How Is a Lumbar Puncture Procedure Done?

Reviewed on 1/29/2021

A lumbar puncture (LP) or spinal tap involves inserting a hollow needle near the spinal cord to collect a small amount of cerebrospinal fluid (CSF) and diagnose meningitis,  hemorrhage,  multiple sclerosis, and  tumors.
A lumbar puncture (LP) or spinal tap involves inserting a hollow needle near the spinal cord to collect a small amount of cerebrospinal fluid (CSF) and diagnose meningitis, hemorrhage, multiple sclerosis, and tumors.

A lumbar puncture (LP) is also called a spinal tap. It involves the insertion of a hollow needle into the space (called subarachnoid space) around the spinal cord for collecting a small amount of fluid (called the cerebrospinal fluid or CSF). 

The procedure is done in the lower back, and the fluid is sent for laboratory analysis. A lumbar puncture may also be done to inject a medication into the subarachnoid space.

The CSF is a clear, watery fluid that is present around the brain and spinal cord (the central nervous system or CNS). The fluid is responsible for various functions, such as protecting the CNS against shock injuries, maintaining optimum pressure in the CNS, providing nutrients to the brain and spinal cord, and carrying away waste products. 

Examining the CSF through a lumbar puncture helps diagnose various conditions affecting the CNS, such as 

It also helps in delivering medicines directly to the CNS in a concentrated form without any side effects to other parts of the body.

A lumbar puncture is generally done as an outpatient procedure. You will be able to go home the same day of the procedure. You will, however, need someone to drive you home. The procedure generally takes 45 minutes to complete.

Before the procedure, your doctor may

  • Order your blood tests.
  • Get a computed tomography (CT) scan done to rule out hydrocephalus (excessive collection of fluid in and around the brain).
  • Ask you about any long-term health conditions.
  • Ask you about any allergies, especially allergies to drugs or anesthetic medications.
  • Tell you not to eat or drink anything after midnight before your procedure.
  • Ask you about any medications (including nonsteroidal anti-inflammatory drugs [NSAIDs] and blood thinners) that you are on. They will also tell you which medications you may take in the morning before the procedure.
  • Discuss your concerns regarding the procedure.
  • Ask you to wear a hospital gown before the procedure.

During the procedure:

  • An intravenous (IV) line will be inserted in your hand or arm to administer a sedative to make you comfortable during the procedure. The procedure generally requires moderate sedation, although some patients may need general anesthesia.
  • You will lie on your sides on the procedure table.
  • The medical team may connect you to monitors to check your vitals (electrocardiography [ECG] and oxygen saturation).
  • The doctor will clean the area with an antiseptic solution and apply surgical drapes.
  • They will inject a local anesthetic (numbing medicine) at the site where the lumbar puncture is to be done.
  • The doctor will insert the lumbar puncture needle through the skin between two lumbar spine bones using fluoroscopy (image guidance) into the spinal canal.
  • You may be asked to change your position slightly once the needle is in the subarachnoid space.
  • Your doctor may remove a small amount of CSF or inject medication depending on the reason for the lumbar puncture through a tube connected to the needle.
  • The needle is withdrawn after the procedure.
  • Pressure may be applied to prevent bleeding.
  • A bandage is applied (stitches are not needed).
  • The IV line is removed.
  • You may be asked to lie on your back or side for a few hours after the procedure.

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References
Shlamovitz GZ. Lumbar Puncture Technique. Medscape.

https://emedicine.medscape.com/article/80773-technique

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