CSF ANALYSIS. CSF Formation. Cerebrospinal fluid (CSF) is the liquid that surrounds the brain & spinal cord. The brain & spinal cord are surrounded by the meninges that consist of three layers: dura matter, arachnoid & pia matter
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Cerebrospinal fluid (CSF) is the liquid that surrounds the brain & spinal cord.
The brain & spinal cord are surrounded by the meninges that consist of three layers:
dura matter, arachnoid & pia matter
the lateral, third, and fourth ventricles;
1- Physical support & protection of the CNS from trauma.
2- Supplying nutrients to the CNS & removal of metabolic wastes from CNS
3- Intra-cerebral transport (neuroendocrine role i.e. distribution of hypothamic hormones within the brain)
CSF is performed in cases of suspected:
1- CNS infections (infectious meningitis & encephalitis)
2- CNS malignancy (as malignant infiltrates as in leukemia ..etc)
3- CNS hemorrhages (as subarachnoid hemorrhage)
4- CNS demyelinating diseases (as multiple sclerosis)
At interspace of vertebrate L3-4 or lower
With complete aseptic techniques
Collected CSF sample is immediately divided into three tubes:
Tube 1: Chemical Investigation (kept in freezer till performed)
Tube 2: Microbiology Investigation (kept in room temperature)
Tube 3: Microscopic Investigation (Cellular Counting – Differential – Cytology)
Normal CSF Analysis
Normal CSF: Clear & colorless
Viscosity: equal to water (increased with increased proteins)
Color and/or turbidity of CSF: observed only in pathological circumstances.
Bacteria, WBCs cells or pus cells: suggestive of a CNS infection (menigitis or encephalitis)
Blood : suggestive of hemorrhage: subarachnoid or artifactual traumatic tap: DIFFERNTIATE?
Red & brown color :
1-Jaundice (bilirubin in CSF)
2- Xanthochromia (hemoglobin breakdown pigments in CSF)
Xanthochromic CSF suggests that a subarachnoid hemorrhagehas recently occurred
(at least within two hours prior to tapping).
The yellow color is due to bilirubin generated in the CNS by the breakdown of hemoglobin released from RBC's. (so jaundice should be excluded).
Normal Total WBCs count: 1-5 lymphocytes /HPF
Normal differential WBCs Count: (in centrifuged cells)
- 62% lymphocytes
- 36% monocytes
- 2% neutrophils
Increased neutrophils: bacterial meningitis
Increased lymphocytes: aseptic and viral meningitis
Normally CSF is blood free
RBCs in CSF: subarachnoid hemorrhage & malignancy
Artifact: traumatic tap (should be excluded)
(Traumatic tap bright red color RBCS in decreasing number as the fluid is sampled)
Elevated CSF / plasma glucose ratio (more than 0.7)
has no CSF diagnostic significance (occurs with hyperglycemia)
Decreased CSF / plasma glucose ratio(hypoglycorrhachia):
1- CNS septic (pyogenic) infections
Due to increased glycolysis by leukocytes and bacteria (with increase CSF lactate)
2- Brain tumors
due to increased metabolism of glucose by CNS
3- TB meningitis & sarcoidosis
Due to inhibition of glucose entry into the subarachnoid space
N.B. in viral CNS infections, CSF glucose is usually normal
Lumbar CSF protein: 15 - 45 mg/dl (mostly albumin)
The majority of CSF protein is derived from the plasma by ultrafiltration
Certain proteins arise within the intrathecal compartment:
1- Immunoglobulinsproduced by CNS lymphocytes
2- Transthyretin(produced by choroid plexus)
3- Various structural proteins found in brain tissue
Increased CSF protein:
1- Lysis of contaminant blood from traumatic tap
2- Increased permeability of epithelial membrane (blood-brain barrier)
in cases of:
- CNS bacterial or fungal infections
- Cerebral hemorrhages
2- Increased production by CNS tissue as in cases of:
- Multiple sclerosis (MS)
- Subacute sclerosing panencephalitis (SSPE)
3- Obstruction as in cases of :
- Tumors or abscess
Analysis of protein fractions: (Albumin & IgG)
is obtained from blood by means of blood-brain barrier (as it is
produced solely by the liver)
In cases of increased permeability of BBB, albumin is increased in
from blood (By BBB) : increase in cases of increase permeab. of BBB
& by local synthesis from plasma cells within CSF (increased in cases of MS)
So, it is essential to determine the source of IgG
SEE NEXT SLIDE PLEAE !!!
BY CSF / serum albumin index calculation
CSF serum albumin index = CSF albumin (mg/dl) / serum albumin (g/dl)
Index less than 9 indicates intact BBB (no increased permeability of BBB)
CSF IgG / Serum IgG
CSF IgG index = ---------------------------------------
CSF albumin / serum albumin
Normal : less than 0.7
Increased in cases of demylineating diseases of CNS as : Multiple sclerosis (MS)
CSF IgG can arise:
from plasma cells within CSF
& from the blood through BBB
↑CSF [IgG] without concomitant ↑ in CSF [Alb] suggests local production of IgG:
multiple sclerosis (MS)
subacute sclerosing panencephalitis (SPEE)
CSF IgG/Serum IgG
CSF IgG index:
Normally: < 0.7
CSF serum /Albumin index
CSF lactate is increased in cases of bacterial meningitis (due to increased glycolysis by bacteria & inflamatory cells)
The level of CSF glutamine reflects level of ammonia in that is normally removed in the CNS by formation of glutamine (amino acid glutamate + ammonia).
Glutamine synthesis helps to protect the CNS from the toxic effects of increased ammonia.
Ammonia production is increase dramatically in patients with liver failure.
Accordingly, CSF glutamine production is increased in cases of hepatic encephalopathy
CSF lactate dehydrogenase (LDH) may be elevated in bacterial meningitis.
CSF adenosine deaminase (ADA) elevations can occur in tuberculous meningitis.
CSF [Calcium], [Potassium] & [Phosphates] are lower than their levels in the blood
CSF [Chloride] & [Magnesium] are higher than their levels in the blood
Abnormal CSF [Chloride]
marked in acute bacterial meningitis
slight in viral meningitis & brain tumors