Cerebrospinal Fluid (CSF) Analysis

Cerebrospinal fluid analysis is a group of tests that examine what’s in your cerebrospinal fluid (CSF). CSF is a clear fluid that cushions your brain and spinal cord.

CSF typically contains water, small amounts of proteins, nutrients and vitamins. Your CSF fluid can change if you have a condition that affects your brain or spinal cord. The fluid can have irregular cells, proteins or bacteria in it. Providers can test a sample to detect these changes. Abnormal results may mean there’s a problem in your central nervous system (brain and spinal cord). A CSF analysis helps your provider figure out what’s wrong.

A lumbar puncture (spinal tap) is the most common way healthcare providers collect CSF.

Your provider may order this test if you have:

• Symptoms that point to a brain or spinal cord infection. These include things like confusion, severe headaches and a stiff neck.
• Symptoms of an autoimmune disease. This includes changes to your vision, loss of balance or muscle weakness.
• A brain or spinal cord injury.
• Changes to your mental status, like mood swings, irritability and depression.

Other times, providers order it to see if cancer has spread into your central nervous system.

What does CSF analysis test for?

CSF analysis helps providers diagnose problems that affect your brain and spinal cord. This includes things like:

• Infections, like meningitis, encephalitis and tuberculosis
• Swelling or other inflammation
• Autoimmune diseases, like multiple sclerosis (MS) or Guillain-Barré syndrome
• Brain bleeds
• Cancer or brain tumors
• Other neurological conditions, like Alzheimer’s disease

Your provider looks at these features and substances in a sample of your CSF:

• Color, clarity and pressure of CSF when they collect the sample
• Glucose
• Protein
• White and red blood cell count
• Bacteria, fungi, viruses
• Antibodies

Some advanced CSF tests may look at things like glutamine, oligoclonal bands and other specific proteins and enzymes.

What can I expect during CSF analysis?

Collecting CSF almost always involves a spinal tap. There are other ways to get CSF, but this is the go-to method. If you can’t have a spinal tap for any reason, there are other ways your provider can obtain a sample of your CSF.

Here’s what you can expect:

1. Your provider cleans an area in your lower back. They apply medications to numb the area, so you feel less pain. You may still feel discomfort and pressure.
2. They insert a thin, hollow needle between two vertebrae in your lower spine. They withdraw a small amount of CSF fluid to test.
3. You must stay very still during the collection. Once they collect the fluid, your provider may ask you to lie down afterward.

You usually don’t need to do anything to prepare for CSF analysis. Just be sure to tell your healthcare provider about any medications or allergies you have before the spinal tap.

Ask your provider if there are special precautions to take after CSF analysis. For example, you may need to avoid exercise or heavy lifting for 24 hours.

How long does it take?

Collecting CSF should take fewer than 30 minutes. You may need to lie down for 30 to 60 minutes after. This could prevent you from getting a headache.

What are the risks and side effects?

There can be mild side effects after the spinal tap. The most common are headaches, back pain and bruising. Rare side effects could include bleeding, infection or tingling in your legs.

Let your provider know if you have severe headaches, fever or numbness after the test. This could mean there was a complication.

What to expect after the test?

You should be able to go back to your normal activities after a CSF analysis. Your provider may ask that you take it easy for the rest of the day. Avoid lifting heavy objects or exercising for at least 24 hours. You should stay hydrated and drink lots of water, too.

Your test results should be ready within a week or so. It depends on what your provider is looking for. Some test results can take longer to come back than others.

What type of results do you get and what do the results mean?

There are normal ranges or values for all the substances in your CSF.

Each of the substances measured in the CSF analysis will have a number next to it. Next to that, it might have the typical range and if your result was higher or lower. Ranges can vary between laboratories.

Here is a general breakdown of what abnormal results on a CSF analysis may mean:

• Color and opening pressure: CSF fluid should be clear. Opening pressure describes how much pressure your CSF is under. High or low pressure can point to certain conditions.
• Glucose: Low levels may suggest an infection.
• Protein: High levels could mean inflammation or infection.
• Cell counts: High white blood cells can mean infection or inflammation. High red blood cells could mean there’s bleeding somewhere.
• Antibodies: CSF shouldn’t contain antibodies. If the test detects antibodies, it could mean you have an infection or autoimmune condition.

If bacteria, viruses or fungi are in CSF fluid, you’ll receive a positive culture. If you don’t have those substances in your fluid, the result will be negative.

Remember, only your healthcare provider can tell you what your test results mean and what comes next.

If the results are abnormal, what are the next steps?

Your healthcare provider uses abnormal results to make a diagnosis and decide how best to treat you. Your provider may also order additional tests after a CSF analysis. These could include imaging tests, like a CT scan or MRI.

A CSF analysis isn’t based on just one value. Your provider will look at the combination of all your results and symptoms so they can see the big picture. For example, CSF with high white blood cell count and high protein with severe headaches points to bacterial meningitis. But high protein and headaches could be bleeding around your brain.

Call your healthcare provider if you have any questions about your test results. They can explain what your results mean and what comes next.