Lumbar Puncture (LP)
Cerebral Spinal Fluid (CSF) is the fluid that surrounds the brain and spinal cord. It is often helpful when diagnosing certain conditions to examine this fluid for cells and chemicals/proteins. A lumbar puncture allows the doctor to examine the content and pressure of this fluid.
A doctor performs the test in the following manner:
- The patient lies on his or her side, with the knees pulled up toward the chest. Sometimes the test is done with the person sitting up, but bent over.
- After the back is cleaned, the doctor injects a local anaesthetic which makes the skin and surrounding area numb.
- A spinal needle (which is long but smaller in diameter to that used to take a blood test) is inserted between two of the lumbar vertebrae (bones at the base of the spine).
- Once the needle is properly positioned, spinal fluid pressure is measured, and fluid is collected.
- The needle is removed, the area is cleaned, and a bandage is placed over the needle site. You will need to lie flat for 20 minutes to one hour after the test.
You may find the position for the lumbar puncture uncomfortable but it is important to stay still. The anesthetic will sting or burn when first injected. There will be a hard pressure sensation when the needle is inserted and there is usually some brief pain. This pain should stop in a few seconds. Overall, discomfort is minimal to moderate. The entire procedure usually takes about 30 minutes. The actual pressure measurements and fluid collection only take a few minutes.
Risks of lumbar puncture include: allergic reaction to the anaesthetic, discomfort during the test, headache after the test, bleeding into the spinal canal (very rare) and damage to the spinal cord particularly if the person moves during the test (very rare as the needle is so small).
These will all be discussed with you before the procedure and you will be given the opportunity to ask questions. You will be asked to sign a consent form.