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.

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

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:

• Infant test or procedure preparation (birth to 1 year)
• Toddler test or procedure preparation (1 to 3 years)
• Preschooler test or procedure preparation (3 to 6 years)
• Schoolage test or procedure preparation (6 to 12 years)
• Adolescent test or procedure preparation (12 to 18 years)

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 known as the lower lumbar region.

A germ cleaning solution will be used to clean off the area. A sterile sheet will be draped over the body. In infants and small children, a numbing cream will be placed on the skin local about 1 hour before the procedure. In adults, numbing medicine will be injected under the skin.

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 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The needle is withdrawn, the sensation subsides and is not permanent.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 a short time to prevent low-pressure headaches. The entire procedure takes approximately 20 minutes.

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.

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

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

• Abscess
• Acute infection
• Encephalitis
• Hemorrhage
• Meningitis
• Multiple sclerosis
• Stroke
• Tumor

The finding of red blood cells may be a sign of bleeding. 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 syndrome
• Hemorrhagic stroke
• Neurosyphilis
• Primary lymphoma of the brain
• Spinal tumor
• Stroke secondary to syphilis
• Syphilitic aseptic meningitis
• Syphilitic myelopathy

Risks of lumbar puncture include:

• Allergic reaction to the anesthetic
• Discomfort during the test
• Headache after the test
• Bleeding into the spinal canal
• Infection

Brain herniation may occur if performed on a person with a mass in the brain such as a tumor or abscess. This can result in brain damage or death. For this reason, a lumbar puncture is not done if other tests show signs of a tumor or abscess.

There may be temporary leg discomfort if a nerve root is irritated by the needle. This passes when the needle is withdrawn.