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Lumbar Puncture

A lumbar puncture is a common medical procedure sometimes used in the diagnosis of childhood cancer. It is also called an “LP” or a “spinal tap.”

During the procedure, a doctor, nurse practitioner, or other qualified medical professional removes a small sample of fluid from around the spine using a thin needle.

The fluid is called cerebrospinal fluid or CSF. It surrounds and protects the brain and spinal cord. Testing the CSF can show if the patient has a disease or infection. The body makes CSF constantly. The patient’s body quickly replaces the small amount removed during the lumbar puncture.

How the Procedure Occurs

  • About 1 hour before the lumbar puncture, a health care provider may put numbing cream on the spot for the test. In most cases, the patient also gets medicine to help him or her sleep through the test.
  • If the patient is awake, he or she may get an injection of liquid numbing medicine at the test spot. The patient will either lie on his or her side or sit on the side of a bed.
  • The health care provider will feel the patient’s lower back to find the right place to put the needle. The provider will clean the patient’s back with an antiseptic. It will probably feel cold. The provider may put a plastic sheet called a “drape” over the patient’s back, so just the test area shows.
  • Next, the provider will insert the needle in the appropriate spot. The needle is hollow with a smaller needle inside. When the larger needle is in place, the doctor takes out the smaller one. This process allows the fluid to go into test tubes. It takes 10 minutes or less to collect fluid. Then the provider takes out the needle, cleans the spot, and applies a bandage.
Patient laying on side with needle being inserted into spine for lumbar puncture

The patient will either lie on his or her side or sit on the side of a bed.

Graphic showing a spinal needle inserted into the spinal column to receive a sample of cerebrospinal fluid.

Testing cerebrospinal fluid can show if the patient has a disease or infection.

What the Patient Feels

  • If awake, the patient may feel a small pinch and some discomfort.
  • Some patients say the lumbar puncture procedure is not painful.


Reviewed: June 2018

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