About Children's Cancer

Lumbar puncture

A lumbar puncture is often called a ‘spinal tap’.

Some cancers can spread into the fluid around the brain and spine. This fluid is called cerebrospinal fluid (CSF). A doctor will use a lumbar puncture to collect the CSF.

Cancer cells or tumour markers in the CSF indicate whether a brain or spinal cord tumour, or another cancer such as leukaemia, has spread to the CSF. The doctors will use the results of a lumbar puncture to guide treatment options.

A lumbar puncture is similar to bone marrow tests. The difference is that the needle is inserted into the lower back, between the bones of the lower part of the spine (also called the lumbar spine), to remove a sample of CSF. This procedure takes around 20 minutes.

Lumbar punctures are painful, and your child needs to stay still during the procedure. Your doctor may give your child either:

  • a general anaesthetic, to put them to sleep so that they don’t feel any pain, or
  • another medicine for ‘conscious sedation’, where your child will be awake during the procedure but will not feel pain.

Your child may also need to lie on their back for up to an hour after the procedure to reduce the chance of developing a headache.

A pathologist will look at the sample under a microscope to determine whether the sample contains cancerous cells. Part of the sample may also be sent to a laboratory to check for tumour markers. It will usually take a few days for you to find out the results.

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