Sympathetic Block is an injection given into or around the sympathetic nerves. The nerves are located on either side of the spine, in the lower back. These nerves control blood flow. A lumbar sympathetic block procedure blocks the sympathetic nerves that go to the leg on the same side as the injection. This reduces pain, swelling, color, sweating and other unusual changes in the lower extremity and improves mobility. It is done as a part of the treatment of Reflex Sympathetic Dystrophy (RSD), Sympathetic Maintained Pain, Complex Regional Pain Syndrome and Herpes Zoster (shingles) involving the legs. Repeat injections are recommended for patients who respond well to the first one and show improvement.