The main feature of CRPS is continuing regional pain that is seemingly disproportionate in time or degree to the usual course of any known trauma or tissue injury. The pain is regional rather than a specific nerve territory and usually has abnormal sensory (painful to light touch), motor (decrease range of motion), sudomotor (sweating), vasomotor (cool/hot), and/or trophic changes. The syndrome shows variable progression over time.
There are other older alternative names to CRPS including Reflex Sympathetic dystrophy (RSD), Causalgia, Algodystrophy, etc.
There are 2 subtypes of CRPS:
Type I also known as RSD corresponds to patients with CRPS without evidence of peripheral nerve injury and represents majority (90%) of clinical presentations.
Type II was formally termed causalgia and refers to cases in which peripheral nerve injury is present.
Pathogenesis: The true pathogenesis of CRPS is unknown and why it affects only certain individuals. The underlying pathophysiology is thought to be multifactorial and involves pain dysregulation in both the sympathetic and the central nervous systems. It likely has genetic, inflammatory, and psychological contributions.
Region: CRPS usually favors the distal extremities. However, spread beyond the initially affected area commonly occurs in the proximal or contralateral limb.
Epidemiology: Population-based studies estimated incidence between 5.46 per 100,000 per year. Women are affected more commonly with a female to male ratio up to 4:1.
The most common inciting events are fractures, crush injuries, sprains, and surgery. However, up to 10% of the patients reported no precipitating factor and developed spontaneous CRPS.
Onset: The onset of CRPS generally occurs within 4 to 6 weeks of the inciting event. The initial symptoms include pain, erythema (red/purple tinge) and swelling of the affected limb.
Evaluation: The diagnosis of CRPS is largely clinical and one of exclusion. The differential diagnoses include small or large fiber sensorimotor neuropathy, cellulitis, vasculitis, vascular insufficiency, lymphedema, deep venous thrombosis, Raynaud’s phenomena etc.
There is no gold standard test or method for confirming the diagnosis. A consensus criterion also known as Budapest criteria was created to help confirming the diagnosis of CRPS. The criteria have several features including:
- continuing pain, which is disproportionate to any inciting event.
- Patient must report one symptom such as allodynia, report temperature asymmetry or skin color changes, reports edema or sweating changes, reports decreased range of motion or motor dysfunction.
- For clinical diagnosis, the symptom is substantiated by one clinical sign at the time of evaluation as well.
- Finally, there is no other diagnoses that better explain the signs and symptoms.
Imaging: Bone scintigraphy is a sensitive technique for the detection of any large variety of bone, joint, periarticular disorders including fracture, infection, tumor, arthritis, and metabolic bone disease. Triple phase bone scintigraphy is used for detecting alterations in bone metabolism in patients with CRPS. Although the results can help determining bone metabolism alterations, the diagnosis of CRPS does not depend on the results of the imaging studies.
Treatment/management: It is prudent to institute aggressive management as soon as possible as a delay may result in an unfavorable outcome for patient suffering with CRPS. Comprehensive treatment involves a multidisciplinary strategy with a rehabilitative program at the forefront including physical and occupational therapy with mirror therapy. Medication treatments can include oral corticosteroids, anticonvulsants such as gabapentin, analgesic antidepressant such as duloxetine, transdermal lidocaine, and opioids. A multimodal pharmacologic regimen that combines several different classes may be superior.
There is data to support the use of interventional treatment options such as serial sympathetic ganglion blocks however data is conflicting based on multiple studies and trials. Still implementation of sympathetic nerve blocks during early CRPS might convey benefit such as decrease pain and sensitivity which allows patient to better tolerate physical therapy and occupational Therapy. Spinal cord stimulation and dorsal root ganglion stimulation is also used as an alternative treatment modality however data shows that 5 years after implantation, the outcome was no different in patients who had spinal cord stimulation therapy versus physical therapy alone. With respect to intravenous infusions, there is evidence to support infusion of ketamine, lidocaine, bisphosphonate etc. (usually performed at academic institutions) however the data was not of high quality.
There is a large overlap in patients suffering with CRPS and association with comorbid psychiatric disorder such as depression and anxiety, cognitive behavior therapy is considered unnecessary compliant in treating CRPS.
In summary, CRPS remains a very complex neuropathic pain disorder that is best managed with a multidisciplinary team approach model to maximize recovery. Delay in recognition and or treatment can result in poor chronic outcomes.