Why do a lumbar puncture

This test is similar to a blood test, in which a needle is inserted into an artery to collect blood for testing. Your brain and spinal cord are surrounded and bathed by a clear fluid called cerebrospinal fluid CSF. This fluid is produced in the ventricles of the brain and circulates through the subarachnoid space of the brain and spinal cord see Anatomy of the Spine. During a lumbar puncture, a hollow needle is inserted through the skin in the lower back.

The needle passes between the vertebrae and into the spinal canal. A lumbar puncture can be used to:. In addition to testing for abnormal cells, the CSF pressure can be measured to determine if you have a condition called hydrocephalus. The normal pressure of CSF is between 70 and mm. On the day of the exam you can eat a regular breakfast. Before the test, you will be asked to change into a hospital gown and an intravenous IV line will be placed in your arm. The doctor or nurse will discuss the test with you, explain the risks, answer any questions, and have you sign consent forms.

You may receive a mild sedative, intravenous fluids, or additional medication before the procedure. Step 1: prepare the patient You may be given a sedative to make you drowsy and relaxed.

A doctor and at least one assistant will be in the room. You will lie on your side with your knees drawn to your chest so that your spine is curved; in some cases you may sit on the table and lean forward onto some pillows instead.

After cleaning your back with a cooling antiseptic, the doctor will numb the area of your lower back where the needle will be inserted. This may cause some brief stinging. Step 2: insert the needle Next, a hollow needle is inserted between the third and fourth lumbar vertebrae into your spinal canal Fig.

The needle doesn't touch the nerves of your spinal cord. Your doctor or nurse will talk to you about the potential risks, and any discomfort you might feel during the procedure. If a child is having a lumbar puncture, a parent may be allowed to stay in the room in some cases.

Talk to your child's doctor or nurse about whether this will be possible. You may be asked to change into a hospital gown, although in some cases you may have the procedure while wearing your own clothing. There are a few possible positions for this test. Usually, you lie on your side with your knees drawn up to your chest, or you sit and lean forward on a stable surface.

These positions flex your back, widening the spaces between your vertebrae and making it easier for your doctor to insert the needle. The procedure usually lasts about 45 minutes. Your doctor or nurse may suggest lying down after the procedure. Sometimes, an ultrasound may be used as a guide during the procedure on infants and young children. The ultrasound can help prevent inserting the needle too far. The spinal fluid samples are sent to a laboratory for analysis.

Lab technicians check for a number of things when examining spinal fluid, including:. Lab results are combined with information obtained during the test, such as spinal fluid pressure, to help establish a possible diagnosis. Your health care professional generally gives you the results within a few days, but it could take longer.

Ask when you can expect to receive the results of your test. Write down questions that you want to ask your doctor or nurse. Don't hesitate to ask other questions that may come up during your visit. Questions you may want to ask include:.

Explore Mayo Clinic studies of tests and procedures to help prevent, detect, treat or manage conditions. Mayo Clinic does not endorse companies or products. Advertising revenue supports our not-for-profit mission. You will remove any clothing, jewelry, or other objects that may interfere with the procedure. During the lumbar puncture you may lie on the exam table on your side with your chin tucked to your chest and knees tucked to your abdomen.

Or you may sit on the edge of an exam 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 spaces between your vertebrae. Your back will be cleansed with an antiseptic solution and draped with sterile towels.

The healthcare provider will wear sterile gloves during the procedure. The provider will numb the skin by injecting a local anesthetic. 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 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 1 tablespoon, will be collected into test tubes. If the provider needs to inject medicine into the spinal canal, it will be given through the same needle after the CSF is collected.

When the procedure is done, the needle will be removed and a bandage will be placed over the injection site. The test tubes will be taken to the lab for testing. Tell the healthcare provider if you feel any numbness, tingling, headache, or lightheadedness during the procedure. You may have discomfort during a lumbar puncture.

Your healthcare providers will use all possible comfort measures and complete the procedure as quickly as possible to minimize any discomfort or pain. You will be asked to drink extra 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. After recovery, you may be taken to your hospital room or discharged to your home.

If you go home, usually your healthcare provider will advise you to only engage in very light activity the rest of the day. If the headaches persist for more than a few hours after the procedure, or when you change positions, contact your provider.

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 healthcare provider may give you other specific instructions about what you should do after a lumbar puncture. Search Encyclopedia. Lumbar Puncture What is a lumbar puncture? Why might I need a lumbar puncture? A lumbar puncture procedure may be helpful in diagnosing many diseases and disorders, including: Meningitis.

Certain cancers involving the brain and spinal cord. An inflammation of the spinal cord or bone marrow. These include: Spinal anesthetics before a surgical procedure Contrast dye for X-ray studies, such as myelography Chemotherapy medicines used to treat cancer Your healthcare provider may have other reasons to recommend a lumbar puncture.

What are the risks of a lumbar puncture? Because this procedure involves the spinal cord and brain, the following complications may occur: A small amount of CSF can leak from the needle insertion site.