Cerebrospinal Fluid Analysis:- Part 2 – Cerebrospinal fluid (CSF) Normal/Abnormal Interpretations

Sample for Cerebrospinal Fluid Analysis

1. The sample is CSF fluid.
2. Three tubes with 2 to 3 ml each of CSF are collected. These tubes are labeled as:
   1.  Sterile tube 1 for chemistry and serology.
   2. Tube 2 for microbiology studies.
   3. Tube 3 for hematology studies.

CSF was collected into three test tubes

4. 4. Don’t use the first tube for culture because this is mostly contaminated.
      1. The first tube can be used for chemistry and serology after centrifugation.
   5. The last tube is best for chemistry and microscopy because it is less hemorrhagic or contaminated.
   6. The third tube is ideal for hematological studies.
   7. Transport the sample immediately to the laboratory.

4. The sample is taken from the spinal canal; the most common position is a lumbar puncture.
5. Keep the patient in a lying position in the bed for 6 to 12 hours.

Lumbar puncture to get CSF

The complication of lumbar puncture for CSF:

1. The patient may have a traumatic lumbar puncture.
2. The patient may have a severe headache.
3. A time may develop an infection at the site of puncture.

Purpose of Cerebrospinal Fluid Analysis (Indications):

1. To Diagnose the type of meningitis.
2. To diagnose the cause of hemorrhage.
3. This test is part of the patient’s workup in a coma.
4. This test can diagnose cerebral malaria in infants and children.
5. CSF electrophoresis is done to diagnose multiple sclerosis where there is an oligoclonal band.

Cerebrospinal Fluid Analysis (CSF) includes:

1. CSF pressure.
2. Volume.
3. Appearance
4. Biochemical tests include:
   1. Glucose.
   2. Protein.
5. The microscopic examination gives the idea about:
   1. A total number of cells.
   2. Type of cells: Neutrophils, Lymphocytes, or RBC.
   3. To rule out the presence of malignant cells.
6. Special stains to find bacteria (Gram stain).
7. Culture.
8. Special studies include:
   1. CSF electrophoresis for the oligoclonal band.
   2. Lactate dehydrogenase (LDH).
   3. Lactic acid.
   4. Chloride.
   5. Serology to rule out syphilis.
   6. Glutamine for hepatic encephalopathy in liver failure.

Interpretations of Cerebrospinal Fluid Analysis (CSF)

CSF pressure:

1. Normal pressure is 50 to 180 mm of water.
2. CSF pressure is increased in:
   1. Congestive heart failure.
   2. Obstruction of superior vena cava.
   3. Cryptococcal meningitis.
   4. Intracranial tumors.
   5. Meningitis of all types.
   6. Cerebral edema.
   7. Subarachnoid hemorrhage.
   8. Thrombosis of venous sinuses.
3. CSF pressure is decreased in:
   1. Circulatory collapse.
   2. Leakage of spinal fluid.
   3. Severe dehydration.
   4. Spinal subarachnoid block.

The appearance of CSF:

1. Normal CSF is crystal clear, like water.
2. The initial color of CSF is due to:
   1. Inflammatory diseases.
   2. Traumatic tap.
   3. Hemorrhage.
   4. Tumors.

How to assess the appearance of Cerebrospinal Fluid:

1. The appearance can be compared to water.
2. Hold the tube containing CSF against the paper, which can be read.

How to judge the CSF appearance

The appearance of CSF in various conditions:

Causes of various appearances of Cerebrospinal Fluid (CSF):

1. Blood-like appearance:
   1. Subarachnoid hemorrhage. If the sample is collected in three tubes, all the tubes will be the same color.
   2. Traumatic tap. Now the third tube will be clear or less in color.
2. Cloudy (Turbid) may be due to:
   1. The presence of WBCs.
   2. Increased protein.
   3. The presence of the microorganism.
   4. RBCs.
   5. Contrast media.
3. Xanthochromia
   1. It is pale pink to yellow, depending on the presence of protein. This may be due to:
      1. Increased protein when more than 150 mg/dL.
      2. Bilirubin when > 6 mg/dL.
      3. The presence of methemoglobin.
      4. Systemic carotenemia.
      5. Oxyhemoglobin due to hemolysis of RBCs.
      6. Melanin in meningeal melanoma.
      7. The yellow color may be seen in hemorrhage 10 hours to 4 weeks before the tap.
      8. The yellow color may also be seen if bilirubin is > 10 mg/dL.

CSF Xanthochromasia

4. The difference between Subarachnoid hemorrhage(SH) and Traumatic tap:
   1. The traumatic tap may form clots, while SH does not form a clot.
   2. Traumatic tap is negative for xanthochromia, while SH is positive.
   3. An immediate repeat at a higher level will show blood in SH while clear in the case of the Traumatic tap.

Cerebrospinal Fluid (CSF) Glucose level:

1. Glucose is utilized by bacteria (pyogenic or mycobacterium bacilli).
   1. Glucose may be utilized by the WBCs or occasionally by the cancer cells in CSF.
   2. This will take place after one hour of the blood glucose.
   3. It becomes normal after the start of the antibiotics.
   4. It decreases  ∼50% of bacterial meningitis.
   5. CSF glucose <45 mg/dL is abnormal.
2. CSF glucose level correlates with blood glucose.
3. This is 60% of the blood glucose.
   1. CSF glucose: blood glucose ratio = 0.6
   2. In bacterial meningitis, this ratio = <0.5
   3. A ratio <0.4 distinguishes acute bacterial meningitis from viral meningitis.
4. Always advise blood glucose whenever there is a CSF examination.
5. There is a lag time in the blood glucose and CSF, which is roughly one hour.
6. Bacteria, more than T.bacilli, utilize glucose.
7. There is no effect of viruses on the glucose level.
8. Normal CSF Glucose:
   1. Adult = 40 to 70 mg/dL.
   2. Child = 60 to 80 mg/dL.
   3. CSF : Plasma ratio = < 0.5
   4. CSF glucose is less than blood glucose = 60 to 70%.

9. Decreased glucose is seen in:

   1. Acute bacterial meningitis.
   2. Tuberculous meningitis.
   3. Subarachnoid hemorrhage.
   4. Diabetes with hypoglycemia.
   5. Malignant tumors with metastases to meninges.
   6. Non-Bacterial meningoencephalitis.
   7. Syphilis.

10. Increased glucose level is seen in:

    1. Diabetic hyperglycemia.

Cerebrospinal Fluid (CSF) Protein:

1. CSF protein is a nonspecific test because it is raised in so many diseases.
2. CSF has a very small quantity of protein because of the blood-brain barrier.
3. Increased CSF protein is caused by:
   1. Increased permeability of the blood-brain barrier.
   2. Decreased resorption by the arachnoid villi.
   3. Obstruction of CSF flow.
   4. Increased synthesis of immunoglobulin in the intrathecal space.
4. Normal CSF Protein:
   1. Adult (Lumbar area) = 15 to 45 mg/dL.
   2. Adult (Cisternal area) = 15 to 25 mg/dL.
   3. Adult (Ventricular area) = 5 to 15 mg/dL.
   4. Neonates (Lumbar area) = 15 to 100 mg/dL.

5. Increased CSF protein is seen in:

   1. Traumatic tap.
   2. Bacterial meningitis may increase even up to >1000 mg/dL.
   3. Tuberculous meningitis leads to a mild increase of 50 to 300 mg/dL.
   4. For fungal meningitis, the increase may be 50 to 300 mg/dL.
   5. Viral meningitis, the increase is mild < 200 mg/dL.
   6. Subarachnoid hemorrhage.
   7. Nonbacterial conditions like Uremia, Hypercalcemia,
   8. Dehydration.
   9. Hypercapnia.
   10. Cerebral thrombosis.
   11. Diabetic neuropathy.
   12. Myxedema.
   13. Hypoparathyroidism.
   14. Drug toxicity, e.g., Phenothiazine, ethanol, and phenytoin.
   15. Guillain-barre syndrome.
   16. Autoimmune diseases.

6. Decreased CSF protein seen in:

   1. Leakage of CSF due to trauma.
   2. Intracranial hypertension.
   3. Hyperthyroidism.
   4. Removal of the large volume of CSF.
   5. Young children between 6 months to 2 years of age.

CSF proteins comparison with serum proteins:

Cerebrospinal Fluid (CSF) Gamma globulin:

1. The albumin is smaller than the globulins, so the globulins cannot cross the blood-brain barrier.
   1. Any alteration in the permeability leads to leakage, and these globulins are found in the spinal fluid.
   2. With raised IgG level and increased IgG ratio to other proteins (albumin), detection of the oligoclonal band is highly suggestive of inflammatory and autoimmune diseases.
2. This is increased in:
   1. Infections or inflammatory processes like meningitis, encephalitis, or myelitis.
   2. A demyelinating disease like multiple sclerosis.
   3. Neurosyphilis.
   4. Other immunologic degenerative diseases.
   5. Guillain-Barre syndrome.

Oligoclonal bands on CSF electrophoresis:

1. These are several narrow bands in the gamma region of CSF electrophoresis called oligoclonal bands.
2. The oligoclonal band is characteristic of multiple myelosclerosis.
3. The ordinary cellulose acetate electrophoresis will not show the oligoclonal band.
   1. This band is seen in polyacrylamide gel, high-resolution agarose, or immunodiffusion methods.
4. The oligoclonal band is seen in 85% to 90% of patients with multiple myelosclerosis.
5. This narrow band may be seen in:
   1. Subacute sclerosing panencephalitis.
   2. Destructive brain lesions.
   3. Brain vasculitis.
   4. SLE.
   5. Sjogren syndrome.
   6. Diabetes mellitus.
   7. Guillain-Barre syndrome.

Cerebrospinal Fluid Analysis: CSF electrophoresis showing the oligoclonal band

CSF Chloride:

1. The chloride concentration in the CSF is higher than in the serum because the protein concentration in the CSF is low.
   1. The normal concentration is 120 to 132 meq/L.
   2. It falls in the CSF in case of bacterial meningitis due to increased proteins in the CSF.
2. This test is not done routinely unless requested.
3. Decreased Chloride is seen in:
   1. Bacterial meningitis.
   2. Tuberculous meningitis.
   3. In low blood chloride level.
4. Its raised level is not neurologically significant; it correlates with the blood chloride level.

CSF lactate dehydrogenase (LDH):

1. The source of LDH is neutrophils, which fight with the bacteria.
2. LDH helps diagnose bacterial meningitis, particularly isoenzyme 4 and 5.
3. It is raised in CNS leukemia, with an increased cell count.
   1. The nerve tissue in the CNS is also high in the LDH isoenzymes 1 and 2.
4. It is also raised in Stroke.
5. The CSF lactate is useful in differentiating bacterial meningitis from viral meningitis.
   1. In viral meningitis, it is <3 mmol/L (normal range).
   2. >4.2 mmol/L indicates bacterial meningitis, including TB meningitis or fungal meningitis.
   3. This is also raised in non-Hodgkin’s lymphoma with meningeal involvement, severe cerebral malaria, head injury, and anoxia.

CSF Lactic acid:

1. CSF lactic acid does not readily pass through the blood-brain barrier; elevated blood lactic acid levels are not reflected in the CSF.
   1. Chronic cerebral hypoxemia or cerebral ischemia is associated with elevated CSF lactic acid levels.
   2. Raised in cerebral hypoxia or ischemia.
2. CSF level of lactic acid increases in bacterial and fungal meningitis.
3. CSF level of lactic acid is normal in viral meningitis.
4. The lactic acid level can also be increased in patients with some forms of mitochondrial diseases that affect the CNS.

CSF protein electrophoresis:

1. Indication:
   1. Electrophoresis is done to find any abnormality of the proteins and immunoglobulins.
2. This helps diagnose:
   1. Multiple sclerosis.
   2. Neurosyphilis.
   3. Autoimmune diseases.
3. In Myelosclerosis, typical findings are:
   1. Increased total proteins and this is mainly gamma globulins.
   2. The gamma region has a discrete sharp band called the oligoclonal band.
4. The oligoclonal band may be seen in HIV.
5. Electrophoresis differentiates CSF from serum, where there is an extra band of transferrin in CSF and not in the serum.

CSF Microscopic examination

1. Normal CSF has very few mononuclear cells. Essentially free of cells.
2. Normal cell count:
   1. Adult = 0 to 5/cmm.
   2. Newborn = 0 to 30/cmm.
   3. Child = 0 to 15/cmm.
3. Neutrophils = 0 to 6% of the total cell count.
   1. Lymphocytes = 40 to 80 % of the total cell count.
   2. Monocytes = 25 to 45 % of the total cell count.
4. Neutrophils in bacterial meningitis may increase from 1000/cmm to > 20,000 /cmm.

Increased Neutrophils are seen in:

1. Bacterial meningitis.
2. Viral meningitis.
3. Tuberculous meningitis.
4. Fungal meningitis.
5. Amoebic encephalomyelitis.
6. Abscess in an early stage.
7. Metastatic tumors.
8. Reaction to repeated lumbar puncture.

Increased Lymphocytes are seen in:

1. Viral meningitis.
2. Syphilis with CNS involvement.
3. Tuberculous meningitis.
4. Multiple sclerosis.
5. Guillain-barre syndrome.
6. Sarcoidosis of meninges.
7. HIV.
8. Fungal meningitis.
9. Polyneuritis.

Increased Monocytes are seen in:

1. Chronic bacterial meningitis.
2. Multiple sclerosis.
3. Rupture of brain abscess.

Plasma cells were seen in:

1. Multiple sclerosis.
2. Sarcoidosis.
3. Acute viral infection.
4. Infiltrate by multiple myeloma.
5. Tuberculous meningitis.
6. Parasitic infestation.
7. Guillain-barre syndrome.

Eosinophils are seen in:

1. Parasitic infestation.
2. Fungal infection.
3. Sarcoidosis.
4. Rocky Mountain spotted fever.

Macrophages are seen in:

1. These may be seen in TB or viral meningitis.

Findings in different types of meningitis:

 Normal/Abnormal findings of CSF