What Is Cerebrospinal Fluid?

Cerebrospinal fluid (CSF) is a clear fluid made in the brain. It coats and protects the brain and spinal cord.

Reason for the Test

You may need a CSF test to look for:

• An infection in the brain or spinal tissues, such as meningitis
• Bleeding in or around the brain
• Inflammation, cancer, dementia, or other health problems of the nervous system

Your doctor may also want to measure the pressure of the fluid in your spinal column.

Type of Sample Taken

CSF will be drawn in a process called a lumbar puncture. This is also called a spinal tap.

During the Sample Collection

This test is done in a clinic or hospital. You will be asked to lie on your side with your knees pulled up to your belly. An area on your back will be cleaned with an antiseptic fluid. An anesthetic medicine will be injected into the area. It will help to numb the area. A second needle will be placed through your lower back and into your spinal canal. A sample of CSF flows into the needle. The pressure of the CSF may be measured.

There is usually a little pain when the needle is first inserted. It should go away in a few seconds. The test may take a half an hour, although the needle may only be in your spine for a few minutes. After the needle is taken out, the area will be cleaned and bandaged.

After Collecting the Sample

You will likely rest lying down.

Drink extra fluid and do not exert yourself for the next 24 hours. You may have these problems after the test:

• Severe headache or headache that lasts more than 24 hours
• Nausea or vomiting
• Signs of infection, such as fever and chills
• Redness, swelling, more pain, bleeding, or leaking from the site of the spinal tap
• Tingling
• Numbness, pain, or weakness in your lower back and legs
• Problems with urination
• Headache
• Stiff neck
• Mental confusion

Call your doctor right away if you have any of these problems. It is rare, but the procedure may cause blood in the spinal fluid or damage to the spinal cord. Let your doctor know if you have any unusual problems after the test.

Results

How long it takes to get your results depends on the urgency of your health and where the test was done. It may take many hours or up to 2 days. Your doctor may do more tests to make a diagnosis.

Findings vary, but can be used to help diagnose:

• Meningitis
• Syphilis
• Subarachnoid hemmorhage
• Multiple sclerosis

Depending on what condition is suspected, the fluid may also be analyzed for:

• Bacteria or other organisms
• Specific proteins for things like multiple sclerosis, Alzheimer disease, and prion diseases
• Cancer cells or tumor markers

Talk to your doctor about your test results. A test may point to an illness that you do not have. It can also miss an illness that you may have. The doctor will check your symptoms and all test results before making a diagnosis.