The central nervous system (CNS) consists of the brain and spinal cord. Cerebrospinal fluid (CSF) is a clear, colorless liquid that surrounds and protects the CNS. It bathes the brain and spine in nutrients and eliminates waste products. It also cushions them to help prevent injury in the event of trauma.
When a person exhibits symptoms of CNS inflammation or infection, a CSF culture may be ordered. It can help diagnose the illness and determine the appropriate treatment.
A CSF culture is used to detect infectious organisms in the CSF. The CNS is vulnerable to infection by bacteria, viruses, and fungi.
A CSF culture can help diagnose several disorders, including:
- bacterial or viral meningitis
- fungal infections
- bleeding around the brain (subarachnoid hemorrhage)
- brain and spinal cord damage
- multiple sclerosis
- Lyme disease
- Guillain-Barré syndrome
CSF pressure may also be measured at the same time a CSF culture is performed.
A lumbar puncture, or “spinal tap,” is used to collect CSF for culture. A physician will insert a needle into the space between two vertebrae in the lower (lumbar) spine. The needle will then be moved carefully into the CSF-filled space surrounding the spinal cord. When the needle is in place, fluid can drip out into a collection vial. More than one vial may be needed. The procedure can take several minutes.
Other methods can also be used to collect CSF. However, they are only used in people who have deformities of the spine or cannot otherwise have a standard lumbar puncture. A needle can be inserted under the occipital bone at the base of the brain. A hole can also be drilled directly into the skull.
Once enough CSF has been collected, it is sent to a laboratory. There it is placed in dishes containing culture medium. The dishes are monitored for the growth of infectious organisms. If there is no growth, the test is considered normal, or negative.
If bacteria, viruses, or fungi are detected in your CSF, the test is considered positive. This means there is an infection.
The CSF culture is not dangerous. However, CSF collection does have risks. Risks of lumbar puncture include:
- discomfort or pain during the procedure
- bleeding into the spinal cord, particularly in people who take blood thinners or have a low platelet count (thrombocytopenia)
- headache as a result of CSF leakage
- nerve damage
Lumbar punctures should not be performed on anyone with a brain tumor or cyst. In such cases, the procedure can cause brain damage and even death.