A lumbar puncture is also called a spinal tap. A small amount of spinal fluid, called CSF, is removed through a very thin needle that is inserted into the lower spine and the fluid is tested for cancer cells or infection.
Chemotherapy can also be given into the spinal fluid, either to treat leukemia that has entered the spinal fluid, or to prevent it from developing in the spinal fluid.
The brain and spinal cord make up the Central Nervous System which is bathed by CSF. The whole system is covered by a membrane. Many medications given intravenously cannot cross the membrane from the blood to the CSF. However, sometimes cancer cells can and do cross this membrane. This is why the CSF fluid is tested and sometimes chemotherapy is given directly into the CSF. This is called intrathecal chemotherapy. Methotrexate and Ara-C are two chemotherapy drugs that are commonly given intrathecally as part of leukemia treatment.
The procedure is usually done in your hospital room. Sometimes, it is done in the Radiology Department. It is done by a physician and takes about 15-20 minutes. You should empty your bladder just before the procedure, as you will be asked to stay in bed for at least one hour after the procedure.
Procedure - What to Expect
For the test to be done, you will be asked to lie on your side with knees pulled up and the chin tucked down. Alternatively, you may be placed in a sitting position, leaning over a bedside table.
The lower back is cleansed with an antiseptic liquid. It will feel cool. An injection of local anaesthetic will freeze the area and may sting or burn for a minute or two. A spinal needle is then inserted. Since the CSF is under pressure, it will drip into a test-tube. At this point, chemotherapy may be put in. A small Band-Aid is placed over the site when finished. The nurse will check your pulse and blood pressure before and after the test.
After the Procedure
Following the procedure, you will be asked to lie with the head of the bed slightly elevated to prevent a headache. If you do get a headache, you should tell the nurse. If your treatment allows, you will be requested to drink plenty of fluids.