Cerebrospinal Fluid

1. BY
SHEEBA.D
2ND M.SC BIOCHEMISTRY

2. Introduction:
 The surface of the central nervous system is
covered by the meninges , THREE layers called as
a. Piameter
b. Arachnoid mater
c. Duramater – is the outermost layer
 CSF is found between the Piameter and the Arachnoid
mater.
 It is not just a plasma ultra filtrate.
 Normal healthy adult – rate of formation of CSF is 100
to 250 ml per 24hours.
 Total volume of CSF is approx 100 -200 ml
 Microbiological & Serological test & chemical test are
commonly carried out on CSF.
 Now a days Chloride tests are rarely done.

3. Site of withdrawal :
 There are 2 sites for withdrawal
a) Lumbar – Generally lumbar CSF is
examined
b) Ventricular
 The spinal cord ends near the 1st lumbar vertebra
and accumulation of fluid below called Lumbar fluid
 Passing a lumbar puncture needle, between 3rd and
4th lumbar vertebrae in to the subarachnoid space.
“Blood-Brain” Barrier – A blood CSF barrier exists for
many substances includes blood constituents ,drugs,
enzymes etc.. Conc. Of CSF is lower than plasma.

4. Collection of sample :
 A sample of CSF submitted for chemical analysis ,
should be fresh and free from blood.
 The fluid should be collected in a sterile
containers and sent to the laboratory at the earliest.
 If the fluid cannot be analyzed for glucose
within1/2 hour of withdrawal , then to prevent
glycolysis by any cells or bacteria present,
 The CSF should be collected in a bottle containing
sodium fluoride.

5. Composition of normal CSF(Lumbar Fluid)
Specific gravity 1.006 to 1.007
Cells 0 to 4 mononuclear cells per C.mm
pH 7.3 (anaerobically)
Protein content 10 to 45 mg/100 ml
Globulins Not increased . Pandy’s test & Nonne- Apelt
tests Negative
Glucose 45 to 100mg/100ml.
Chlorides 700 to 760 mg /100 ml as NaCl
Urea 20 to 40 mg /100 ml
Calcium 5.5 to 6 mg/100 ml
Colour and appearance clear ,colourless , no coagulum or deposit.
Pressure 60 to 150 mm.CSF

6. Appearance of CSF
 Normal CSF_ Colourless & gives no coagulam or sediment
 Abnormalities _ Colour ,Turbidity , Coagulum
a) Colour _ The presence of blood is the main cause of an
abnormal colour
1) Trauma _ In Lumbar puncture 1st few drops is mixed
with blood. – supernatant fluid after centrifugation would
also be cleared.
2) Pathological _ Haemorrhagic fluid obtained in sub-
arachnoid haemorrhage ,haemorrhage in ventricles.

7. 3) Xanthochromia _ This is the yellow coloration of CSF. Either
due to Hb or other pigments usually billirubin or carotenoids.
after Haemorrahage converted to Oxy –Hb then converted in
to billirubin
Billirubin – Detected in CSF after 6hours after haemorrhage
reaches maximum conc. in approx 10 daystime after RB cells
disappear the supernatant fluid obtained after centrifugation
shows yellow colour
4) Froin’s syndrome – This term denote to xanthochromic fluid
obtained from lumbar region in case there is complete block
due to a tumour . The fluid has high protein conc. Which can
coagulate spontaneously . Cause of xanthochromia is
capillary haemorrhage.
5) Other cause of yellow coloration _ Due to cholestatic jaundice
& icterus neonatorum . (Billirubin)
Carotenoids _ it can pass from plasma in to CSF when the Blood
– Brain Barrier altered or inflammatory disorder or in a
space below spinal block

8. B) Turbidity
It is seen where there is marked increased in the number of cells or when
Organism are present and hence found in meningitis specially in coccal type.
 Atleast 400 to 500 polymorphs per c.mm are needed to give a visible
turbidity.
 Note;
Small numbers of red cells may also give CSF an opalascent
appearance.
 The traces of substances such as alcohol are mixed with the fluid
during its collection some opalascene may result .
C) Coagulum:
Normal CSF does not form a fibrin clot on standing .
Causes
 Fibrinogen present in the blood of CSF may be sufficient to form a
clot.
Fibrin clot is formed readily on standing , when the protein content of
CSF is high. Such fibrin clot can occur , when the CSF protein is above
2g/l.
CSF obtained from below a spinal block usually contains a high conc.
Of fibrinogen.

9. In tuberculous meningitis : A fine delicate cob- web like coagulum fluid is
allowed to stand overnight . Such a “web” may take up myco-bacterium
tuberculosis & easily demonstrated when a smear is made, stained and
seen microscopically.
Fine clot may develop – neurosyphilis or polio –meningitis.
Note : CSF must be examined for “ clot formation” -24 hours of
withdrawal, autolysis destroys the fibrin.
PRESSURE OF CSF
when collecting sample of CSF one can measure its pressure within the
lumbar sac.
Patient lying on his side, pressure- normally 60 to 150mm CSF -40 to90 in
children
On sitting – It increases 200 to 250mm.
Causes:
 Raised intracranial pressure can occur – eg. Meningitis, & in
tumors.
Low pressure may be seen below a block –tumors compessing
spinal cord.

10. Note:
If too much of fluid is removed there is a danger of “coning” of
the brain and sudden death
BIOCHEMICAL CHANGES IN CSF
A)pH value;
Is collected anaerobically is 7.31 approx and is approx. and
is mainly dependant on the pCO2 content . The pH may be a
major regulator of respiratory centre , CO2 equilibrates between
plasma and CSF quickly, changes in HCO3 conc. are slower .
Hence too rapid replacement of a HCO3 – deficit in plasma may
affect the CSF pH.
B) Chemical constituents :
I. Estimation of Glucose in CSF: Done by any of the usual
blood glucose methods.

11. Precautions :
Glucose conc. in CSF is normally somewhat lower than in
blood , larger volume of CSF may be used , anticipated that there
may be gross reduction of CSF glucose in certain disease .
streptomycin given intrathecally shortly before CSF
sampling may interfere with routine method of copper reduction
used.
It is contaminated during laboratory sampling may
show a fall in glucose content if kept at a room temperature.
Clinical significance:
A) Normal value : Varies from 50 to 80mg/100ml . CSF glucose
level is slightly lower than the blood glucose. The ventricular CSF
glucose is rather higher than the lumbar CSF glucose and
approximates to blood glucose.

12. B) Decrease in CSF Glucose: Decrease in CSF glucose is the most
important pathological change seen.
In coccal meningitis: due to meningococci, staphylococci,
pneumococci ,etc.. Glucose often disappear completely in CSF
and it may be totally absent.
 In viral meningitis : The glucose conc. is often normal, but it
occasionally as low as 20mg%
 In tuberculous meninigitis: glucose content may be reduced
but rarely absent completely, usually it varies from 10 to 40mg
/100ml.
C)Increase in CSF glucose:
small increases are found in some cases of
encephalitis, poliomyelitis & cerebral abscess & values between
150 to 180 mg% have been found in some cases, but this is of
little diagnostic value.

13. II ) Estimation of chlorides in CSF: This is rarely done now.
Determination of chlorides in CSF: Titrate most CSF directly
appropriate AgNO3 soln. using potassium dichromate as
indicator.
Clinical significance:
a) Normal value – 700 to 760mg NaCl/100ml
b) Decrease in CSF chloride in meningitis – 700 to 600 mg
NaCl%
III) Estimation of CSF proteins :
Usually done by turbidmetric method but some of the
colorimeteric method for estimation of proteins have been used.
Methodology:
1) sulphosalicyclic acid 3% soln.
2) proteinometer standards – one set
Clinical significance:
Normal value- 15 to 45mg/100 ml
Increase of CSF protein .