Lumbar Puncture Health Article

Definition

Lumbar puncture (LP) is the technique of using a needle to withdraw cerebrospinal fluid (CSF) from the spinal canal. CSF is the clear, watery liquid that protects the central nervous system from injury and cushions it from the surrounding bone structure. It contains a variety of substances, particularly glucose (sugar), protein, and white blood cells from the immune system.

Purpose

Lumbar puncture, or spinal tap, is used to diagnose some malignancies, such as certain types of brain cancer and leukemia, as well as other medical conditions that affect the central nervous system. It is also used for injecting chemotherapy directly into the CSF. This type of treatment is called intrathecal therapy. Other medical conditions diagnosed with lumbar puncture include:

• viral and bacterial meningitis
• syphilis, a sexually transmitted disease
• bleeding (hemorrhaging) around the brain and spinal cord
• multiple sclerosis, a disease that affects the myelin coating of the nerve fibers of the brain and spinal cord
• Guillain-Barré syndrome, an inflammation of the nerves

Precautions

In some circumstances, a lumbar puncture to withdraw a small amount of CSF for analysis may lead to serious complications. Lumbar puncture should be performed only with extreme caution, and only if the benefits are thought to outweigh the risks, in certain conditions. For example, in people who have blood clotting (coagulation) or bleeding disorders or who are on anticoagulant treatment, lumbar puncture can cause bleeding that can compress the spinal cord. The term for this condition is spinal subdural hematoma, and it is a rare complication. However, it is of concern to some cancer patients whose low platelet counts (thrombocytopenia) make them more susceptible to bleeding. In some cases, these patients are given a platelet transfusion prior to lumbar puncture, but this procedure is still under investigation. A 1984-88 study, supported in part by the National Cancer Institute, researched the risk of lumbar puncture on children with acute lymphoblastic leukemia (ALL). No serious lumbar puncture complications were observed in this study of over 5, 000 children.

A traumatic lumbar puncture (TLP) occurs when a blood vessel is inadvertently ruptured during the procedure. If this happens as part of a diagnostic leukemia workup, there is the potential of contaminating the CSF specimen that has been removed with leukemia cells, causing a false positive test result.

If there is a large brain tumor or other mass, removal of CSF can cause pressure shifts within the brain (herniation), causing compression of the brain stem and other vital structures, and leading to irreversible brain damage or death. These problems are easily avoided by checking blood coagulation through a blood test and by doing a computed tomography scan (CT) or magnetic resonance imaging (MRI) scan before attempting the lumbar puncture. In addition, a lumbar puncture procedure should never be performed at the site of a localized skin infection on the lower back because the infection may be introduced into the CSF and may spread to the brain or spinal cord.