The sympathetic nerve ganglions (clusters) can be found along the front of the spinal column and are part of the autonomic nervous system. This system controls bodily functions like blood pressure, heart rate, and digestion. After an injury or surgical procedure, these nerves may continue to transmit pain signals, which is a condition known as Chronic Regional Pain Syndrome or CRPS. The pain caused by this condition may be severe and burning in nature. CRPS may also cause localized swelling and changes in the appearance of the skin. The lumbar sympathetic block is a diagnostic procedure, involving injection of local anesthetic near the sympathetic nerves. If the patient experiences pain relief in the immediate time following the injection, a series of injections may be recommended to provide long-term pain relief.