A lumbar puncture involves putting a needle into the lower back to reach the fluid that sits around the spinal cord. This can help to diagnose and sometimes treat problems of the brain and spinal cord. Lumbar puncture is sometimes called ‘spinal tap’.
Why is a lumbar puncture performed?
A lumbar puncture is performed to sample the fluid, called cerebrospinal fluid or CSF, that sits around the brain and spinal cord. It can then be sent for laboratory testing.
Lumbar puncture is also sometimes used to treat certain problems, either by injecting something into this fluid, or by removing some of the fluid.
How to prepare for a lumbar puncture
Usually, no preparation is needed for a lumbar puncture, but everybody’s situation is different. You should ask your doctor if there is anything you need to do to prepare.
What happens during a lumbar puncture?
You will be asked to keep very still, either lying on your side with your knees close to your chin, or seated. Your back will be cleaned thoroughly and a small amount of local anaesthetic injected into the lower back. Once the area is numb, another needle will be put into your back, through the skin and between the bones of your spine to reach the fluid around your spinal cord. A small amount of fluid will be withdrawn. Once the procedure is finished, the needle will be taken out and a dressing will be put on the injection site.
What to expect after a lumbar puncture
You might be asked to lie down for an hour or more after the procedure, to prevent a headache. You shouldn’t need to stay in hospital overnight, but someone should drive you home.
What can go wrong?
This is usually a very safe procedure. Some people experience headache, backache, or pain in the legs. This usually gets better by itself. There can be bleeding, especially if you are taking blood thinning medication. An infection is possible, but is very rare. If you have worsening headache, fever, or weakness in the legs, you should see a doctor urgently.
About lumbar puncture
Visit the Lab Tests Online website for more information about lumbar punctures.
About surgical procedures
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Last reviewed: November 2016