Lumbar puncture (spinal tap)

Lumbar puncture (spinal tap) is performed in your lower back, in the lumbar region. During lumbar puncture, a needle is inserted between two lumbar bones (vertebrae) to remove a sample of cerebrospinal fluid — the fluid that surrounds your brain and spinal cord to protect them from injury.

A lumbar puncture can help diagnose serious infections, such as meningitis; other disorders of the central nervous system, such as Guillain-Barre syndrome and multiple sclerosis; or cancers of the brain or spinal cord. Sometimes doctors use lumbar puncture to inject anesthetic medications or chemotherapy drugs into the cerebrospinal fluid.


Why it's done Risks How you prepare What you can expect Results

Lumbar puncture may be done to:

  • Collect cerebrospinal fluid for laboratory analysis
  • Measure the pressure of your cerebrospinal fluid
  • Inject spinal anesthetics, chemotherapy drugs or other medications
  • Inject dye (myelography) or radioactive substances (cisternography) into cerebrospinal fluid to make diagnostic images of the fluid's flow

Information gathered from a lumbar puncture can help diagnose:

  • Serious bacterial, fungal and viral infections, including meningitis, encephalitis and syphilis
  • Bleeding around the brain (subarachnoid hemorrhage)
  • Certain cancers involving the brain or spinal cord
  • Certain inflammatory conditions of the nervous system, such as multiple sclerosis and Guillain-Barre syndrome
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