What It Is

A lumbar puncture (also called a spinal tap) is a common medical test that involves taking a small sample of cerebrospinal fluid (CSF) for examination. CSF is a clear, colorless liquid that delivers nutrients and "cushions" the brain and spinal cord, or central nervous system. In a lumbar puncture, a needle is carefully inserted into the lower spine to collect the CSF sample.

Why It's Done

Medical personnel perform lumbar punctures and test the cerebrospinal fluid to detect or rule out suspected diseases or conditions. CSF testing looks for signs of possible infection by analyzing the white blood cell count, glucose levels, protein, and bacteria or abnormal cells that can help identify specific diseases in the central nervous system.

Most lumbar punctures are done to test for meningitis, but they also can determine if there is bleeding in the brain, detect certain conditions affecting the nervous system such as Guillain Barré syndrome and multiple sclerosis, and administer chemotherapy medications.

Preparation

After the procedure is explained to you, you'll be asked to sign an informed consent form — this states that you understand the procedure and its risks and give your permission for it to be performed.

The doctor doing the lumbar puncture will know your child's medical history but might ask additional questions, such as whether your child is allergic to any medicines.

You might be able to stay in the room with your child during the procedure, or you can step outside to a waiting area.