Lumbar Puncture Information
A lumbar puncture (LP), also known as a spinal tap, is a diagnostic and/or therapeutic procedure performed by a doctor. 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.
Cerebrospinal fluid (CSF), is a clear, colorless liquid that fills and surrounds the brain and spinal cord it provides a mechanical barrier against shock. The cerebrospinal fluid supports the brain and provides lubrication between surrounding bones and the brain and spinal cord. When an individual suffers a head injury, the fluid acts as a cushion, dulling the force by distributing its impact. The fluid helps to maintain pressure within the cranium at a constant level. An increase in the volume of blood or brain tissue results in a corresponding decrease in the fluid. Conversely, if there is a decrease in the volume of matter within the cranium, as occurs in atrophy of the brain, the CSF compensates with an increase in volume. The fluid also transports metabolic waste products, antibodies, chemicals, and pathological products of disease away from the brain and spinal-cord tissue into the bloodstream. CSF is slightly alkaline and is about 99 percent water.
How Does a Lumbar Puncture Help Diagnose Multiple Sclerosis?
The cerebrospinal fluid (CSF), contains glucose (sugar), proteins, and other substances that are also found in the blood. Analysis of the fluid includes looking at the number and types of white blood cells (infection-fighting cells), the level of glucose, the types and levels of various proteins (especially immune system proteins called antibodies or immunoglobulins), and testing for bacteria, fungus, or abnormal cells.
A lumbar puncture that reveals a large number of immunoglobulins (antibodies) as well as oligoclonal bands (the pattern of immunoglobulins on a more specific test) or certain proteins that are the breakdown products of myelin is suggestive of MS. These findings indicate an abnormal autoimmune response within the brain and spinal cord, meaning that the body is attacking itself.
Over 90% of people with MS have oligoclonal bands in their CSF. While increased immunoglobulin in the CSF and oligoclonal bands are seen in many other brain and spinal cord conditions, their presence is often useful in helping to establish a diagnosis of MS.
However, a “negative” spinal tap does not rule out MS or other diseases; some 5% to 10% of people with MS never show CSF abnormalities. And, an abnormal autoimmune response in CSF is found in a number of other diseases, so the test is not specific for MS. Therefore, a spinal tap by itself cannot confirm or rule out a diagnosis of MS. It must be part of the total picture that takes into account other diagnostic procedures such as evoked potentials and magnetic resonance imaging (MRI).
How do I prepare for a lumbar puncture?
If you are having a lumbar puncture a neuroradiologist should contact you by phone to discuss the procedure and answer any questions you may have.
Please inform the neuroradiology physician if you are:
- On antibiotics – you may need to wait to do the procedure if currently on antibiotics. If you have an active infection or fever, your procedure will need to be rescheduled.
- On anticoagulant therapy (blood thinners)
If you are pregnant or think you might be pregnant, please check with your doctor before scheduling the exam. Other options will be discussed with you and your doctor.
You must completely change into a patient gown. A gown will be provided for you. Lockers are provided to secure your personal belongings. Please remove all piercings and leave all jewelry and valuables at home.
Do not eat or drink anything three (3) hours prior to your lumbar puncture. You may have water to take your medications. Please limit the amount of water to only what is needed to comfortably swallow the medication.
All patients can take their prescribed medications as usual. Please bring a current list of your medications and allergies with you.
You must have an adult driver accompany you so they can drive you home after the procedure. This is for your safety and comfort.
- Please note: You will be unable to drive for 24 hours after the procedure. If you are taking a cab or using public transportation, you need to bring a friend or family member to accompany you after the procedure to your home or hotel. A cab or public transportation driver is not considered an escort.
- If your ride home is longer than 30 minutes, we advise that on your ride home you be in a reclined position with one or two pillows supporting your head.
- Arrive one hour prior to the scheduled procedure time for check-in and to be prepped for the procedure.
What Happens During a Lumbar Puncture?
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.
- You will be reminded to empty your bladder prior to the start of the procedure.
- 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 should notify the doctor if you feel any numbness, tingling, headache, or lightheadedness during the procedure.
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 Happens After a Lumbar Puncture?
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.
Once you are at home, notify your doctor of any abnormalities, such as numbness and tingling of the legs, drainage of blood or pain at the injection site, inability to urinate, or headaches. If the headaches persist for more than a few hours after the procedure, or when you change positions, you should contact your doctor.
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.
Risks of Puncture Safe?
Yes, a lumbar puncture is safe; however, as with most tests, there are a few minor risks.
These risks include:
- Headache. Approximately 10% of people develop a spinal headache (one that worsens when sitting or standing and is instantly relieved by lying down).
- Infection. The risk of infection is extremely low.
- Bloody tap. Occasionally, a small blood vessel is pierced during the procedure, causing a “bloody tap.” No treatment is needed, but in some cases, the spinal tap will need to be repeated at a later date to get a “clear” sample.
- 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.
Call your doctor immediately if you notice any unusual drainage, including bloody discharge, or worsening pain symptoms.