Cerebrospinal fluid analysis

Cerebrospinal fluid (CSF), a clear, colorless fluid produced in the brain, contains glucose, proteins, and other substances also found in the blood. CSF surrounds the brain and spinal cord, serving as a cushion for the brain in the skull. CSF bathes the brain and spinal cord with nutrients filtered from the blood and helps to eliminate waste products from the brain. CSF analysis can be used to diagnose a number of neurologic diseases, including MS.

In some situations, analysis of a patient’s cerebrospinal fluid (CSF) may be needed to confirm a diagnosis of MS. CSF is obtained during a lumbar puncture, a procedure that involves insertion of a needle into the lower spine to withdraw enough fluid for analysis. Analysis of cerebrospinal fluid may not be required to make an MS diagnosis, but it can be useful in ruling out other diseases.

How does analysis of cerebrospinal fluid provide evidence of MS?

Analysis of cerebrospinal fluid measures levels of glucose, white blood cells, proteins, bacteria, and abnormal cells. In testing for changes indicative of MS, CSF analysis measures immune system proteins called immunoglobulins (or antibodies), specifically immunoglobulin G, A, or M (IgG, IgA, IgM). The patient’s blood is also tested and the results are compared. Elevated levels of IgG and other immune system proteins found in the CSF but not in the blood indicate the kind of abnormal immune response seen in MS.

While blood cells called B-lymphocytes secrete immunoglobulins (IgG) in response to invasion of a foreign substance (an antigen) in the body. In MS, IgG is thought to be produced within the brain. This means that IgG does not pass into the cerebrospinal fluid from the blood, but is produced by a certain group of immune cells within the CNS.

When a specific type of IgG is present in the cerebrospinal fluid, a method of DNA analysis called protein electrophoresis will result in oligoclonal bands (shown below). Oligoclonal bands (O-bands) are present in the cerebrospinal fluid of 80% to 90% of people with MS. However, CSF analysis is normal in 10% to 20% of people with MS and O-bands are also present with other diseases, thus results from CSF analysis cannot be used alone to diagnose MS.

Revised McDonald Criteria provide guidelines for using increased levels of IgG and the presence of oligoclonal bands to help confirm diagnosis of MS.

Written by: Jonathan Simmons | Last reviewed: May 2015.
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