Spinal Tap Diagnostic
What is a spinal tap or lumbar puncture?
A lumbar puncture (LP), also known as a spinal tap, is a diagnostic and/or therapeutic procedure. The procedure is performed by inserting a hollow needle into the subarachnoid space in the lumbar area (lower back) of the spinal column. The subarachnoid space is the canal in the spinal column that carries cerebrospinal fluid (CSF) between the brain and the spinal cord.
CSF is a clear fluid that bathes the brain and spinal cord while protecting it, like a cushion, from exterior injury. The fluid is produced and reabsorbed in the brain on a continuous basis. CSF is composed of cells, water, proteins, sugars, and other vital substances that are essential to maintain equilibrium in the nervous system.
What are the risks or side effects of the procedure?
Because this procedure involves the spinal cord and brain, the following potential complications may occur:
- A small amount of CSF can leak from the needle insertion site. This can cause headaches after the procedure. If there is a persistent leak the headache can be severe.
- There is a slight risk of infection because the needle breaks the skin’s surface, providing a possible portal of entry for bacteria.
- A temporary pain or numbness to the legs or lower back pain may be experienced.
- There is a risk of bleeding in the spinal canal.
- Should there be increased pressure or swelling in the brain before the procedure, a lumbar puncture can cause fluctuations in the CSF fluid levels, resulting in brain herniation. Herniation is a dangerous event in which the brain stem or top of the spinal column is compressed by swelling of the brain. This will occur only in the most rare of circumstances because your doctor will almost always have determined the safety of a lumbar puncture by first reviewing some kind of radiographic imaging of your brain.
There may be other risks depending on your specific medical condition. Be sure to discuss any concerns with your doctor prior to the procedure.
What should I expect before the procedure?
- Your doctor will explain the procedure to you and offer you the opportunity to ask any questions that you might have about the procedure.
- You will be asked to sign a consent form that gives your permission to do the procedure. Read the form carefully and ask questions if something is not clear.
- Generally, fasting is not required prior to a lumbar puncture unless a sedative is prescribed. Your doctor will instruct you prior to the procedure of any necessary fasting requirements.
- Notify your doctor if you are pregnant or suspect you may be pregnant.
- Notify your doctor of all medications (prescribed and over-the-counter) and herbal supplements that you are taking.
- Notify your doctor if you have a history of seizures or if you are taking any prescribed medications for seizures.
- Notify your doctor if you have a history of bleeding disorders or if you are taking any anticoagulant (blood-thinning) medications, aspirin, or other medications that affect blood clotting. It may be necessary for you to stop these medications prior to the procedure.
- If the procedure is performed on an outpatient basis, you may be asked to remain in the hospital for several hours following the procedure. You should plan to have another person drive you home.
- Based on your medical condition, your doctor may request other specific preparation.
What should I expect during the procedure?
A lumbar puncture procedure may be performed on an outpatient basis or as part of your stay in a hospital. Procedures may vary depending on your condition and your doctor’s practices.
Generally, a lumbar puncture follows this process:
- You will be asked to remove any clothing, jewelry, or other objects that may interfere with the procedure.
- You will be given a gown to wear.
- During the lumbar puncture you may lie on the examination table on your side with your chin tucked to your chest and knees tucked to your abdomen. Alternatively, you may sit on the edge of an examination table with your arms draped over a table positioned in front of you. In either position the back is arched, which helps to widen the intervertebral spaces.
- A lumbar puncture is a sterile procedure. Therefore, your back will be cleansed with an antiseptic solution and draped with sterile towels. The doctor will wear sterile gloves during the procedure.
- The doctor will anesthetize the skin by injecting a local anesthetic that numbs the site. This injection may sting for a few seconds, but makes the lumbar puncture less painful.
- The hollow needle will be inserted through the numbed skin and into the subarachnoid space where the CSF is located. You will feel some pressure while the needle is inserted. You must remain absolutely still during the insertion of the needle.
- The CSF will begin to drip out of the needle and a small amount, about one tablespoon, will be collected into test tubes.
- If the doctor needs to inject medication into the spinal canal, it will be given through the same needle after the CSF is collected.
- When the procedure is completed, the needle will be removed and an adhesive bandage will be placed over the injection site. The test tubes will be taken to the laboratory for analysis.
You may experience discomfort during a lumbar puncture. The doctor will use all possible comfort measures and complete the procedure as quickly as possible to minimize any discomfort or pain.
What should I expect after the procedure?
You usually will be asked to lie flat for about one hour after the lumbar puncture is completed. This helps reduce the incidence of a headache. You will be allowed to roll from side to side as long as your head is not elevated. If you need to urinate, you may be asked to urinate in a bedpan or urinal during the time that you are required to stay flat.
You will be asked to drink additional fluids to rehydrate after the procedure. This replaces the CSF that was withdrawn during the spinal tap and reduces the chance of developing a headache.
When you have completed the recovery period, you may be taken to your hospital room (if the procedure was performed elsewhere in the hospital) or discharged to your home. If you go home, usually your doctor will advise you to only engage in very light activity the rest of the day.
You may be instructed to limit your activity for 24 hours following the procedure. Generally, if no complications occur, you may return to your normal diet and activities.
Your doctor may give you additional or alternate instructions after the procedure, depending on your particular situation.