Download 10-Cerebrospinal fluid

Cerebrospinal fluid
 Cerebrospinal fluid (CSF) is an ultrafiltrate of plasma formed in the brain.
 It is clear bodily fluid that occupies the subarachnoid space and the
ventricular system around and inside the brain.
 It is an approximately isotonic solution and acts as a "cushion" or buffer for
the cortex, providing also a basic mechanical and immunological protection
to the brain inside the skull.
 It is produced in the brain at a rate of 500 ml/day, since the brain can only
contain 150 ml, large amounts are drained primarily into the blood through
arachnoid granulations.
Functions:
The cerebrospinal fluid has many roles including:
1. Mechanical protection of the brain.
2. Distribution of neuroendocrine factors.
3. Prevention of brain ischemia. The prevention of brain ischemia is made by
decreasing the amount of cerebrospinal fluid in the limited space inside the
skull. This decreases total intracranial pressure and facilitates for blood
perfusion.
Diagnosis
 Cerebrospinal fluid can be tested for the diagnosis of a variety of diseases.
 It is usually obtained by a procedure called lumbar puncture in an attempt to
count the cells in the fluid and to detect the levels of protein and glucose.
 These parameters alone may be extremely beneficial in the diagnosis of
subarachnoid hemorrhage and central nervous system infections (such as
meningitis).
 Moreover, a cerebrospinal fluid culture examination may yield the
microorganism that has caused the infection. By using more sophisticated
methods, such as the detection of the oligoclonal bands, an ongoing
inflammatory condition (for example, multiple sclerosis) can be recognized.
 A beta-2 transferrin assay is highly specific and sensitive for the detection for
e.g. cerebrospinal fluid leakage.
 Lumbar puncture can also be performed to measure the intracranial pressure,
which might be increased in certain types of hydrocephalus.
 Since only a small amount of CSF can be safely collected, it is imperative that
it is handled carefully. If the CSF pressure is normal, at least 20 mL can be
removed for testing without injury to the patient.
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 Due to the small volume, CSF must be shared between several testing areas, so
it is necessary to conserve the sample and follow proper handling and transport
requirements to avoid the need for recollection.
 Ideally, the specimens should be collected into three sterile tubes that are
labeled sequentially.
 The first tube should be used for chemical and immunologic studies, since it is
most likely to be contaminated with dermal bacteria and therefore is not
suitable for microbiological assays.
 The second tube is generally used for microbiological testing, and the third
tube is used for total cell count, differential count, and cytological testing.
Cerebrospinal Fluid Supernatant Colors and Associated Conditions or Causes
Color of CSF supernatant
Yellow
Orange
Pink
Green
Brown
Conditions or causes
Blood breakdown products, Hyperbilirubinemia
CSF protein >=150 mg per dL (1.5 g per L)
>100,000 red blood cells per mm3
Blood breakdown products
High carotenoid ingestion
Blood breakdown products
Blood breakdown products
Meningeal melanomatosis
Cerebrospinal Fluid Proteins
 CSF contains much less protein than serum and cannot be analyzed by biuret
reactions or other methods used in measurement of total serum proteins.
 Elevated CSF protein is seen in infections, intracranial hemorrhages,
multiple sclerosis, Guillain Barré syndrome, malignancies, some endocrine
abnormalities, certain medication use, and a variety of inflammatory
conditions
Glucose Level
 CSF glucose=60% of serum or plasma level.
 Chemical meningitis, inflammatory conditions, subarachnoid hemorrhage,
and hypoglycemia also cause hypoglycorrhachia (low glucose level in CSF).
 Elevated levels of glucose in the blood is the only cause of having an
elevated CSF glucose level.
 There is no pathologic process that causes CSF glucose levels to be elevated.
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Typical Cerebrospinal Fluid Findings in Various Types of Meningitis
Test
Bacterial
Viral
Fungal r
Tubercular
Opening
Elevated
Usually
Variable
Variable
pressure
normal
White blood
>=1000 per
<100 per
Variable
Variable
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cell count
mm
mm3
Cell
Predominance Predominance Predominance Predominance
differential
of PMNs
of
of
of
lymphocytes
lymphocytes
lymphocytes
Protein
Mild to
Normal to
Elevated
Elevated
marked
elevated
elevation
CSF-to-serum Normal to
Usually
Low
Low
glucose ratio
marked
normal
decrease
PMNs = polymorphonucleocytes
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