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

Intrathecal chemotherapy is where chemotherapy is given into the fluid around the spinal cord during a lumbar puncture.

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.

A lumbar puncture may be done:

• to take a sample of CSF to help the doctors make a diagnosis -for example, to look for infection or cancer cells in the CSF
• to measure the pressure of 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.

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

Only certain chemotherapy drugs can be given in this way. The chemotherapy drugs that are most commonly given intrathecally are methotrexate and cytarabine.

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

You will also be asked to sign a form if you’re going to have chemotherapy during the lumbar puncture. Specially trained staff will do the lumbar puncture 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 be 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).

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.

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.

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.

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 be asked to:

• lie on one side with your knees drawn up towards your chest; or
• sit up, bent over a table and supported by pillows.

These positions allow 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 part of your back 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 then 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.

There are very strict guidelines for giving chemotherapy in this way. The doctor and nurses will do a number of safety checks to ensure you are only given the medicines that have been prescribed for you, and this can take time. 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.

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. Let the doctor or nurse know if you have a headache, as they can give you mild painkillers to help. You’ll need to lie flat for a while after the procedure – from one hour to several hours, depending on how you feel. You’ll be able to roll from side to side, but if you have a headache, sitting up can make it worse.

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. However, 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 and will need to have a lumbar puncture each time.