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Compiled By:
Hyun M. Song, M.D.
History:
77 year-old man complaining of right foot and ankle pain for 3 days. Negative for DVT. Question occult fracture or Charcot arthropathy.
Exam:
Short axis T1, T2 FSE fat sat; Sagittal T1, STIR; Long axis coronal STIR through the forefoot.
Findings and Differential Diagnosis:
Marked swelling and edema involving the subcutis soft tissues compatible with lymphedema but sheet like distribution suspicious for reflex sympathetic dystrophy. Paucity of osteoedema (which mitigates against Charcot joint).
Discussion:
Reflex sympathetic dystrophy is known by many different names, including Sudek’s atrophy, causalgia, algodystrophy and shoulder-hand syndrome. This occurs in any nerually related visceral, musculoskeletal, neurologic or vascular condition. The most frequent precipitating even is physical injury/trauma (including surgery and fracture) but it is also incited by cental nervous system tumors/brain injury and myocardial infarction. Symptoms tend to occur distal to the area of inciting injury.
Reflex sympathetic atrophy is commonly divided into three stages: in stage 1 (warm vasodilatory ) disease, the patient presents with diffuse pain, inflammation, edema and hyperthermia. This hyperesthetic, acute stage may last for 2-3 months, and it is the stage at which MR is most accurate in the diagnosis of RSD.
In stage 2 (vasoconstictive), or the dystrophic stage, decreased sensitivity to temperature/pressure, mild skin atrophy and pain at exercise are present. This stage may last from 3 to 24 months, at which MR is least sensitive, due to paucity of soft tissue or muscle edema. Enhancement is also unusual at this stage.
Stage 3 (atrophic) is the final, irreversible, cold stage where pain is decreased, the skin can be smooth or cyanotic and no enhancement is present on IV contrast administration. Muscle atrophy with aponeurotic or tendinous retraction/contracture occur. The large majority of RSD resolve without clinical sequela but a minority may progress to stage 3. Therefore, therapy prior to this last stage is necessary to prevent loss of extremity function. Treatment options include NSAIDs, alpha/beta blockade, early mobilization, corticosteroids and physiotherapy.
Clinical diagnosis may be made by history, physical examination and confirmation by symptomatic relief following sympathetic nerve block.
On plain radiography, soft tissue swelling and periarticular osteopenia are present. RSD can be distinguished from arthritides by the absence of substantial intraarticular erosions and joint space loss. That is, preservation of the joint space is a clue favoring RSD. Unfortunately, radiographic signs are nonspecific and is a later manifestation of RSD.
Bone scintigraphy demonstrates periarticular uptake on blood pool and delayed images but it is only about 60% sensitive.
MR findings in stage 1 RSD demonstrates skin and subcutaneous soft tissue edema and thickening (fig 1a, 1b). IV gadolinium administration demonstrates periarticular and subcutaneous soft tissue enhancement. Muscle and fascial edema are occasionally demonstrated.
Differential diagnoses for the soft tissue appearance of above cases include hematoma, cellulitis, lymphedema, phlebedema and insect bite. However, lymphedema would be more reticulated, rather than “sheet like” soft tissue edema/thickening. Phlebedema would be more generalized in distribution, with greater prominence of veins. Inflammatory arthritis may be considered, but effusions and synovitis would be evident.
Images:
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Figure 1A:
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Figure 1B:
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Figure 2A:
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Figure 2B:
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RSD demonstrates osteopenia, and in some cases scattered pattern of osteoedema (fig. 2a, 2b) may be seen. The differential diagnosis for this scattered osteoedema includes stess reaction. History and distribution of marrow change are helpful: In stress reaction, marrow changes are more juxtaarticular or juxtacortical. In RSD, foci of osteoedema don’t quite reach the cortex or articular surface, likened to a “window framed” appearance.
As mentioned previously, MR is most useful for diagnosis at stage 1 RSD. Clues provided by the patient’s history, physical exam and imaging findings will help in the diagnosis of, and timely intervention for RSD.
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