Complex regional pain syndrome: mystery explained?

Patients initially diagnosed as 'warm' or 'cold' CRPS 1 show differences in central sensory processing some eight years after diagnosis: a quantitative sensory testing study

We used quantitative sensory testing (QST) to gain further insight into mechanisms underlying pain in CRPS 1. Specific goals were: (1) to identify altered patterns of sensory processing some 8 years after diagnosis, (2) to document differences in sensory processing between 'warm' and 'cold' diagnostic subgroups, (3) to determine relationships between changed sensory processing and disease progression regarding pain. The study was performed on a cohort of patients (n=47) clinically diagnosed with CRPS 1 of one upper extremity approximately 8 years previously. Pain was quantified by VAS and MacGill Pain Questionnaire (MPQ), and all subjects underwent electrical and mechanical QST. Cold patients (n=13) had poorer MPQ scores than warm ones (n=34), and more pain on electrical stimulation. Their evoked pain increased with disease progression and correlated with clinical pain measures. For both diagnostic subgroups, thresholds to pressure pain were lower on the affected extremity and with disease progression. Eight years after original diagnosis, cold CRPS 1 patients have poorer clinical pain outcomes and show persistent signs of central sensitisation correlating with disease progression. The latter is not the case for warm CRPS 1 patients. Both diagnostic subgroups show greater pressure hyperalgesia on the affected limb and with disease progression. QST may prove useful in the subdiagnosis of CRPS 1 and in quantifying its progression, with both applications warranting further investigation for clinical and research use.

Sensorimotor retuning [corrected] in complex regional pain syndrome parallels pain reduction

Patients with complex regional pain syndrome (CRPS) and intractable pain showed a shrinkage of cortical maps on primary (SI) and secondary somatosensory cortex (SII) contralateral to the affected limb. This was paralleled by an impairment of the two-point discrimination thresholds. Behavioral treatment over 1 to 6 months consisting of graded sensorimotor retuning led to a persistent decrease in pain intensity, which was accompanied by a restoration of the impaired tactile discrimination and regaining of cortical map size in contralateral SI and SII. This suggests that the reversal of tactile impairment and cortical reorganization in CRPS is associated with a decrease in pain.

Autonomic dysfunction in rheumatic diseases

Patients who have rheumatic diseases often present with dysfunctions that are related to the autonomic nervous system (ANS) and are due to peripheral autonomic neuropathy or central changes. This article describes the prevalence of autonomic dysfunctions in patients who have rheumatic diseases. In the second part of this article, another form of ANS dysfunction-complex regional pain syndromes-is demonstrated. Clinically, these syndromes are characterized by pain (spontaneous, hyperalgesia, allodynia); active movement disorders, including an increased physiologic tremor, abnormal regulation of blood flow and sweating, edema of skin and subcutaneous tissues; and trophic changes of skin, appendages of skin, and subcutaneous tissues. In conclusion, this discussion shows that alterations of the ANS occur in rheumatic and related diseases, that these alterations may be involved in the pathogenesis of these diseases, and that we need more refined methods to study the changes that are related to the ANS.

Understanding neuropathic pain

Neuropathic pain is defined as a chronic pain condition that occurs or persists after a primary lesion or dysfunction of the peripheral or central nervous system. Traumatic injury of peripheral nerves also increases the excitability of nociceptors in and around nerve trunks and involves components released from nerve terminals (neurogenic inflammation) and immunological and vascular components from cells resident within or recruited into the affected area. Action potentials generated in nociceptors and injured nerve fibers release excitatory neurotransmitters at their synaptic terminals such as L-glutamate and substance P and trigger cellular events in the central nervous system that extend over different time frames. Short-term alterations of neuronal excitability, reflected for example in rapid changes of neuronal discharge activity, are sensitive to conventional analgesics, and do not commonly involve alterations in activity-dependent gene expression. Novel compounds and new regimens for drug treatment to influence activity-dependent long-term changes in pain transducing and suppressive systems (pain matrix) are emerging.

Chronic regional pain and chronic pain syndromes

This paper seeks to consider the validity and utility of two related terms in spinal and other injuries: complex regional pain syndrome (CRPS) and chronic pain syndrome (CPS). It is argued that the words chronic regional pain syndrome convey neither understanding of the condition nor of its mechanism. They simply redefine the clinical problem, but fail to establish specific diagnostic features or consistent primary pathogenesis. CRPS is best construed as a reaction to injury, or to excessive, often iatrogenic, immobilization after injury; but it is not an independent disease. The diagnosis of CPS groups together ill-defined symptoms under a convenient, but medically untestable and therefore inept label. Patients, lawyers, and support groups commonly deny psychogenesis, with the sadly mistaken notion that this implies a bogus or spurious cause.

Role of alendronate in therapy for posttraumatic complex regional pain syndrome type I of the lower extremity

OBJECTIVE

To evaluate the effects of the antiresorptive agent alendronate at a daily oral dose of 40 mg in patients with posttraumatic complex regional pain syndrome type I (CRPS I) of the lower extremity.

METHODS

Forty patients were enrolled in this 8-week randomized, double-blind, placebo-controlled study of alendronate therapy for CRPS I, a condition associated with regional osteoclastic overactivity. An optional 8-week open extension of alendronate therapy (weeks 12-20) was available after a 4-week period without therapy. Clinical assessments included joint mobility, edema of the lower extremity, tolerance to pressure in the lower extremity, and levels of spontaneous pain. Urinary levels of type I collagen N-telopeptide (NTX) were assessed by enzyme-linked immunosorbent assay. Patients were examined at weeks 4, 8, 12, 16, 20, and 24. Statistical analysis included two-way factorial analysis of variance.

RESULTS

In contrast to placebo-treated patients (n = 20), all of the alendronate-treated patients (n = 19) exhibited a marked and sustained improvement in levels of spontaneous pain, pressure tolerance, and joint mobility, as well as a significant reduction in urinary levels of NTX at weeks 4 and 8. The improvement was maintained at week 12. Twelve patients from each treatment group volunteered for the 8-week open trial, and all of them had a positive response to alendronate.

CONCLUSION

Our findings support the use of oral alendronate in posttraumatic CRPS I. By reducing local acceleration of bone remodeling, alendronate might relieve pain by effects on nociceptive primary afferents in bone, pain-associated changes in the spinal cord, and possibly also through a central mechanism.

Interventional modalities in the treatment of complex regional pain syndrome

Complex regional pain syndrome (CRPS) applies to a variety of conditions in which symptoms such as allodynia and hyperalgesia predominate along with hyperpathia and vasomotor/sudomotor disturbances. The incidence of CRPS in the chronic pain population varies and is difficult to determine, though it appears to affect women more than men. Treatment is multidisciplinary, and recovery of function and the reduction of pain are the main goals of treatment;this article addresses some of the interventional modalities that are used.

Pathophysiology of pain

Pain is a major symptom of many different diseases. Modern pain research has uncovered important neuronal mechanisms that are underlying clinically relevant pain states, and research goes on to define different types of pains on the basis of their neuronal and molecular mechanisms. This review will briefly outline neuronal mechanisms of pathophysiological nociceptive pain resulting from inflammation and injury, and neuropathic pain resulting from nerve damage. Pain is the sensation that is specifically evoked by potential or actual noxious (i.e. tissue damaging) stimuli or by tissue injury. Pain research has not only explored the neuronal and molecular basis of the "pain system" of the healthy subject but has also provided insights into the function and plasticity of the "pain system" during clinically relevant pains such as post-injury pain, inflammatory pain, postoperative pain, cancer pain and neuropathic pain. This review will briefly describe the "pain system" and then address neuronal mechanisms that are involved in clinical pain states.

Graded motor imagery is effective for long-standing complex regional pain syndrome: a randomised controlled trial

Complex regional pain syndrome type 1 (CRPS1) involves cortical abnormalities similar to those observed in phantom pain and after stroke. In those groups, treatment is aimed at activation of cortical networks that subserve the affected limb, for example mirror therapy. However, mirror therapy is not effective for chronic CRPS1, possibly because movement of the limb evokes intolerable pain. It was hypothesised that preceding mirror therapy with activation of cortical networks without limb movement would reduce pain and swelling in patients with chronic CRPS1. Thirteen chronic CRPS1 patients were randomly allocated to a motor imagery program (MIP) or to ongoing management. The MIP consisted of two weeks each of a hand laterality recognition task, imagined hand movements and mirror therapy. After 12 weeks, the control group was crossed-over to MIP. There was a main effect of treatment group (F(1, 11) = 57, P < 0.01) and an effect size of approximately 25 points on the Neuropathic pain scale. The number needed to treat for a 50% reduction in NPS score was approximately 2. The effect of treatment was replicated in the crossed-over control subjects. The results uphold the hypothesis that a MIP initially not involving limb movement is effective for CRPS1 and support the involvement of cortical abnormalities in the development of this disorder. Although the mechanisms of effect of the MIP are not clear, possible explanations are sequential activation of cortical pre-motor and motor networks, or sustained and focussed attention on the affected limb, or both.