Cerebrospinal fluid (CSF) analysis is a laboratory test to examine a sample of the fluid surrounding the brain and spinal cord. This fluid is a clear, watery liquid that protects the central nervous system from injury and cushions it from the surrounding bone structure. It contains a variety of substances, particularly glucose (sugar), protein, and white blood cells from the immune system. The fluid is withdrawn through a needle in a procedure called a lumbar puncture.
The purpose of a CSF analysis is to diagnose medical disorders that affect the central nervous system. Some of these conditions include:
bleeding (hemorrhaging) around the brain and spinal cord
multiple sclerosis, a disease that affects the myelin coating of the nerve fibers of the brain and spinal cord
Guillain-Barré syndrome, an inflammation of the nerves.
In some circumstances, a lumbar puncture to withdraw a small amount of CSF for analysis may lead to serious complications. Lumbar puncture should be performed only with extreme caution, and only if the benefits are thought to outweigh the risks, in certain conditions. For example, in people who have blood clotting (coagulation) or bleeding disorders, lumbar puncture can cause bleeding that can compress the spinal cord. If there is a large brain tumor or other mass, removal of CSF can cause the brain to droop down within the skull cavity (herniate), compressing the brain stem and other vital structures, and leading to irreversible brain damage or death. These problems are easily avoided by checking blood coagulation through a blood test and by doing a computed tomography scan (CT) or magnetic resonance imaging (MRI) scan before attempting the lumbar puncture. In addition, a lumbar puncture procedure should never be performed at the site of a localized skin infection on the lower back because the infection may be introduced into the CSF and may spread to the brain or spinal cord.
Martha Floberg Robbins, The Gale Group Inc., Gale, Detroit,