A lumbar puncture is a medical procedure where a thin needle is inserted into the lower back to access the fluid that surrounds the brain and spinal cord, called cerebrospinal fluid (CSF).^ It is also commonly known as a “spinal tap.”^

What it is

  • A lumbar puncture involves placing a needle between the bones of the lower spine to enter the spinal canal and reach the CSF around the spinal cord.^
  • A small amount of this fluid can be removed for testing, or medicines can be injected into it for treatment.^

Why it’s done

Doctors recommend a lumbar puncture for several reasons.^

  • To help diagnose infections of the brain or spine, such as meningitis or encephalitis.^
  • To look for bleeding around the brain or diseases like multiple sclerosis or certain cancers affecting the nervous system.^
  • To give medicines (for example some chemotherapy drugs) or spinal/epidural anaesthetic directly around the spinal cord.^

What happens during the procedure

  • You are usually asked to lie curled on your side or sit leaning forward so the spaces between the vertebrae open up.^
  • The skin on the lower back is cleaned and numbed with local anaesthetic; this can sting briefly.^
  • A thin hollow needle is then guided into the lower spine; you might feel pressure or brief pins-and-needles as it passes in.^
  • CSF is collected in tubes, or medication is injected, and then the needle is removed and a small dressing is placed.^

Common side effects and risks

  • The most common side effect is a headache afterwards, often called a “post–lumbar puncture headache,” which usually improves with fluids, rest, and simple pain relief.^
  • There may be mild back discomfort or tenderness at the puncture site for a short time.^
  • Serious complications like infection, bleeding, or nerve injury are uncommon but are part of the risk discussion and screening before the test.^

Quick reassurance

  • The procedure is a routine part of modern neurology and emergency medicine, done worldwide for both adults and children.^
  • Before a lumbar puncture, the medical team checks for conditions that might make it unsafe and explains the benefits, risks, and what to expect so you can give informed consent.^

If this is being considered for you or someone close to you, a direct conversation with the treating doctor or nurse specialist can clarify personal risks, alternatives, and how to prepare.