Lumbar puncture

A lumbar puncture is a procedure in which a hollow needle is inserted between the bones of the lower back and into the fluid around the lower part of the spinal cord.

This procedure can be used to collect a sample of cerebrospinal fluid (CSF) for examination in a laboratory. It may also be done to inject drugs into the CSF or to measure the pressure of the CSF.

Before the lumbar puncture you should be given detailed information about the procedure and will be asked to sign a consent form.

You will be asked to lie or sit in a curved position, so that the bones of the spine (vertebrae) are widely separated. Before the hollow needle is inserted, you will be given a local anaesthetic. A lumbar puncture is not usually painful, but you may feel some pressure.

Once the lumbar puncture is over, you will need to lie on your back for a couple of hours. You can return to normal activities as soon as you feel well. It's best not to drive or operate machinery for 24 hours after a lumbar puncture.

What is a lumbar puncture?

A lumbar puncture is a procedure in which a hollow needle is inserted between the bones of the lower back and into the fluid around the lower part of the spinal cord. A sample of the fluid is then drawn off to be examined in the laboratory.

A lumbar puncture is carried out by a doctor or specially trained nurse. It can be done in the outpatients department or on a ward at the hospital. Lumbar punctures are usually carried out under local anaesthetic. However, lumbar punctures for children are sometimes carried out under general anaesthetic.


Cerebrospinal fluid

A watery fluid called cerebrospinal fluid (CSF) surrounds the brain and spinal cord. The CSF protects the brain and spine from injury by acting as a shock absorber.

The brain and spinal cord are known as the central nervous system.


Why a lumbar puncture may be done

A lumbar puncture may be done:

  • to take a sample of CSF to help the doctors make a diagnosis - for example, a sample of CSF may be taken to look for infection or cancer cells in the CSF
  • to inject a drug into the CSF - drugs that may be injected into the CSF include some types of chemotherapy drugs, antibiotics, pain-relieving drugs and anaesthetics
  • to measure the pressure of the CSF.


When intrathecal chemotherapy may be given

In some cancers, such as some types of leukaemia or lymphoma, cancer cells can pass into the CSF. Chemotherapy given into a vein or by mouth can’t easily get into the CSF. Therefore if cancer has spread to the CSF or there is a risk it could, intrathecal chemotherapy may be given. The chemotherapy drugs that are most commonly given intrathecally are methotrexate and cytarabine.


Before the lumbar puncture

Before your lumbar puncture, your doctor will explain why it is recommended that you have this procedure. You’ll usually be asked to sign a form saying that you give your permission (consent) for the hospital staff to do the lumbar puncture.

If you are going to have chemotherapy during the lumbar puncture, you will also be asked to sign a form to agree to have this. The lumbar puncture will be done by specially trained staff and in a particular room of the hospital. Very occasionally, you may have to travel to a different hospital if it can't be done where you normally have your treatment.

Before you are asked to sign the consent form, you should have been given full information about:

  • the reasons for the lumbar puncture
  • the procedure
  • the chemotherapy treatment (if this is being given)
  • any other tests or treatments that may be available
  • any risks or side effects of the lumbar puncture (and chemotherapy).

If you don't understand what you've been told, let the staff know straight away so they can explain again. It isn't unusual for people to need repeated explanations.

It's often a good idea to have a relative or friend with you when the procedure is explained to help you remember the discussion more fully. You may also find it useful to write down a list of questions before you go for your appointment.

People sometimes feel that the hospital staff are too busy to answer their questions, but it's important for you to be aware of how the lumbar puncture is likely to affect you, and the staff should be willing to make time for your questions.


The lumbar puncture

You’ll have your blood pressure and pulse checked before your lumbar puncture. You may also find it helpful to go to the toilet beforehand, as you’ll need to lie flat for some time after the procedure.

During your lumbar puncture, you’ll either be asked to lie on one side with your knees drawn up towards your chest or to sit up, bent over a table and supported by pillows. This positioning allows your back to curve as much as possible so that the bones of the spine (vertebrae) are widely separated.

The area of skin over the lower spine is cleaned with an antiseptic solution. Local anaesthetic is injected to numb the area. The doctor or nurse will wait for a few minutes for the anaesthetic to take effect.

A hollow needle is inserted between two of the spinal bones and into the spinal canal.

You’ll need to stay as still as possible at this time. You may feel a sensation of pressure as the needle is put in. Samples of CSF may then be withdrawn and/or chemotherapy drugs may be injected.

If chemotherapy drugs are being given, the doctor and nurses will do a number of safety checks to ensure you are given only the medicines that have been prescribed for you. This is because only certain drugs are suitable to be given in this way. If you would like to, you can also check the drugs before they are given.

If you’re also having chemotherapy into a vein (intravenous chemotherapy), you’ll be given this first. The intrathecal chemotherapy will only be given after the other chemotherapy has finished.

After the lumbar puncture has been completed, the needle is removed and a small dressing is put on. The entire procedure normally takes around 20 minutes.

An illustration of a lumbar puncture being done (lying down).
An illustration of a lumbar puncture being done (lying down).

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An illustration of a lumbar puncture being done (sitting up).
An illustration of a lumbar puncture being done (sitting up).

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After the lumbar puncture

Having a lumbar puncture is not usually painful, although some people may find it uncomfortable. Some people may have a headache for a few hours afterwards. You’ll need to lie flat for a while after the procedure – from one hour to several hours, depending on how you feel. You will be able to roll from side to side, but if you have a headache, sitting up can make it worse.

Let the doctor or nurse know if you have a headache, as mild painkillers can be given to help. You will also have your blood pressure and pulse checked again during this time. Ask the doctor or nurse when it will be safe for you to sit up. Once you have rested and feel well, you can safely return to your normal activities, although it's best not to drive or operate machinery for 24 hours after a lumbar puncture. Sometimes a lumbar puncture is done more than once. For example if you’re having intrathecal chemotherapy, you may need several doses of this and will need to have a lumbar puncture each time.