A sympathetic nerve block is believed by many pain health care providers to be an effective method for controlling chronic pain.  However, there is not a great deal of medical evidence to show whether these blocks are actually helpful. This therapy targets the sympathetic nervous system, a series of nerves that spread out from your spine to your body to help control several involuntary body functions, or body functions that you have no control over. These include blood flow, digestion, and sweating.

When can a nerve block be used?

A sympathetic nerve block can be used to diagnose or treat pain involving the nerves of the sympathetic nervous system. Examples of conditions for which a sympathetic nerve block might be used include:

• Pain from spasms in the blood vessels 

• Complex regional pain syndrome, previously called reflex sympathetic dystrophy and causalgia

• Raynaud's syndrome

• Some types of chronic stomach pain

• Excessive sweating

Sympathetic nerve block procedure

The location of your pain usually determines where you'll receive the nerve block. Your sympathetic nerves come together outside your spine area in thick networks of nerves called ganglions. If you have pain in the upper part of your body, you may get pain relief from blocking the stellate ganglion in your neck area. If you have pain in the lower part of your body, a ganglion near the lower spine may be targeted with a lumbar sympathetic block.

This is what may happen during a sympathetic block procedure:

• You will meet with a pain management specialist experienced in conducting nerve blocks.

• Your health care provider will ask about all the medicines you're taking, including vitamins and supplements, and whether you have any allergies.

• You may be asked to fast for about 6 hours before the procedure.

• The medical team may start an intravenous line and monitor your vital signs carefully.

• You may be given some medicine through the IV line to make you relaxed and sleepy.

• Before the actual block, the area in your neck or back will be made numb with a local anesthetic.

• X-rays (or fluoroscopy) may be used to help the specialist find the right ganglion.

• Once the ganglion is located, it is blocked by injecting it with an anesthetic solution, or sometimes other chemicals are used.

After nerve block treatment

A sympathetic nerve block is a relatively safe procedure. You can usually go home afterward and return to your normal activities after a day of rest. If you had IV sedation, you'll probably need to have someone drive you home.

Side effects after a sympathetic block may include temporary soreness, a feeling of warmth, or some weakness. If you've received a nerve block in the stellate ganglion, you may experience some temporary voice changes, eyelid droop, or difficulty swallowing. Until swallowing is back to normal, avoid large bites of food and sip liquids carefully.

Physical therapy, talk therapy, and pain medicine may all be part of your treatment along with sympathetic block. In most cases, you will be given a series of blocks to get the best possible response.

Sympathetic blocks don't work for everyone. Also, the pain relief they give may lessen over time. But for some, a sympathetic block may provide weeks or months of pain relief.