Lumbar sympathetic blocks are done for people with RSD (Reflex Sympathetic Dystrophy), also called CRPS (Complex Regional Pain Syndrome) of the legs. RSD may result from an impaired sympathetic nervous system (the fight or flight part of the nervous system). Typically RSD occurs after an injury, fracture or surgery to the leg resulting in a very sensitive lower extremity with vascular changes such as edema and/or color changes and often decreased range of motion. The lumbar sympathetic ganglia live in front of the L2, L3, and L4 vertebrae. Blocking the ganglia interrupts the sympathetic nervous system in an attempt to "reset" the sympathetic nervous system. With a sympathetic block, you should not experience numbness or weakness, however, you should feel a warmth in your extremity. A sympathetic block allows less pain and better movement of the extremity.