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 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 by a pathologist (a doctor who specialises in diagnosing disease by looking at body tissues and cells).
A lumbar puncture is carried out by a doctor or sometimes a specially-trained nurse. It can be done in the outpatients department or on a ward at the hospital.
Intrathecal chemotherapy is where chemotherapy is given into the fluid around the spinal cord during a lumbar puncture.
Cerebrospinal fluid
Surrounding the brain and spinal cord is a watery fluid known as cerebrospinal fluid (CSF). 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 (CNS).
Why a lumbar puncture may be done
There are a number of reasons why a lumbar puncture may be done:
Changes in the CSF can help doctors to diagnose diseases of the brain and nervous system. The fluid that is drawn off is sent to the laboratory where it is examined under the microscope. In some types of cancer, tiny cancer cells can spread into the CSF, affecting the brain and, more rarely, the spinal cord. By taking a sample of the CSF, doctors can see whether it contains any cancer cells.
A lumbar puncture may also be used to inject chemotherapy drugs into the CSF. This can be done for people whose cancer has spread into the CSF, or to help prevent it from happening. Injecting chemotherapy into the CSF is known as intrathecal chemotherapy.
Other reasons for doing a lumbar puncture are:
- to measure the pressure of the CSF
- to inject a dye so that specialist x-rays can show the structure of the spinal cord
- to inject a local anaesthetic (known as an epidural) so that surgery can be performed on the lower part of the body without having to give a general anaesthetic, or to give pain-relieving drugs. These drugs are not injected into the CSF but into other areas, or 'spaces' around the spinal cord.
Giving your consent
Before you have your lumbar puncture, your doctor will explain why it is recommended that you have this test, and you will 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 will be in a particular area of the hospital.
Before you are asked to sign the consent form you should have been given full information about:
- the procedure and (if needed) the chemotherapy treatment
- the reasons for the lumbar puncture
- any possible other tests or treatments that may be available
- any risks or side effects of the lumbar puncture (and chemotherapy).
If you do not understand what you have been told, let the staff know straight away so that they can explain again. It is not unusual for people to need repeated explanations.
It is often a good idea to have a friend or relative with you when the procedure is explained, to help you to 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 often feel that the hospital staff are too busy to answer their questions, but it is 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 you to ask questions.
The lumbar puncture
Before the lumbar puncture is done, you may have your blood pressure and pulse checked. As you will need to lie flat for some time following the procedure, remember to go to the toilet beforehand.
While the lumbar puncture is being done, you will need either 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 moments for the anaesthetic to take effect.
A hollow needle is inserted between two of the spinal bones and into the spinal canal. You will 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 inserted.
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. If you would like to, you can also check the drugs before they are given.
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, although this can vary depending on the reasons for why it is being done.
After the lumbar puncture
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 will 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 sitting up can make the headache 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 is best not to drive or operate machinery for 24 hours after a lumbar puncture.
Sometimes a lumbar puncture is done more than once. Often, several doses (cycles) of chemotherapy are needed and a lumbar puncture will be done during every cycle until all of the planned treatment is completed.
References
This section has been compiled using information from a number of reliable sources, including:
- Diagnostic investigations Part 1: lumbar puncture. Blows, W (2002). Nursing Times; 98:36 25–26.
- Nurse Manual of Laboratory and Diagnostic Tests (3rd Edition). Cavanagh et al. FA Davies Company, 1999.
- NHS Direct Online Health Encyclopaedia: www.nhsdirect.nhs.uk/nhsdoheso/media
- Diagnostic procedures. Nursing Times. Emap Healthcare Limited, 2002.
- Updated national guidance on the safe administration of intrathecal chemotherapy – HSC 2003/010. Department of Health website: www.dh.gov.uk
For further references, please see the general bibliography.
Via: http://www.cancerbackup.org.uk
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