Complex Regional Pain Syndrome - Diagnosis

Diagnosis

CRPS types I and II share the common diagnostic criteria shown below. Spontaneous pain or allodynia (pain resulting from a stimulus which would not normally provoke pain, such as a light touch of the skin) is not limited to the territory of a single peripheral nerve, and is disproportionate to the inciting event.

1. There is a history of edema, skin blood flow abnormality, or abnormal sweating in the region of the pain since the inciting event.
2. No other conditions can account for the degree of pain and dysfunction.

The two types differ only in the nature of the inciting event. Type I CRPS develops following an initiating noxious event that may or may not have been traumatic, while type II CRPS develops after a nerve injury.

No specific test is available for CRPS, which is diagnosed primarily through observation of the symptoms. However, thermography, sweat testing, x-rays, electrodiagnostics, and sympathetic blocks can be used to build up a picture of the disorder. Diagnosis is complicated by the fact that some patients improve without treatment. A delay in diagnosis and/or treatment for this syndrome can result in severe physical and psychological problems. Early recognition and prompt treatment provide the greatest opportunity for recovery.

The International Association for the Study of Pain (IASP) lists the diagnostic criteria for complex regional pain syndrome I (CRPS I) (RSDS) as follows:

1. The presence of an initiating noxious event or a cause of immobilization
2. Continuing pain, allodynia (perception of pain from a nonpainful stimulus), or hyperalgesia (an exaggerated sense of pain) disproportionate to the inciting event.
3. Evidence at some time of edema, changes in skin blood flow, or abnormal sudomotor activity in the area of pain
4. The diagnosis is excluded by the existence of any condition that would otherwise account for the degree of pain and dysfunction.

According to the IASP, CRPS II (causalgia) is diagnosed as follows:

1. The presence of continuing pain, allodynia, or hyperalgesia after a nerve injury, not necessarily limited to the distribution of the injured nerve
2. Evidence at some time of edema, changes in skin blood flow, or abnormal sudomotor activity in the region of pain
3. The diagnosis is excluded by the existence of any condition that would otherwise account for the degree of pain and dysfunction.

The IASP criteria for CRPS I diagnosis has shown a sensitivity ranging from 98–100% and a specificity ranging from 36–55%. Per the IASP guidelines, interobserver reliability for CRPS I diagnosis is poor. Two other criteria used for CRPS I diagnosis are Bruehl's criteria and Veldman's criteria which have moderate to good interobserver reliability. In the absence of clear evidence supporting 1 set of criteria over the others, clinicians may use IASP, Bruehl’s, or Veldman’s clinical criteria for diagnosis. While the IASP criteria are nonspecific and possibly not as reproducible as Bruehl’s or Veldman’s criteria, they are cited more widely the literature including treatment trials.