Lumbar Puncture

Lumbar Puncture

A lumbar puncture (also called a spinal tap) is a procedure to collect and look at the fluid (cerebrospinal fluid, or CSF) surrounding the brain and spinal cord.

During a lumbar puncture, a needle is carefully inserted into the spinal canal low in the back (lumbar area). Samples of CSF are collected. The samples are studied for color, blood cell counts, protein, glucose, and other substances. Some of the sample may be put into a special culture cup to see if any infection, such as bacteria or fungi, grows. The pressure of the CSF also is measured during the procedure.
Why It Is Done

A lumbar puncture is done to:

    Find a cause for symptoms possibly caused by an infection (such as meningitis), inflammation, cancer, or bleeding in the area around the brain or spinal cord (such as subarachnoid hemorrhage).
    Diagnose certain diseases of the brain and spinal cord, such as multiple sclerosis or Guillain-Barr� syndrome.
    Measure the pressure of cerebrospinal fluid (CSF) in the space surrounding the spinal cord. If the pressure is high, it may be causing certain symptoms.

A lumbar puncture may also be done to:

    Put anesthetics or medicines into the CSF. Medicines may be injected to treat leukemia and other types of cancer of the central nervous system.
    Put a dye in the CSF that makes the spinal cord and fluid clearer on X-ray pictures (myelogram). This may be done to see whether a disc or a cancer is bulging into the spinal canal.

In rare cases, a lumbar puncture may be used to lower the pressure in the brain caused by too much CSF.