Lumbar puncture consists of inserting a hollow needle between two of the spinal bones. This may be used to take a sample cerebrospinal fluid—the fluid that surrounds and protects the brain and the spinal cord-or to inject chemotherapy medication. This is called intrathecal chemotherapy.

Intrathecal chemotherapy may be given if the cancer has spread to the cerebrospinal fluid or if there is a suspicion that it has done so. This may happen in some types of leukemia or lymphoma.

The doctor numbs an area of skin over your spinal column using a local anesthetic. After a few minutes, a needle is gently inserted between two of the bones of the spinal column into the cerebrospinal fluid. If you are receiving intrathecal chemotherapy, your doctor injects the chemotherapy through the needle into the cerebrospinal fluid. The entire procedure normally takes about 20 minutes.

Having a lumbar puncture is not normally painful, though some people do experience discomfort. The most common side effect of a lumbar puncture is a headache. To help prevent this from happening, you will need to lie down for a few hours after the procedure and drink lots of fluids.