Lumbar Puncture: Everything you Need to Know

Lumbar puncture


A lumbar puncture, also known as a spinal tap, is a medical procedure performed to collect a sample of cerebrospinal fluid (CSF) for diagnostic or therapeutic purposes. It involves inserting a needle into the space between two lumbar vertebrae in the lower back to access the subarachnoid space, which contains CSF.

Lumbar punctures are commonly performed to diagnose conditions affecting the central nervous system, such as infections, bleeding, and neurological disorders. In addition to diagnostic purposes, lumbar punctures can also be used therapeutically to relieve increased pressure within the skull or to administer medications directly into the CSF. The procedure carries some risks, including headache, infection, bleeding, or nerve injury, but serious complications are rare when performed by skilled healthcare professionals.

What is a lumbar puncture?

A lumbar puncture, also known as a spinal tap, is a medical procedure used to collect a sample of cerebrospinal fluid (CSF) from the space around the spinal cord. It involves inserting a needle into the lower back, specifically between two lumbar vertebrae, to access the subarachnoid space where CSF is located.

Lumbar,Puncture also known as a spinal tap
Lumbar puncture is performed by inserting needle into the subarachnoid space between two lumbar vertebrae

When is a lumbar puncture performed?

Lumbar punctures help doctors diagnose and treat conditions related to the central nervous system (the brain and spine). We’ll discuss some of these scenarios below:

Diagnostic purposes

A lumbar puncture is commonly used to diagnose conditions affecting the central nervous system. It helps identify infections like meningitis, encephalitis, or neurosyphilis. It can also detect certain types of cancers that spread to the brain or spinal cord, such as leukemia or lymphoma. In addition, a lumbar puncture assists in diagnosing neurological disorders like multiple sclerosis, Guillain-Barré syndrome, or certain autoimmune conditions.

Measurement of intracranial pressure

Lumbar puncture allows doctors to measure the pressure within the skull, known as intracranial pressure. This can be helpful in evaluating conditions like hydrocephalus (excess fluid in the brain), and idiopathic intracranial hypertension (increased pressure without an apparent cause). Monitoring intracranial pressure helps guide treatment decisions and assess the effectiveness of interventions.

Therapeutic Purposes

In some cases, a lumbar puncture is performed for therapeutic reasons. It can help relieve symptoms caused by increased intracranial pressure due to conditions like hydrocephalus. By removing excess cerebrospinal fluid, a lumbar puncture can alleviate pressure and reduce symptoms like headaches or visual disturbances. Additionally, medications can be directly administered into the cerebrospinal fluid through a lumbar puncture for targeted treatment of certain conditions, such as delivering chemotherapy drugs to the central nervous system.

What happens during a lumbar puncture?

During a lumbar puncture, several steps are involved:

  1. Positioning: The patient is usually positioned either on their side with their knees pulled up towards their chest or sitting and leaning forward. This position helps to create space between the vertebrae in the lower back and allows for easier access to the spinal canal.
  2. Sterilization and anesthesia: The lower back area is cleaned and sterilized to reduce the risk of infection. Local anesthesia is then administered to numb the skin and tissues in the area where the needle will be inserted. This helps minimize pain or discomfort during the procedure.
  3. Needle insertion: Using a sterile technique, the healthcare provider inserts a thin needle through the skin and tissues of the lower back. The needle is carefully advanced between the vertebrae and into the spinal canal, which contains the cerebrospinal fluid (CSF). The patient may feel some pressure or a brief sharp sensation during this step.
  4. CSF collection: Once the needle is in the spinal canal, the healthcare provider collects a small amount of CSF. This is done by attaching a syringe or collection tubes to the needle and allowing the CSF to flow into them. The amount of fluid collected can vary depending on the specific purpose of the lumbar puncture.
  5. Needle removal and site care: After the CSF has been collected, the needle is gently withdrawn. A small bandage or dressing may be applied to the puncture site to keep it clean and to protect it from infection. The patient may be asked to lie flat for a short period to help prevent headaches.

The entire procedure usually takes around 30 minutes, although the actual collection of CSF only takes a few minutes. The collected CSF is then sent to a laboratory for analysis.

Do lumbar punctures hurt?

You may feel a brief pinch or stinging sensation when the anesthetic is administered, but it should quickly numb the area.

During the procedure, you may feel some pressure or a sensation of movement as the needle is inserted into the lower back. This is usually described as a pushing or pushing sensation rather than sharp pain. It’s important to communicate with your healthcare provider if you experience any significant pain or discomfort so that they can adjust their approach or provide additional anesthesia if necessary.

What is the recovery time?

After the procedure, you may be asked to lie flat for a short period, usually around 30 minutes to an hour. This helps minimize the risk of developing a headache. The medical staff will monitor you during this time to ensure you are stable.

Once you’re allowed to sit up or move around, you can typically resume normal activities. It’s common to experience some mild soreness or discomfort at the puncture site in your lower back. Over-the-counter pain relievers, such as acetaminophen (Tylenol), can help manage any discomfort.

Drinking plenty of fluids, such as water, can help replenish the cerebrospinal fluid that was removed during the lumbar puncture. Staying well-hydrated can also help prevent headaches.

What are the risks of a lumbar puncture?

While lumbar punctures (spinal taps) are generally safe, there are potential risks and complications associated with the procedure. It’s important to be aware of these risks, although they are relatively uncommon. The risks include:

  • Headache: The most common side effect of a lumbar puncture is a headache, which can occur in up to one-third of patients. This headache is usually mild and goes away on its own within a few days. In some cases, the headache may be more severe and require medical intervention.
  • Infection: While rare, there is a small risk of infection associated with lumbar punctures. The procedure involves piercing the skin and introducing a needle into the spinal canal, creating a potential route for infection. Healthcare providers take precautions to minimize this risk, such as using sterile techniques and properly disinfecting the puncture site.
  • Bleeding: In rare cases, a lumbar puncture can cause bleeding around the spinal canal. This is more likely to occur if you have a bleeding disorder or are taking blood-thinning medications. Healthcare providers will assess the risks and benefits before performing the procedure.
  • Nerve injury: Although extremely rare, there is a minimal risk of nerve injury during a lumbar puncture. The spinal cord and nerves are in close proximity to the site of the procedure. Skilled healthcare professionals take care to avoid any nerve damage during the insertion of the needle.


A lumbar puncture, or spinal tap, is a procedure used to collect cerebrospinal fluid (CSF) for diagnosis and treatment purposes. By accessing the subarachnoid space in the lower back, healthcare professionals can gather valuable information about central nervous system conditions. This procedure is commonly employed to diagnose infections, bleeding, and neurological disorders. Additionally, lumbar punctures can serve therapeutic purposes by relieving pressure or delivering medications directly to the CSF. While there are risks involved, such as headaches or infections, they are generally rare when performed by experienced healthcare providers. Overall, lumbar punctures play a vital role in helping healthcare professionals understand and manage central nervous system disorders.

About the Author

Dave Harrison, MD

Dr. Harrison is a board certified Emergency Physician with a part time appointment at San Francisco General Medical Center and is an Assistant Clinical Professor-Volunteer at the UCSF School of Medicine. Dr. Harrison attended medical school at Tufts University and completed his Emergency Medicine residency at the University of Southern California. Dr. Harrison manages the editorial process for