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Lumbar Sympathetic Plexus Block

The sympathetic nervous system is a set of nerves that regulate the body’s unconscious actions such as heart rate, blood pressure, sweating, and digestion. Typically these nerves do not conduct pain signals.

Sometimes, after a peripheral nerve is damaged by trauma, infection or other causes, the sympathetic nervous system can become a generator of pain signals. When this happens, symptoms include color changes, swelling of the affected body part, significant sensitivity to touch and pressure, and abnormal hair growth or sweating.

One specific portion of this sympathetic nervous system is the lumbar sympathetic plexus. It is a collection of sympathetic nerves found at the level of the second, third, and sometimes fourth lumbar vertebrae. The nerves are located in front of the vertebrae and run as a pair to provide sympathetic function for the right and left lower extremities.

A lumbar sympathetic plexus block has two primary purposes:

  • The first purpose is diagnostic. If a sympathetically-driven pain state is suspected as a cause of lower extremity pain, this block may help confirm this suspicion.
  • In addition, this procedure can provide sustained relief, especially when performed as a series of blocks over a few weeks as opposed to a single injection. This allows a window of opportunity to maximize additional treatments for pain such as physical therapy.

How It Works

A lumbar sympathetic plexus block is administered to block the sympathetic nerves that provide information and function to the lower extremities. This treatment may in turn, reduce pain, swelling, color and sweating changes in the lower extremity, and may also improve mobility.

It is done as a part of the treatment of complex regional pain syndrome (CRPS, and sometimes called reflex sympathetic dystrophy or RSD) and herpes zoster (shingles) involving the legs.

  • During the procedure, you will be asked to lie on your stomach.
  • Your lower back will be cleaned with an antiseptic, and a sterile drape will be placed.  
  • Your physician will inject a numbing medication (local anesthetic) to numb the skin. 
  • A needle will then be guided to the targeted vertebral body — typically L2 and L3. 
  • Contrast dye will be injected to confirm the location of the needle along the targeted landmark and to ensure the needle is in safe position. 
  • A small volume of numbing medicine will be injected onto the lumbar sympathetic plexus. 
  • The needles will be removed, and a sterile dressing will be applied. 

There are some expected changes that result from blocking the sympathetic nerves. These changes are temporary and may last about 4-6 hours. Such changes include the following symptoms on the same side as the injection: a temperature increase in the leg. You may also experience some fullness of the leg due to increased blood flow from the nerve block. This is a normal and expected outcome.


This procedure is safe. However, with any procedure there are risks, side effects and possibility of complications. The most common side effect is temporary pain at the injection site. Other less common risks include bleeding, infection, spinal block, epidural block, and injection into blood vessels and surrounding organs. Fortunately, serious side effects and complications are uncommon. X-ray guidance to provide visualization of the targeted structures significantly minimizes risk.