What happens during the test?
Before the test starts, you will be asked to empty your bladder. Then you will be asked to undress either partially or fully and put on a hospital gown. You will lie down on an examination table or hospital bed and draw your knees up to your chest. Your doctor may ask you to take another position; however, this is the most common position for the test.
The doctor looks at your spinal column, then marks where a needle will be inserted into your spine. Cleaning the area with an antiseptic solution prepares the area and reduces the number of bacteria that may cause infection.
A local anesthetic is used to freeze the area before another needle is inserted for the test. The doctor inserts the needle where CSF is likely accessible. If the doctor is successful, CSF is supposed to leak out the needle. If no CSF comes out, the doctor must reposition the needle. You may feel stinging or discomfort during this process. It is important to stay completely still while the needle is being inserted.
Your doctor may take pressure readings, one when the spinal canal is first punctured, and another before the needle is removed. The readings are called the opening and closing pressures, respectively.
The test takes approximately half an hour.
How should I prepare for this test?
As always, it is important to discuss your current medications and medical conditions with your doctor before the test. Some medications and medical conditions may affect the test. Blood disorders or medications that decrease the ability of the blood to clot (e.g., blood thinners) may increase the chances of internal bleeding.
Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any medication allergies and medical conditions that you may have. Tell your doctor before the test if you are allergic to anesthetic or if you are or may be pregnant.
Your doctor will review the risks and benefits of the test with you. Ask any questions you may have to fully understand the procedure.
Do not eat for 8 hours before the procedure. You may continue to drink clear liquids until 2 hours before the procedure. If your doctor has recommended different times, follow the timing recommended by your doctor.
Ask your doctor or pharmacist whether you need to stop taking any of your medications before the procedure.
Arrange for someone to drive you home from the hospital.
What can I expect after the test?
After testing, you will probably be asked to lie flat in bed for several hours. To replace any fluid removed, you may need to drink extra liquids. Follow your doctor's instructions closely after the test to reduce any risk of complications. If you are planning to return home on the day of the test (i.e., if you have not been admitted to the hospital), you should arrange for someone to drive you home.
You can usually return to your normal activities 24 hours after the test is completed, but check with your doctor for instructions.
You may also notice fatigue, a mild backache, or difficulty sleeping for a day or two after the test.
Results
A neurologist usually interprets the test results. Some test results are ready immediately after the test. Others take a few days or several weeks to return from laboratory analysis.
The laboratory looks at various characteristics of the CSF. Your doctor considers the color, pressure, protein levels, glucose levels, cell counts (e.g., red and white blood cell counts), and other results from the test to help with your diagnosis.
Generally, problems with pressure of the CSF indicate swelling, infection (e.g., meningitis), or bleeding in the brain. High protein levels may be caused by a variety of factors, including blood in the CSF, a tumor, an infection, inflammation due to multiple sclerosis, or nerve damage (e.g., Guillain-Barré Syndrome). Glucose levels are also measured. High glucose levels are associated with diabetes, while low glucose levels are often caused by bacterial infections.
The results will help your doctor decide on a diagnosis, treatment options, and whether other tests may be needed.