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Spinal Tap

Spinal Tap Introduction

  • A spinal tap is a procedure performed when a doctor or health care professional needs to evaluate the cerebrospinal fluid (also known as spinal fluid or CSF). Spinal tap is also referred to as a lumbar puncture, or LP.
  • Some of the reasons your doctor may want to do a spinal tap include the following:
    • To look for infection (bacteria can be found in the spinal fluid)
    • To check to see if there is bleeding around the brain (subarachnoid hemorrhage; small amounts of blood will be found in the fluid)
    • To look for causes of unexplained seizures
    • To look for causes of headaches
    • To evaluate for uncommon diagnoses such as multiple sclerosis, Lyme disease, Guillain-Barré syndrome, and several others.
    • To administer certain types of chemotherapeutics medications in the treatment of some cancers
  • Cerebrospinal fluid is a liquid that bathes the brain and spinal cord. An adult has about 140 mL (just under 5 oz) of spinal fluid. Typically, an adult makes 30-100 mL of spinal fluid daily.
  • A spinal tap can be performed in any person and at any age.

Spinal Tap Risks

The spinal cord ends at the level of the first or second lumbar vertebrae, and the needle is usually inserted at a level between the third and fourth or the fourth and fifth lumbar vertebrae, keeping the spinal cord completely out of danger.

Although very infrequent, several complications can occur as a result of a spinal tap.

  • Headache
    • A few people get what is commonly referred to as post-lumbar puncture headache.
    • The headache may start up to 48 hours after the procedure and usually lasts for two days or less.
    • The headache typically worsens in an upright position and lessens lying flat.
    • The cause of the headache is leakage of the spinal fluid from around the puncture site.
    • Younger people and males have an increased risk of headaches after lumbar puncture compared with older people and females.
    • The chance of getting one of these headaches is reduced by drinking plenty of fluids, especially caffeine products such as tea, coffee, and cola.
    • Occasionally, the only way to treat the headache is with a procedure called a blood patch. An anesthesiologist or pain management specialist injects a small amount of your own blood at the site where the spinal tap was performed. You usually experience relief within 30 minutes after this procedure.
  • Herniation
    • A herniation can occur if an abscess (pocket of infection) or increased intracranial pressure (ICP) is present during your spinal tap.
    • If the pressure in your brain is elevated when the spinal tap is performed, the flow of fluid from the brain down the cord may cause the brain to get squeezed down into the direction of the spinal cord. This is extremely rare and occurs only with significantly elevated intracranial pressure.
    • If a person has signs and symptoms consistent with meningitis (fever, headache, and stiff neck), then the spinal tap may be performed immediately to avoid delays in treatment. In some people, a CT scan of the brain is performed first, however, to rule out the possibility of bleeding or other causes that may increase the pressure within the skull or around the brain.
    • If increased intracranial pressure is suspected, great caution is taken and your condition is carefully discussed before a spinal tap is performed, if it is performed at all.
  • Bleeding
    • Injury to the blood vessels that surround the covering of the spinal canal may occur when the needle is being inserted. Frequently referred to as a traumatic tap, this may cause a small amount of localized bleeding.
    • Sometimes this can affect the results of the procedure, which would mean that the doctor would have to reinsert the needle into another area of the back, frequently an inch or so away from the first site. Proper numbing medicine, if needed, is injected to decrease any pain.
  • Epidermoid cyst
    • Rarely, certain tissues (epidermoid) are accidentally implanted into the spinal canal when the spinal tap is performed.
    • The likelihood of an epidermoid cyst is much greater when a needle without a stylet is used, and this almost never occurs today. All spinal tap kits used today have needles with stylets.

Spinal Tap Preparation

  • No special preparation is needed on your part before a spinal tap.
  • Always ask your doctor to fully explain the process to you as she or he is doing it. This talking through helps to lessen any anxiety that you may experience.
Medically Reviewed by a Doctor on 11/17/2017
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What Happens During the Spinal Tap?

  • The doctor and possibly a nurse or a technologist will be in the room with you during a spinal tap.
  • Pre-medication may be given to help you relax.
  • You will wear a hospital gown during the test.
  • You will either: Lie on your side with your knees drawn as close to your chest as possible and your chin toward your chest; or lie on your stomach with a small pillow beneath your lower abdomen.
  • After cleaning your back with an antiseptic, sterile cloths will be placed around the area.
  • A local anesthetic (pain-relieving medication) will be injected into the area of your back that the fluid will be drawn from. You may feel a slight burning sensation.
  • When the area is numb, a hollow needle is inserted in the lower back between the two lumbar vertebrae. This sometimes causes pressure.
  • The spinal canal is penetrated, and fluid is collected (the spinal cord is not touched by the needle during the test).
  • The needle is removed after the fluid is removed. The area will be cleaned with an antiseptic and covered with a small bandage.
  • A blood sample may be taken from a vein in your arm and tested, along with the spinal fluid, in the laboratory.

SOURCE: WebMD Medical Reference

Read What Your Physician is Reading on Medscape

Lumbar Puncture (CSF Examination) »

Cerebrospinal fluid (CSF) was first examined in the 19th century using primitive techniques (eg, sharpened bird quills).

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