Lumbar Sympathetic Nerve Blocks
The lumbar sympathetic nerve block is performed to diagnose and treat leg pain caused by a dysfunction of the sympathetic nerves. The lumbar sympathetic nerves transmit signals to the lower extremities that affect blood flow and sweating. Injuries to the lower extremities can impair the function of these nerves, resulting in burning pain in the leg or foot. This condition is called Complex Regional Pain Syndrome or Reflex Sympathetic Dystrophy. Often, the pain is so severe that even the touch of clothing to the area is unbearable. Skin color and temperature changes can also be noted in the painful extremity.
The procedure involves an injection of local anesthetic and steroid solution into the lower back, just in front of the vertebra, where the sympathetic chain is located. A warm feeling in the foot is indicative of a successful block. If the patient experiences pain relief, the diagnosis of sympathetically mediated pain is confirmed.
Risks of the procedure are rare, but include bleeding, infection, injection into blood vessels, nerve injury, or spinal or epidural block. Localized bruising and pain at the injection site are more common complications and these usually resolve in 2-4 days. Some numbness of the lower extremity may occur after the procedure from the local anesthetic. Patients need to have someone to drive them home after the procedure.
The success of lumbar sympathetic block varies, and has been found to be most effective when it is performed within the first few months after the injury. Some studies say that the success rate is about 72% if the procedure is performed in the first six months after the injury. (Pain Digest. 1999; 9: 1-24)