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Complex Regional Pain Syndrome Diagnostic Tests
Sympathetic Nerve Blocks
Sympathetic nerve blocks are essentially injections of a local anesthetic at various places in the body, which in turn block the sympathetic nerves of each area. The only way a doctor can find out if a CRPS patient’s pain is sympathetically-maintained pain (SMP), which is pain stemming from problems in the sympathetic nervous system, is to do a sympathetic nerve block (25). CRPS patients can be said to have SMP if they experience pain relief from sympathetic nerve blocks (25).
Raja et al pointed out that only some patients with CRPS respond to a sympathetic nerve blockade, and they proposed that patients’ pain be defined as “sympathetically-maintained" or "sympathetically-independent" according to their response to temporary sympathetic nerve blocks (26).
According to Stanton-Hicks, although a positive response to a sympathetic block was necessary historically before a diagnosis of CRPS would be made, because it is not known how the sympathetic nervous system is involved in the pathophysiology of CRPS, it is necessary to abandon this convention (27).
Since current critiques of sympathetic nerve blocks raise concerns about the benefit to risk ratio of permanent sympathetic nerve damage, and identifying which patients will have pain relief from more invasive procedures, according to an editorial by Max and Gilron, more research must be done on this technique (28).
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Updated December 20, 2007 |
