Cerebrospinal fluid (CSF) is a clear, colorless liquid that surrounds the brain and spinal cord. While the primary function of CSF is to cushion the brain within the skull and serve as a shock absorber for the central nervous system, CSF also circulates nutrients and chemicals filtered from the blood and removes waste products from the brain. In MS, damage to myelin causes certain types of proteins to be released into the spinal fluid. When these proteins are identified in the spinal fluid, but not in the blood, MS is thought to be one of the possible diagnoses. Spinal fluid is obtained through a lumbar puncture (also known as a spinal tap). In this procedure, while lying on your side or bending forward while seated, an area of your lower back is cleansed and a numbing medicine is injected. Following this a hollow needle is inserted and small amount of spinal fluid is removed with a syringe and sent for testing.
The CSF of people with MS usually contains:
- A specific group of proteins called oligoclonal bands
- Elevation of the level of protein
These findings indicate an abnormal immune response within the central nervous system, and may be suggestive of MS. It is important to know that an abnormal immune response in the CSF is found in a number of other diseases, so the test is not specific for MS. In people with a confirmed diagnosis of MS, 5-10% do not show abnormalities in the CSF. Therefore, CSF analysis by itself cannot confirm or exclude a diagnosis of MS
. The results are used in combination with the history, neurological examination, MRI and other tests to help make an accurate diagnosis.