A lumbar puncture is a medical procedure where a sample of fluid is taken from inside the lower back for testing.
A hollow needle is inserted between two bones, called vertebrae, at the base of the spine and is used to draw fluid out.
A lumbar puncture is most commonly carried out when it's thought that a condition such as meningitis has developed inside the brain or nervous system. Meningitis is a serious infection of the membranes that surround the brain and spinal cord.
Cerebrospinal fluid
Cerebrospinal fluid (CSF) is a colourless fluid that surrounds and supports the brain and spinal cord. In the same way that studying a blood sample can tell doctors about the health of a person’s body, studying a sample of CSF can often reveal a great deal about the health of a person’s brain and nervous system.
For example, if bacteria are found in a sample of CSF, it's highly likely to be the result of a brain infection. If a large number of red blood cells are found in a sample of CSF, it may be due to bleeding inside the brain.
When a lumbar puncture is used
The most common reason for a lumbar puncture being carried out is to diagnose a suspected case of:
How a lumbar puncture is done
During a lumbar puncture, a hollow needle is inserted in between the two bones at the base of your spine and into the space surrounding the spinal cord. A small sample of a few millilitres of CSF is removed for testing.
A lumbar puncture takes around 45 minutes and is carried out under local anaesthetic, so you should not feel any pain.
If your child needs to have a lumbar puncture, they will be given medication to help relax them and keep them calm.
Read more about how a lumbar puncture is performed.
Safety
A lumbar puncture is generally safe and the risk of developing serious side effects from a lumbar puncture is relatively low.
A headache is the most common side effect and occurs in about one-third of cases. It can develop 24–48 hours after the procedure and can be moderate or severe.
Reducing risk
A study conducted in France found that about 14% of lumbar punctures detected a serious condition.
As conditions such as meningitis can be life threatening if they're not quickly diagnosed and treated, it's considered better to carry out a lumbar puncture than to take any chances.
Being told that you or your child need a lumbar puncture may cause you a lot of worry, but it doesn't necessarily mean that you have a serious condition.
