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:
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.
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.