Lumbar puncture

A lumbar puncture is a medical procedure where a needle is inserted into the lower part of the spine to look for evidence of conditions affecting the brain, spinal cord or other parts of the nervous system. 

During the procedure, pressure measurements are recorded and samples of fluid are taken from inside the spine. The fluid is known as cerebrospinal fluid (CSF) and it can be tested to help diagnose various conditions, such as:

• meningitis – an infection of the layers (membranes) that surround the brain and spinal cord
• subarachnoid haemorrhage – a type of stroke caused by bleeding in and around the brain
• Guillain-Barré syndrome – a rare condition that causes inflammation of the nerves in the arms and legs

If you are advised to have a lumbar puncture, it doesn't necessarily mean you have one of these conditions or another serious disorder. Instead, the procedure may be used to exclude such conditions.

A lumbar puncture can also be used to treat some conditions. For example, it can be used to inject antibiotics or chemotherapy medication into the cerebrospinal fluid.

Read more about why lumbar punctures are used.

How is a lumbar puncture carried out?

A hollow needle is inserted into the base of the spine under local anaesthetic. The needle passes into the spinal canal, the channel running down the spine that contains the spinal cord and the nerves that come off it.

The pressure within the spinal canal is usually measured, after which some of the cerebrospinal fluid (CSF) is removed. The fluid is removed either to reduce the pressure or so a sample can be sent to the laboratory for testing.

In most cases, the lumbar puncture is carried out while you are lying on your side with your legs pulled up and your chin tucked in. Alternatively, the procedure may be carried out while you are seated and leaning forwards. The procedure usually takes around 30-45 minutes to complete. 

It is often possible to get the results of laboratory tests on CSF samples within 48 hours, but it can take several weeks for the results of more specialised tests to become available.

Read more about how a lumbar puncture is performed.

Are there any risks?

A lumbar puncture is generally safe and the risk of serious complications is low.

Serious side effects are uncommon, although many people experience headaches caused by CSF leaking out through the hole made in the spine by the needle. You won't see this leakage because it occurs internally.

The headaches are typically worse when in the upright position and can usually be relieved by lying down. Drinking plenty of fluids and taking simple painkillers will also help. It can take up to a week for the hole to heal and the fluid to stop leaking.

Read more about the possible side effects of a lumbar puncture.