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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.

A sample of CSF is needed. A lumbar puncture (spinal tap) is the most common way to collect this sample. For information on this procedure, see the article on lumbar puncture.

Other methods for collecting CSF are rarely used, by may be recommended in some cases. They include:

• Cisternal puncture
• Ventricular puncture
• Removal of CSF from a tube that is already in the CSF, such as a shunt or ventricular drain.

After the sample is taken, it is sent to a laboratory for evaluation.

See: Lumbar puncture

See: Lumbar puncture

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

Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

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

Finding red blood cells in the CSF may be a sign of bleeding. However, red blood cells in the CSF may also be due to the spinal tap needle hitting a blood vessel while entering the skin or dura.

It is important to see if the red blood cell count returns to normal 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.

Griggs RC, Jozefowicz RF, Aminoff MJ. Approach to the patient with neurologic disease. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier. 2007: chap 418.

Updated by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; Daniel B. Hoch, PhD, MD, Assistant Professor of Neurology, Harvard Medical School, Department of Neurology, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.