Macroscopic (gross) Examination OF CSF (Cerebrospinal Fluid)

• ROUTINE LABORATORY EXAMINATION OF CSF

Macroscopic (gross) Examination OF CSF

Appearance of Cerebrospinal Fluid (CSF)

Turbidity of Cerebrospinal Fluid (CSF)

Blood in Cerebrospinal Fluid (CSF)

Clot of Cerebrospinal Fluid (CSF)

Cells count in Cerebrospinal Fluid (CSF)

Calculations of blood cells count in csf

Cells in CSF in various disease conditions

Macroscopic (gross) Examination OF CSF

Appearance- Normal CSF is clear and colourless. Colour can be evaluated by holding CSF tube beside a distilled water tube against a clean white paper.

Turbidity- Apurulentor turbidor markedly cloudy CSF is associated with meningitis 

caused by pyogenic bacteria such as Neisseria meningitidis, Streptococcus pneumoniae, and Haemophilus influenzae. The turbidity may be due to large numbers of pus cells (leucocytes above 200 x 10°/) or bacteria. It may be slightly cloudy in tuberculous or viral meningitis and trypanosomiasis.

Blood- The presence of blood in CSF is often a result of traumatic lumbar puncture. Pathological causes of blood in CSF include a recent subarachnoid bleeding and meningoencephalitis caused by pathogenic amoebae such as Naegleria species. Blood stained CSF is not suitable for biochemical analysis. 

If blood in CSF is due to a traumatic tap, the first tube collected will contain more blood than the succeeding tubes. If all the tubes are bloody to the same degree a haemorrhage in the brain or spinal cord is more likely.

Xanthochromia Pale yellow or yellow coloured CSF is described as xanthochromic. It is associated with the breakdown of haemoglobin as a result of earlier subarachnoid haemorrhage, cerebral tumour or jaundice. Yellow colour may also be due to high level of protein (over 100 mg %) or contamination of CSF by iodine or methiolate used to disinfect the skin.

Note

1. Xanthochromia due to subarachnoid bleeding appears in CSF within 2-12 hours in most cases.

2. Xanthochromia due to jaundice appears within 2-4 days and may persist for up to 40 days.

3. Blood in CSF due to subarachnoid bleeding may disappear within 24 hours but generally persists for up to 14 days.

Clot:- Clotting or coagulation occurs on standing in specimen containing enough fibrinogen. It is usually indicative of markedly elevated protein concentration. It can also occur in moderately elevated protein concentration as in TB meningitis where a web-like clot usually forms; this usually contains the tubercle bacilli. Clotting is also a common feature of traumatic tap.

Cell Count:- Normally there are no red cells in CSF. The normal white cell count in CSF is 0-5/cu.mm. (ul). A predominance of polymorphonuclear cells indicates a pyogenic bacterial infection while the presence of many mononuclear cells indicates a viral, tubercular or fungal infection.

Many workers place emphasis on white blood cell count only. The argument is that the number of red blood cells counted is not an important diagnostic tool. What is important is to describe CSF as slightly, moderately or grossly blood stained.

The rules of counting cells in blood are loosely applied to CSF. The Fuch-Rosenthal counting chamber was originally designed for counting cells in CSF. It has a depth of 0.2 mm and the ruled area has 16 squares, 1 mm-each, divided by triple lines. Each of these 16 squares is subdivided into 16 smaller squares, each with an area of 1/16 of 1 mm. The new type of Fuch-Rosenthal counting chamber has the same depth but is ruled over 9 mm* only. Many workers prefer to use the popular improved Neubauer counting chamber which has a depth 0.1 mm and is ruled over 9 mm'.

Diluting the CSF- CSF is diluted 1:20 with the WBC diluting fluid which lyses all the red blood cells present and makes the WBC easily visible. A suitable diluting fluid is 2% acetic acid (20 ml per litre) tinged with a few drops of crystal or gentian violet. This fluid also stains the white cells. 

A simple, though not very accurate, method for dilution is I drop of CSF + 19 drops of diluting fluid. The drops must be of the same size. Leave for about 2-3 minutes and then charge the chamber to count the white cells.

For a clear and colourless CSF the count can be done using the neat specimen.

 Calculations

1. Count cells in 4 large squares (4 mm) of improved Neubauer counting chamber.

Number of cells counted =N

Dilution factor = 20

Depth of chamber = 0.1

Therefore white cell count =  N×50/CU MM

2. Using improved Neubauer counting chamber and neat sample.

White cell count = 
 

3. Using Fuch-Rosenthal counting chamber and neat sample

Count cells in 5 large square = N

Cell count is N cells/cu.mm

Differential count Spin the CSF and make smears from the deposit. Stain with Leishman or Giemsa stain as for blood smear. Count the cells, expressing the number and type of white blood cells as percentages, with more emphasis on polymorphs and mononuclear cells. For example, polymorphs 70%, mononuclear cells 30%. If any abnormal cells, such as tumor cells are detected, the specimen should be referred for 

cytological examination.

Types of cells in CSF in various disease conditions:

1. Large numbers of polymorphs are seen inpyogenic meningitis caused by	2. Mixed cellular representation (polymorphs,lymphocytes and monocytes) is seen in cases of	3. Large numbers of lymphocytes and monocytes are seen in cases of
- Neissria meningitidis – -- Haemophilus influenzae - Streptococcus pneumoniae - Streptococcus Group B - Staphyloccus aureus - Escherichia coli	- Subacute bacterial meningitis - Tuberculous meningitis - Fungal meningitis - Viral meningoencephalitis	- Viral meningoencephalitis - Multiple sclerosis - Tuberculous meningitis - Fungal meningitis - Syphilitic meningitis