Is a CSF Analysis?
Cerebrospinal fluid (CSF) analysis is a way of looking for
conditions that affect your brain and spine. It’s a series of laboratory tests
performed on a sample of CSF. CSF is the clear fluid that cushions and delivers
nutrients to your central nervous system (CNS). The CNS consists of the brain
and spinal cord.
CSF is produced by the choroid plexus in the brain and then
reabsorbed into your bloodstream. The fluid is completely replaced every few
hours. In addition to delivering nutrients, CSF flows around your brain and
spinal column, providing protection and carrying away waste.
A CSF sample is commonly collected by performing a lumbar
puncture, which is also known as a spinal tap. An analysis of the sample
involves the measurement of and examination for:
- fluid pressure
- red blood cells
- white blood cells
- other invasive organisms or foreign substances
Analysis can include:
- measurement of the physical characteristics and
appearance of CSF
- chemical tests on substances found in your
spinal fluid or comparisons to levels of similar substances found in your blood
- cell counts and typing of any cells found in your
- identification of any microorganisms that could
cause infectious diseases
CSF is in direct contact with your brain and spine. Therefore,
CSF analysis is more effective than a blood test for understanding CNS
symptoms. However, it’s more difficult to obtain a spinal fluid sample than a
blood sample. Entering the spinal canal with a needle requires expert knowledge
of the spine’s anatomy and a clear understanding of any underlying brain or
spinal conditions that might increase your risk of complications from the
CSF Samples Are Taken
A lumbar puncture usually takes less than 30 minutes. It’s
performed by a doctor who is specially trained to collect CSF.
CSF is usually taken from your lower back area, or the
lumbar spine. It’s very important to remain completely still during the
procedure. This way you avoid incorrect needle placement or trauma to your
You may be seated with the spine curled forward. You may
also lie on your side with your spine curved and your knees drawn up to the
chest. Curving your spine makes a space between your bones in the lower back.
Once you’re in position, your back will be cleaned with a
sterile solution. Iodine is often used for cleaning. A sterile area is
maintained throughout the procedure. This reduces the risk of infection.
A numbing cream or spray is applied to your skin. Your
doctor will then inject anesthetic. Once the site is fully numb, your doctor
will insert a thin spinal needle between two vertebrae. A special type of X-ray
called fluoroscopy is sometimes used to guide the needle.
First, the pressure inside the skull is measured using a
manometer. Both high and low CSF pressure can be signs of certain conditions.
Fluid samples are then taken through the needle. When fluid
collection is complete, the needle is taken out. The puncture site is cleaned
again. A bandage is applied.
You’ll be asked to remain lying down for about one hour.
This reduces the risk of a headache, which is a common side effect of the
Sometimes a patient cannot have a lumbar puncture because of
a back deformity, infection, or possible brain herniation. A more invasive CSF
collection method can be used in these cases. These methods require
hospitalization. They include the following:
- During a ventricular puncture, your doctor
drills a hole into your skull and inserts a needle directly into one of the
ventricles of your brain.
- During a cisternal puncture, your doctor inserts
a needle into the back of your skull.
- A ventricular shunt or drain can collect CSF
from a tube that your doctor places in your brain. This is done to release high
CSF collection is often combined with other procedures. For
example, dye might be inserted into your CSF for a myelogram. This is an X-ray
or CT scan of your brain and spine.
of Lumbar Puncture
This test requires a signed release that states you
understand the risks of the procedure. Before the test, you’ll be asked to
empty your bowels and bladder.
Primary risks associated with lumbar puncture include:
- bleeding from the puncture site into the spinal
fluid, which is called a traumatic tap
- discomfort during and after the procedure
- an allergic reaction to the anesthetic
- an infection at the puncture site
- a headache after the test
People who take blood thinners have a heightened risk of
bleeding. Lumbar puncture is extremely dangerous for people who have clotting
problems such as a low platelet count, which is called thrombocytopenia.
There are serious additional risks if you have a brain mass,
tumor, or abscess. These conditions put pressure on your brain stem. A lumbar
puncture could then cause brain herniation to occur. This can result in brain
damage or even death.
Brain herniation is a shifting of structures of the brain.
It’s usually accompanied by high intracranial pressure. The condition
eventually cuts off blood supply to your brain. This causes irreparable damage.
The test will not be done if a brain mass is suspected
Cisternal and ventricular puncture methods carry additional
risks. These risks include:
- damage to your spinal cord or brain
- bleeding within your brain
- disturbance of the blood-brain barrier
the Test Is Ordered
CSF analysis may be ordered if you’ve had CNS trauma. It may
also be used if you have cancer and your doctor want to see if the cancer has
spread to the CNS.
In addition, CSF analysis may be ordered if you have one or
more of the following symptoms:
- severe, unremitting headache
- stiff neck
- hallucinations, confusion, or dementia
- flu-like symptoms that persist or intensify
- fatigue, lethargy, muscle weakness
- changes in consciousness
- severe nausea
- fever or rash
- light sensitivity
- numbness or tremor
- speaking difficulties
- trouble walking or poor coordination
- severe mood swings
- intractable clinical depression
Detected by CSF Analysis
CSF analysis can accurately distinguish between a wide range of
CNS diseases, which can otherwise be difficult to diagnose. Conditions found by
CSF analysis include:
Viruses, bacteria, fungi, and parasites can all infect the CNS. Certain
infections can be found by CSF analysis. Common CNS infections include:
- fungal infections
- West Nile virus
- eastern equine encephalitis virus (EEEV)
Intracranial bleeding can be detected by CSF analysis.
However, isolating the exact cause of bleeding may require additional scans or
tests. Common causes include high blood pressure, stroke, or an aneurysm.
Immune Response Disorders
CSF analysis can detect immune response disorders. The immune
system can cause damage to the CNS through inflammation, destruction of the
myelin sheath around the nerves, and antibody production.
Common diseases of this type include:
- Guillain-Barré syndrome
- multiple sclerosis
CSF analysis can detect primary tumors in the brain or
spine. It can also detect metastatic cancers that have spread to your CNS from
other body parts.
Spinal Fluid (CSF) Analysis and Multiple Sclerosis
CSF analysis may also be used to help diagnose multiple
sclerosis (MS). MS is a chronic condition in which your immune system destroys
the protective covering of your nerves, which is called the myelin. People with
MS may have a variety of symptoms that may be constant or come and go. They
include numbness or pain in their arms and legs, vision problems, and trouble
CSF analysis may be done to rule out other medical
conditions that have symptoms similar to MS. The fluid may also show signs that
your immune system isn’t functioning normally. This can include high levels of
IgG antibodies and the presence of certain proteins that form when myelin
breaks down. About 85
to 90 percent of people with MS have these abnormalities in their cerebral
Some types of MS progress quickly and can be
life-threatening within weeks or months. Looking at the proteins in CSF may
help doctors develop “keys” called biomarkers. Biomarkers can help identify the
type of MS you have earlier and more easily. Early diagnosis can help you get treatment
that could extend your life if you have a form of MS that’s rapidly
Testing and Analysis of CSF
The following are often measured in CSF analysis:
- white blood cell count
- red blood cell count
- glucose, or blood sugar
- lactate dehydrogenase, which is a blood enzyme
- antigens, or harmful substances produced by
- total proteins
- oligoclonal bands, which are specific proteins
- cancer cells
- viral DNA
- antibodies against viruses
Your Test Results
Normal results mean that nothing abnormal was found in the
spinal fluid. All measured levels of CSF components were found to be within
Abnormal results may be caused by one of the following:
- a tumor
- metastatic cancer
- encephalitis, which is an inflammation of the
- an infection
- Reye’s syndrome, which is a rare, often fatal
disease affecting children and associated with viral infections and aspirin
- meningitis, which you can get from fungus, tuberculosis,
virus, or bacteria
- viruses such as West Nile or Eastern equine
- Guillain-Barré syndrome, which is an autoimmune
condition that causes paralysis and occurs after viral exposure
- sarcoidosis, which is a granulomatous condition
of unknown cause affecting many organs (primarily the lungs, joints, and skin)
- neurosyphilis, which happens when an infection
with syphilis involves your brain
- multiple sclerosis, which is an autoimmune
disorder that affects your brain and spinal cord
Up After a CSF Analysis
Your follow-up and outlook will depend on what caused your
CNS test to be abnormal. Further testing will most likely be required in order
to get a definitive diagnosis. Treatment and outcomes will vary.
Meningitis caused by a bacterial or parasitic infection is a
medical emergency. Symptoms are similar to viral meningitis. However, viral
meningitis is less life threatening.
People with bacterial meningitis may receive broad-spectrum
antibiotics until the cause of the infection is determined. Prompt treatment is
essential to save your life. It can also prevent permanent CNS damage.