis
20. Cell Count…
• A white cell count with an indication whether
the cells are pus cells or lymphocytes, is
required when the c.s.f. appears slightly
cloudy or clear or when the
• Gram smear does not indicate pyogenic
21. Chemistry Tests
• Because CSF is formed by filtration of the plasma,
chemicals in the CSF are that are found in the
• chemical composition is controlled by the blood-
• normal values for CSF chemicals are not the same
as the plasma values.
• Abnormal values result from alterations in the
permeability of the blood-brain barrier or increased
production or metabolism by the neural cells in
response to a pathologic condition.
22. Measurement of c.s.f total protein
• Use the supernatant fluid from centrifuged
c.s.f. or uncentrifuged c.s.f. when the sample
• Total protein can be measured in c.s.f. using a
colorimetric technique or a visual comparative
• Normal Total c.s.f. protein is normally 0.15–
0.40 g/l (15–40 mg%).
23. Measurement of c.s.f total protein ….
• When the total protein exceeds 2.0 g/l (200
mg%), the fibrinogen level is usually increased
sufficiently to cause the c.s.f. to clot. This may
occur in severe pyogenic meningitis, spinal
block, or following haemorrhage.
24. Clinical Significance of Elevated Protein
• The causes of elevated CSF protein include
damage to the blood-brain barrier, production of
immunoglobulins within the CNS, decreased
clearance of normal protein from the fluid, and
degeneration of neural tissue.
• Meningitis and hemorrhage conditions that
damage the blood-brain barrier are the most
common causes of elevated CSF protein.
• Many other neurologic disorders can elevate the
CSF protein, and finding an abnormal result on
clear fluid with a low cell count is not unusual
26. Increased CSF Protein >80mg/dL…
Syphilis (protein may be normal if longstanding)
Guillain-Barre Syndrome (Infectious polyneuritis)
Connective tissue disease
27. Cerebrospinal Fluid Glucose
• Glucose enters the CSF by selective transport
across the bloodbrain
• barrier, a normal value 60% to 70% that of the
• If the plasma glucose is 100 mg/dL, then a normal
CSF glucose would be approximately 65 mg/dL.
For an accurate evaluation of CSF glucose, a
blood glucose test must be run for
comparisonCSF glucose is analyzed using the
same procedures employed for blood glucose.
• Specimens should be tested immediately because
glycolysis occurs rapidly in the CSF.
28. Clinical Significance of Elevated
The diagnostic significance of CSF glucose is confined
to the finding of values that are decreased in relation to
Elevated CSF glucose values are always a result of
Low CSF glucose values can be of considerable
diagnostic value in determining the causative agents
The finding of a markedly decreased CSF glucose
accompanied by an increased WBC count and a large
percentage of neutrophils is indicative of bacterial