Cerebrospinal Fluid (CSF) Analysis

Urgent safety information

Some infections, such as meningitis caused by bacteria, are life-threatening emergencies. If your provider suspects you have bacterial meningitis or another serious infection, you may need to start medicine before you have a final diagnosis.

Why this test may be ordered

• Symptoms of an infection or bleeding in the brain or spinal cord
• Symptoms of an autoimmune disorder, such as multiple sclerosis (MS)
• Had a brain injury or an injury to your spinal cord
• Have cancer that may have spread to your central nervous system
• Symptoms that may be from another central nervous system condition, such as headaches

Preparation and collection

You don't need any special preparations, but you may be asked to empty your bladder and bowels before the test.

A provider will perform a spinal tap (lumbar puncture): you lie on your side or sit, your back is cleaned and numbed, then a thin needle is inserted between two vertebrae in your lower spine to withdraw a small amount of CSF. The fluid withdrawal takes about five minutes. You may be asked to lie on your back for an hour or two afterward.

There is very little risk to having a spinal tap. You may feel a little pinch or pressure when the needle is inserted. After the test, you may feel some pain or tenderness in your back at the site, have some bleeding, or get a headache that may last for several hours or up to a week or more. Your provider may suggest treatment to help relieve the pain.

Understanding results

A CSF analysis may include a variety of different tests on your sample. The measurements on your test results will depend on which tests were done. Your provider can explain what your results mean.

• Abnormal levels of certain substances (e.g., white blood cells, bacteria, proteins) are found: May indicate an infection, an autoimmune disorder such as multiple sclerosis (MS), bleeding in the brain, a brain tumor, or another disease or injury of the brain or spinal cord. Your provider will likely order more tests to confirm the diagnosis. Limitation: These results are not diagnostic on their own; further testing is needed to confirm a specific condition. Next step: Your provider will likely order more tests to confirm your diagnosis.
• No abnormal levels of substances are found: May suggest that your central nervous system is not affected by the conditions tested for, or that the condition is not detectable by this analysis. Your provider will interpret this result in the context of your symptoms and other tests. Limitation: A normal result does not rule out all central nervous system conditions. Next step: Your provider may recommend other tests or follow-up based on your symptoms.

• The test results depend on which specific tests are included in the analysis.
• A normal result does not rule out all central nervous system conditions.
• Abnormal results are not diagnostic on their own; further testing is needed to confirm a specific condition.

What to do next

Your provider will explain what your results mean and may order more tests to confirm a diagnosis.

• What specific tests are included in my CSF analysis?
• What do my results mean for my health?
• Do I need any additional tests or follow-up?

Evidence source

U.S. National Library of Medicine: Cerebrospinal Fluid (CSF) Analysis