Lumbar puncture

Lumbar puncture

A lumbar puncture is usually done to find out if your child has an infection of the lining or the fluid around their brain. A doctor inserts a needle in the lower back to get a sample of the fluid that moves around the brain and spine.

Key points to remember

  • a lumbar puncture is usually done to find out if your child has an infection of the lining or the fluid around their brain
  • a doctor inserts a needle in the lower back to get a sample of the fluid that moves around the brain and spine

What is a lumbar puncture?

A lumbar puncture is also called a spinal tap or LP. A doctor inserts a needle in the lower back to get a sample of cerebrospinal fluid (CSF) that moves around the brain and spine. The needle does not go near the spinal cord.

Why would my child need a lumbar puncture?

A lumbar puncture is usually done to find out if your child has an infection of the lining or the fluid around their brain. This type of infection is called meningitis (see Meningococcal fact sheet). Occasionally lumbar punctures are done for other reasons that your doctor will explain.

How is it done?

  • the doctor or nurse may put a local anaesthetic patch on the skin first to numb the area where they will put the needle - it takes about 30 - 60 minutes for the patch to work
  • your doctor may also use local anaesthetic that is injected
  • if your child is very scared or anxious the doctor may give them some medicine that will help them to relax
  • it is very important that during this test your child does not move so a nurse will hold them gently but firmly to make sure they stay still
  • your child must lie curled up on their side with their knees tucked up under their chin
  • a doctor will clean the skin on the lower half of your child's back and then carefully insert the needle
  • the drops of spinal fluid are collected quickly into small tubes, and then the needle is removed
  • the test may be a little bit awkward as your child needs to be still the whole time and may feel some discomfort

What problems can occur?

  • sometimes the lumbar puncture is not successful - either it is not possible to get any fluid, or blood is collected instead of fluid
  • the doctor will make sure that it is safe for your child to have the test and there are very few side effects from a lumbar puncture
  • after the test a small number of children may complain of feeling sore where the needle went in, and some may have a headache for up to a couple of days
  • complications such as nerve trauma and infection are very rare. A lumbar puncture is done below where the spinal cord ends, so it is not possible to injure the spinal cord

What happens after the lumbar puncture?

If the lumbar puncture is done to look for infection, the results will usually be available within a few hours. There may be a dressing or a plaster covering the spot where the needle went in. You may notice a little bit of swelling where the needle went in, but this should disappear over the next couple of days.

What can I do to help during the test?

  • if your child asks about what is happening, be honest, reassure them and explain the test in simple terms
  • be comforting and reassuring even though you are concerned - your child will be more relaxed if you appear relaxed
  • you may be able to comfort and reassure your child while the lumbar puncture is being done but if you are not able to stay with your child, then a staff member will stay and comfort them
  • the staff are there to help and you are welcome to ask them if you would like more information
  • see 'Helping your child manage their treatment'

What can I do to help after the test?

  • if your child complains of a headache or a sore back, it may be helpful to give your child some mild pain relief such as paracetamol and allow your child to rest. When giving paracetamol, you must follow the dosage instructions on the bottle. It is dangerous to give more than the recommended dose 
  • if the headache becomes severe or does not go away your child should see their doctor

The Paediatric Society of New Zealand acknowledge the co-operation of The Children's Hospital at Westmead, Sydney Children's Hospital at Randwick, and Kaleidoscope - Hunter Children's Health Network in making this content available to patients and families.

This page last reviewed 30 June 2015.
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