Cerebrospinal Fluid Results (CSF) Interpretation

Cerebrospinal fluid (CSF) is collected by performing a lumbar puncture on your patient.  This is performed if the doctor suspects certain conditions such as meningitis or subarachnoid haemorrhage.

You will not be expected to know this skill for examinations, however you may be asked to interpret some CSF results.

This station tests your knowledge of both the normal values of various components of CSF, and also your ability to make a differential diagnosis of a condition purely from a set of CSF results.

Subject steps

  1. The most important knowledge to have for this station are the normal values. The most important of these are given in the table below. Note that these are for adults only:

  2. Systematically you will now take the examiner through the results which have been given. Start at the top and comment whether each result is normal or not. If any result is abnormal, it should be commented whether the result is slightly or very deranged.

    Normal Range

    Appearance
    Clear & colourless

    White Cells
    0 – 5 x 106 per litre (all lymphocytes with no neutrophils)

    Red Cells
    0 – 10 x 106 per litre

    Protein
    0.2 – 0.4 grammes per litre (or less than 1% of the serum protein concentration)

    Glucose
    3.3 – 4.4 mmol per litre (or ≥ 60% of a simultaneously derived plasma glucose concentration)

    pH
    7.31

    Pressure
    70 – 180 mmH2O

  3. Now it will be most likely that you are asked to make a differential diagnosis based upon the results given. A number of conditions give deranged CSF readings and therefore knowledge of which conditions affect the different values is vital.

    The changes in various conditions are given below:

    Bacterial Meningitis

    Appearance
    Cloudy & Turbid

    White Cells
    Raised neutrophils

    Red Cells
    Normal

    Protein
    High or Very High

    Glucose
    Very Low

    Viral Meningitis

    Appearance
    Normal

    White Cells
    Raised lymphocytes

    Red Cells
    Normal

    Protein
    Normal or High

    Glucose
    Normal or Low

    Tuberculous Meningitis

    Appearance
    Normal or Slightly Cloudy

    White Cells
    Raised lymphocytes

    Red Cells
    Normal

    Protein
    High or Very High

    Glucose
    Very Low

    Subarachnoid Haemorrhage

    Appearance
    Usually blood stained

    White Cells
    Normal

    Red Cells
    Very High

    Protein
    Normal or High

    Glucose
    Normal or Low

    Guillan-Barré Syndrome

    Appearance
    Normal

    White Cells
    Normal

    Red Cells
    Normal

    Protein
    High (only after one week)

    Glucose
    Normal or Low

    Multiple Sclerosis

    Appearance
    Normal

    White Cells
    Raised lymphocytes

    Red Cells
    Normal

    Protein
    High

    Glucose
    Normal

  4. Although initially daunting, obvious patterns will become recognisable. It is also more likely that you will be asked about the more common conditions, such as bacterial and viral meningitis.

    If the condition asked about is either kind of meningitis, it is most likely that a causative organism will be asked for. Therefore make sure to learn the common causes of meningitis for varying age groups as well as the treatment.