A lumbar puncture (also called a spinal tap) is a procedure to collect and look at the fluid (cerebrospinal fluid, or CSF) surrounding the brain and spinal cord.
During a lumbar puncture, a needle is carefully inserted into the spinal canal low in the back (lumbar area). Samples of CSF are collected. The samples are studied for color, blood cell counts, protein, glucose, and other substances. Some of the sample may be put into a special culture cup to see if any infection, such as bacteria or fungi, grows. The pressure of the CSF also is measured during the procedure.
Why It Is Done
A lumbar puncture is done to:
Find a cause for symptoms possibly caused by an infection (such as meningitis), inflammation, cancer, or bleeding in the area around the brain or spinal cord (such as subarachnoid hemorrhage).
Diagnose certain diseases of the brain and spinal cord, such as multiple sclerosis or Guillain-Barré syndrome.
Measure the pressure of cerebrospinal fluid (CSF) in the space surrounding the spinal cord. If the pressure is high, it may be causing certain symptoms.
A lumbar puncture may also be done to:
Put anesthetics or medicines into the CSF. Medicines may be injected to treat leukemia and other types of cancer of the central nervous system.
Put a dye in the CSF that makes the spinal cord and fluid clearer on X-ray pictures (myelogram). This may be done to see whether a disc or a cancer is bulging into the spinal canal.
In rare cases, a lumbar puncture may be used to lower the pressure in the brain caused by too much CSF.
How To Prepare
Before you have a lumbar puncture, tell your doctor if you:
Are taking any medicines. If you take medicines every day, ask your doctor whether you should take these medicines on the day of the lumbar puncture.
Are allergic to any medicines, such as those used to numb the skin (anesthetics).
Have had bleeding problems or take blood-thinners, such as aspirin or warfarin (Coumadin).
Are or might be pregnant.
Take any herbal remedies. Some of these remedies may thin the blood.
You will empty your bladder before the procedure.
For a lumbar puncture, you will be asked to sign a consent form. Talk to your doctor about any concerns you have regarding the need for the procedure, its risks, how it will be done, or what the results will mean. This procedure is often done in an emergency situation. If you are scheduled to have this procedure, you can understand the importance of it by filling out the medical test information form
How It Is Done
A lumbar puncture may be done in your doctor’s office, in an emergency room, or at your bedside in the hospital. It may also be done in the radiology department if fluoroscopy is used.