Imaging Studies
Radiography
Soft-tissue swelling and regional osteopenia may be present in patients with reflex sympathetic dystrophy (RSD; also referred to as complex regional pain syndrome [CRPS] type 1). Regional osteopenia is evident on plain films in 80% of extremities (see the image below).
Radiograph of affected extremity, depicting regional osteopenia contrasted with normal radiographic appearance of the opposite extremity.
The following five radiographic patterns were described by Genant et al [16] :
-
Irregular resorption of trabecular bone giving patchy appearance
-
Subperiosteal bony resorption
-
Intracortical bone resorption
-
Endosteal bone resorption
-
Surface erosions in subchondral and juxtacortical bone
Bone scanning
Three-phase technetium-99m scanning is commonly used. Scan findings are considered positive if flow is asymmetric in phases 1, 2, and/or 3. Bone scans do not correlate with symptoms or provide prognostic information.
Magnetic resonance imaging
In a study by Im et al, diffusion tensor imaging was used to assess the structural integrity of prefrontal white matter in CRPS patients and patients without CRPS, and the degree of pain catastrophizing was assessed in the CRPS patients. [17] The CRPS patients had lower structural integrity in the prefrontal cortext, and lower structural integrity was correlated with a higher degree of pain catastrophizing.
Other Tests
Other tests to be considered include the following:
-
Diagnostic sympathetic blockade - Pain relief following sympatholytic intervention (eg, IV phentolamine administration) is indicative of RSD; a positive result to a phentolamine block test usually indicates a good prognosis with significant relief following administration of IV sympatholytic drugs
-
Thermography [18] - Sweating is analyzed by using the resting sweat output (RSO) or the quantitative sudomotor axon reflex test (QSART)
Tests under investigation include the following:
-
Total digital blood flow using digital temperature measurements and laser Doppler flowmetry
-
Vital capillaroscopy - A technique using Doppler flowmetry to gauge anatomic vascular mapping and capillary blood flow in the affected extremity; in such an extremity, enlarged, dilated, distorted, and irregularly spaced capillary loops are depicted, and in addition, nail-fold capillaries may be absent in patients with underlying connective-tissue disease
Questionnaires used for subjective complaints of pain include the following:
-
Visual analogue score (VAS)
-
McGill pain questionnaire
CRPS patients may exhibit visuomotor impairments during pointing tasks. [19]
The quantitative sensory axon reflex test (QSART) is sometimes used for evaluation of sudomotor function in the diagnosis of CRPS, but a study by Lee et al found it to be of low diagnostic value for either screening or confirmation. [20]
The tourniquet ischemia test has not been frequently used for the workup of suspected CRPS but may be useful for confirmation in patients who meet the clinical criteria for the diagnosis. [21]
Histologic Findings
Because RSD is a condition that seldom is treated surgically, histopathologic descriptions are rare.
Pathologic findings from osteonecrotic femoral head specimens have been studied extensively on the basis of intramedullary pressures (IMP) and intraosseous phlebography.
The gross appearance is as follows:
-
Spongy bone
-
Easily collapsible trabeculae
-
Medullary necrosis
-
Trabecular necrosis
The microscopic appearance is as follows:
-
Areas of vascular stasis and fibrosis
-
Lipoblastomatosis
-
Thickened arteriolar walls
-
Preserved articular cartilage and synovium
-
Thickening and retraction of the joint capsule limiting movements of the joints
-
No tendon involvement
Staging
The triphasic course of vasomotor instability has been used to stage RSD, as follows:
-
Phase 1 - The limb is swollen, hot, pink, and dry
-
Phase 2 - The limb is swollen, cool, blue, and damp with sweat
-
Phase 3 - The edema and vasomotor irritability have settled, resulting in a largely contracted extremity
-
Reflex sympathetic dystrophy following surgery for Dupuytren contracture.
-
Radiograph of affected extremity, depicting regional osteopenia contrasted with normal radiographic appearance of the opposite extremity.
