While the use of sympathetic blocks (injections) is controversial, in this study, 20 patients suffering from complex regional pain syndrome (CRPS) were given injections to examine the method's contribution "as prospective predictors of outcome."
The patients, who exhibited allodynia, or pain with light touch, were given an initial "diagnostic" injection after which results were analyzed to determine if further treatments would be advantageous. This treatment consists of injections into the sympathetic nerves that run along the front side of the spinal column.
Those who showed at least a 50% improvement were treated with subsequent blocks. Patients who did show initial improvement were considered to have "sympathetically maintained pain" (SMP) and were also more likely to experience greater long-term improvement as well. Cases in which patients did not have significant improvement were considered to have "sympathetically independent pain" (SIP) and no further treatment was given.
Previous studies by Cepeda et al (1) showed that less than one-third of CRPS patients are likely to respond to this type of procedure.
"Reserving these invasive procedures for patients who will receive the greatest benefit could have significant value by reducing unnecessary risk for adverse events, as well as significant economic benefit by limiting the costs associated with unnecessary procedures," states lead researcher, Dr. Craig T. Hartrick.
Although this study was not randomized and was not placebo-controlled, it "speaks to the rational use of sympathetic block" and suggests that this procedure is especially useful when allodynia is present.