Reflex Sympathetic Dystrophy Imaging

Updated: Dec 31, 2015
  • Author: Lawrence E Holder, MD; Chief Editor: Felix S Chew, MD, MBA, MEd  more...
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Overview

Overview

Reflex sympathetic dystrophy (RSD), considered by many to be part of a broader group of pain syndromes known as complex regional pain syndrome (CRPS), is an incompletely understood response of the body to an external stimulus, resulting in pain that is usually nonanatomic and disproportionate to the inciting event or expected healing response. Reflex sympathetic dystrophy is also known as CRPS-I. [1, 2, 3, 4]

As early as the 1930s and 1940s, a short circuit in the reflex arc between somatic afferent sensory fibers and autonomic sympathetic efferents was postulated to explain overall increased sympathetic stimulation. Currently, no specific pathologic, histologic, or biochemical markers of either RSD or CRPS exist. [5, 6, 7, 8, 9, 10]

Although controversy continues regarding the term, definition, and process of diagnosis, the presence of sympathetically maintained pain is accepted as an etiology for, or at least as a significant component of, many regional pain problems. [11, 12] All sympathetically maintained pain syndromes (SMPS) are probably not RSD. [11]

Radiologists and orthopedic surgeons usually agree to define reflex sympathetic dystrophy (RSD) (as stated by Schutzer [13] ) as an "excessive or exaggerated response to an injury of an extremity, manifested by 4 somewhat constant characteristics: (1) intense or unduly prolonged pain, (2) vasomotor disturbances, (3) delayed functional recovery, and (4) various associated trophic changes."

The term complex regional pain syndrome has been introduced to encompass a variety of chronic pain syndromes, with RSD part of the type I group. [14, 15, 16, 17] Despite the efforts of several consensus groups, primarily working in the field of pain medicine, CRPS itself continues to be an incompletely understood group of conditions. [18, 19] More information about RSD and CRPS can be found in other sections of Medscape Reference.

The radionuclide bone scans below depict patients with RSD.

Reflex sympathetic dystrophy of the hand. Delayed Reflex sympathetic dystrophy of the hand. Delayed image palmar view reveals increased tracer diffusely involving the entire right wrist, metacarpals, and phalanges, with juxta-articular accentuation. Relatively less increased uptake is observed distally, but all areas are involved. The dot of increased activity distal to the third ray is a hot marker indicating the right side.
Reflex sympathetic dystrophy of the foot. Delayed Reflex sympathetic dystrophy of the foot. Delayed image plantar view reveals increased tracer uptake diffusely involving the lowermost right leg, ankle, tarsals, metatarsals, and phalanges. Uptake is less distally than proximally, but all areas are involved. The dot of increased activity distal to fifth toe is a hot marker indicating the right side.

Preferred radiologic examination

Radionuclide bone imaging (RNBI) is the only generally accepted imaging technique to provide objective and relatively specific evidence of reflex sympathetic dystrophy (RSD) in the upper and lower extremities, predominantly the hands and feet. [20, 21, 22, 23, 24] Delayed bone imaging has been reported to be up to 100% sensitive for the variant of sympathetically maintained pain termed RSD by hand and foot surgeons. [25, 26]

Plain radiography is only 60% sensitive and not specific; when positive, radiographs often show only osteoporosis, occasionally in combination with soft tissue swelling or diffuse soft tissue atrophy.

No consistent findings have been found in the occasional study done with other imaging modalities, and none are suggested for diagnosis.

Nonimaging diagnostic testing

Pain in response to mild cooling stimuli: A drop of acetone or ethyl chloride spray provoking severe pain suggests SMPS rather than a sympathetically independent pain syndrome (SIPS).

Phentolamine test: The blocking of alpha-adrenergic receptors by intravenous phentolamine compared to a placebo helps classify patients as SMPS versus SIPS.

Limitations of techniques

Patients are observed who present with acute or subacute pain and vasomotor or neuroregulatory signs or symptoms and who do not demonstrate the classic diffuse increased uptake on delayed RNBI. The relationship of these patients to those with abnormal RNBI remains unexplained.

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Radiography

Osteoporosis, although found in as many as 60% of patients with upper extremity reflex sympathetic dystrophy (RSD), is not specific, often representing changes of disuse secondary to the pain associated with RSD. Occasionally, soft tissue swelling or diffuse soft tissue atrophy may be seen; these are nonspecific findings.

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Magnetic Resonance Imaging

MRI changes in established reflex sympathetic dystrophy (RSD) rarely have been evaluated, and as with studies using other modalities, the definition of RSD has varied considerably. In one study by Schweitzer et al [27] involving the lower extremity (n=35), soft tissue thickening with and without contrast enhancement (n=31) was demonstrated without any marrow changes, while in another study of the upper extremity (n = 17) by Koch et al, [28] no marrow changes and only inconsistent soft tissue or muscle signal changes were seen.

In the hand, Sintzoff et al [29] used MRI to detect what was believed to be bone marrow edema and then equated bone marrow edema to RSD. MRI thus is not an established technique in the imaging evaluation of RSD.

MRI has been used in attempts to understand some of the postulated central mechanisms that may be a part of complex regional pain syndrome (CRPS). [25]

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Ultrasonography

A single-power Doppler study by Nazarian et al [30] involving the lower extremities suggested increased flow without side-to-side asymmetry in patients with reflex sympathetic dystrophy (RSD). Pekindi et al in another study concluded that Doppler sonography cannot be used for the diagnosis of RSD but may help in assessing hemodynamic stages of the disease. [31] Ultrasound thus is not an established technique in the imaging evaluation of RSD.

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Nuclear Imaging

Three-phase radionuclide bone imaging (RNBI) is performed primarily because the differential diagnosis often includes infection or other lesions for which information about the perfusion to the extremity (phase I) or relative vascularity of the extremity (phase II) is helpful. [32, 33, 34, 35]

For regional reflex sympathetic dystrophy (RSD) of the hand or foot, the hallmark on the radionuclide angiogram (RNA; phase I) is diffuse increased perfusion to the entire extremity, including the distal forearm or leg and, occasionally, reaching the shoulder or hip, even when the inciting lesion is distal.

Similar diffuse increased vascularity, manifested by diffuse increased tracer accumulation on blood pool or tissue-phase images (phase II) is seen. On these images, juxta-articular accentuation may be seen. RNA findings are abnormal in approximately 40% of patients and blood pool findings in approximately 50%, most often in clinical stage I or II of the disease.

Delayed images demonstrate diffuse increased tracer throughout the hand or foot, including the wrist or ankle, with juxta-articular accentuation and, often, proximal uptake involving the forearm or leg and, occasionally, the shoulder and arm or hip and femur. Activity in the hands or feet usually is more prominent proximally than distally, but the amount of abnormal tracer uptake has not been correlated with clinical severity. Quantification occasionally has been helpful but is not used routinely. See the images below.

Reflex sympathetic dystrophy of the hand. Delayed Reflex sympathetic dystrophy of the hand. Delayed image palmar view reveals increased tracer diffusely involving the entire right wrist, metacarpals, and phalanges, with juxta-articular accentuation. Relatively less increased uptake is observed distally, but all areas are involved. The dot of increased activity distal to the third ray is a hot marker indicating the right side.
Reflex sympathetic dystrophy of the foot. Delayed Reflex sympathetic dystrophy of the foot. Delayed image plantar view reveals increased tracer uptake diffusely involving the lowermost right leg, ankle, tarsals, metatarsals, and phalanges. Uptake is less distally than proximally, but all areas are involved. The dot of increased activity distal to fifth toe is a hot marker indicating the right side.

Pediatricians report a moderate frequency of lower extremity neurovascular or neuroregulatory disease in children that has been termed reflex sympathetic dystrophy (RSD). In these children, a bone scan pattern often reveals marked decreased tracer uptake on delayed images compared to increased uptake in adults; therefore, this may represent a different condition, such as pseudodystrophy.

When radionuclide bone imaging (RNBI), especially in the upper extremity, demonstrates classic diffuse findings, reflex sympathetic dystrophy (RSD) is certain (specificity). When RNBI does not demonstrate that pattern, the most common variant of sympathetically maintained pain syndrome (SMPS) or complex regional pain syndrome (CRPS) type 1 is excluded (sensitivity).

In the lower extremity, patients with severe infection, especially if underlying diabetes mellitus is present, may demonstrate diffuse increased delayed image tracer uptake on RNBI performed to diagnose osteomyelitis. This is not usually a diagnostic issue clinically.

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Intervention

CT-assisted temporary thoracic sympathetic nerve blockade

According to Andresen et al, outpatient CT-assisted temporary thoracic sympathetic nerve blockade is an effective adjunct therapy, with a low complication rate, for complex regional pain syndrome (CRPS).

In their study, in addition to physiotherapy and pharmacotherapy with analgesics and calcitonin, sympathetic nerve blockade was performed 3 times, at 2-day intervals. The CT-assisted puncture was performed in the prone position at the level of the intervertebral space of the second and third thoracic vertebrae. All patients reported immediate pain relief. Color-coded duplex ultrasonography of the arteries of the affected limb was performed before and after puncture and showed increased peripheral blood flow. [36]

More recently Kastler has reported using CT-guided radiofrequency neurolysis for treating patients with refractory type I CRPS of the upper limb. [37] Inclusion criteria were clinically based using the International Association for the Study of Pain (IASP) criteria plus a positive stellate ganglion block. [18]

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