CSF cell count

Definition
A CSF cell count is a test to measure the number of red and white blood cells that are in cerebrospinal fluid (CSF). CSF is a clear fluid that circulates in the space surrounding the spinal cord and brain.

How the test is performed
The CSF is usually obtained through a lumbar puncture (spinal tap). The cerebrospinal fluid is analyzed in the lab.

How to prepare for the test
Drink plenty of water prior to the test.

Infants and children:
The preparation you can provide for this or any test or procedure depends on your child’s age, previous experience, and level of trust. For specific information regarding how you can prepare your child, see the following:

How the test will feel

Patients will be asked to either sit up or lie down on their sides with the back parallel to the bed and the chin tucked under and the legs curled in the fetal position. The healthcare provider will use the bony protrusions of the hip to determine the most appropriate location to remove fluid. This is usually at what is known as the L3-L4 vertebral level.

Subsequently iodine will be used to clean off the area and a sterile sheet will be draped over the surrounding area. In infants and small children, EMLA cream, a local anesthetic cream will be used to numb the skin and will be applied about 1 hour prior to the procedure. In adults, lidocaine will be injected under the skin initially, and then deeper such that tissue beneath the skin will also be numbed.

A thin 20-gauge needle will then be inserted into the interspace between the vertebra. Depending on how much subcutaneous tissue there is, this may require shallow or deeper penetration of the needle. There may be an audible “pop” when the needle penetrates the dura (membrane that surrounds the spinal cord and encases the fluid).

At that point there will be fluid flowing out of the needle and this will be collected in plastic containers. Under normal circumstances, the opening pressure will be measured with a manometer and then about 20-30 cc of spinal fluid will be collected and sent for evaluation under the microscope.

Under experienced hands there should not be any pain. There may be a feeling of pressure when the needle is inserted but with appropriate anesthetic, this should not hurt. Occasionally, some people may feel numbness shooting down the leg. This may be due to irritation of a nerve root.

The needle is withdrawn, the sensation subsides and is not permanent. Following the procedure, the patient is advised to remain lying down for an hour or two to prevent low-pressure headaches. The entire procedure takes approximately 20 minutes.

Why the test is performed
The CSF cell count may help diagnose Meningitis and infection of the brain or spinal cord, a tumor, abscess, or area of tissue death (infarct), and it helps identify inflammation. The cell count may also help identify a hemorrhage.

Normal Values
The normal white blood cells are between 0 and 5. The normal red blood cell count is 0.

What abnormal results mean
An increase of white blood cells indicates infection, inflammation or bleeding into the cerebrospinal fluid. Some causes include:

     
  • Meningitis (inflammation of the membranes covering the brain and spine)  
  • encephalitis (inflammation of the brain substance itself)  
  • acute infection  
  • tumor  
  • abscess  
  • infarct  
  • multiple sclerosis  
  • hemorrhage

The finding of red blood cells may indicate a hemorrhage. However, red blood cells in the CSF may also be due to a traumatic spinal tap which can happen if the spinal tap needle hits a blood vessel while entering the skin or dura. It is important to see if the red blood cell count clears in samples taken later in the procedure as opposed to earlier. A ratio of the red blood cells to the white blood cells is also calculated to help with diagnosis.

Additional conditions which this test may help diagnose include:

     
  • Arteriovenous malformation (cerebral)  
  • cerebral aneurysm  
  • delirium  
  • Dementia  
  • epilepsy  
  • Guillain-Barre  
  • Hemorrhagic stroke  
  • neurosyphilis  
  • primary lymphoma of the brain  
  • spinal tumor  
  • stroke secondary to syphilis  
  • syphilitic aseptic meningitis  
  • syphilitic myelopathy

What the risks are

     
  • Risks of lumbar puncture include:       o hypersensitivity (allergic) reaction to the anesthetic       o discomfort during the test       o headache after the test       o bleeding into the spinal canal       o infection  
  • Brain herniation (if performed on a person with increased intracranial pressure), resulting in brain damage and/or death. This test is not done if an examination or a CT scan or MRI reveals signs of increased intracranial pressure.  
  • Damage to the spinal cord does not occur as the needle is inserted below the level where the cord ends. However, there may be transient leg discomfort if a nerve root is irritated by the needle. This passes when the needle is withdrawn and replaced.

Johns Hopkins patient information

Last revised: December 6, 2012
by Simon D. Mitin, M.D.

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All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.