Complex regional pain syndrome

Last revised by Khalid Alhusseiny on 9 Apr 2023

Complex regional pain syndrome (CRPS), also known as Sudeck atrophy, is a condition that can affect the extremities in a wide clinical spectrum. No one imaging study is sensitive or specific to rule in or rule out the syndrome. 

Two forms of complex regional pain syndrome have been described 8:

  • type 1: no underlying single nerve lesion (formerly known as reflex sympathetic dystrophy) and considered the commonest type 21

  • type 2: underlying nerve lesion identified (formerly known as causalgia)

Patients often have both types present.

Complex regional pain syndrome is principally a clinical diagnosis seen more commonly in females than males with a mean age of presentation of 50 to 70 years 12.

Patients present after an initiating event (see causes below) with symptoms of more than 6 months duration such as edema, changes in skin blood flow, abnormal motor activity, allodynia, hyperalgesia or hyperesthesia 11, 21. Symptoms are often out of proportion to the initiating event and not limited to a single peripheral nerve 8.  

  • trauma: often minor

  • surgery 11

  • idiopathic: immobilization

  • unknown in many cases

  • CNS disorders

  • myocardial infarction

Complex regional pain syndrome occurs in hands and feet distal to the injury.

It is important to differentiate this from disuse osteopenia since the clinician could initiate aggressive physical therapy for the latter.

  • patchy bone marrow edema signal (particularly subcortical), although bone marrow signal may be normal in some cases

  • soft tissue edema and enhancement

  • skin thickening

  • joint effusion

  • synovial hypertrophy

  • muscle atrophy in later stages

  • presence of complex regional pain syndrome can be evaluated with a 3-phase bone scan:

    • the classical presentation is increased bisphosphonate tracer uptake in the affected limb on all three phases (seen less than 50% of the time, but has the highest diagnostic accuracy)

    • diffusely increased juxta-articular activity around all joints of the affected hand or foot on delayed images is the most sensitive indicator (infection and arthritis are potential false-positive findings)

In most cases of complex regional pain syndrome, a multidisciplinary approach is required whereby a combination of various treatments may be employed, such as physical therapy, systemic or regional medications, sympathectomy or spinal cord stimulation, and psychotherapy. 

Interventional radiology can offer pain relief by peripheral nerve block procedures.

Paul Hermann Martin Sudeck (1866-1945) 17 was a German surgeon who described this condition in 1900 16,18,19. He was erroneously said to be an early radiologist in an article published in 1994, but this is probably because his paper in 1900 was the first to describe the characteristic osteopenia seen on radiographs in this condition 16,20.

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Cases and figures

  • Case 1
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  • Case 2
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  • Case 3
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  • Case 4: type 2
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  • Case 5
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  • Case 6
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  • Case 7: following Colles fracture
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  • Case 8: due to screw malposition
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  • Case 9
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