Sympathetic nerves run on the front surface of the spinal column and not inside the spinal canal, like the nerves that provide sensation and strength to the legs. These nerves are part of the autonomic nervous system, which controls functions such as blood flow and temperature regulation to the arms and legs, sweating, heart rate, digestion, and blood pressure, among others.

A sympathetic nerve block involves using fluoroscopic guidance (x-ray) to inject numbing medicine around the sympathetic nerves in the low back or neck to temporarily 'switch the nerves off' in hopes of reducing or eliminating pain. If pain is substantially improved after the block, then a diagnosis of sympathetically mediated pain is established.

The therapeutic effects of the anesthetic may occur for a more extended period than would be normally expected. The goal is to reset the sympathetic tone to a healthy state of regulation. If the initial block is successful, then additional blocks may be performed if the pain continues to decrease sequentially.

Sympathetic nerve blocks are helpful in treating back pain, complex regional pain syndrome (CRPS), neuropathy, peripheral vascular disease, and neurological symptoms due to trauma.