What is a Lumbar Sympathetic Block (LSB)

The lumbar sympathetic chain is a group of nerves located along the lower spine. These nerves help regulate blood flow, sweating, temperature, and nerve activity in the legs and feet. In conditions such as Complex Regional Pain Syndrome (CRPS) or other sympathetic-mediated pain disorders, these nerves can become overactive and cause:

  • Burning or sharp pain
  • Swelling
  • Skin color or temperature changes
  • Hypersensitivity to touch
  • Changes in sweating
  • Reduced movement due to pain

A lumbar sympathetic block is a minimally invasive injection designed to temporarily interrupt this abnormal nerve activity and provide pain relief.

Goal of the Procedure

The lumbar sympathetic block is performed to:

  • Reduce pain related to CRPS or sympathetically maintained pain in the leg or foot
  • Improve blood flow to the affected limb
  • Reduce swelling and skin temperature changes
  • Decrease hypersensitivity and nerve overactivity
  • Support physical therapy and functional recovery
  • Determine if the sympathetic nerves are contributing to the patient’s pain (diagnostic purpose)

Some patients achieve short-term relief after one injection, while others may benefit from a series of blocks for longer-lasting improvement.

Procedure Overview

  • You are brought into a sterile procedure suite and positioned on your stomach.
  • The skin over your lower back/flank is cleansed thoroughly with an antiseptic solution.
  • Using fluoroscopy (X-ray guidance), your provider identifies the appropriate lumbar sympathetic chain location.
  • The skin and deeper tissues are numbed with a local anesthetic.
  • A thin needle is guided toward the sympathetic nerve bundle along the front side of the spine.
  • Once the needle is correctly positioned, a small amount of local anesthetic, and sometimes a steroid, is injected.
  • You will then be transferred to the recovery area for monitoring before being discharged home.

The injection itself is quick, but positioning and imaging guidance ensure safety and accuracy.

After the Procedure

Please follow discharge instructions carefully:

  • Mild warmth, increased blood flow, or a feeling of heaviness in the treated leg may occur. This is a sign that the block is effective.
  • Avoid driving or operating machinery for the rest of the day if you received sedation.
  • Soreness at the injection site may last 24–48 hours.
  • Apply ice packs if needed.
  • You may resume normal activities the day after the procedure, as tolerated.
  • The care team will follow up with you to evaluate your response to the injection and discuss next steps.

Expected Results

Warmth or increased blood flow to the leg usually occurs within minutes.

  • Pain relief may happen immediately or gradually over a few hours.
  • Some patients may need repeated blocks to achieve longer-lasting improvement.
  • Treatment may improve the ability to participate in physical therapy and daily function.
  • If the block provides relief, you may be a candidate for additional procedures such as radiofrequency ablation of the sympathetic chain (varies by provider and insurance).

If Your Procedure Includes Sedation

(Not every patient requires sedation.)

  • No solid food for 8 hours before your procedure.
  • Clear liquids are allowed up to 2 hours before (water, broth, clear juices without pulp, black coffee or tea).
  • No carbonated drinks, chewing gum, candy, mints, or lozenges within 2 hours of the procedure.
  • The care team will contact you in advance to review your medications and guide you on what to take the morning of your appointment.

Failure to follow these guidelines may result in rescheduling.

Potential Risks

Lumbar sympathetic blocks are generally safe, but risks include:

  • Pain, bruising, or soreness at the injection site
  • Infection (rare)
  • Bleeding or hematoma
  • Temporary leg weakness or numbness
  • Low blood pressure
  • Allergic reaction to medications
  • Injury to nearby nerves or blood vessels (rare)
  • No improvement in pain symptoms
  • Intravascular injection (minimized by imaging guidance)

Serious complications are extremely uncommon.

Insurance Requirements

Insurance companies may require documentation showing:

  • A confirmed diagnosis of CRPS or suspected sympathetic-mediated pain
  • Failure of conservative treatments (medications, physical therapy, home exercises)
  • Relevant imaging or clinical evaluation ruling out other causes of symptoms
  • Symptoms consistent with sympathetic overactivity (color changes, temperature changes, swelling, hypersensitivity)