The cerebrospinal fluid ( C.S.F)
Introduction
The cerebrospinal fluid is a modified tissue fluid.
The fluid flows through the subarachnoid space located between the
arachnoid and pia mater.
A clear, colorless liquid that fills the ventricles (cavities) of the brain and the
spinal cord.
CSF replaces lymph in the CNS.
The total quantity of CSF is about 150 mL in adult and and 10 to 60 mL in
neonates.
Approx. 30 ml in the spinal cord.
It is formed at the rate of about 0.35 ml per min OR 20 mL hour = 500 ml
per day.
Functions of the CSF
The CSF is believed to be nutritive for both neurons and glial cells.
The CSF provides a medium for removing waste products of cellular
metabolism form the nervous system.
The presence of a number of biologically active principles (releasing factors,
hormones, neurotransmitters, metabolites) within the CSF suggests that it
may function as a transport system.
CSF Formation
The bulk of CSF is formed by the Choroid plexuses of lateral ventricles and
lesser amount by the Choroid plexuses of third and fourth ventricles.
The circulating fluid is reabsorbed back into the blood capillaries in the
arachnoid granulations (villae) at a rate equal to its production.
The cells of the arachnoid granulations act as one-way valves that respond to
pressure within the central nervous system (CNS) and prevent reflux of the
fluid.
Lumbar Puncture
Lumbar puncture is used to obtain a sample of cerebrospinal fluid (CSF) to
aid in the diagnosis or the therapeutic of various conditions.
Indications: diagnostic and Therapeutics.
THERAPEUTICS
Treatment
Obstructive hydrocephalus
Drug administration
Anesthesia
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Antibiotic
Chemotherapy
Indications
Fever of unknown origin
Children from 1 month to 3yrs having fever and vomiting.
Over age 3yrs having nuchal rigidity, Kernig’s sign, and Brudzinski’s sign
Partially treated children are less likely to be febrile or exhibit an altered
mental status
Cont…
LP in adults and in older children may be performed from L2 to L3
interspaces' to the L5 to S1 interspaces'.
At birth, the cord ends at the level of L3.
LP in infant may be performed at the L4 to L5 or L5 to S1 interspaces'.
Sterile gloves MUST be used.
Wash back with antiseptic solution.
Sterile towel under hips.
The skin and deeper subcutaneous tissue are infiltrated with local anesthetic.
Procedure
Tube 1: is used for chemical and serologic tests because these tests are least
affected by blood or bacteria introduced as a result of the tap procedure.
Tube 2: is usually designated for the microbiology Laboratory.
Tube 3: is used for the cell count, because it is the least likely to contain
cells introduced by the spinal tap procedure.
Tube 4: reserve tube for any special tests or for the microbiology laboratory
to provide better exclusion of skin contamination or for additional serologic
tests.
Purpose of CSF Analysis
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The purpose of a CSF analysis is to diagnose medical disorders
that affect the central nervous system. Some of these conditions
include:
Viral and bacterial infections, such as meningitis and encephalitis .
Tumors or cancers of the nervous system.
Bleeding (hemorrhage) around the brain and spinal cord.
Multiple sclerosis: a disease that affects the myelin coating of the nerve
fibers of the brain and spinal cord.
Syphilis, a sexually transmitted disease .
Complications
Headache
Headache After Lumbar Puncture
Most common complication
Occurs 5-30% of all spinal taps
Usually starts up to 48 hours after to procedure.
Usually lasts 1-2 days (occas 14 days)
Caused by leaking of fluid through dural puncture site.
Treatment
Opening Pressure
Normal opening pressure is
90~180mmH2O in adults
10~100mmH2O in children.
In Obese pts: up to 250mmH2O can be normal
CSF pressure
Elevated pressure
Congestive heart failure
Meningitis
Cerebral edema
Mass lesion
Decreased pressure
Spinal-subarachnoid block
Dehydration
Circulatory collapse
CSF leakage
Macroscopic examination
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Total volume
In adult, CSF volume is 90-150 ml.
In neonates, CSF volume is 10 -60 ml.
Production is approx. 0.35 ml/min.
Distribution
20 ml in the ventricles.
60 ml in the subarachnoid space.
70 ml in the spinal canal.
Specific gravity:
1.006 – 1.008
pH
:
Alkaline
Appearance
Normal CSF is crystal clear and the consistency of water. The major
terminology used to describe CSF appearance includes clear, cloudy or
turbid, milky, xanthochromic, and bloody.
Cloudy, turbid or milky
Increased protein or lipid concentration, but it may also be indicative of
infection.
May be caused by WBCs (over 200 cells/µl).
RBCs (over 400 cells/µl).
Xanthochromia is a term used to describe CSF supernatant that is pink,
orange or yellow.
Pink: very slight amount of oxyhemoglobin
Orange: heavy hemolysis
Yellow: conversion of oxyhemoglobin to unconjugated bilirubin
Xanthochromic
Other causes of xanthochromia include
Oxyhemoglobin: from lysed RBCs present in CSF before lumber puncture,
or traumatic tap with lysis of RBCs after lumber puncture.
Bilirubin from lysed RBCs in CSF, or increased direct bilirubin with normal
blood-brain barrier, or in premature infants an immature blood-CSF barrier
plus elevated total bilirubin.
increased protein concentrations, and melanoma pigment.
Presence of the pigment carotene.
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Traumatic tap: Grossly bloody CSF can be an indication of intracranial
hemorrhage (subarachnoid hemorrhage), but it may also be due to the
puncture of a blood vessel during the spinal tap procedure. Three visual
examinations.
We can differentiate between both by:
Uneven distribution of blood: Traumatic tap often shows significant clearing
of blood between the first and third tubes.
Centrifugation: Traumatic tap often shows significant clear supernatant after
centrifugation.
Clot formation: Fluid collected from traumatic tap may form clots due to the
introduction of plasma fibrinogen into the specimen.
Microscopic examination
CSF cell count
Normal CSF RBCs are less than 5/mm3.
Counts that are otherwise unexplained may be due to a traumatic tap.
The cell count that is routinely performed on CSF specimen is the WBC's
count.
NOTE: Cell counts should be done within 30 minutes after withdrawal of
the specimen to avoid cell disintegration. Specimen that can't be analyzed
immediately should be refrigerated.
Normal adult CSF contains 0 to 5 WBC's /µl. the number is higher in
children and as many as 30 WBC's /µl can be consider normal in newborns.
Causes for increased Neutrophils
Meningitis (Bacterial meningitis, Early viral meningoencephalitis).
Reaction to repeated lumber puncture.
Injection of foreign materials in subarachnoid space.
Causes for increased Eosinophil
Parasitic infestations.
Fungal infection.
Rickettsial.
Glucose
Glucose enters the CSF by selective transport across the bloodbrain barrier,
The CSF glucose concentration is slightly lower than that plasma and
usually between 60 – 70 % of plasma glucose concentration.
The normal range of CSF glucose is between 50 and 80 mg/dl
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The blood glucose sample is needed for comparison.
The blood glucose should be drawn about 2 hours prior to the spinal tap to
allow time for equilibration between the blood and fluid.
CSF glucose is analyzed using the same procedures employed for blood
glucose. Specimens should be tested immediately because glycolysis occurs
rapidly in the CSF.
Clinical significance
Low CSF glucose values can be of considerable diagnostic value in
determining the causative agents in meningitis.
The finding of markedly decreased CSF glucose accompanied by:
An increased WBC's count and a large percentage of Neutrophil is most
indicative of bacterial meningitis.
WBC's count and a large percentage of lymphocytes is most indicative of
tubercular meningitis.
Proteins
The most frequently performed chemical test on CSF is the protein
determination. Normal CSF contains a very small amount of protein.
Normal CSF protein concentration (mg/dl) is less than 1% of serum protein
concentration (g/dl) and usually listed as 15 to 45 mg/dl with slightly higher
values found in infants and elderly people.
A rise in CSF protein is seen in various diseases as a result of three primary
mechanisms:
Decreased clearance of normal protein from the fluid and degeneration of
neural tissue.
Increased local synthesis of immunoglobulin.
Increased capillary permeability due to the blood-brain barrier damage.
Clinical Significance of Elevated Protein Values
Elevated total protein values are most frequently seen in pathologic
conditions.
Meningitis
Hemorrhage
Primary CNS tumors
Diabetes
Uremia
Methodology : The two most routinely used techniques for measuring total
CSF protein use the principles of turbidity production or dye binding ability.
CSF Lactate
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Measurement of lactate concentrations in cerebrospinal fluid (CSF) may be
useful as part of the investigation of inborn errors of metabolism in which
lactic acidosis occurs.
This includes disorders of gluconeogenesis, pyruvate dehydrogenase
complex, the Krebs cycle and the mitochondrial electron transport chain.
In bacterial, tubercular and fungal meningitis elevations of CSF lactate
greater than 25mg/dl.
Destruction of tissue within the CNS owing to oxygen deprivation (hypoxia)
causes the production of increased CSF lactic acid levels.
Measurement of lactate in CSF has also been advocated for investigating
children with unexplained neurological disease.
Levels greater than 35 mg/dL are frequently seen with bacterial meningitis,
whereas in viral meningitis, lactate levels remain lower than 25 mg/dL.
CSF lactate levels remain elevated during initial treatment but fall rapidly
when treatment is successful, thus offering a sensitive method for evaluating
the effectiveness of antibiotic therapy.
Microbiology test
Bacterial Infections
The Gram stain is of great importance, because this often dictates the initial
choice of antibiotic.
Gram-negative diplococci intracellular or extracellular are indicative of
Neisseria meningitidis
Small Gram-negative bacilli may include Haemophilus influenza, especially
in children.
Gram-positive cocci indicates Streptococcus pneumoniae, other
Streptococcus species, or Staphylococcus.
Serologic testing
Serologic testing of the CSF is performed to detect the presence of
neurosyphilis. However, detection of the antibodies associated with syphilis
in the CSF still remains a necessary diagnostic procedure.
Serologic tests:
VDRL (Venereal Disease Research Laboratory )
FTA –ABS (Confirmatory test )
Summary
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