A lumbar puncture (also known as a spinal tap) is a procedure used to take a sample of cerebrospinal fluid (CSF) from the spinal canal so that it can be tested. The spinal canal is the passageway through the back bones (vertebrae) which contains the spinal cord.
A hollow needle is inserted into the lower part of the spinal canal to draw out the CSF (see How it is performed). Usually only a few millilitres are taken.
The procedure is very safe and takes place routinely without complications.
Why is a lumbar puncture done?
A lumbar puncture is normally used to diagnose meningitis, but can also diagnose other conditions of the brain and spinal cord. These include multiple sclerosis and cancer (see Why it is necessary). A lumbar puncture can also be used to give chemotherapy drugs to the patient.
Continue to next section: Why it is necessary