A lumbar sympathetic block is an injection that is administered to patients in order to reduce pain that is caused by lumbar nerves. A sympathetic chain is an essential nerve bundle that is the length of the spine and runs parallel to the spinal cord. The roots of the nerves are located in the spine, and they extend to various regions of the body in order to regulate important biological functions. A bundle or a cluster is also referred to as a ganglion and this structure is comprised of numerous nerve endings. The clusters form a chain that runs from the upper region of the body to the lower region, which controls movement, sensations, and blood flow to the lower extremities.