Reflex Sympathetic Dystrophy - 1

Abstract

To the Editor: The editorial by Ochoa, which was published in the November 1995 issue of the Mayo Clinic Proceedings (pages 1124 to 1126), focused heavily on his views of “reflex sympathetic dystrophy” (RSD) and less on our article. We wish to respond to the editorial to the extent that it bears on our report. The issue of sensitivity and specificity was misconstrued. In our retrospective review, we were gratified that variables could be selected that resulted in a 94&x0025; specificity. Our approach was hypothesis generating rather than definitive. A follow-up prospective study is needed to test the hypothesis. We did not approach the study with preconceived notions about the role of the sympathetic nervous system in RSD. The term “RSD” was criticized. This is “old hat,” and the name used has no bearing on the validity of the findings. Our article, as with most reports published during the past 2 decades, has a disclaimer on the term, with the clear understanding that the term is appreciated for its longevity and name recognition rather than for its appropriateness. Much ado was also made of the issue of whether RSD is a syndrome. The theory that most clinicians embrace is that a syndrome is a recognizable gestalt of clinical features and does not subsume a single cause. For instance, many syndromes in neurology are due to multiple causes. Thus, a group of patients defined by a syndrome constitute a heterogeneous population. The logic that follows, however, was flawed. One may explain the absence of important findings on this basis. A finding remains a finding and must be accepted or disputed on its own merits. We believe the heterogeneous population makes this finding of even more interest, as it suggests hidden underlying homogeneity. Allusion was made to the fact that only one in three patients in our retrospective study underwent an examination by a neurologist. This criticism assumes that only a neurologist can recognize RSD, a viewpoint that we and most pain clinicians reject. Furthermore, the diagnosis of RSD was not based on the caregiver's opinion but rather on the individual person's observations, which were subsequently integrated by a neurologist into the clinical score. Animal models were criticized. We do not embrace animal models as mimicking all relevant aspects of the human condition. Animal models are, however, uniquely appropriate in generating basic preclinical hypotheses and in supplementing human studies. They currently provide important information on the effects of nerve injury. For instance, current animal research on the effects of injury causing sensitization at various sites-the nerve, the dorsal root ganglion,1McLachlan EM Jang W Devor M Michaelis M Peripheral nerve injury triggers noradrenergic sprouting within dorsal root ganglia.Nature. 1993; 363: 543-546Crossref PubMed Scopus (637) Google Scholar, 2Bennett GJ An animal model of neuropathic pain: a review.Muscle Nerve. 1993; 16: 1040-1048Crossref PubMed Scopus (135) Google Scholar, 3Bennett GJ Xie YK A peripheral mononeuropathy in rat that produces disorders of pain sensation like those seen in man.Pain. 1988; 33: 87-107Abstract Full Text PDF PubMed Scopus (4489) Google Scholar, 4Kajander KC Bennett GJ Onset of a painful neuropathy in rat: a partial and differential deafferentation and spontaneous discharge in A beta and A delta primary afferent neurons.J Neurophysiol. 1992; 68: 734-744Crossref PubMed Scopus (337) Google Scholar, 5Kajander KC Wakisaka S Bennett GJ Spontaneous discharge originates in the dorsal root ganglion at the onset of a painful peripheral neuropathy in the rat.Neurosci Lett. 1992; 138: 225-228Crossref PubMed Scopus (355) Google Scholar and the nerve root entry zone—and by different mechanisms potentially could generate important hypotheses for testing in humans. Animal models clearly necessitate final assessment in humans but that in no way diminishes their role. The allusion to a change in emphasis between our preliminary report and our final report was at best inaccurate and at worst offensive. None of our statements were contradictory. Much of the information contained in complete articles is not contained in a 10-minute platform presentation. The long gestation of the article relates to the lengthy distance between our statisticians and the first author and his desire to explore meticulously various statistical relationships.