A CSF glucose test measures the amount of sugar (glucose) in the cerebrospinal fluid (CSF). CSF is a clear fluid that flows in the space surrounding the spinal cord and brain.
How the Test is Performed
The health care provider will place a needle into the lower spinal area and take a sample of cerebrospinal fluid. This is called a spinal tap or lumbar puncture. The entire procedure takes about 20 minutes. For detailed information, see the article on lumbar puncture.
The fluid is sent to a lab, where it is examined under a microscope.
How the Test Will Feel
Under experienced hands there should not be any pain. You may feel pressure when the needle is inserted. Occasionally, some people may feel numbness shooting down the leg. This may be due to irritation of a nerve root.
Following the procedure, you will be asked to remain lying down for a while to prevent headaches associated with spinal taps.
Why the Test is Performed
This test may be done to diagnose tumors, infections, inflammation of the central nervous system, delirium, and other neurological and medical conditions.
The glucose levels should be between 50 to 80 mg/100 mL. Levels may vary slightly depending on the amount of glucose in the blood. However, the level in the CSF should be about two-thirds the level in the blood.
Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
What Abnormal Results Mean
Abnormal results include increased and decreased glucose levels. Abnormal results may be due to:
Infection (bacterial or fungus)
Inflammation of the central nervous system
Risks of lumbar puncture include:
Allegic reaction to the anesthetic
Discomfort during the test
Headache after the test
Bleeding into the spinal canal
Brain herniation may occur if a lumbar puncture is done on a person with a mass in the brain (such as a tumor or abscess). This can result in brain damage or death. A lumbar puncture is not done if an exam or other tests show signs of a tumor or abscess.
Some persons have temporary leg numbness or tingling due to irritation of a nerve root by the needle