What is a Cerebrospinal Fluid (CSF) Analysis?
Cerebrospinal fluid (CSF) is a clear, colorless, watery fluid that flows in and around your brain and spinal cord. Your brain and spinal cord make up your central nervous system. It controls and coordinates everything you do, including your ability to move, breathe, see think, and more.
Cerebrospinal fluid acts like a cushion that helps protect your brain and spinal cord from sudden impact or injury. The fluid also removes waste products from the brain and helps your central nervous system work properly.
Other names: Spinal Fluid Analysis, CSF Analysis
What is it used for?
A CSF analysis is used to measure different substances in your cerebrospinal fluid. It may include tests to diagnose:
- Infectious diseases of the brain and spinal cord, including meningitis and encephalitis. CSF tests for infections look at white blood cells, bacteria, and other substances in the cerebrospinal fluid
- Autoimmune disorders, such as Guillain-Barré Syndrome and multiple sclerosis (MS). CSF tests for these disorders look for high levels of certain proteins in the cerebrospinal fluid.
- Bleeding in the brain
- Brain tumors, including from cancers in other parts of the body that may spread to the central nervous system
- Alzheimer's disease, the most common form of dementia, which includes memory loss, confusion, and changes in behavior
Why do I need a CSF analysis?
Your health care provider may order a CSF analysis if you have:
- 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
Symptoms of a brain or spinal cord infection include:
- Severe headache
- Stiff neck
- Nausea and vomiting
- Sensitivity to light
- Double vision
- Changes in behavior
Symptoms of MS often vary and come and go, or they may steadily get worse. They may include:
What happens during a CSF analysis?
To get a sample of cerebrospinal fluid, a provider will do a procedure called a spinal tap, also known as a lumbar puncture. A spinal tap is usually done in a hospital. During the procedure:
- You will lie on your side or sit on an exam table.
- A provider will clean your back and inject an anesthetic into your skin, so you won't feel pain during the procedure. Your provider may put a numbing cream on your back before this injection.
- When the area on your back is completely numb, your provider will insert a thin, hollow needle between two vertebrae in your lower spine. Vertebrae are the small backbones that make up your spine.
- Your provider will withdraw a small amount of cerebrospinal fluid for testing. This will take about five minutes.
- You'll need to stay very still while the fluid is being withdrawn.
- Your provider may ask you to lie on your back for an hour or two after the procedure. This may prevent you from getting a headache afterward.
Will I need to do anything to prepare for the test?
You don't need any special preparations for a CSF analysis, but you may be asked to empty your bladder (pee) and bowels (poop) before the test.
Are there any risks to the test?
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 where the needle was inserted.
You may also have some bleeding at the site or get a headache. The headache may last for several hours or up to a week or more, but your provider may suggest treatment to help relieve the pain.
What do the results mean?
A CSF analysis may include a variety of different tests on your sample. So, the measurements on your test results will depend on which tests were done. Your provider can explain what your results mean.
In general, your CSF analysis results may show that you have an infection, an autoimmune disorder, such as multiple sclerosis (MS), or another disease or injury of the brain or spinal cord. Your provider will likely order more tests to confirm your diagnosis.
Learn more about laboratory tests, reference ranges, and understanding results.
Is there anything else I need to know about a CSF analysis?
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.
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