Lumbar puncture

A lumbar puncture removes a small amount of cerebrospinal fluid (CSF) from the space around the spinal cord so that it can be looked at under a microscope. CSF is the fluid that surrounds and cushions the brain and spinal cord. A lumbar puncture is also called a spinal tap or CSF collection.

A lumbar puncture may be done to:

• examine the CSF for cell counts, and for protein and sugar (glucose) levels
• measure the pressure of CSF in the space around the spinal cord
• remove CSF to decrease pressure in the space around the spinal cord
• check for cancer or other diseases of the brain and spinal cord
• look for cancers that may involve the central nervous system, such as leukemia or lymphoma
• check for an infection, inflammation or bleeding around the brain or spinal cord
• put an anesthetic into the CSF to freeze the spinal cord (called a spinal anesthetic)
• inject chemotherapy drugs into the CSF to treat leukemia and other types of cancer of the central nervous system (called intrathecal chemotherapy)
• put a contrast medium into the CSF to make the spinal cord and CSF appear clearer on an x-ray

Most people feel pressure or a stinging sensation when the needle is inserted. If the needle touches a nerve, you may also feel tingling down one of your legs. This is temporary.

The pressure of the CSF is measured by a special instrument before any fluid is removed. A small amount of CSF is collected and sent to be looked at in a lab. More CSF may be removed if the pressure around the spinal cord needs to be lowered. Chemotherapy or another medicine may be injected into the CSF if that is part of your treatment plan.

Once the needle has been removed, the area is cleaned and a small bandage is put on.

After the procedure, to lower the chance of a headache, you will lie on your back for 1 to 2 hours at the clinic or hospital. When you leave, you’ll be told to drink extra fluids and rest for a few more hours when you get home.

Serious problems from a lumbar puncture are not common. Tell your healthcare team if you have side effects that you think are from the lumbar puncture. The sooner you tell them of any problems, the sooner they can suggest ways to help you deal with them.

Most side effects of a lumbar puncture are temporary. They may include:

• a headache
• a sore back
• nausea and vomiting
• dizziness
• temporary numbness, tingling or pain down your legs due to an irritated nerve
• an infection where the needle was inserted
• bleeding into the spinal canal (the space created by the vertebrae that contains the spinal cord)

Call your healthcare team if you have:

• a severe headache or a headache that lasts longer than a week
• signs of an infection such as a fever or chills, redness, swelling, pain, bleeding or discharge from the area where the needle was inserted
• tingling or numbness in your lower back or legs.

The CSF, which is generally clear and colourless, is examined and tested in the lab.

• Cloudy CSF or a high white blood cell count in the CSF may mean you have an infection.
• Blood or red blood cells in the CSF may mean there is bleeding in or around the brain or spinal cord.
• Cancer cells in the CSF may indicate a primary or metastatic brain tumour, leukemia or lymphoma.
• A large amount of protein may suggest an infection, bleeding or a disease.
• A low sugar (glucose) level may mean you have an infection.
• Increased CSF pressure may be caused by swelling or bleeding in the brain, or by an infection or something else.

Depending on the result, your doctor will decide if you need more tests, any treatment or follow-up care.

Preparing children before a test or procedure can lower anxiety, increase cooperation and help them develop coping skills. Preparation includes explaining to children what will happen during the test, including what they will see, feel, hear, taste or smell.

You may be able to be in the room with your child during a lumbar puncture.

Keeping still or holding a certain position for a long time can be stressful for a child. Practising the position before the test can help your child understand what they need to do and make them feel more in control. A nurse may help your child stay still by holding them in place during the procedure.

Younger children may be given a general anesthetic before a lumbar puncture. It is given through an intravenous (IV) line placed in a vein in the child’s hand.

Sometimes an older child can have a local anesthetic and a sedative. The healthcare team will put a numbing cream on the biopsy area before the test begins. If you need to put the cream on at home before going to the clinic or hospital, the doctor or nurse will show you what to do.

How you prepare your child for a lumbar puncture depends on your child’s age and experience. Find out more about helping your child cope with tests and treatments.