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Until recently, sympathetic nerve block played an important role in the diagnosis and treatment of RSD. If a sympathetic nerve block was performed on a patient and there was relief from pain, the diagnosis of RSD was confirmed. Currently, however, since there is ongoing debate over the exclusive role of the sympathetic nervous system in RSD, it plays a less prominent role now in RSD, although it is still performed often. There are few rigorous studies on any of these nerve blocks in RSD and data is unclear regarding long-term efficacy.

If the sympathetic nerve block is effective, it usually provides immediate, although temporary, pain relief and also increases the patient's level of comfort and function. This provides the patient with a window of opportunity for more intense efforts to restore function with increased physical therapy. In addition, this procedure does not interfere with motor activity so the patient can remain mobile and active after nerve block administration. Recurrence of pain after the initial nerve block occurs in many patients and subsequent sympathetic nerve blocks or stronger measures are required.

Despite popular opinion, there is little evidence-based information regarding the best timing for administering nerve blocks, the number that should be administered, or its long-term efficacy. In any event, nerve blockade should always be accompanied by aggressive physical rehabilitation. Because a variety of complications can occur following a nerve block, it is prudent for patients to select a pain management specialist, such as an anesthesiologist, who is experienced with this technique.

Potential complications that may result from sympathetic nerve blocks include:

• Nerve injury
• Bleeding - nerve blocks are usually contraindicated in patients who are taking anticoagulant medications
• Allergic reactions - nerve blocks with local anesthetics are contraindicated in patients who are allergic to these medications
• Psychological reactions - anxiety and fear related to apprehension about the nerve block procedure

There are no universally accepted guidelines regarding the choice of anesthetic for the blockade, which patients benefit the most from the blockade, and which type of nerve block is most effective. The most commonly used anesthetic is lidocaine.

Sympathectomy

Sympathectomy is a procedure that is intended to destroy the collection of sympathetic nerve cells (sympathetic ganglion) along the spinal cord and to suppress or block the sympathetically-maintained pain in the affected area. Because a sympathectomy is a procedure that carries significant risks (which will be discussed below) and the outcome may vary from patient to patient, the decision to undergo this procedure should be carefully assessed. Patients who are offered a surgical sympathectomy as a treatment option for their RSD pain should carefully find out about the surgeon's experience and success rate with this procedure before undergoing the procedure.

Patients are considered as potential candidates for sympathectomy only if response to a sympathetic nerve block shows that the source of the RSD pain is sympathetically-maintained pain. If the source of the RSD pain is determined to be sympathetically-independent pain (i.e., no reduction of pain is noted after a nerve block), a sympathectomy is not a viable treatment option.