Complex Regional Pain Syndrome
Abstract & Commentary
Source: Rho RH, et al. Mayo Clin Proc. 2002;77:174-180.
Reflex sympathetic dystrophy (RSD) as a syndrome is so broad that some feel it has lost its use as a clinical diagnosis. Neither reflex arcs nor the sympathetic nervous system are necessarily involved in RSD. Hence a new nosologic term, complex regional pain syndrome (CRPS), has been offered as a substitute. Two types of CRPS are proposed based on the presence (type II) or absence (type I) of an overt nerve lesion. Both types are otherwise clinically identical, with the development of a pain syndrome following an initial painful event. Pain, usually burning in character but also throbbing, aching, or shooting, allodynia (disproportionate pain to a non-noxious stimulus), hyperalgesia (disproportionate pain to a mildly noxious stimulus), and occasionally hyperpathia (disproportionate subjective response to noxious stimuli) are characteristic. Vasomotor and sudomotor abnormalities, including changes in color, temperature, and sweating, as well as hypertrophic or atrophic nails, increased or decreased hair growth, and skin atrophy, complete the clinical picture. Painful swollen joints, dystonia, and weakness are not uncommon.
No test is diagnostic for CRPS but vascular, electrodiagnostic, and radiographic studies must be normal (beyond any specific nerve injury) to exclude other etiologies. Examples of these include bone or soft tissue pathology, infection, vascular compression, or collagen vascular disease. Additional studies, including thermography, three-phase bone scintigraphy, sweat testing, and sympathetic blocks, are optional but may provide ancillary evidence of autonomic involvement.
Treatment centers on physical therapy as limb mobilization is the ultimate goal. Pain control is usually necessary and may require tricyclic antidepressants (amitriptyline, nortriptyline, doxepin), anticonvulsants (gabapentin), corticosteroids (early on and only short-term), or opioids if pain persists and interferes with therapy. Regional anesthetic sympathetic blocks (stellate or lumbar) may benefit patients with a sympathetic component to their CRPS but somatic blocks will be required if the former is ineffective. For recalcitrant cases, spinal cord stimulation or intrathecal analgesia with opioids or baclofen may be warranted.
Problems dealing with RSD remain with CRPS. To evaluate RSD diagnostic criteria, as well as the effect of introducing the nosologic term CRPS, 20 years (1980- 2000) of randomized trials and clinical studies in RSD were reviewed using a PubMed search (van De Beek WJ, et al. Neurology. 2002;58:522-526). Case reports were excluded and only the last of multiple studies by van De Beek et al were included to avoid repetitive reporting bias. Seventy-three papers satisfied criteria for review. Among these, variance reigned. Disparate diagnostic criteria were used, some papers requiring from 2-6 mandatory features to make a diagnosis, others from 4-10 nonmandatory features, and yet others a combination of mandatory (1-5) and nonmandatory features (2-9). Although numerous sensory, autonomic, and motor features were criteria for diagnosis, in 30%, 20%, and 88% of studies, respectively, these were not required. Numerous alternative features were cited among diagnostic criteria but, again, these varied widely and included a precipitating factor (26%), radiographic changes (25%), trophic changes (21%), involvement of an area beyond the area of injury (11%), and contracture (10%). Of the 23 studies reported after the introduction of CRPS nosology (1995), equal variability of diagnostic criteria was evident. Only 10 studies used the term CRPS and, among these, at least 2 different sets of criteria were used. Two CRPS-entitled papers did not use CRPS criteria. Two studies used previously defined CRPS criteria but had altered them slightly. RSD, CRPS, or causalgia remains a confusing morass and changing its name does not clear the inexactitude. A rose by any other name remains a rose, and wilted at that! —Michael Rubin
Dr. Rubin, Professor of Clinical Neurology, New York Presbyterian Hospital-Cornell Campus, is Assistant Editor of Neurology Alert.