Cerebrospinal Fluid Collection and Testing

What is Cerebrospinal fluid (CSF)?

Cerebrospinal fluid (CSF) is formed within the brain. It circulates through the spaces both within and surrounding the brain. A major function is to protect the brain and spinal cord, acting as a cushion or shock absorber.

What is the purpose of CSF testing?

Due to its intimate contact with the nervous tissue of the brain and spinal cord, examination of CSF often yields important clues to assist in the diagnosis of patients showing clinical signs such as inco-ordination, fits (seizures), paralysis, etc.

How is CSF collected?

A general anaesthetic is usually necessary since a special needle has to be inserted into the spinal canal and stillness is essential. The sample can be obtained either from a site just at the back of the head (cerebellomedullary cistern) or just in front of the pelvis (lumbar cistern).

The site is shaved so that the skin can be sterilized- similar to the procedure when a blood sample is taken from the neck or leg. Only a small quantity of CSF is required, usually 2-3ml (about half a teaspoon).

What risks are involved with CSF collection?

The usual risks involved with general anaesthesia have to be considered. These are usually minimal since the procedure only takes a few minutes. However if we have any concerns we will discuss these with you and may advise some additional pre-anaesthetic tests.

In addition there are certain risks specific to CSF collection. These include:-

1.  Damage to nerve tissue due to needle insertion.

2.  Introduction of infection

3.  Herniation problems that can sometimes occur if the CSF pressure is very high

We will be more than happy to discuss your concerns and explain the risks and benefits of the procedure

How does CSF investigation help?

Laboratory examination of the sample will give an indication of the various constituents and highlight any abnormalities. Sometimes bacteria, other infective organisms or abnormal cells (eg cancer cells) are isolated which can lead to a rapid specific diagnosis. Alternatively specific antibody tests may be necessary in some cases to establish if infections such as toxoplasmosis or crptococcosis are present.

Does CSF evaluation usually provide a definite diagnosis?

As indicated above, this is possible (e.g. meningitis, toxoplasmosis, etc.). However more usually it will provide further evidence to support the most likely diagnosis already suspected based upon the age, breed and clinical signs being shown by the patient.