Lumbar Puncture
all information

Lumbar Puncture

(Cerebrospinal Fluid Analysis; Cerebrospinal Fluid Tap; Puncture, Lumbar; Spinal Tap)

En Español (Spanish Version)


This is a procedure to collect cerebrospinal fluid (CSF). It involves inserting a needle between the third and fourth lumbar vertebrae in the back and extracting a sample of fluid.

Lumbar Puncture Method

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Parts of the Body Involved

Done between the third and fourth lumbar vertebrae

Reasons for Procedure

A lumbar puncture is done when the following conditions are suspected:

  • Meningitis (inflammation of the membranes that cover the brain and spinal cord)
  • Encephalitis (inflammation of the brain)
  • Guillain-Barré syndrome (inflammation of the nerves outside the brain and spinal cord)
  • Multiple sclerosis (disease caused by inflammation, destruction, and scarring of the sheath that covers nerve fibers in the brain and spinal cord)
  • Any disorder affecting the nervous system
  • Central nervous system syphilis
  • Lymphoma , leukemia , or other cancers involving the brain or central nervous system
  • Certain forms of hydrocephalus (water on the brain)
  • Bleeding in the brain or spinal cord

The procedure may also be done to:

  • Administer dye for imaging studies
  • Drain spinal fluid to lower pressure within the brain
  • Administer medications (eg, chemotherapy, anesthesia)

Risk Factors for Complications During the Procedure

  • A local infection at the site where the needle would be inserted
  • Elevated pressure in the skull

What to Expect

Prior to Procedure

  • CT scan—a type of x-ray that uses a computer to make pictures of structures inside the body (This test may be done.)
  • Your back will be cleaned at the site where the needle will be inserted.


Local anesthesia

Description of the Procedure

You lie on your side with knees drawn up to abdomen. A needle is inserted into the spinal canal through your lower back. A sample of CSF is withdrawn through the needle. The pressure of the CSF is measured. If you experience discomfort, the needle may need to be repositioned. If you have a problem with your lower back and cannot lie on your side, the CSF may be taken from the top of the spine.

After Procedure

The fluid is sent to a lab for analysis. You lie down for 10-15 minutes. Unless you have a severe headache, you can leave.

How Long Will It Take?

30 minutes or more

Will It Hurt?

Overall, discomfort is minimal to moderate. The anesthetic will sting when first injected. There is usually a little pain when the needle is first inserted, but it should subside in a few seconds.

Possible Complications

These complications are rare:

  • Herniation and death
  • Local infection
  • Pain or abnormal burning, pricking, or tingling sensations in your legs
  • Hematomas (blood clots)
  • Inflammation of the arachnoid mater (a delicate membrane lining the nervous system)
  • Temporary paralysis of a cranial nerve
  • Rupture of the soft, central portion of the intervertebral disk (called the nucleus pulposus)
  • Tumor (called intraspinal epidermoid tumor)
  • Meningitis

Average Hospital Stay

This is typically an outpatient procedure. It does not require a hospital stay.

Postoperative Care

When at home, follow your doctor's instructions, such as:

  • Drink extra fluids for the next 24 hours.
  • Rest and remain quiet for at least 24 hours.


Based on the pressure and contents of the CSF, a diagnosis can often be made. High pressure can indicate swelling, bleeding, a tumor, or hydrocephalus.

The CSF is also analyzed for:

  • Antibodies
  • Bacteria, viruses, fungi
  • Cancer cells
  • Excess protein
  • White blood cells

Normal CSF is clear and contains no blood. If there is blood or a yellowish color, it may indicate an obstruction or bleeding in the brain or spinal cord.

Call Your Doctor If Any of the Following Occurs

  • Severe headache or headache lasting for more than 24 hours
  • Nausea or vomiting
  • Signs of infection, including fever and chills
  • Redness, swelling, increasing pain, bleeding, or discharge from the site of the spinal tap
  • Tingling
  • Numbness or pain in your lower back and legs
  • Problems with urination


American Academy of Family Physicians

National Library of Medicine


About Kids Health

Health Canada


Lumbar puncture. JAMA website. Available at: Updated July 2008. Accessed July 22, 2008.

The PDR Family Guide Encyclopedia of Medical Care. New York, NY: Three Rivers Press; 1997.

The University of Iowa website. Available at: Accessed July 22, 2008.

Last reviewed February 2008 by Robert Leach, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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