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.
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Terminology
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.
Epidemiology
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.
Clinical presentation
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.
Pathology
Etiology
trauma: often minor
surgery 11
idiopathic: immobilization
unknown in many cases
CNS disorders
Location
Complex regional pain syndrome occurs in hands and feet distal to the injury.
Radiographic features
Plain radiograph
severe patchy osteopenia, particularly in the periarticular region
soft tissue swelling, with eventual soft tissue atrophy
preservation of joint space
It is important to differentiate this from disuse osteopenia since the clinician could initiate aggressive physical therapy for the latter.
MRI
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
Nuclear medicine
-
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)
Treatment and prognosis
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.
History and etymology
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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