Lumbar Puncture

What is a lumbar puncture?

A lumbar puncture, also known as a LP or spinal tap, is a test where a doctor uses needle to collect fluid from your child’s lower back. This fluid is called cerebrospinal fluid, or CSF, which surrounds the brain and spinal cord. A small amount of CSF is collected and sent to the laboratory for testing.

Why does my child need a lumbar puncture?

A lumbar puncture is needed to test the fluid around the brain and spinal fluid. This is most commonly to look for infection. In this case, the test is done to find out if a child has an infection called meningitis, which is a serious infection around the brain.

It is important for your child to have the lumbar puncture as it is the only way to know for sure if they have meningitis. Early diagnosis of meningitis can greatly improve long term outcomes. Having a lumbar puncture doesn’t necessarily mean that your child has meningitis but is an important test to rule this serious infection out.

A lumbar puncture may sometimes be carried out to look to for rarer conditions, often involving the neurology team.

How is a lumbar puncture carried out?

Younger children will be placed on their side with their knees tucked into their chest or curled up into a ball and will be held in this position by an assistant. Older children may be asked to sit on the edge of the bed, leaning forward hugging a pillow.

The back is carefully cleaned and the surrounding parts of the back draped with a sterile gown. The doctor puts a needle into the spaces between the vertebrae (bones of the spine) below the level of the spinal cord. The fluid will be collected into special containers and will be sent to the laboratory for testing.

The whole procedure may take up to 45 minutes, although much of this is preparation time. We generally advise parents to step outside during the procedure.

Does it hurt?

It is an uncomfortable and sometimes painful test. Your child will be held still, and babies and small children do not like this and will often cry.

Depending on the age of your child we can help to numb the skin with some cream, or with an injection, or we may be able to give your child some medicine to make them feel calmer and less scared.

Is it dangerous?

A lumbar puncture is a very safe test and it is unusual for something to go wrong. Sometimes we are not able to get fluid and may have to try more than once. A small number of children may have headache or backache for a day or two after the test. The risk of any serious complications, including bleeding, infection or damage to nerves is extremely small.

It understandable to feel uneasy or anxious but it is important to know that a lumbar puncture is a very safe and common test, and complications are rare.

Care after the procedure

A plaster or dressing will be placed on your child’s back which can be taken off the next day or left to fall off by itself. If they have a headache or backache painkillers can be given. Your child will be encouraged to lie flat for about an hour afterwards. When he or she is fully awake, you should encourage him or her to drink normally.

Getting the results

The fluid is sent to the laboratory for testing.

If the lumbar puncture was carried out to look for infection then some results will be available within 4-6 hours while others, including trying to identify the specific bacteria, will usually take 48 hours, and sometimes up to 5 days. 

If the lumbar puncture was carried out for any other reason it is likely that some results will be available in 4-6 hours, but the most important tests may take days, or in some cases weeks. The team performing the test should be able to advise you when to expect to hear the results.

The doctors will give you the results when they become available.


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